Marine Jullien

Thibault Reichert

Pascal D'anella

Frederic Castinetti

Anne A Barlier

Thierry Brue

David Taieb

Thomas Cuny
email: thomas.cuny@ap-hm.fr

Frédéric Castinetti

Comparison of 68Ga-Dotatate PET/CT and 18F-FDOPA PET/CT for the diagnosis of pancreatic neuroendocrine tumors in a MEN1 patient

Keywords: 18F-FDOPA PET, CT 68Ga-Dotatate PET, CT MEN1 Neuroendocrine Pancreas

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Mots clés :

(18)F-FDOPA TEP/TDM 68(Ga)-DOTATATE TEP/TDM NEM1 Neuroendocrine Pancréas r é s u m é Contexte. -Les tumeurs neuroendocrines pancréatiques (TNEPs) surviennent chez 80 % des patients atteints de néoplasie endocrinienne multiple de type 1 (NEM1), avec une prédominance de petites tumeurs (< 1 cm), non fonctionnelles, suivies par les gastrinomes et les insulinomes. Du fait de leur petite taille, la performance diagnostique de l'imagerie conventionnelle (IRM et TDM) est variable, pouvant conduire à d'authentiques situations de faux-négatifs. Le 111In-DTPA-Octreotide SPECT (Octréoscan ® ) (scintigraphie des récepteurs de la somatostatine) constitue l'imagerie fonctionnelle de préférence, mais avec une sensibilité de seulement 80 %. En parallèle, le développement de l'imagerie par tomographie par émission de positons couplée au scanner (TEP/TDM) utilisant la 18Ffluorodihydroxyphenylalanine ((18)F-FDOPA) ou plus récemment le 68(Ga)-DOTATATE sont des options intéressantes, en cas d'Octréoscan ® négatif. Cas clinique. -Une patiente âgée de 55 ans, suivie pour une NEM1, fut admise en raison de TNEPs multiples non symptomatiques et progressives objectivées en écho-endoscopie. L'Octréoscan ® était non contributif, de même que la (18)F-FDOPA TEP/TDM, alors que le 68(Ga)-DOTATATE TEP/TDM identifiait l'ensemble des TNEPs détectées en endoscopie.

Introduction

Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant disorder characterized by the occurrence of parathyroid, anterior pituitary and pancreatic neuroendocrine neoplasms (PNENs) [START_REF] Thakker | Clinical practice guidelines for multiple endocrine neoplasia type 1 (MEN1)[END_REF]. It is genetically related to mutations in the MEN1 gene, causing an automosal dominant inheritance with more than 1500 mutations currently described. Molecular alterations affecting the MEN1 signaling pathway have been identified in familial as well as in sporadic PNENs [START_REF] Scarpa | The landscape of molecular alterations in pancreatic and small intestinal neuroendocrine tumours[END_REF]. Furthermore, the latter occur in more than 80% of MEN1 patients, with an overrepresentation of small (i.e. < 1 cm in size) and multiple non-functioning tumours followed by gastrinomas and insulinomas [START_REF] Yates | Challenges and controversies in management of pancreatic neuroendocrine tumours in patients with MEN1[END_REF]. The diagnosis of PNENs relies on both conventional imaging such as CT scan or pancreatic MRI and nuclear medicine imaging modalities, headed by In-pentetreotide single-photon emission computed tomography (CT) (octreoscan). However, in the particular setting of MEN1, octreoscan fails to image 35 to 50% of PNENs < 1 cm in diameter [START_REF] Ito | Imaging in multiple endocrine neoplasia type 1: recent studies show enhanced sensitivities but increased controversies[END_REF]. As such the work conducted by Morgat et al. is of importance as it showed in a series of 19 patients with MEN1, respective sensitivities of 20% for octreoscan and 76% for (68)Ga-DOTA-TOC PET/CT for the detection of duodenopancreatic NENs [START_REF] Vélayoudom-Céphise | Étude comparative de la TEP au68GaDOTATOC et de la tomoscintigraphie à l'111In-DTPA-octréotide pour le dépistagedes tumeurs neuroendocrinesduodénopancréatiques des patients porteursd'une NEM1: étude pilote[END_REF]. (68)Ga-DOTA tracers used the PET technique and have high affinity for the somatostatin receptor subtype 2 (SSTR2), which is highly expressed in neuroendocrine neoplasms [START_REF] O'toole | The analysis of quantitative expression of somatostatin and dopamine receptors in gastro-entero-pancreatic tumours opens new therapeutic strategies[END_REF]. Besides SSTR2-derived imaging modalities, F-FDOPA PET/CT also emerged as reliable imaging technique for the detection of NENs, especially in cases of pancreatic insulinomas (after carbidopa premedication) [START_REF] Leroy-Freschini | Early 18F-FDOPA PET/CT imaging after carbidopa premedication as a valuable diagnostic option in patients with insulinoma[END_REF] or small intestine neuroendocrine neoplasms (SiNENs) [START_REF] Santhanam | Role of 18 F-FDOPA PET/CT imaging in endocrinology[END_REF]. Its performance for the diagnosis of (other) PNENs in the setting of MEN1 syndrome is currently unknown.

We here report the first case of a MEN1 patient who successfully underwent a 68(Ga)-DOTATATE PET/CT for the detection of small multiple PNENs after both negative 18F-FDOPA PET/CT (with carbidopa premedication) and 111In-DTPA-Octreotide SPECT (OctreoScan).

Case report

In 2018, a 55 year-old woman was referred to our department for the follow up of a MEN1 syndrome diagnosed in 1999. Her diagnosis was made in a context of genetic screening because her sister was the index case and exceptionally, she belonged to a family of 11 siblings (Fig. 1) and carried the MEN1 mutation Exon 9, c.1192delc; p.(Gln398Argfs*47). In her past history, she has been treated for a primary hyperparathyroïdism (subtotal parathyroidectomy) secondary to multiglandular disease at the age of 45 and is also regularly followed up for a non-secreting 3mm-right sided pituitary microadenoma. She underwent several abdominal CT-scan which found two hypervascular lesions of 8 mm each, at the posterior face of both the pancreatic body and the tail, respectively. An echoendoscopy was subsequently performed and further identified two more lesions in the pancreas between the body and the tail: in total, there were 4 lesions whose maximal diameter size were 10, 12, 14 and 15 mm, respectively. An ultrasound-guided fine needle aspiration was performed on the larger lesion and the histology was consistent with a PNEN grade 1 (Ki67 < 2%, no mitose). A complete hormonal assessment was strictly negative which meant that those PNEN lesions were non-secreting. Importantly, there was no argument for the possibility of an (occult) insulinoma. As compared to the previous echoendoscopy, the size of the 15-mm lesion increased, the reason why we sought for another and less invasive imaging modality in the follow-up of this patient. We thus performed an octreoscan (132MBq Octreotide indium 111) which was negative for all the lesions previously described (Fig. 2). We, thus, referred the patient to the nuclear medicine for the realization of a (18)F-FDOPA PET/CT with carbidopa premedication (Timone, GE Discovery 710 Premedication with Carbi dopa (200 mg). Activité: 179 MBq -4.53 mCi,). However, the lesions did not uptake at all the radiotracer and the exam was considered as non contributive (Fig. 2). Eventually, a multidisciplinary decision suggested to perform 68(Ga)-DOTATATE PET/CT (hôpital de la Timone, PET CT Discovery 710; PDL 236mGy.cm, CTDI 2,3mGy). All of the 4 lesions showed an uptake of the radiotracer with respective maximum SUV of 28.4 (lesion 1), 7.2 (lesion 2), 7.4 (lesion 3) and 14.6 (lesion 4), respectively (Fig. 3B). There was no hypermetabolic adenopathy or further lesions. The patient is currently treated by somatostatin analogs monthly.

Discussion

The diagnosis of digestive neuroendocrine neoplasms in the context of MEN1 remains a real challenge in clinical practice, in more than one way. First, PNENs represent one of the main cause of death in patients with MEN1, a majority of these being attributable to gastrinomas, responsible for gastric acid hypersecretion, multiple duodenal ulcers and eventually life-threatening gastrointestinal haemorrhage [START_REF] Goudet | Risk factors and causes of death in MEN1 Disease. A GTE (Groupe d'Étude des Tumeurs Endocrines) cohort study among 758 patients[END_REF]. Second, MEN1related PNENs are, unlike their sporadic counterparts, usually small (i.e., < 1 cm), multiple, and occur on a background of diffuse pancreatic microadenomatosis [START_REF] Yates | Challenges and controversies in management of pancreatic neuroendocrine tumours in patients with MEN1[END_REF]. Based on those characteristics, classic imaging procedures such as C T scan, MRI or Octreoscan ® can be faulted in terms of sensitivity as well as in terms of specificity, the latter being related to the fact that different phenotypes All values are IC50 ± SEM in nM. Adapted from [START_REF] Cuny | Targeting somatostatin receptors in gastroenteropancreatic neuroendocrine tumours (GEPNETs): which radiotracers for which tumours?[END_REF].

of PNENs can coexist in a MEN1 patient (insulinoma and nonsecreting tumors for instance). In the case of insulinoma, it is well established that the density of SSTR2 is lower as compared to other types of PNENs, which could, coupled to the small size of the lesion, be a source of false-negative during Octreoscan ® . Today, echoendoscopic ultrasound remains the "gold-standard" to both accurately localize lesions equivocal of PNENs and perform histopathological analysis, as illustrated in our clinical case [START_REF] Thakker | Clinical practice guidelines for multiple endocrine neoplasia type 1 (MEN1)[END_REF]. However, its invasive procedure as well as its exclusive focus of the pancreas gland, considerably limit its use for appreciating the extension of the disease (e.g. liver metastasis) and for the periodic followup of the patient. Due to its low sensitivity, octreoscan has been recently challenged by other nuclear imaging modalities, such as SSTR2-PET/CT using Gallium-68 (Table 1). There are currently three studies which assessed the diagnosis value of (68)Ga-DOTATATE or -DOTATOC PET/CT for the diagnosis of PNENs in MEN1 patients [START_REF] Morgat | Evaluation of 68Ga-DOTA-TOC PET/CT for the detection of duodenopancreatic neuroendocrine tumors in patients with MEN1[END_REF][START_REF] Sadowski | Results of 68Gallium-DOTATATE PET/CT Scanning in Patients with Multiple Endocrine Neoplasia Type 1[END_REF][START_REF] Lastoria | Role of 68Ga-DOTATATE PET/CT in patients with multiple endocrine neoplasia type 1 (MEN1)[END_REF]. In the study by Morgat et al. (N = 19), patients with MEN1) the sensitivity of (68)Ga-DOTATOC PET/CT was 76% as compared to 20% with octreoscan, respectively (P < 0.0001). Moreover, (68)Ga-DOTATOC PET/CT detected lesions of smaller size than octreoscan (10.7 ± 7.6 and 15.2 ± 5.9 mm, respectively, P < 0.03) [START_REF] Morgat | Evaluation of 68Ga-DOTA-TOC PET/CT for the detection of duodenopancreatic neuroendocrine tumors in patients with MEN1[END_REF]. Likewise, the results observed by Lastoria et al. (N = 18 MEN1patients) and Sadowski et al. (N = 26 MEN1 patients), also confirmed a higher sensitivity of (68)Ga-DOTATATE PET/CT as compared to conventional imaging (including octreoscan) for the detection of both PNEN lesions in a MEN1 patients as well as the diagnosis of liver metastasis [START_REF] Sadowski | Results of 68Gallium-DOTATATE PET/CT Scanning in Patients with Multiple Endocrine Neoplasia Type 1[END_REF][START_REF] Lastoria | Role of 68Ga-DOTATATE PET/CT in patients with multiple endocrine neoplasia type 1 (MEN1)[END_REF]. Besides SSTR2-related imaging, (18)F-FDOPA PET/CT is now routinely used in many referal centers to confirm the neuroendocrine nature of pancreatic lesions. A carbidopa premedication is commonly proposed to optimize the sensitivity of this imaging procedure in the detection of insulinomas [START_REF] Leroy-Freschini | Early 18F-FDOPA PET/CT imaging after carbidopa premedication as a valuable diagnostic option in patients with insulinoma[END_REF], as well as in case of non-secreting PNENs [START_REF] Helali | Carbidopa-assisted 18F-fluorodihydroxyphenylalanine PET/CT for the localization and staging of non-functioning neuroendocrine pancreatic tumors[END_REF]. In the latter study, its sensivity was even better when compared to Octreoscan ® . A preliminary study suggested a better diagnosis performance of (68)Ga-DOTANOC over (18)F-FDOPA for the detection of digestive NENs [START_REF] Ambrosini | Comparison between 68Ga-DOTA-NOC and 18F-DOPA PET for the detection of gastro-entero-pancreatic and lung neuro-endocrine tumours[END_REF], however, the respective performance of these imaging modalities in the setting of MEN1 remains unstudied. Overall, it has to be recalled that significant technical differences exist between all those imaging modalities. Even though the same somatostatin receptor subtype (i.e. SSTR2) is targeted by (68)Ga-DOTATATE and In-pentetreotide, the spatial resolution of SPECT/CT is clearly lower that the one obtained with TEP/CT. Therefore, small lesions PNEN are likely less detected by Octreoscan ® , independently of the density of membranous SSTR2. Concerning (18)F-FDOPA PET/CT, a diffuse uptake from the pancreas usually occurs and constitutes an obvious limitation for the detection of small neuroendocrine lesions of the pancreas.

In that respect, carbidopa premedication is necessary to improve the sensitivity of the exam for the analysis of the pancreas.

Our clinical case illustrates that (18)F-FDOPA PET/CT can lead to false negative results in a MEN1 patient and therefore should prompt clinicians to prefer (68)Ga-DOTATATE PET/CT. As others [START_REF] Marx | Recent Topics Around Multiple Endocrine Neoplasia Type 1[END_REF], we think based on this observation, that (68)Ga-DOTATATE PET/CT should be now systematically performed at the initial diagnosis and in the follow-up of a patient with a MEN1 syndrome. Another interesting aspect of this statement is that (68)Ga-DOTATATE PET/CT, when positive, could pave the way for a theranostic approach in MEN1 patients with PRRT (peptide radionuclide receptor therapy) using 177 Lu-DOTATATE [START_REF] Vija | Receptor radionuclide targeting for neuroendocrine tumors (NET) diagnostic and therapy[END_REF]. The latter recently showed to be a valuable therapeutic option in patients with SiNENs [START_REF] Strosberg | renning E 177 Lu-Dotatate for Midgut Neuroendocrine Tumors[END_REF], although its efficacy in PNENs, especially in MEN1, remains to be studied.

Ethical approval

This article does not contain any studies with animals and human participants performed by any of the authors.

Informed consent

Informed consent was obtained from all individual participants included in the study.

Fig. 1 .

 1 Fig.1. Family tree of the proband and her siblings.

Fig. 2 .

 2 Fig. 2. A. MIP (Maximal Intensity Projections) pictures of (18)F-FDOPA and (68)Ga-DOTATATE of the patient. B. Octreoscan ® of the patient which was non contributive for the detection of the pancreatic neuroendocrine lesions.

Fig. 3 .

 3 Fig. 3. (18)F-FDOPA [A] and (68)Ga-DOTATATE [B]. PET/CT images of the MEN1 patient with PNENs identified by echoendoscopy. (68)Ga-DOTATATE [B] detected the different lesions (arrows 1 to 4) in the pancreas while (18)F-FDOPA was negative.

Table 1

 1 Affinity profiles (IC50) for human somatostatin receptors (SSTR) of a series of somatostatin analogs.

	Peptides	SSTR1	SSTR2	SSTR3	SSTR4	SSTR5
	Somatostatin 28	5.2 ± 0.3	2.7 ± 0.3	7.7 ± 0.9	5.6 ± 0.4	4.0 ± 0.3
	Octreotide	> 1,000	2.0 ± 0.7	187 ± 55	> 1,000	22.6 ± 6
	Lanreotide	> 1,000	1.8 ± 3.4	771 ± 229	> 1,000	53 ± 12
	In-DTPA-octreotide (pentetreotide)	> 1,000	22 ± 3.6	182 ± 13	> 1,000	237 ± 52
	Ga-DOTATOC	> 1,000	2.5 ± 0.5	613 ± 140	> 1,000	73 ± 21
	Ga-DOTATATE	> 1,000	0.2 ± 0.04	> 1,000	300 ± 140	377 ± 18

Funding

This study was not funded.

Disclosure of interest

The authors declare that they have no competing interest.


Lise-Marie Lacroix
email: lmlacroi@insa-toulouse.frhomepage

Dr Christophe Gatel

Dr Raul Arenal

Dr Cécile Garcia

Dr Sébastien Lachaize

Dr Thomas Blon

Dr Bénédicte Warot-Fonrose

Etienne Snoeck

Bruno Chaudret

Guillaume Viau

Dr L.-M Lacroix

Pr B Chaudret

Pr G Viau Lpcno

Pr E Snoeck

Tuning complex shapes in Pt(0) nanoparticles : from cubic dendrites to five-fold stars

Keywords: Platinum nanoparticles, Shape control, 5-fold twinned nanostars, Dendritic nanocubes, Decahedra

Synthesis of nanoparticles (NPs) exhibiting large surface-area-tovolume ratio has been a long-sought goal in developing various applications such as ultra-sensitive sensors 1 or highly active catalysts. 2 In addition to a large specific area, crystallographic planes exposed on the surface of the NPs are key parameters for the reactivity and selectivity of NPs in catalytic processes. 3 Thus, intense researches have been devoted to the shape control of noblemetal nanocrystals. 4 For instance for Pt based nanoparticles, dendritic nanostructures, 5 branched-NPs, 6 or multipods 7 exhibit enhanced catalytic activities compared to their spherical counterparts. 8 Such shape control could be obtained by manipulating the reduction kinetics 6 through temperature, 6a,9 pH, 10 ligands, 11 or addition of small amounts of nucleating agents. 6b Interestingly, in this variety of shapes, only few groups reported multiply-twinned Pt nanoparticles 12 while decahedrons are fairly common for most of the noble metals (Au, Ag, Rh…). 13 However, these twinned NPs could offer significant benefits toward catalysis due to {111} faces mainly exposed. 14 Herein we report complex platinum nanoobjects of unprecedented shapes (monodisperse cubic dendrites and five-fold stars) and the fine tuning between two growth mechanisms. The platinum concentration is finely tuned in a fairly simple reaction of H2PtCl6 in oleylamine under dihydrogen pressure. Amine plays the role of solvent, stabilizer and can assist the reduction process. Previous work has shown that the room temperature reduction of HAuCl4 by neat oleylamine yielded unique Au nanowires. 15 However, in the same conditions, Pt required higher temperature to be reduced (250°C). 9 In the present study, addition of dihydrogen, a well-known reducing agent, 16 lowered the reduction temperature and, in the same time, played an important role in the shape control of NPs. Indeed, H2 can "clean" the NP surface by temporarily removing weak coordinating ligands such as amines, leading to coalescence or ripening. 17 H2 can also generate surface hydrides which stabilize the NP and perform hydrogenation reactions. 18 An ex-situ kinetic study, followed by High Resolution Transmission Electron Microscopy (HRTEM), has evidenced two growth mechanisms based respectively on cubic or decahedric seeds (cf Scheme 1) leading to monodisperse cubic dendrites or five-fold stars.

Scheme 1. General overview of the versatile synthesis of Pt(0) NPs. Shape could be controlled by the platinum concentration, and the nature of the seeds formed.

Pt NPs were produced by reduction of H2PtCl6 in oleylamine under an H2 atmosphere (3 bars) at 150°C (Experimental Section, Scheme 1). The shape of Pt NPs could be easily tuned by varying the experimental parameters, in particular the Pt concentration from low (2 mM) to high (10 mM) values. For instance, a dendritic growth was observed at high Pt concentration ([Pt] > 5mM) (Figure 1a-b, S1 and S2). The resulting objects were obtained quantitatively with a Pt yield over 95%. The most striking feature, compared to previously reported dendrites, 5 was their cubic contour. Figure 2 shows a high-magnification Transmission Electron Microscopy (TEM) image of a single dendrite exhibiting a dense organization of branches with defined orientations. Outer faces of the cubes coincided with {100} planes of the crystallographic structure of fcc-Pt. Selective Area Electron Diffraction (SAED) pattern on a single cube (Figure 2b) shows a fourfold symmetry, characteristic of a single-crystalline fcc-crystal observed along the <100> zone axis. The elongation of the diffraction spots {200} and {220} indicates a slight misorientation between the branches (ca 10°). These results demonstrate that cubic dendrites adopt a singlecrystalline structure slightly distorted.

The growth mechanism of such peculiar dendrites has been investigated by stopping the reaction at different stages (Figure 3 and S3). The reaction is very fast as shown by the octapods already observed after 1 min of reaction at 150°C. These octapods result from a growth on <111> directions on cubic seeds. {100} facets are observed, concomitant with closing {110} facets. After 3 minutes of reaction, the selected growth on {100} facets leads to the appearance of bifurcations, new branches start to grow along 3 different <111> growth directions. Such a selected growth is repeated until the total consumption of the platinum precursor. While the diameter of the branches was rather constant at ca. 5.5 nm, the mean size of the cubic dendrites could be tuned from 30 to 100 nm by varying the reaction time between 10 min and 2h (Figure S4). The dendrites finally obtained, exhibit a high proportion of {100} and {110} facets, as in the earlier growth stage (Figure S5). Such dendritic structures, which have no precedent, were stable at 150°C for days, the complex branches architecture did not collapse into denser crystals.

At low Pt concentration ([Pt] = 2mM), star-shaped NPs were obtained (Figure 1c-d andS6). Samples were composed of nanocrystals exhibiting a well-defined morphology with ~ 20 % of 5-fold stars, ~ 70% of 3-fold stars (planar tripods) and ~ 10 % of multipods or undefined shapes. This ratio could vary: the proportion of multipods increased with the [Pt] concentration. 3-fold stars, have previously been obtained using a different approach (reduction of Pt(acac)2 by a diol at 160°C) 7a . However, the present 5-fold Pt stars are unique. Their arm length could be tuned from 30nm to 120nm by varying the reaction time between 6 and 48h (Figure S7).

Figure 4 shows a high magnification image of a single 5-fold star and the corresponding SAED pattern along the <110> zone axis. The complex pattern displays a 5-fold symmetry of the fcc structure spots, similar to the SAED pattern obtained on Au decahedra. 19 HRTEM image of the core clearly shows the non-crystallographic five-fold axis and the five resulting twinning boundaries. Periodic lattice fringes could be clearly resolved for 3 families of planes. Lattice spacings of 2.26 Å and 1.96Å correspond to the {111} and {100} planes of fcc-Pt respectively. The rotation of these planes along the five-fold axis is evidenced on Figure 4c: single-crystalline tetrahedra were observed between two successive twin-boundaries. Figure 4d shows a HRTEM image of the branch tip. The branches are highly crystalline, exposing mainly {111} facets (Figure S8-10). These branches grow symmetrically along the twinning plane, from each corner of the central decahedra as revealed by TEM images taken after different growth stages (Figure 5). Such a growth on decahedra corners has been recently reported by Zhang et al. on Rh star-fish like NPs, but the crystallinity of the branches was not clearly evidenced. 13c If Pt decahedra are fairly rare objects, highly crystalline five-fold Pt stars represent a unique result to the best of our knowledge.

X-ray Photoelectron Spectroscopy (XPS) and Energy Dispersive X-ray Spectroscopy (EDS) analyses have been performed on cubic dendrites and stars. As expected, the Pt NPs resulting from the different syntheses consisted of pure Pt(0) (Figure S11-12). The surface of the particles was stabilized mostly by amine groups, although chloride anions and ammonium groups could be detected as traces.

It is noteworthy that reaction times were considerably expanded at low [Pt] concentration compared to the few minutes required for high [Pt] concentration synthesis. At 2mM, the yellowcolour, characteristic of the Pt precursor, vanished after at least 24h of reaction. The shape control in this versatile synthesis looked then strongly correlated to the reaction rates. Three experimental parameters can be adjusted to quicken the reaction kinetic: [Pt] concentration, temperature (T) and dihydrogen pressure (pH2). Increasing the temperature and pressure yield cubic dendrites after only 1 hour (Figure S13) even at low [Pt] concentration (2mM). Thus, we could induce a dendritic growth by fastening the reaction kinetic. An illustration of this difference of kinetic between cubic dendrites and stars is given by the variation of dihydrogen pressure profile with time (Figure S14). A fast consumption of dihydrogen was observed for dendritic growth, while no abrupt drop was detected in the case of star-shape growth. These two hydrogenation profiles combine multiple reactions (reduction of platinum, corresponding to ca. 0,3 bars of H2, and hydrogenation catalysed by Pt NPs and/or molecular species) in different experimental conditions. Thus the catalytic activities of dendrites vs. stars cannot be directly compared. However, we can conclude that very catalytically active species were quickly formed at high temperature and pressure, while this was not the case under lower conditions. The shape control reported here for Pt(0) NPs (planar tripods, five-fold stars and cubic dendrites) is achieved by playing with the reaction conditions in a relatively narrow range of concentration or temperature. The nature of the seeds, cubic, exposing non compact faces, or triangular and decahedric, exposing {111} faces, is determinant in the final morphology reached (Scheme 1).

At fast reaction rates, cubic seeds, exhibiting fcc structure, are quickly formed as shown by ex-situ HREM study and the evolution of H2 pressure as a function of time. The very fast consumption of H2 is due to a fast reduction of Pt precursor and to the hydrogenation of oleylamine by reactive seeds. Non compact faces ({100} and {110}) are known to be active towards the reduction of internal olefins for Pd. 20 These cubic seeds, though very reactive, are relatively limited in numbers. The stability of H2PtCl6 precursor is indeed a determinant factor in this dendritic growth. The reduction of Pt(acac)2 under similar conditions yielded multiple seeds and thus multiarmed NPs (Figure S15). Few seeds and a fast reduction is characteristic of an auto-catalytic process, previously reported for Pt. 3 Such auto-catalytic process combines a surface reaction between the precursor and preferential faces, leading here to a growth direction along <111> directions. The outer cubic shape of these nearly single-crystalline cubic dendrites, so peculiar, results from the strong crystallographic driving force combined with the tendency of dihydrogen to repair surfaces. The large cubic dendrites obtained at the end of the reaction expose non compact faces, which are not energetically favoured. Such structures represent kinetic products and result from a growth limited by the diffusion of adatoms at the surface. Such diffusion-limited process is also known to be responsible for the size monodispersity of the final objects. 21 When the reaction rates were decreased, via the platinum concentration or via the lowering of the reaction temperature, the reduction of the platinum precursor occurred during a longer period of time and yield seeds exhibiting compact {111} faces. The profile of dihydrogen consumption is drastically modified compared to dendritic growth, due to the formation of a very limited number of seeds and to their nature. Indeed, under these conditions, stable twinned decahedra or triangular seeds could grow, resulting from the minimization of surface energy. These objects expose only {111} compact crystallographic planes. The successive growth of decahedra seeds into 5-fold stars could be explained via multiple nucleation events. Decahedra are composed of 5 tetrahedra. However, these tetrahedra cannot fill the entire space and leave an empty angle of 7,3°, unless they adopt a highly strained structure as reported for Au decahedra. 19 Since strain increases with the particle size, above a critical size, corresponding to the highest strain in Pt decahedron, the structure relaxes. In our case, this relaxation corresponds to the nucleation and growth of the arms at each corner of the decahedra core (Figure 5). Further crystallographic studies will be performed on these 5-fold stars to determine the structural strain contained at the vicinity of the core and of the arms to confirm our growth model hypothesis. Such multi-step process has already been proposed by Maksimuk et al. 7a for the growth of planar tripods. According to their model, branches grow at the corner of triangular twinned seeds, which act as preferential nucleation sites for a second growth process. In our reaction, five-fold stars and planar tripods coexist, giving strength to our growth hypothesis.

In summary, we have demonstrated that quasi singlecrystalline Pt nanoparticles with peculiar morphologies -cubic dendrites, planar tripods and 5-fold stars-, can be obtained selectively and in high yield from a very simple procedure by tuning the reduction kinetics of a platinum salt under a dihydrogen atmosphere in presence of an amine. The control of experimental parameters such as Pt concentration, reaction temperature and dihydrogen pressure, leads to a fine tuning of the kinetics of the reaction and of the nature of seeds formed during the nucleation step. Though, the reason for such an abrupt transition between cubic or twinned seeds is still unknown, numerical simulations of the energy of the seeds could give us some important highlights.

A slow reaction leads to twinned seeds which evolve into planar tripods (3-fold stars) and 5-fold stars. Such multiply twinned NPs are unique for Pt and could open new perspectives for fundamental research on strained materials. In addition to this fundamental interest, catalytic activities could benefit from the presence of almost exclusively crystallographic surface orientation {111} for selectivity purposes.

A fast reaction leads to cubic seeds and thus to a dendritic growth. The peculiarity of these objects is their outer cubic shape and an unprecedented size control of their envelope. Such dendritic cubes display a high surface-to-volume ratio, while their cubic shape enables their self-assembly on surfaces which should be of high interest in catalysis. Structural characterization of the exposed surfaces, reactivity and catalytic activity of these novel species will be evaluated to attest the potential of these unique cubic dendrites.

Experimental Section

Typical synthesis of dendritic NPs : H2PtCl6 (Alfa Aesar, 51mg, 0,1 mmole) and oleylamine (Aldrich, 10mL) were mixed in a vial, and placed 15mn in an ultrasonic bath to dissolve the Pt precursor. The 10mM solution was transferred in a Fisher-Porter bottle and pressurized up to 3 bars of H2. The bottle was then let to react at 150°C in a pre-heated oil bath for 1 hour. At the end of the reaction, a black precipitate was obtained while the supernatant is transparent. Typical yellow-coloured Pt precursor traces were no longer observed. The bottle was then cooled down to room temperature, resulting in a solidification of the supernatant. 40mL of hexanes (Aldrich) was added to solubilise the NPs. The suspension, after the addition of 40mL of absolute ethanol (VWR), was then centrifugated (4000rpm, 6min) to separate the NPs. The process is repeated 3 times to remove the excess of surfactants. The final product (ca. 25mg) was kept in powder form or diluted in 5mL Toluene (Carlo Erba) for further use.

Multiply-twinned NPs were synthesized by a similar procedure except that the Pt concentration was decreased below 5mM. The reaction time was expended to 48h since the reaction kinetic is drastically reduced.

Characterizations: Samples for TEM were prepared by depositing few drops of diluted solution on amorphous carbon coated cupper grid. Low resolution images were obtained with a JEOL-1400 microscope, operating at 120kV. HRTEM images were obtained with a Tecnai F20 (200kV) equipped with a spherical aberration corrector. X-ray photoelectron spectra were recorded using a Kratos Analytical Limited Axis ultra limited system fitted with a microfocused monochromatic Al Kα X-ray source (1486,6 eV, 12kV * 120W). The pass energy was set at 160 eV and 20 eV for the survey and the regions spectra respectively.

Stars and dendrites

Figure 1 .

 1 Figure 1. TEM images of Pt nanocrystals prepared at different concentrations of platinum (a-b) dendritic cubes obtained for [Pt] = 10mM, (c-d) Pt stars obtained at [Pt] = 2 mM.

Figure 2 .

 2 Figure 2. (a) HREM image of a single Pt dendritic cube obtained after 1h of reaction. (b) Selective Area Electron Diffraction (SAED) along [001] axis on a 60nm-cube obtained after 2h of reaction, as shown in the inset.

Figure 3 .

 3 Figure 3. Nanoparticles obtained after (a-c) 1 min and (d-f) 3 min of reaction. (a, d) TEM micrograph and the corresponding (c, f) HREM micrographs. {100} facets are highlighted along the <111> growth directions. (b, e) are schematic view of the objects at this growth stage.

Figure 4 .

 4 Figure 4. (a) TEM micrograph of a single Pt 5-fold star and (d) its corresponding ED pattern. HRTEM images of (c) the core and (d) a branch tip as shown in figure (a) by respectively white and black boxes.

Figure 5 .

 5 Figure 5. High Angle Annular Dark Field and TEM images of Pt NPs obtained for [Pt] = 2mM at a) 2h and b) 4h of reaction.

  L.-M. Lacroix,* C. Gatel, R. Arenal, C. Garcia, , S. Lachaize, T. Blon, B. Warot-Fonrose, E. Snoeck, B. Chaudret and G. Viau __________ Page -Page Access to complex shapes in Pt(0) nanoparticles: from cubic dendrites to five-fold stars Quasi single-crystalline Pt nanoparticles with peculiar morphologies, cubic dendrites, planar tripods and 5-fold stars, can be synthesized selectively and in high yield by finely tuning the kinetics of an amine-based reaction under dihydrogen.

Figure S3 :

 S3 Figure S3 : HRTEM images of cubic dendrites obtained at 150°C, 3bars H2, [Pt] = 10mM after different reaction times : a-b) 1min, c-d) 3min, e) 20min and f) 60 min of reaction.

Figure S4 :

 S4 Figure S4 : TEM images of cubic dendrites obtained at 150°C, 3bars H2, [Pt] = 10mM after different reaction times : a) 10min, b) 20min, c) 1h and d) 6h of reaction.

Figure S5 :

 S5 Figure S5 : HRTEM image of a detailed of a cubic dendrite obtained at 150°C, 3bars H2, [Pt] = 10mM after 60 min of reaction.

Figure S6 :

 S6 Figure S6 : TEM images of Pt NPs obtained after 32h at 150°C, 3bars H2, [Pt] = 2mM. a) general view and high magnification images of b) 3-fold star.

Figure S7 :

 S7 Figure S7 : TEM images of Pt NPs obtained for [Pt] = 2mM after a) 6h, b) 24h and c) 48h of reaction at 150°C and 3 bars of H2.

Figure S8 :

 S8 Figure S8 : Tilting series of TEM images of Pt NPs obtained for [Pt] = 2mM at a) 0°, b) ca. 40° and c) ca. 90°. The rotation axis is represented by the white dashed line in figure a. Numbers are added on each arm as a guide for the eye during the tilting. Circles around arms 4 and 5 indicate anchoring point during the tilting of the star.

Figure S9 :

 S9 Figure S9 : (a-c) HRTEM images and corresponding (b-d) fast fourier transformed images of 5-fold star arm observed along respectively (a-b) [111] and (c-d) [01-1] zone axes.

Figure S10 :

 S10 Figure S10 : Schematic view of the arms of 5-fold star displaying the corresponding faces and angles. The twinned boundary is represented in red.

Figure S11 .

 S11 Figure S11. (a) HAADF-TEM image of a single dendrite and (b) the corresponding EDS spectrum obtained. Apart from the Cu grid, Pt is the only element detected.

Figure S12 .

 S12 Figure S12. (a) XPS survey spectra of a) powders of Pt stars (black line) and dendrites (red line). The inset shows the Pt 4f high-resolution spectra. b) N 1s spectra and c) Cl 1s spectra. For b) and c) Pt NPs spectra (black line) and references of ammonium chloride (red line) and amine (blue line, not used for c).

Figure S13 :

 S13 Figure S13 : TEM images of Pt NPs obtained for [Pt] =2mM, 1 hour at 170°C, 6 bars H2.

Figure S14 :

 S14 Figure S14 : Evolution of dihydrogen pressure (red solid line) and temperature (black dashed line) with time (a) for dendritic growth at 170°C and 6 bar of H2 and (b) for star-shape growth at 150°C and 3 bar H2. Note the different time scale used.

Figure S15 :

 S15 Figure S15 : TEM images of Pt NPs obtained with Pt(acac)2 for [Pt] =10mM after 1 hour at 150°C and 3 bars H2.

the European FP7-Train2 project and the French network METSA. We thank G.

Supplementary Information


Hugo Nihous

Nicolas Macagno

Jessica Baud-Massière

Aurélie Haffner

Jean-Luc Jouve

Jean-Claude Gentet

Camille Touzery

François Le Loarer

Corinne Bouvier

Genetic variant of SRF-rearranged myofibroma with a misleading nuclear expression of STAT6 and STAT6 involvement as 3′ fusion partner

Keywords: SRF, RELA, STAT6, Pediatric, Leiomyoma, Smooth muscle neoplasm, Myofibroma, Myopericytoma, Myofibroblastic proliferation

Pediatric neoplasms with a myofibroblastic differentiation are frequent in children, in particular myofibroma. Recently, a novel deep soft tissue myofibroblastic neoplasm has been described with high cellularity, a smooth muscle phenotype and SRF-RELA fusion. We report the case of a 15-year-old boy who presented with a tumor of the deep soft tissue of the arm, with overlapping histological features with the recently described SRF-RELA group of myofibromas but differing by the presence of calcifications, a novel SRF-STAT6 fusion transcript and nuclear expression of STAT6. No local recurrence nor distant metastasis was detected at the current follow-up of 29 months. The clinical relevance of this novel fusion requires further investigations.

Introduction

In children, the most frequent sarcoma with muscle differentiation is rhabdomyosarcoma. Sarcomas harboring a smooth muscle phenotype, such as leiomyosarcoma, are conversely much more uncommon in children, accounting for 2-4% of soft tissue sarcomas [START_REF] Hoda | Enzinger and Weiss's soft tissue tumors, 6th edition[END_REF]. Their benign counterpart, namely, pediatric leiomyoma, is even more exceptional. Most leiomyomas arise in adult women, in a gynecological context. Leiomyoma of the deep soft tissue (LDST) is a rare neoplasm, accounting for 4% of all benign soft tissue tumors [START_REF] Kransdorf | Benign soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location[END_REF].

In contrast to smooth muscle tumors, neoplasms with a myofibroblastic differentiation are much more common in children, in particular myofibroma, which usually harbor PDGFRB mutations [START_REF] Agaimy | Recurrent somatic PDGFRB mutations in sporadic infantile/solitary adult myofibromas but not in angioleiomyomas and myopericytomas[END_REF]. A subset of cellular myofibromas of the deep soft tissues have been recently characterized by fusions of SRF-RELA or SRF-ICA1L, with potential prognostic implications [START_REF] Antonescu | Recurrent SRF-RELA fusions define a novel subset of cellular variants in the myofibroma/myopericytoma spectrum: a potential diagnostic pitfall with sarcomas with myogenic differentiation[END_REF][START_REF] Suurmeijer | Novel SRF-ICA1L fusions in cellular myoid neoplasms with potential for malignant behavior[END_REF]. In contrast to conventional myofibromas, these SRF-rearranged neoplasms display a high cellularity and myoid phenotype.

In this report, we present the case of a 15-year-old boy that developed a deep soft tissue tumor of the arm, expressing a full smooth muscle phenotype and harboring a SRF-STAT6 fusion transcript, a fusion which had not been reported in this spectrum of neoplasm yet. This case is of potential interest as it also displayed nuclear expression of STAT6, a potential diagnostic pitfall with solitary fibrous tumors.

Materials and methods

Immunohistochemistry

Immunohistochemical studies were performed on 4 μm sections cut from the paraffin block using a fully automated system (Benchmark XT System; Ventana Medical Systems Inc., Tucson, AZ) and the following primary antibodies: smooth muscle actin alpha (clone 1A4, prediluted; Microm), desmin (clone DE-R-11, prediluted; Roche), h-caldesmon (clone h-CD, 1: 2; Dako), calponin (clone h-cp,1: 20000; Sigma), myogenin (clone F5D, 1: 2; Dako), MyoD1(clone EP212, prediluted; Cell Marque), cluster of differentiation 34 (CD34) (clone QBend10, prediluted; Roche), epithelial membrane antigen (EMA) (clone E29, 1: 500; Dako), PS100 (polyclonal, 1: 400; DBS), Fumarate Hydratase (clone J-13, 1: 100; Santa Cruz Biotechnology), Ki67 (clone MIB-1, 1: 100; Dako), and STAT6 (clone YE361, 1: 250; Abcam Cambridge UK).

Total RNA extraction

Total RNA was extracted from formalin-fixed paraffin-embedded (FFPE) tissues using TRIzol reagent (Invitrogen). RNA quality was assessed by Eukaryote Total RNA Nano Assay (Agilent, cat. No. 5067-1511), and DV200 was determined. RNAs were stored at -80 °C.

RNA sequencing

Libraries were prepared with 100 ng of total RNA using TruSeq RNA Access Library Prep Kit (Illumina, San Diego, USA). Libraries were pooled by group of 12 samples. Pairedend sequencing was performed using the NextSeq 500/550 High Output V2 kit on Illumina NextSeq 500 platform (Illumina, San Diego, CA). The read length was 75 bp.

Sequencing data (average of 65 million reads per sample) were aligned with STAR on GRCh 38 reference genome. The fusion transcripts were called with STAR-Fusion, FusionMap, FusionCatcher, ERICSCRIPT, and TopHat-fusion and validated if present in fusion list of at least two algorithms.

Case report

A 15-year-old boy presented with a lump of the left forearm. Radiological investigations revealed a partially calcified mass, developed in the deep soft tissue, between the radial biceps and the pronator teres. The mass displayed hypersignal on T2 FS (fat-suppressed) and a heterogeneous contrast enhancement on T1 FS (Fig. 1) MRI sequences. The two main radiological hypotheses were synovial sarcoma and extraskeletal osteosarcoma. Fine-needle biopsy revealed a spindle cell neoplasm, with a low mitotic activity and a smooth muscle morphology and phenotype, without overt malignant criteria. Surgical excision of the mass was performed. Gross examination revealed a well limited white and firm tumor measuring 5 × 3 × 2 cm with calcifications.

Histologically, the neoplasm showed a fascicular proliferation of moderate cellularity, composed of spindle cells with ample eosinophilic cytoplasm (Fig. 2a,b,c). Neoplastic cells displayed oval monotonous nuclei, with a finely granular chromatin and occasional pinpoint nucleoli. No pleomorphism nor high-grade nuclear atypia were observed. In some areas, a biphasic morphological appearance was identified owing to a higher cellularity and more basophilic cells. Hyperintense signal of a well-limited oval formation, with stellar and punctiform central calcifications. This formation is located on the external side of the distal part of humeral artery, and in front of the insertion of brachial biceps. This lesion extends over 33 × 24 mm on the axial axis.

There is also an edematous infiltration around the periphery of the lesion. b (Coronal-enhanced T1 FS). Heterogenous enhancement of the formation, with a higher enhancement around the periphery of the lesion. This lesion extends over 54 × 28 mm on the coronal axis Numerous calcifications of variable size were intermingled with tumor cells and were not associated with necrosis (Fig. 2d). Mitotic activity was 1 mitosis per 25 mm 2 . Immunostains revealed diffuse expression of smooth-muscle-actin alpha, desmin, h-caldesmon, and calponin, without expression of myogenin, MyoD1, CD34, EMA, or PS100 (Fig. 2e-g). The expression of fumarate hydratase was retained, and Ki67 labeling index was 1%. many small roundish psammomas and calcifications of a larger size are frequently observed, haphazardly distributed within the neoplasm, without being associated with infarction or necrosis. e h-caldesmon and f desmin are diffusely and intensely expressed, revealing the fascicular architecture of the neoplasm and its smooth muscle phenotype. g Ki67 is expressed in 1% of the nuclei; h STAT6 is intensely and diffusely expressed in the nuclei, a peculiar finding that is usually observed in the spectrum of solitary fibrous tumors and constitutes a diagnosis pitfall. Of note, nuclei of endothelial cells are negative A provisory diagnosis of "smooth muscle neoplasm of uncertain malignancy" was proposed. Ancillary genetic investigations were performed to assess its aggressiveness. Arraybased comparative genomic hybridization revealed no cytognetic gain nor loss across the tumor genome, raising suspicion for a translocation-related tumor. No genomic breakpoint was stated across genome, especially in STAT6 nor SRF loci. Next-generation sequencing (NGS) revealed no alteration of TP53 nor RB1. Whole genome RNAsequencing revealed a SRF-STAT6 fusion transcript (Fig. 3a). Interestingly, the neoplasm displayed a diffuse and intense nuclear expression of STAT6 by immunohistochemistry (Fig. 2h). No local recurrence nor distant metastasis was detected during a 29-month follow-up.

Discussion

We report a new fusion involving SRF and STAT6 in a mesenchymal neoplasm with a full smooth muscle phenotype. This case illustrates the recent molecular findings in cellular myoid neoplasms, a subset of which are associated with recurrent fusions involving SRF with RELA, C3orf62, or ICA1L [START_REF] Antonescu | Recurrent SRF-RELA fusions define a novel subset of cellular variants in the myofibroma/myopericytoma spectrum: a potential diagnostic pitfall with sarcomas with myogenic differentiation[END_REF][START_REF] Suurmeijer | Novel SRF-ICA1L fusions in cellular myoid neoplasms with potential for malignant behavior[END_REF] (Table 1).

Tumors with rearrangements of SRF have been linked to myofibroma and myopericytoma. This group of neoplasm was characterized by a biphasic architecture: spindle cells with abundant eosinophilic cytoplasm arranged in fascicles, alternating with ovoid cells arranged in a syncytial growth or nested architecture, with a rich capillary network. Nuclei were ovoid with fine or vesicular chromatin, without high-grade atypia, and mitotic activity was generally low. In some cases, areas of infarction were present associated with dystrophic calcifications. These neoplasms expressed a smooth muscle differentiation: all reported cases stained for smooth muscle actin alpha, while desmin and h-caldesmon were more variably expressed [START_REF] Hoda | Enzinger and Weiss's soft tissue tumors, 6th edition[END_REF][START_REF] Kransdorf | Benign soft-tissue tumors in a large referral population: distribution of specific diagnoses by age, sex, and location[END_REF][START_REF] Antonescu | Recurrent SRF-RELA fusions define a novel subset of cellular variants in the myofibroma/myopericytoma spectrum: a potential diagnostic pitfall with sarcomas with myogenic differentiation[END_REF]. Our case displayed similarities with this group of neoplasm, on both histopathological and immunohistochemical grounds (Table 1). However, our case lacked necrosis associated with dystrophic calcifications. Instead, the calcifications were rather scattered within the proliferation. SRF-RELA neoplasms are thought to carry a low risk of recurrence.

A recent report also described another subset of cases with SRF-ICA1L fusions, further expanding this group of neoplasms [START_REF] Suurmeijer | Novel SRF-ICA1L fusions in cellular myoid neoplasms with potential for malignant behavior[END_REF]. However, these neoplasms did not express desmin nor h-caldesmon and displayed worrisome histological features, such as an increased mitotic activity and necrosis (Table 1).

Our case harbored a novel translocation, fusing exon 5 of SRF with exon 17 of STAT6. Serum response factor (SRF) is a member of the MADS box superfamily of transcription factors, which play a role in cell proliferation and migration, muscle development and differentiation, cardiac muscles homeostasis [START_REF] Miano | Role of serum response factor in the pathogenesis of disease[END_REF], leiomyomatosis, and fumarate hydratase deficiency [START_REF] Raimundo | Downregulation of SRF-FOS-JUNB pathway in fumarate hydratase deficiency and in uterine leiomyomas[END_REF]. Fumarate hydratase-deficient leiomyoma was excluded by immunohistochemistry in our case. SRF-fusions have been reported in other mesenchymal neoplasms, such as SRF-NCOA2 in infantile spindle cell rhabdomyosarcoma [START_REF] Mosquera | Recurrent NCOA2 gene rearrangements in congenital/infantile spindle cell rhabdomyosarcoma[END_REF], SRF-FOXO1 and SRF-NCOA1 in a new distinctive subset of well-differentiated rhabdomyosarcoma [START_REF] Karanian | SRF-FOXO1 and SRF-NCOA1 fusion genes delineate a distinctive subset of well-differentiated rhabdomyosarcoma[END_REF], and SRF-E2F1 in myoepithelioma [START_REF] Urbini | Identification of SRF-E2F1 fusion transcript in EWSR-negative myoepithelioma of the soft tissue[END_REF].

STAT6 is a cytoplasmic transcription factor, which belongs to the STAT family of proteins that regulate gene expression. These key transcription factors are necessary for embryonic development, immune function, cell differentiation, growth, and apoptosis. STAT6 protein is composed of a DNA-binding domain, a SH2 domain, and a C-terminal transcriptional activation domain (TAD) (Fig. 3b). In mesenchymal neoplasms, fusions of STAT6 typically occur in solitary fibrous tumors, for which NAB2-STAT6 fusions are highly specific [START_REF] Urbini | Identification of SRF-E2F1 fusion transcript in EWSR-negative myoepithelioma of the soft tissue[END_REF][START_REF] Doyle | Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics[END_REF]. In solitary fibrous tumors, over 40 types of NAB2-STAT6 fusion proteins have been reported and all the predicted NAB2-STAT6 fusion proteins retain the Cterminal portion of STAT6, which contains the domain of transactivation. The fusion induces a permanent nuclear translocation of this portion of STAT6, which is easily detected by immunohistochemistry and widely used for the pathological diagnosis of solitary fibrous tumors [START_REF] Robinson | Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing[END_REF][START_REF] Demicco | Extensive survey of STAT6 expression in a large series of mesenchymal tumors[END_REF][START_REF] Cheah | STAT6 rabbit monoclonal antibody is a robust diagnostic tool for the distinction of solitary fibrous tumour from its mimics[END_REF]. In the present case, a similar STAT6 nuclear immunostaining was observed, representing a potential diagnostic pitfall. Nevertheless, solitary fibrous tumors display a diffuse expression of CD34 and do not display a biphasic pattern nor a myoid cytology. The nuclear overexpression of STAT6 has also been reported in dedifferentiated liposarcoma, albeit not associated with translocations but rather with amplifications of 12q13 on which MDM2 and STAT6 are mapped [START_REF] Doyle | STAT6 is amplified in a subset of dedifferentiated liposarcoma[END_REF].

In our case, as exon 5 of SRF and exon 17 of STAT6 were involved, the predicted fusion protein contained the MAD box domain of SRF and the whole transcriptional activation domain (TAD) of STAT6 (Fig. 3b): therefore, the predicted chimeric SRF-STAT6 fusion protein displayed both a DNA binding capacity from SRF and a transcriptional activation potential from STAT6.

Interestingly, all SRF-RELA, SRF-ICA1L fusion neoplasms, and the present SRF-STAT6 case show a similar SRF breakpoint, retaining the MADS box domain. Also, the retained parts of RELA, ICA1L, or STAT6 within the fusion proteins always contain their respective domain of transactivation.

As this is the only case so far reported, the relationship of this tumor with respect to the SRF-rearranged group of myoid neoplasms requires further investigations, in particular its prognostic relevance.

Conclusion

Altogether we have described a new variant of SRFrearranged neoplasm sharing histological features with the recently described group of SRF-rearranged myofibroblastic neoplasms. The case involved STAT6 as 3′ fusion partner, which resulted in a strong nuclear expression of STAT6, a potential diagnosis pitfall with solitary fibrous tumors. The clinical relevance of this novel fusion requires further investigations.

Fig. 1

 1 Fig. 1 MRI of the forearm: a (Axial T2 FS (fat-suppressed)).Hyperintense signal of a well-limited oval formation, with stellar and punctiform central calcifications. This formation is located on the external side of the distal part of humeral artery, and in front of the insertion of brachial biceps. This lesion extends over 33 × 24 mm on the axial axis.

Fig. 2

 2 Fig. 2 Histopathology and immunophenotype: a low-power view of the mass, which is well demarcated, without a fibrous capsule, with a multinodular growth of myoid nodules, ectatic vascular channels, and numerous calcifications. Myoid fascicles are intermingled with more cellular area displaying a biphasic architecture. b Microscopic detail of a myoid nodule: the proliferation is arranged in fascicles and composed of spindle cells displaying an intermediate myoid-myofibroblastic morphology, associating an eosinophilic myoid, somewhat fibrillar, cytoplasm, and a myofibroblastic central oval and elongated nuclei, with vesicular chromatin, centered by a pinpoint nucleoli. c Detail of a hypercellular area: neoplastic cells are more densely packed, smaller, with less

Fig. 3

 3 Fig. 3 Schematic transcript and predicted chimeric protein. a SRF-STAT6 fusion transcript identified by RNA sequencing (RNAseq), representation of the transcript with the identification of the exact breakpoints, occurring at position 4314623 (forward strand) in exon 5 of SRF and on position 57492861 (reverse strand) in exon 17 of STAT6. b Predicted domains of the chimeric protein, the breakpoint within STAT6 occurs inside the SH2

Acknowledgments The authors thanked Dr. C. Charon-Barra and Dr. R. Boidot for NGS data.

Compliance with ethical standards

This manuscript is a report of one case with a review of the literature. Research work with human and animal subjects was not conducted in preparation of this manuscript.

Author contributions CB conceived the study, analyzed and acquired the data, then critically reviewed and revised the manuscript.

HN analyzed the data and wrote the manuscript. AH summarized bibliography of all published cases. CT refined radiological description and images. NM analyzed the data, critically reviewed and revised the manuscript. JLJ and JCG acquired clinical data and critically reviewed the manuscript.

JBM and FLL acquired and analyzed the data, then critically reviewed and revised the manuscript.

All authors gave final approval for publication.

Conflict of interest

The authors declare that they have no conflict of interest.

Publisher's note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.


Barbara Szafrajzen

Karen Ferreira-Meyers

Critical review of an e-learning tool

Keywords: Communicative study, distance learning, meaningful learning experiences, constructivism, community of practice

come

Introduction

The place of communication and information technology in the current academic landscape is indisputable. E-learning and e-education has grown significantly in many universities, thanks to various factors (technological, pedagogical, psychosocial, cognitive, socio-economic, etc.). The integration of computer science tools in this new type of learning device (Choplin, 2002) has led to learners greatly modifying their learning experiences in a meaningful way, forcing the university to adapt to these changes. In addition, new problems inherent to the students' needs to "tame distance" [START_REF] Jacquinot | Apprivoiser la distance et supprimer l'absence ? Ou les défis de la formation à distance[END_REF] have thus emerged.

In human and social sciences, many researchers have been interested in cyberspace, especially the emergence of an "ideology" community within it. In the early 1990s, science education literature concerned with models of collaborative work and distributed cognition is already abundant (Resnic, Levine, Teasley, 1991). In anthropology, research on collective intelligence and virtual agora offers, at the same time, a cyberspace anthropology as "public service" and "collective intelligence" (Levy, 1994). More recently in sociology the work of Maria C. Papadakis summarizes the main characteristics specific to these communities [START_REF] Papadakis | People Can Create a Sense of Community in Cyberspace[END_REF].

To understand the place of ICT in learning environments, we base our comments on some of the meaningful learning experiences from the concrete example of an e-learning education program in communication and information sciences 1 . We investigate how a communicative study helps to understand and analyze meaningful learning experiences of learners in this type of training.

To understand how the social actors, specifically the learners, co-construct their collective learning reality in their e-learning environment, we choose to first adopt an epistemological position which follows a "constructivist convention" (Le [START_REF] Moigne | Le constructivisme. Modéliser pour comprendre[END_REF]. The methodology involves two main qualitative methods of data analysis: the method of qualitative content analysis and the method of qualitative systemic analysis (Mucchielli, 2004). In a third step, we describe the device as well as the e-learning learning situation. Finally, we look at how students bridge the distance through the emergence of a learning community.

The epistemological framework

We wish to determine the meaning that each learner gives to his or her learning situation 2 . For this, we make our first assumption 3 that meaning is only constructed in situations and in interactions with the learning device (whether human entities, material and/or ideational). Situational semiotics focuses on the idea of emerging meaning in situations and interactions. The genesis of shared meaning is the issue at the heart of this research method. Moving away from compartmentalised representations which the actors have of their situation, this method offers a new vision of a much broader and more complex situation. We also assume that there are collective learning situations within this distance elearning learning 4 . To understand how the learners co-construct their collective learning reality, we choose to adopt the constructivist epistemological position [START_REF] Moigne | Le constructivisme. Modéliser pour comprendre[END_REF]. 1 This article reiterates and elaborates some of the results obtained in one of the authors' recent doctoral research in communication and information sciences, entitled « Etude communicationnelle de deux dispositifs d'apprentissage mis en place au sein d'un même département universitaire. Le cas de la Licence en sciences de l'information et de la communication », PhD obtained on 10 December 2010 in Montpellier (France).

2

We understand the term "learning" in the sense of Etienne Wenger: Learning has a social dimension and manifests itself in social interactions of actors engaged in a common practice [START_REF] Wenger | Communities of Practice : Learning, Meaning and Identity[END_REF].

3

We seek to confirm these assumptions in our field study.

4

As part of the doctoral research, we tried to explore some meaningful learning experiences of students in distance education. Our study also observed the emergence of a learning community born of a collective approach to knowledge sharing. However, we do not want to consider construction and sharing of knowledge in a limited way, namely as an exclusively collective dynamic. This is why we specify that we are interested in players (specifically learners) situations and interactions with their learning device, so that they understand the representations of their distance learning.

Jean-Louis Le Moigne proposes the term "constructivist convention" to scientific communities: "In presenting itself as an alternative convention, constructivism also reveals the conventional positivist epistemologies"(ibid.: 61). The term "constructivist convention" also highlights the possible nuances in the different ways of understanding the constructivist posture and "allows a 'generally accepted' representation of "the classic or institutional epistemological convention" (op. cit.: 45).

Within this convention, learning is seen as an active mechanism; the learner seeks the meaning of his action with regard to the meaning 5 that can be grafted to this action. To better understand this, our approach is based on constructivism as described by Alex Mucchielli [START_REF] Mucchielli | La place du constructivisme pour l'étude des communications[END_REF]. This author postulates that knowledge is constructed, unfinished, plausible, suitable and contingent, purpose-oriented, dependent on the actions and experiences of the knowing subjects, structured by the process of knowledge while also and at the same time structuring it, and, finally, forged in and through the interaction of the knower with the world (Mucchielli, 2004). We take the term constructivism to the extent that we construct the meaning given by the actors in a situation through a contextualization of their words and actions, without reading grids or a priori considerations of data. It is therefore a progressive construction of signification. Other authors, such as Peter Ludwig Berger and Thomas Luckman ( 2006) also developed the idea of collective construction of social reality. "Construction" then is only the reality constructed by those involved in the situation. Therefore, a constructivist learning device would be a device offering construction of knowledge routes to each of the actors present in the learning situation. The search for meaning is therefore based on items deemed relevant and interesting for the actors. Then, taking the precepts of Paul Watzlawick, we can say that the actors then produce "secondary realities" (Watzlawick).

Knowledge is not an acquired given but rather something that is constructed. Thus, the researchers consider that reality in itself does not exist; there are only representations co-constructed by the actors: "Under this assumption the path of knowledge does not exist a priori, it is constructed along the way" (Thiétart, 2007: 24). Therefore, we choose to think of learning situation as built by the actors while present. In this sense, we try to find the meanings they give from their point of view; this is precisely why we speak of 5 Etienne Wenger speaks of "negotiation of meaning" to define the concepts of community of practice [START_REF] Wenger | Communities of Practice : Learning, Meaning and Identity[END_REF]. For him, the negotiation of meaning during the action which is taking place is the most relevant stage to analyze the collective practices. It is precisely within this idea, mentioned by Etienne Wenger, of negotiation of meaning that we situate our discussion, or even "sense-making" (creative meaning) as Karl Weick understands it: The dynamic process of creating sense in construction [START_REF] Weick | Sensemaking In Organizations[END_REF].

"point of view of the actors in a situation", to borrow a phrase previously used by Talcott Parsons and Alfred Schütz [START_REF] Parsons | The Theory of Social Action[END_REF].

What interests us here are the points of view of individual and collective actors in educational systems: their projections, their visions, in other words what they think, what they are, or what they claim to do. It is through different questionnaires but also simple participant observations that we focus on the vision they have of their learning, whether classroom based or at a distance. Indeed, to highlight the views of stakeholders, also equates to bringing out the meanings for the actor, "meanings" that are key to understanding and therefore to learning (Depover, Giordana and Marton, 1998).

In addition, each player has its mode of operation, method of thinking, experience, knowledge, and it is within social interaction that s/he will give them meaning. In this regard, Anne-Nelly Perret-Clermont considers that these are "[...] interactions that require the subject to coordinate its actions with those of others, as the result of a process of decentering that engages in a conflict between his point of view and that of its partners" (Perret-Clermont, 1979: 136). In this sense, the idea of socio-cognitive conflict refers to "cognitive restructuring" (ibid.) and implies the existence of different points of view which have to be taken into consideration.

The construction of knowledge is an iterative phenomenon as it occurs gradually, individually, but also collectively (we will also discuss collective construction of meaning in this article). This idea echoes that of recursion loops; a role player from the situation's point of view is ultimately the result of a constant interaction between the individual, the surrounding environment, and all other involved individuals.

In view of this "constructivist agreement", knowledge is regarded as inherent in human constructions. Therefore, a learning device, whether face-toface or at a distance, offers knowledge construction that the learner should own (so we also position ourselves in the idea of action, or the learner taken as an actor of his learning). Many educationalists, also in pedagogics, studied and demonstrated the importance of distinguishing the terms "knowledge" and "expertise". To understand the distinction we make between these two terms, we take the two definitions recently proposed by Renald Legendre. According to him, knowledge includes "facts, information, concepts, principles we acquire through study and experience" (Legendre, 2005: 274), while expertise is "to have in mind a set of information, ideas and data, which are knowledge of a field of activity, an object or a person" (ibid.). These two definitions correspond to our point of view and it is precisely because we are interested in the construction of this knowledge that we prefer to invoke the term knowledge.

Following these epistemological precepts we chose to do our fieldwork first, anchoring our methodology on a qualitative approach.

The methodological framework from a qualitative approach

Our research problem leads us to construct a methodology in terms of practices and perspectives of actors in a given situation. We formulate our problem statement as follows: "How can a communications study allow us to understand and analyze meaningful learning experiences of students in a distance e-learning set-up?". This statement highlights our commitment to focus on the construction of knowledge among students. However, the research problem can be considered in three parts: first, we seek to understand the meaning given by the role players of their learning situation. This understanding will enable us, secondly, to understand the functioning of e-learning. Finally, through the understanding of how this works, we question the idea of sharing knowledge in a process that we see as collective and shared by the community of learners.

To avoid the "critique of the arbitrary choice of data" (Matthey, 2003: 39) collected and analyzed, we choose to use methodological triangulation, which refers to crossing different data gathering techniques, so as to "improve the validity of the proposed results" 6 [START_REF] Mangenot | Analyser les interactions pédagogiques en ligne, pourquoi, comment ?[END_REF].

We therefore prefer a qualitative approach bringing together four main data collection techniques: observations (made during monthly face-to-face meetings), interviews (centered non-directive and active directive interviews), keeping of a diary (technique used throughout our study), as well as the analysis of several conversations on the discussion forum. This qualitative methodological approach led us to mobilize two main methods of data analysis: the method of qualitative content analysis and the method of qualitative systemic analysis (Mucchielli, 2004).

The method of qualitative content analysis, also called method of categorization, enabled us to deal with three main themes with our learners (having induced the questions during the interviews, with various sub-categories such as the relationship system, the organization of work, etc.): the learners' profile, their meaningful learning experiences and their views on their learning paths. After completing each interview, we inserted all the comments gathered in a reading grid. We then compared each of these opinions, in order to bring out differences, recurrences, etc. [START_REF] Szafrajzen | Lecture communicationnelle de deux dispositifs d'apprentissage au sein d'un même département universitaire[END_REF].

The second method is called the method of qualitative systemic analysis. By combining conventional techniques (interview and observation, thematic content analysis and graphical representation), the so-called systemic qualitative analysis method wishes to understand and analyze the meaning given by role 6

We understand the concept of practice (just like learning) within the meaning proposed by Etienne Wenger, namely in terms of a social approach. players in a given situation. Complemented by an analytical commentary showing the circular causalities, the method also highlights the system's logic (implicit and latent rules directing the role players) and "game rules" of the present role players, or repetitive scenarios [START_REF] Mucchielli | Un nouveau domaine des sciences info-com : la formation à distance[END_REF]. It is to highlight the encompassing system, that is to say, the environment for a pre-defined framework and then to understand the existential and secondary benefits that role players take from their interactions.

In line with the comprehensive approach, the qualitative systemic method adds six reading and interpretation principles of any communication: -The systemic principle: a phenomenon has to be analyzed in conjunction with a range of other phenomena; -The framework principle asking the role players to look at and define the environment of any phenomenon; -The principle of the primacy of systemic context: a phenomenon exists and has meaning only in conjunction with the given context created by the system itself; -The principle of circular causality: a chain of cause and effect acting through feedback to enhance or inhibit the mechanism; -The homeostatic principle: a phenomenon system develops an internal force that holds it together; -The principle of emergence of paradoxes: "in a system, each phenomenon is both autonomous and forced, organized and organizing, informing and informed" (Mucchielli, 2004).

It is in line with the work of the school of Palo Alto in the sense that the researcher highlights the significance of the interaction between the different actors. This method interprets the operation of communicational phenomena by attempting to explain the meanings of the exchanges between the different actors involved in the situation (Mucchielli, 2004). Alex Mucchielli (2004) affirms that it is qualitative in that it allows the emergence of the meanings of the exchanges in a communicative system. It is also scientific as it is the researcher with his/her epistemological intellectual, analytical and methodological referents who makes the meanings emerge. Finally, it is part of constructivist paradigm insofar as it highlights the construction of meaning in emerging situations: "The systemic theory of communication is a constructivist theory of the meaning of communications (and of the remainder of communicational phenomena)" (Mucchielli, 2006: 54-55).

Having clarified our epistemological and methodological coordinates, we now propose to introduce e-learning in the field of communication and information sciences.

E-learning in communication and information sciences

The definitions stemming from the learning device typology now distinguish "enriched face-to-face" situations: situations of education or training in which there is multimedia usage in the presence of students, and "enhanced face-to-face" situations: teaching or training situations carried out upstream and/or downstream at a distance with a face-to-face component. They must also be distinguished from so-called mixed situations (or blended learning), situations where education or training activities take place outside the physical presence of the teacher and can lead to "light", "reduced" or "almost nonexistent" face-to-face components.

This plurality of denominations supports all our research, whether bibliographical or web-related, having made us encounter a large amount of names to define distance education, depending on the amount of face-to-face and distance: embedded learning, distance learning, blended learning, full elearning, mix learning, etc.

According to some authors, we have now arrived in the era of integrated learning: "After "distance learning" and "blended learning", this is the era of the "integrated learning"" 7 .

The term "Integrated Learning" was proposed by Pierre Dillenbourg to explain the current development of blended learning with complementary faceto-face teaching and distance learning, making the link between different pedagogical and technological strategies: • integration of an educational strategy to develop both individual, group and classroom work, • integration of classroom teaching (lecture, exercises, practical work, etc.) and distance teaching (forum, exercises, etc.), the so-called the pedagogical scenario, • integration of different technologies,

• integration of theoretical and practical knowledge/skills. "Therefore, instead of speaking of CSCL in such a broadened sense of the concept, we tend to use the notion of integrated learning, i.e. integration within a coherent pedagogical scenario of activities that occur across multiple social planes (individual, group and class) and places, and can be supported with multiple tools. In formal and informal learning settings, CSCL activities are embedded in more comprehensive sets of activities." (Dillenbourg, Fischer, 2007).

7

During the fourth edition of the Forum des TIC held at the Université du travail de Charleroi (Belgium), Pierre Dillenbourg proposed, in a visioconference, an intervention provocatively entitle "The end of e-learning" ("La fin du e-learning").

Therefore it is necessary to talk about integrated learning to discuss learning devices bringing together face-to-face and distance modalities, such as the ones we studied.

The presentation of the field of study inevitably leads us to begin by distinguishing two frames of research: that of the learning tool and that of the elearning situation. In this sense, our approach can be described as "tooloriented", seeking to bring out the meaning of the communication through its interaction with components of the learning tools [START_REF] Wilhelm | Emergence d'une culture communicationnelle au sein d'un dispositif international en ligne, Distances géoculturelles et proximité axioliogique[END_REF]. To define the term learning device or learning tool, we choose to use Georges Le Meur's definition, the "educational provision" (Le [START_REF] Meur | Université ouverte, formation virtuelle et apprentissage : communications francophones du cinquième Colloque européen sur l'autoformation[END_REF]:

"A learning tool can be defined as a set of services, organized in time and in space, to allow students to perform learning [...]. The online learning tools are characterized from a technological point of view by a strong digital instrumentation of the act of learning" (Ibid.: 185).

Thus, a learning (or training) tool can be considered as a set of components (in terms of resources/learning tools) available to students to learn. It is also "a body, a place of social interaction and cooperation with its intentions, its material and symbolic functioning and, finally, its own modes of interactions" (Peraya, 1999: 153).

Our research focuses on the third year Bachelor's degree, called Licence 3 in France (a National Diploma accredited by the Ministry of National Education) provided in face-to-face format (over a year), but also at a distance, as e-learning (over two years). The main difference between e-learning and classroom training lies in the components of each of the two learning systems. Classroom training is usually provided by a trainer to learners in the same specialized environment, relying on a direct teaching relationship and in a lecture mode, for a predetermined period.

The studied e-learning environment here is only open under the Continuing Vocational Training format and has a limited number of spaces for about thirty students (called student interns) and it does this because it wants to be a successful educational program in which teachers and student trainees or interns are committed 8 . The students engaging in such training are required to sign a learning contract between the two parties (students and teachers). By signing this document, the student intern agrees to be present at all face-to-face sessions and perform the required work in a timely manner. More symbolically, the learning agreement means the student interns are "responsible for their training": the system leads them to take responsibility for the success or failure of their training. The learners have to pay for this programme. In general, businesses support them as most of the learners are employees.

The program is based on "a specific support tool" whose components are:

• Monthly gatherings: a meeting is organized by the teaching staff every month. Students emphasize the importance of these meetings, allowing them to meet, to encourage each other, to materialize and individualize relationships. • An educational site: a platform provides for the organization of activities and access to online resources. The intern (student) also has access to a discussion forum; these forums are free and organized by theme and everyone can participate by writing a message at any time and reading the other posts. The written and asynchronous aspects of the forum allows for the "sharing of experiences" (Develotte, Mangenot, 2004). • Telephone tutorials: Every week, teachers (who then take the role of tutors) provide individualized assistance in answering direct questions from students. The telephone tutorials, an integral part of the learning environment, offer students the opportunity to get in touch with their teachers (synchronous mode). They can then ask any question directly, ask for help and advice. • Online appointments ("Chat"): students and teachers have the opportunity to meet regularly to discuss and apply technological knowledge by discussing a particular topic.

All components of this learning tool allow the researchers to assume from the onset of the study that there are collective learning situations, as we shall see in the following description of the learning situation.

The actual operation of these components is what we call the learning situation. We are interested in actors and their actions, 'actual actions': what the stakeholders are doing (effective actions or informal practices), saying (remarks) and the visions they have of their actions and words (depending on how they perceive the learning tool). It is also about the ways of organizing work under the constraints inherent to their non-academic life (personal and professional constraints of the student) 9 . We use "learning situation" to describe the concrete and real actions, the various components of discretionary learning that we just described. In this study, we look at "how theythe learnersdo" or the actual concrete actions of the learners.

During the investigation, 19 people were registered for the course: the average age of these students is thirty years (we see a very large majority of 9 These factors inevitably single out the actor in a particular situation as we consider his tastes, choices and personal opinions, values, past, culture, challenges, positioning. This set of elements is what is called the system of relevance.

women in this training: one man only per eighteen women). Half of the students10 are married, one quarter are single and the last quarter are people who are cohabiting. More than one in two has at least one dependent child. Over three-quarters of them are employees and provide various functions depending on their areas of activity: journalist, assistant manager, administrative manager in an engineering school in computer science, communication assistant in the metalworking sector, medical assistant in a pharmaceutical laboratory, a person in charge of a logistical team. They come from various educational backgrounds (Accounting and Management, Communication-advertising, Graphics, Business Communication, Services and communication networks). This description raises the primary characteristic of these students: they work while studying.

The reasons that led students to choose this type of course are very diverse and range from the fact that this type of training offers the opportunity to learn in an institution without having to move from home (and especially without having to change their personal and professional organization), an interest in the content of the training itself, the desire to grow professionally, the desire to obtain a Bachelor's Degree recognized by the state, the opportunity to be able to grow and to enrich oneself intellectually as well as the department's theoretical position.

After having identified the different student profiles and the reasons for their enrollment in distance education, we wanted to investigate their views on the relations they had with each other and with the teaching team. With these, the opinions of students 11 indicate a strong need to "tame distance" [START_REF] Jacquinot | Apprivoiser la distance et supprimer l'absence ? Ou les défis de la formation à distance[END_REF] and to overcome geographical distance between them: "We are really waiting for an immediate return from the teaching staff in terms of information, certainly, but also and especially in terms of relationships, support and counseling", two students noted. Indeed, since they see the pedagogical staff on very limited occasions, students say they expect ongoing support and high reactivity when sending messages to their teachers, or when asking questions during the telephone tutorials. The main criticisms of students emerge from the technical tools, and more specifically the platform, which is not as good as they would like it to be (connection problems or disconnections without apparent reasons, etc.).

However, more than half of the students surveyed said that the platform, including the discussion forum, help to maintain close relations between them, giving them the opportunity to recreate links, to comfort themselves and others, to situate themselves as compared to others, to feel supported and understood by other people sharing the same learning situation12 .

In addition, students also use, on a regular basis, other means of communication, especially online conversations on servers like Msn Messenger or on social networking sites like Facebook. Thus, they argue that their exchanges are more "individualized", more "discrete" and more "friendly". Just like the forum discussions, telephone tutorials are components of the course appreciated by students for availability and demonstrated commitment of tutors, for the psychological support they represent, or for the informational assistance provided.

We propose now to look back on this situation from a communicational viewpoint and thus better understand how students bridge the distance through the emergence of a learning community.

Bridging the gap/distance through the emergence of a learning community

Whatever the reasons for the student interns to choose e-learning rather than traditional classroom training, this choice is meaningful and relevant to the personal/professional projects of the actors concerned and emphasizes the indisputable motivation they have to complete their project. These student interns allow a new meaning to emerge around this action related to the choice of training; this new meaning is intrinsic to the actor himself, his challenges, his personal objectives related to his identity, his professional objectives and, finally, the objectives of his university.

Through the description of the learning tool as well as the situation of elearning, we were able to check our own postulate of the existence of collective learning situations. Indeed, whether at monthly face-to-face meetings, in their discussions on social networks or on the discussion forum, these students share their personal, psychological and academic problems but also try to create opportunities to study together outside of the framework provided by the training system (despite the distance between them). These practices emphasize a strong need to address the latent lack induced by this type of learning tool. In fact, a student can not be an isolated actor alone in the course and must be considered in interaction with others of the same learning tool. At the onset, when the learner enters the course, s/he does not know the other learners (whom s/he never meets often anyway). To counter this, the students will get to know each other through various technological media: "Education and training are ways to build and assert oneself, against oneself, but also to be recognized in a community, the small community of peers and the wider community of professional and social relationships" (Glikman, 2002: 253).

Students build these relationships through the different technological tools; this is how a learning community is constructed. In this sense, the digital space "can be conceptualized as community support, shared space of the collective" (Wilhelm, 2010: 98).

In 1991, in a study conducted by Jean Lave and Etienne Wenger (Situated Learning: Legitimate Peripheral Participation), the term community of practice appears for the first time. This concept initially refers to various social groups setting up places and times allocated to learning and incoming students. They then hypothesized that learning is a process of participation in social practices, or "communities of practice". They then sought to understand the process of acquisition of knowledge/expertise in a way of belonging to social groups rather than in terms of cognitive construction. Thus the act of learning becomes a way to participate in social practice or a way of belonging to a community.

In 1998, Etienne Wenger continues his ethnographical study by developing the theory of communities of practice. He then proposed a mapping of communities of practice, including 3 features which enable these communities to be identified: mutual engagement, joint enterprise and shared repertoire. Mutual commitment ensures the existence of shared practice and points to ordinary relationships between members of a community within a social entity (which we found in our study, especially during the observation of the face-toface sessions).

The joint enterprise is between what the organization requires in terms of objectives and activities and what the role players actually do in the organization.

Finally, the shared repertoire refers to tools (documents, etc.), gestures, codes, routines even becoming elements of practice (as we have observed in the analysis of the conversations on the discussion forums in particular).

As such, students say they can refer to other students who share the same problems, the same needs, and have the same definition of the learning situation: "We know it is not enough to develop communication tools for people to communicate, but it is important that they can co-build a dynamic exchange" (Paquelin, in Le Meur, 2002: 181, our translation). The observations made in the discussion forum and the outspoken freedom of speech observed lead us to analyze this collective exchange approach as an emerging trend within a learning community.

Many authors from the field of educational technology have analyzed the different types of online communities to highlight classifications or typologies. Thus, France Henry and Beatrice Pudelko (2006) define four types of virtual communities: the community of interest, the community of intellectual interest, the community of learners and the community of practice. According to their definitions, the community of learners that we present here corresponds to a community of practice characterized by the identification of the flow of knowledge, mutual assistance, exchange of information, building relationships, sharing of know-how.

Scientific literature on the concept of community establishes distinction and demarcation levels of practices, according to the strength of the social ties developed the community and the didactic intent (Henry Pudelko). Thus the notion of community of practice can sometimes be used in conjunction with other theories such as epistemic communities (Hass, 1992), professional communities (Vaast, 2002) or virtual communities (Rheingold, 1995) 13 .

While initially the communities, in the traditional sense of the term, are characterized by a certain geographic proximity 14 , the virtual learning communities compensate for this distance through sharing of common interests, common projects, but also common values. Without a doubt, in the present study, the creation of this learning community is facilitated by the participants' own cultural and identity backgrounds 15 : "For there to be a sense of belonging to a community, the scene of the interactions (in face-to-face or electronically) must bring together to persons who own or build common bonds between them and whose interactions are reciprocal, sustained, long lasting" (Proulx, 2004: 4).

Indeed, these commonalities undoubtedly facilitate the establishment of common and ritualized type of frequent informal conversations outside the university with other means of communication than those available to them in the learning device (conversations via Msn or Facebook) as we have seen in our research.

By engaging in this course, students sign a learning agreement; this demand for commitment reflects an autonomous operating injunction [START_REF] Wilhelm | Emergence d'une culture communicationnelle au sein d'un dispositif international en ligne, Distances géoculturelles et proximité axioliogique[END_REF] made by the learning device. Especially as we have seen in the analysis of conversations on the discussion board, students try to recreate a true learning community, transcending the boundaries of distance in their training by finding cues and spaces of acceptance in this new device training, instilling a group 13 It is also worth noting that some researchers and theorists radically question the very notion of community developed by Lave and Wenger in particular: we think of James Gee who, in 2005, proposed the notion of "affinity space", but the present paper chooses not to develop this theory. 14 We refer to the notion of territorial anchoring of a community. 15 As such, it should be noted that virtual communities may reflect a social structure reproducing some characteristics of the structure, rules, norms, implicit or explicit codes of conduct, sanctions of a face-to-face society.

dynamic, thus overcoming latent loneliness (students work remotely). In doing so, they remind everyone that they have the same goal of a successful training, and they must help each other, regardless of how they operate and consider the various components of the device. Christine Develotte and François Mangenot cite Barry Wellman, who, in 2001, defines learning communities as follows: "Communities are networks of relationships between people who contribute to conviviality, help, information, a sense of belonging and social identity" (Develotte, Mangenot, 2004, our translation). This definition takes into account the socio-emotional dimension, as well as the cognitive and stresses the importance of social ties, particularly through the "help" that can be given by tutors.

Through these means of communication, students can then overcome the problem of the distance between them, "tame the distance and delete the absence" [START_REF] Jacquinot | Apprivoiser la distance et supprimer l'absence ? Ou les défis de la formation à distance[END_REF].The spontaneity of online interactions in small groups of learners [...] having a common activity and animated appropriately produces a feeling of closeness and solidarity between students and a spirit of cooperation and mutual encouragement. A familiarity between online learners is thus created, despite the age, culture, initial training and professional differences, despite the distance or thanks to it and the differences between the learners. And in this climate of sympathy, spontaneity and mutual support, the relationships of the online learners with their trainer quickly lose their hierarchical nature (Bates, 1995: 209-210, quoted by Develotte andMangenot, 2004: 331). Students try to move beyond the boundaries of distance; they have to find back references in this new learning environment, to instill group dynamics, thus overcoming latent loneliness (of the student in an e-learning environment). The creation of this learning community (virtual or real) becomes a challenge for each of them, placing them in a collective intellectual practice and inspiring a motivational dynamic of participation 16 .

We speak of a collective approach to knowledge sharing to the extent that we observe that these student interns share their responses to their difficulties, as well as their knowledge. This idea of collaboration allows them to reach a common goal, a common interest, namely the successful completion of the course, or more concretely work together on a joint project to submit thereafter (group work).

Thus, students have completely transformed their relationship to knowledge, now evolving into a whole new work environment, with practices 16 This social phenomenon is at the heart of the dialectical process that Wenger called "participation" and "reification": by participating, each member of the group seems to be involved in this community and the meaning given to this action becomes that of identity construction [START_REF] Wenger | Communities of Practice : Learning, Meaning and Identity[END_REF].

very different from the traditional face-to-face set-up. The insertion of an information tool within the learning environment leads the learners to change their environment; learning is more of self-centered, autonomous and brings learner empowerment.

Conclusion

The presentation of an e-learning course in communication and information sciences has enabled us to highlight some of the meaningful learning experiences for students using the learning tool. In particular, we found that loneliness -very present in the training -induced the emergence of a learning community, with students venturing on a collective and shared path. This understanding of the stakeholders' views in a learning situation is only possible given the meaning that each student gives to his/her learning situation, experiencing and interacting with other components of the course (be these human entities, material or ideational).

This study highlighted that students were forced to change their position of learning alone at a distance to that of a learner belonging to a learning community. Their respective behaviors in the group then take on new meanings, revolving mainly around identity recognition of shared interests and objectives (to the extent they deal with other students sharing the same situations, needs, issues, problems, and thereby the same meaning).

We can then assume that the creation of this community is a way for them to move beyond the virtual group and to project, in an imaginary or symbolic way, social and relational characteristics inherent to any physical and real community. It now remains to be examined what the scope, importance or social and cultural engagement, of such communities can be in the implementation of social projects.

Bibliography

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  Choplin, H., (dir.), Les TIC au servicede nouveaux dispositifs de formation -Éducation permanente, n° 152, 2002. Depover C., Giardina M., Marton P., Les environnements d'apprentissage multimédia, Paris, l'Harmattan, 1998. Develotte C., Mangenot F., « Tutorat et communauté dans un campus numérique non collaboratif », Distances et savoirs, vol. 2, n° 3, 2004, p. 309-333. DILLENBOURG P., FISCHER F. « Basics of Computer-Supported Collaborative Learning », Zeitschrift für Berufs-und Wirtschaftspädagogik. 21, 2007, p. 111-130. Glikman V., Des cours par correspondance au « e-learning », panorama des formations ouvertes et à distance, Paris, Presses Universitaires de France, 2002.

To be clear, we have chosen to quantify the given information, even if the sample is small.

This is precisely why we often find, on the discussion forums, personal and/or professional information, showing inherent constraints in their learning situation.