Marc-Antoine Mahieu

The Genitive Case

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

Introduction 1

Finnish is the most widely spoken of the languages comprising the Finnic branch of the Uralic family. It has some five million speakers, most of them in Finland. The complexity of its case system has been remarked upon since the 17 th century (Korhonen 1987:92-100); the modern grammatical tradition identifies fifteen different case morphemes in all. Table 1 shows Setälä's (1898:47-52) analysis of this system. This work is a school grammar which remained the model for codification up to the 1950s. 2 Nowadays, the partitive is usually grouped with the nominative, the accusative, and the genitive on the grounds that these four morphemes share the property of being able to affect the subject and/or the direct object. 3 At first glance, the Finnish genitive seems to be just what a "genitive" is usually assumed to be. As suggested by the word omanto, which is sometimes used to designate this case in Finnish, it is ostensibly the case that expresses possession. Examples like (1a) or (1b) can be adduced as evidence. At the same time, though, in this language without a verb 'have', the possessive construction uses the adessive and not the genitive. This construction, illustrated by (1c), is generally analyzed as an existential sentence where the adessive has its characteristic locative sense. In this analysis, the literal meaning of (1c) is 'at Pekka is a car'.

( This paper will argue against all of the viewpoints expressed thus far.

First of all, the broad distribution of the Finnish genitive implies that it cannot be reduced to the "case expressing possession". This is true even in the loose sense assigned to "possession" by linguists, i.e. "inclusion of an entity (usually called the thing possessed) within the personal sphere of an individual [or of some cognitively more salient/individuated entity] (usually called the possessor)" (Creissels 2006:143-144). It will be argued here that the Finnish genitive is in fact a structural case, i.e. the simple manifestation of relationships of syntactic dependency.

Secondly, uses of type (1b) should not be conflated with those of type (1c). In a few more or less fossilized constructions, (1b) among them, the case marked by -n is not a true genitive but rather in all probability a vestige of what this case once was, before it became grammaticalized as a genitive morpheme. It will be argued here that -n is a semantic case in such uses, rightly called datiivigenetiivi ('dative-genitive') in traditional grammar, i.e.

the manifestation of a P-category head (or adposition).

Thirdly, contrary to what an analysis based solely on noun and verb morphology would suggest, it can be shown that the Finnish possessive construction cannot be treated as an existential sentence, i.e. an utterance composed of an initial locative phrase, a verb 'be', and a postposed subject.

A set of convergent arguments can be used to show, firstly, that the postverbal constituent behaves like a direct object of a 'have'-like head and then, that the initial constituent is not an adpositional phrase but rather a nominal subject, where the adessive becomes something other than a semantic case.

This paper is organized as follows: in part 2, the structural nature of the Finnish genitive case is demonstrated, and the range of syntactic configurations in which this case can be found is set out. From a typological perspective, the most interesting phenomenon here is without doubt the object genitive and the way it contrasts with other cases. Part 3 discusses the constructions where the morpheme -n, though still called genitive, is not a structural case but rather a semantic one with a dative sense. The analysis will include a brief discussion of the origin of the genitive and its cognates in other Uralic languages. Part 4 is devoted entirely to the possessive construction. It will be pointed out that the apparent conclusions drawn from morphology, namely, that this construction is a locative inversion, cannot be reconciled with what can be learned about its structure from a certain number of systematic syntactic manipulations. A transformational analysis is proposed which eliminates the apparent contradiction in the data from a synchronic perspective.

The genitive as a structural case

This section will show that the Finnish genitive is not definable as the case expressing possession, and more broadly speaking, is not a case expressing any semantic operation at all (in this regard, see [START_REF] Jaakola | Suomen genetiivi[END_REF]), but rather a structural case. This means that it is merely the surface reflex of a relationship of syntactic dependency, i.e. it is not itself a syntactic category (adpositional head) with a set of semantic properties.

More precisely, I will argue here that the Finnish genitive reflects not just one but a number of different dependency relationships, since it appears in a range of syntactic configurations which cannot be reduced to each other.

This means that Vainikka's (1989:126-183;1993:132-140) theory according to which the Finnish genitive can invariably be analyzed as "the structural default case for the specifier position of each of the lexical categories N, A, P and V" must be rejected.

Preposed NP modifier of a N head

To begin with, the genitive can express a relationship of modification of a nominal head by a preceding NP. This relationship is often assumed to express "possessivization of the noun" on the basis of examples like (1a). It is obvious, however, that an NP in the genitive can take on any one of the many other admissible semantic roles with respect to the nominal head it modifies, e.g. Agent in (2a), Patient in (2b), Theme in (2c), Experiencer in (2d), Beneficiary in (2e), Location in (2f), Source in (2g), or Destination in (2h).

( Given these facts, it can be said that the relationship holding between a genitive NP and the nominal head it modifies is totally unspecified. The only requirement is that the genitive noun phrase restricts the set of possible referents for the head noun to those which may stand in a given relationship to itself, whatever that relationship may be. It is not only impossible to give an a priori definition of the semantic role between the genitive NP and the head noun, it is also impossible to say that the genitive NP will invariably take on any given role. Thus, for instance, there are structures like (5),

where the NP does no more than identify the entity referred to, in this case by giving its name.

( Of course, it may still be assumed that the genitive case has a semantic value insofar as it restricts the possible referents of the head N. This is not the position that will be defended here. Instead, I will argue that the semantic operation of restriction is a function, not of the genitive marking of the premodifier, but rather of the syntactic relationship of premodification itself, which is defined within a given structural configuration. In other words, the source of the restriction is not the genitive case; the genitive is merely the surface reflex of the dependency relationship that assigns a restrictive function to any preposed NP.

There is at least one good argument in favor of this assumption, viz. the fact that the dependency relationship and its associated semantic function persist, even when genitive case is not allowed on the restricting NP. This happens when the restricting NP has a possessive suffix, as in the Finnish example ( 6). This has become the regular situation in Livonian, another Finnic language where the genitive case has practically disappeared. Vainikka (1993:132-133), the prenominal genitive is the case of the nominal specifier. Nelson (1998:216-217) takes a similar position. This approach ignores important data, however. First of all, the position of the restrictive NP varies with respect to adjectives. When an NP refers to a clearly individuated entity, and takes on a concrete and easily defined semantic role, it precedes the adjective. When, on the other hand, its referent is less individuated, and it has an abstract or less easily defined semantic role, it follows the adjective. This contrast is illustrated in ( 7).

( In addition, the head noun is sometimes preceded by two restrictive NPs. This is illustrated by the examples in (8), taken from Vilkuna (2000:189-193). In (8b), the head of the second restrictive NP (ranskan kielen) is itself modified by an NP in the genitive case. In (8c Given these facts, it can be assumed that the first position is that of the specifier of a D head (which selects the maximal projection of N) and the second, that of the specifier of the head N. The descriptive domain of N itself consists of any adjectives that may be adjoined to the maximal projection of N. This dual configuration for the assignment of the prenominal genitive is represented in (9). 5 ( 9)

[ DP NP-GEN [ D' D … [ NP NP-GEN [ N' N ]]]]

Preposed AP modifier of an A or Adv head

The second dependency relationship expressed by the genitive in Finnish is the modification of an A or Adv head by a preceding AP phrase. Thus, the adjective kamala, in the nominative in (10a), takes the genitive in (10b)

where it modifies another adjective. The same adjective cannot modify the VP in (10c); the deadjectival adverb, formed with the suffix -sti, is required instead. Example (10d) illustrates the case where the adjective in the genitive premodifies an Adv rather than an A head.

(10)a. Ilma ol-i kamala.

weather.NOM be-PRET.3SG It is not straightforward to determine the syntactic position in which the genitive is assigned to the complement of postpositions. According to Vainikka (1993:135-137), the position is that of specifier of a P head. The partitive in turn should be assigned to the sister-of-P position. There are indeed several arguments which support this point. One is that most postpositions were originally nouns in a locative case with the genitive NP as premodifier (see § 2.1). Sometimes this is evident (edessä 'in front of' < ete-+ -ssA), sometimes less so (kanssa 'with' < kansa + -ssA 'in company of'). Furthermore, the constraints on the complement of a P head vary according to whether it is preposed or postposed. For example, a preposed NP cannot contain a postmodifier: pullon (*vettä) sisällä 'in the (water) bottle'.

In spite of this, it is hard to maintain that postpositions assign the genitive to their specifier, not just because of examples like ( 21), but also because the specifier position can perfectly well be independently filled: (lähes) kuvan keskellä '(nearly) in the middle of the photo'; (osittain) rahan vuoksi '(partly) for money'; (vähän) Pekan takana '(a little) behind Pekka'; (ihan) talon vieressä '(right) beside the house'. Given these facts, it seems preferable to assume that the genitive case of the NP comes from its position as sister of the P head: 9

(25) [ PP …[ P' NP-GEN P]]

NP subject of participial clauses

In Finnish, participial forms (i.e. those verb forms which are neither finite nor infinitive) can be heads of dependent clauses. There is a large array of participial clauses, all of which have a (more usual) finite clause as a functional equivalent. These participial clauses do not always have an overt subject, in particular when the external argument is a non-generic unspecified human agent (in which case the participle appears in the socalled "passive" form), when it is expressed solely by a so-called "possessive" suffix on the participle, or when it is the relativized element in a participial relative clause.

Whenever there is an NP in subject position, however, it takes the genitive case. Clauses that display this phenomenon may be completive or not, and if not, they must be either circumstantial or relative. A few examples follow with comments. 10

In ( 26), the bracketed participial clause is the direct object of the verb uskoo. If it were finite, it would have to be introduced by a complementizer (että 'that'), and have a nominative subject (Pekka) with which its tensed verb would agree (nukkuu in the present, nukkui in the past). Here, however, there is no complementizer, the subject is in the genitive, and the verb has a participial morpheme: either -vAn, which expresses the non-anteriority of the process with respect to the finite verb, or -neen, which expresses the anteriority of the process with respect to the finite verb. It is interesting to note that both these morphemes contain a vestige of an earlier genitive (< -vA-n ; <-nee-n), which was assigned to the participle as head of the direct object of the finite verb (see § 2.6). This -n can no longer be analyzed as a genitive marker, since it does not alternate with the partitive as it otherwise should (Vilkuna 2000:293).

( This type of case marking varies in an interesting way in two contexts. In (27a), the finite verb näyttää is inaccusative (does not take an external argument), which implies that Pekka, the external argument of the participle, must appear in the subject position of the finite verb and take nominative case. (Another option would be to replace the participial proposition by a finite one: nayttää siltä, että Pekka nukkui huonosti 'it seems that Pekka slept badly'.) In (27b), on the other hand, it is the participle olevan that is inaccusative. It is therefore a part of its complement, the NP kuolleita, that appears in the subject position of the participle. Since this NP takes the partitive from the outset, and the partitive is not a structural case, it retains this case as subject of the non-finite verb. Hence, the subject of a participle is exceptionally not in the genitive. 11 believe-1SG dead-PL-PART be-PTCP.PRS.n ten-PL-PART 'I believe that dozens of people died.'

In ( 28), the bracketed participial clause is a circumstantial adjunct. It is not selected but simply modifies the tensed clause. Again, there is no complementizer, the subject Pekan is in the genitive, and the verb has a participial morpheme: either -essA (known in traditional grammar as the "inessive of the second infinitive"), which expresses the non-anteriority of the process with respect to the finite verb, or -(t)tUA ("partitive of the past passive participle"), which expresses anteriority. This construction is strictly equivalent to a finite clause introduced by kun 'when' where the subject would take the nominative case. Finally, though this is not the only possible analysis, the bracketed participial clause in (30) can be treated as relative. In the corresponding finite clause, which would have to be postposed to the N auto, there would be a relative pronoun referring to this N and standing as direct object (jonka 'which'), then a nominal subject (Pekka) followed by a tensed verb agreeing with the subject (osti 'bought'). Here, the participial clause has no relative pronoun; the relativized element, i.e. the internal argument of the participial verb, is not realized. Reference to it is established by the relationship obtaining with the N auto which the participial clause premodifies: the head of this clause, i.e. the participle marker -mA-, agrees in case (here inessive)

with the N auto. The subject is in the genitive.

(30) Istu-i-n [Peka-n osta-ma-ssa] auto-ssa. sit-PRET-1SG Pekka-GEN buy-PTCP-INE car-INE
'I was sitting in the car which Pekka bought.'

Vainikka 's answer (1993:138-139) to the question which syntactic configuration leads to assignment of the genitive to the subject of all these clauses is: specifier of the V head. This position is hard to maintain. If it were true, one would expect the subject of tensed clauses also to take the genitive. Vainikka accepts this consequence and argues that the situation arises whenever the subject does not agree with the tensed verb. (In case of agreement, it would take the nominative as specifier of Infl, and the genitive should then percolate down to the direct noun object in sister-of-V position, see § 2.6.) In part 3 of this paper, however, I will show that what Vainikka and many other Finnish grammarians analyze as a genitive subject of a personal verb is actually always an oblique modifier of an impersonal verb.

If the subject takes the genitive only in participial clauses, it seems natural to argue that the participle itself, i.e., the Ptcp head, assigns the genitive to its specifier. This is consistent with the partially nominal status of participles.

(

) [ PtcpP NP-GEN [ Ptcp' Ptcp VP]] 31

Direct NP object of certain kinds of VP

The Finnish genitive also contrasts with other cases in one last basic dependency relationship. This is the object relationship, i.e.

complementization of a V head by an NP. Consider as an initial example:

(32) Pekka ost-i auto-n.

Pekka.NOM buy-PRET.3SG car-GEN 'Pekka bought a car.'

The interpretation of the -n on the direct object is a matter of some debate. As table 1 shows, traditional Finnish grammar, which many scholars follow on this point, takes this to be an accusative rather than a genitive case marker. This is how it is usually glossed, and it is traditionally called genetiivinkaltainen akkusatiivi 'genitive-like accusative' or genetiiviakkusatiivi 'genitive-accusative'. Another name for it is accusative-1, in contrast to accusative-2 which designates the object's nominative case (see below).

The arguments for this approach are based on historical linguistics.

Firstly, some Uralic languages (Nenets, Mari, and Southern Saami) have an accusative case in -m. In addition, there is good reason to believe that the rule [-m → -n /__#] applied during the transition from Proto-Finno-Saamic (or "Pre-Finnic") to Proto-Finnic. Hence, it can be concluded that the object suffix -n comes from a Proto-Uralic accusative *-m, and thus remains an accusative.

This conclusion is rejected here. First of all, the identity of -n on the direct object needs to be determined synchronically, and must therefore be decided on the basis of synchronic arguments. But there is no synchronic formal reason to distinguish object -n from a genitive. On the contrary, there are positive reasons for identifying this -n with the genitive marker. Kiparsky (2001:320-321) gives the following example: since human pronouns are the only NPs to have an undeniably accusative form (-t), it might be expected that adjectives modifying these pronouns (as parka 'poor' in minä parka 'poor me') would agree with them in the same (accusative) case, as they do with other cases. This does not in fact happen.

(One finds, for example, minulla paralla in the adessive, but *minut paran is ill-formed, showing that -n is not an accusative on a par with -t). Finally, it is far from evident that object -n comes from an accusative *-m. Briefly stated (see Mahieu 2007:163-174 for details), if this were true, Proto-Finnic would have had syntactic transitivity and purely verbal predication. The fact is, however, that today's finite forms derive from earlier verbonominal predicates which are known to assign the genitive to their internal argument as a matter of course (cf. the object of verbal nouns in Celtic). For all these reasons, -n on the object should be treated as a genitive.

As already mentioned, the genitive is not the only case that can affect the direct object. There are several conditions to be met which keep it from marking more than one object in five on average [START_REF] Hakulinen | Iso suomen kieloppi[END_REF](Hakulinen et al. :1182)). The two most frequent cases are the partitive and the nominative, while the accusative is much rarer still.

Which of these cases is chosen can be seen as the result of a hierarchy of constraints which can be stated as follows. Firstly, any one of the following four conditions will suffice for the object to appear in the partitive: (1) the sentence is in the negative;

(2) the VP denotes a process without a "telos", i.e. without an end goal;

(3) the process denoted by the VP is viewed as "imperfective", i.e. as in the process of coming about; (4) the object denotes an indeterminate quantity of something. 12 Each of these criteria is illustrated in (33). In (33a), the VP is within the scope of negation which, in Finnish, is an inflectional head agreeing with the subject. In (33b), the VP is intrinsically atelic. In (33c), the verb is telic but viewed as not having reached its telos. In (33d), the object is a quantitatively indeterminate mass noun.

( Secondly, whenever none of the conditions for assigning the partitive is met, it suffices that the object should be in the plural for it to take the socalled "nominative plural" morpheme -t. The analysis of this morpheme is not without difficulties of its own. It is open to question whether it truly has the plural number feature and the nominative case feature, and whether it is not rather an allomorphic variant of the plural (-i-) before nominative case (Ø), or even something quite different, e.g. a "specific plural" marker, as Renault (1991:42-49) Fourthly, if the partitive is not required and the object is a singular noun, it will suffice that there be no nominative subject in the sentence for the object itself to take the nominative. This situation occurs in first and second person imperatives, in so-called "passive" sentences where the verb inflection is exempted from specifying a subject, the latter being interpreted as a non-generic human agent, and in infinitive clauses complementing an impersonal verb. Thus, the object is unquestionably in the nominative in (36), rather than in a special form of the accusative, as traditional grammar would have it (Kiparsky 2001:319-320).

( from.here get.3SG easily malaria-GEN 'One easily catches malaria here.'

To conclude this overview of the main data, it should be noted that in an infinitive clause which complements or modifies a noun, the object will not usually appear in the genitive. If it cannot be assigned either the partitive or the accusative, it takes the nominative. Apparent exceptions can be explained (Ikola 1964:66-80).

On the other hand, in infinitive clauses which complement a finite verb or are separated from a finite verb only by other non-finite clauses, the object takes the genitive whenever the finite verb has a nominative subject.

An example of this kind of "long-distance" dependency [START_REF] Mahieu | Les cas structuraux finnois: anti-ergativité scindée et dépendances longue distance[END_REF]) is given in (39). From a typological perspective, the case marking system for verb arguments in Finnish is quite unusual. Once the partitive and plural forms, whose use depends on semantic factors, are set aside, the system can be called "antiergative", a term used by [START_REF] Comrie | The antiergative: Finland's answer to Basque[END_REF]. The distribution of the genitive forms a mirror image of the ergative case-marking system as found in syntactically accusative languages: the object is only marked when there is an unmarked subject. It may be added that this "antiergativity" is contravened by the human pronouns which follow an accusative marking type. 14 Comrie (1975,1977:7) provides a purely functionalist interpretation of antiergativity: the distribution of -n can be explained simply by a need to distinguish subject and object when both are present in a sentence. This explanation leaves something to be desired. It cannot explain why one marking type occurs rather than another; it cannot explain the existence of split distributions; it cannot explain why one morpheme rather than another is chosen to mark a given relationship; and finally, it does not take into account the fact that subject and object can be distinguished in various other ways, even in a language with loose word order like Finnish.

More complex explanatory hypotheses have since been proposed (see particularly Milsark 1985;[START_REF] Taraldsen | On the distribution of nominative objects in Finnish[END_REF][START_REF] Vainikka | Deriving syntactic representations in Finnish[END_REF][START_REF] Vainikka | The three structural cases in Finnish. Case and other categories in Finnish syntax[END_REF][START_REF] Maling | Of nominative and accusative: the hierarchical assignment of grammatical cases in Finnish. Case and other categories in Finnish syntax[END_REF][START_REF] Reime | Accusative marking in Finnish. Case and other categories in Finnish syntax[END_REF][START_REF] Toivainen | The nature of the accusative case in Finnish. Case and other categories in Finnish syntax[END_REF][START_REF] Nelson | Grammatical case assignment in Finnish[END_REF][START_REF] Mahieu | Cas structuraux et dépendances syntaxiques des expressions nominales en finnois[END_REF]), but they cannot be discussed here.

There is at least one point that can easily be defended: the genitive is assigned to the object for syntactic reasons; it has no more meaning content than the nominative with which it alternates automatically. Furthermore, the syntactic configuration for its assignment cannot be reduced to any single one of the configurations discussed here thus far.

In particular, it is clear that the source of the object genitive is not the same as that of the subject genitive. This was the theory proposed by Vainikka (1989:151-181), who saw the genitive appearing as specifier of V in both cases, and presumably percolating down to sister-of-V position whenever the subject is raised to agree with an Infl head. If this were true, one would expect that both subject and object could never bear the genitive in the same clause. While this expectation is met in finite clauses, it is contradicted in participial clauses. In (41), both verb arguments in the bracketed completive can be seen to bear genitive marking. (Here again, the object would only be in the nominative if there were no possible nominative subject of the finite verb.) Given these facts, it must be assumed that the genitive is assigned to subject and object in different configurations. With regard to the object, the simplest hypothesis would be to assume that assignment takes place directly in sister-of-V position as shown in ( 42).

(41) Tiedä-n [Peka-n osta-neen auto-n].

know-1SG Pekka-GEN buy-PTCP.PST.n car-GEN 'I know that Pekka bought a car.'

(42) [ VP …[ V' V NP-GEN]]

Postposed NP modifier of certain types of VP

Finally, the genitive expresses a somewhat marginal but nonetheless unexpected dependency relationship under conditions which are nearly identical to the ones which lead to the genitive being assigned to objects.

The relevant context is the modification of a VP by an NP denoting quantity, often distance, duration, or frequency. The rule is as follows: if the VP is not within the scope of negation, and the sentence has or can have a subject in the nominative, then the quantifying modifier takes the genitive, provided it is not invariable (as joka päivä 'every day', which is always nominative).

Otherwise, it takes either the partitive or the nominative. The only real difference with respect to the object marking system is that the quantifying modifier does not take the partitive if the VP is atelic or the viewpoint is imperfective. For example, one finds odotin tunnin 'I was waiting for an hour' with genitive modifier, but odotin häntä 'I was waiting for him' where the object must be partitive. These may be compared with odota tunti! 'wait for an hour', where the modifier is in the nominative in the absence of any possible nominative subject.

In view of these data, it might be assumed that the case marking of the modifier takes place within the same syntactic configuration as the marking of the object, with the NP taking the genitive in sister-of-V position. This does not, however, seem to be true. The VP can quite easily have a direct object in addition to the quantifying modifier, as in ( 44).

( All in all, it would be better to allow that the quantifying modifier does not take the genitive in sister-of-V position but rather as an adjunct following the VP, as represented in (45).

(

) [ VP [ VP …[ V' V …] NP-GEN]] 45
This section has made it clear that there is enough evidence for the conclusion that the genitive in Finnish is neither the case of possession nor, more widely speaking, the case of any given semantic operation. It is a structural case standing in a complex system of contrasts with other cases and reflecting an irreducible range of syntactic relationships.

The "dative-genitive" issue

A good number of ordinary Finnish constructions contain an -n morpheme which recent grammars (starting with [START_REF] Hakulinen | Iso suomen kieloppi[END_REF]) do not distinguish from the genitive. It can be shown, however, that this morpheme is not a structural case but rather a semantic case with dative sense, corresponding to a P category in syntactic structure. In traditional Finnish grammar, this case, formally identical to the genitive, was called "dativegenitive".

The constructions in which this -n appears will now be described, and the main reasons for not treating it as a structural case will be set out. Its relationship to the genitive will then be examined from a historical perspective, with a view to providing a general explanation of the diachronic origin of the genitive case. It will be glossed "DAT.GEN" to distinguish it from the genitive proper.

The necessive construction

As a general rule, the necessive construction consists of a necessive predicate and its infinitival complement. The "necessive predicate" can be defined as follows: "a single verb like täytyy, pitää, tarvitsee 'must, have to, need to', kannattaa 'be worthwhile', sopia 'be suitable', or a copular construction like on hyvää / sopiva / turha / pakko 'be good / suitable / in vain / a necessity'. One [special] type of necessive construction consists of a copula and the [so-called] passive participle of the verb, as in on tehtävä 'has to be done'" (Laitinen and Vilkuna 1993:24). The important point to note here is that a necessive construction can always be preceded by an NP with the -n suffix expressing the experiencer of the obligation.

( case. Yet it has in fact dative meaning (the obligation falls to this or that person) and can alternate with the allative -lle. Where alternation is allowed, it is furthermore associated with a meaning difference which is too complicated to be discussed here. Good treatments of this subject can be found, for example, in Laitinen and Vilkuna (1993:33-34) and Hakulinen et al. (2004:878).

Experiencer -n is therefore not a genitive but rather a semantic case with dative sense. This means that, unlike the genitive, it is not the morphological reflex of a syntactic dependency relationship. It is itself the manifestation of a syntactic category connecting the NP to the rest of the sentence. The fact that the semantic cases are derived from former postpositions which have gradually been cliticized on nouns (Korhonen 1996:195-206, 219-234) gives grounds for assuming that the semantic cases are P heads, and this can be widely confirmed by synchronic analysis. 16 It can therefore be concluded that the experiencer in the necessive construction is the complement of a dative P head, that this P head is realized by the case marker -n, and that the PP in which the experiencer is embedded is an adjunct to the necessive VP.

The permissive construction

The so-called "permissive" construction minimally consists of one of the five permissive verbs and its infinitival complement. These verbs are antaa 'let (someone do)' (the primary meaning of this verb being 'give'), sallia 'permit', käskeä 'order', suoda 'grant', and more marginally luvata when it means 'authorize, allow' (and not 'promise'). The permissive verb is usually followed by an -n-bearing NP which expresses the experiencer of the permission.

( It should also be impossible to delete the marked NP, and the case marker should have no meaning. Yet it is in fact possible for the experiencer of permissive sentences to be omitted (Hakulinen et al. 2004:498), and -n clearly has basic dative value, just as in necessive sentences (permission is granted to someone or other). It is furthermore well known that permissive sentences derive from the reanalysis of ordinary sentences where the -nbearing NP was the Beneficiary of the verb antaa 'give', as in anna minu n syödä ruokaa! 'let me eat some food!' < anna minu n ruokaa syödä! 'give me some food to eat!' (expressed in contemporary Finnish by anna minu lle ruokaa syödäkseni!). (On this point, see [START_REF] Leino | Antaa sen muuttua. Suomen kielen permissiivirakenne ja sen kehitys[END_REF] Given these facts, it can reasonably be concluded that the -n marking the experiencer in the permissive construction is not a genitive but again the manifestation of a dative P head having the function of joining its complement, the experiencer, to the rest of the sentence. The PP is thus an adjunct to the permissive VP.

The experiencer construction

In what is called the "experiencer construction" here, a predicate expressing a feeling or sensation is preceded by an NP marked by -n designating the experiencer. The predicate is composed of one of the verbs on 'is', tulee 'comes', or käy 'goes', followed by a noun, an adjective, or an adverb denoting what is felt. This construction is less susceptible to manipulation than the preceding ones, but it is even more obvious that the initial NP does not have structural genitive marking.

( almost inconceivable that -n should be the meaningless reflex of a syntactic dependency relationship here; it is clearly this case which relates the initial NP syntactically and semantically to the predicate. In its absence, the nature of this relationship could not always be inferred as can be seen from the question mikä sinun on? 'what's up with you?'. Finally, the experiencer case can often be replaced by a locative case as in hänelle kävi hassusti 'she was unlucky'. In short, the experiencer again appears as the complement of a dative P head projected as a PP adjunct to the predicate of feeling.

The "dative-genitive" predicate

In the construction exemplified by (1b) and repeated below as (49a), the semantic role of the -n-bearing NP is not that of experiencer but rather that of possessor. This NP is furthermore part of the predicate whose subject designates the thing possessed.

( Once again, -n cannot be treated as a meaningless case marker. Unlike

Pekan auto 'Pekka's car' where the case marked by -n is assigned for purely structural reasons and independently of the semantic role assumed by the modifier (see § 2.1), here it is the element which establishes the syntactic and semantic relationship between the two NPs. Furthermore, the dative sense is again recognizable (a thing belongs to someone or other).

Given these facts, it can be concluded that the -n marker is the realization of a P head taking the possessor as its complement. The PP is itself the complement of the verb olla 'be', and the NP expressing the thing possessed is realized as the subject of this verb. 17

The loose "dative-genitive"

The four constructions described above are the only ones in the standard language to use the -n case marker with dative sense. This use is also found in at least one other construction in dialect which is cited here both because it has been a topic of prior research (see in particular [START_REF] Huumo | Irrallinen genetiivi ja omistusrakenteen ongelma[END_REF], and because it provides support for the positions taken here.

In this construction, the -n-bearing NP has the semantic role of possessor At first glance, this construction might be analysed as resulting from inversion involving the movement of the verb to a position between the head of a complex NP subject and its preposed genitive modifier. (50a)

would thus derive from [Pekan auto] on rikki. Huumo and Inaba (ibid.) provide numerous convincing arguments to show that this analysis is incorrect.

Here are a few of these arguments. First of all, the semantic role of the NP marked by -n is restricted to that of possessor in the strict sense of 'owner'. This would be incomprehensible if the NP were really a preposed genitive modifier of a N head. The situation is thus the same as in 3.4: the case marked by -n is used to indicate to whom something belongs.

Furthermore, the NP marked by -n is not always linked to the subject. In pojan meni tikku sormeen 'a splinter got stuck in the boy's finger', the possessive relationship is established with the locative complement.

Analysis as inversion is thus unsuitable, and the initial constituent is more like an added element. Finally, there is good reason to think that sentences like (50) are related to an earlier possessive construction, still found in Mordvin and Mari, where the case marked by -n was clearly semantic with dative sense. The replacement of this case in Finnic by the external locative cases was probably responsible for marginalizing "loose dative-genitive" sentences. Sentences like Pekalla on auto rikki, or minulta kuoli kissa, are in any case much more common. In short, we may conclude that the case marked by -n in (50) constitutes a dative P head with the possessor as its complement.

The historical background

It may be helpful at this point to look briefly at the links between the structural genitive case described in part 2 and the semantic dative case presented in this section. The need to distinguish the two synchronically does not of course imply that they cannot have a common origin. There are two positions on this question, the second of which currently prevails.

The first, discussed in Hakulinen (1968:86), asserts that there is no historical relationship between the two case forms. The structural genitive case is assumed to have existed in Proto-Uralic where it had the same form, *-n, as in modern Finnish. It has on occasion been suggested that this Proto-Uralic genitive may itself have come from a very ancient adjectival derivational morpheme which can still be observed in Mari, Mordvin, and Southern Saamic. (Thus in Mari, lun is either the genitive of the noun 'bone'

or an adjective meaning 'made of bone'.) The "dative-genitive" in turn is thought to derive from a Proto-Uralic *-ń marking the lative case. This morpheme is also assumed to have played a role in the creation of the two directional cases, the illative (-hVn < *-se + *-ń) and the allative (-lle < *-le + *-ń). It must then have merged formally with the genitive in the transition to Proto-Finnic as a result of the process [-ń → -n]. In Old Finnish, it must have remained productive and continued to contrast with the genitive as dative for a long period (see Hakulinen ibid. for the data). It later lost ground to the two directional cases.

There are at least two problems with this first approach. The notion that the Proto-Uralic lative must have been a palatalized *-ń, i.e. formally distinct from the hypothetical genitive *-n, is totally ad hoc. Vestiges of the "lative-dative" exist in all Uralic languages, and invariably allow reconstruction as non-palatal *-n. Furthermore, the structural genitive case in -n is totally absent from some branches of Uralic, in particular ancient branches like Ugric and Permian. This would mean that the structural genitive must have been lost there.

The second approach is much more convincing. It postulates that the two cases are historically related (Itkonen 1968:202), and that the structural genitive is the outcome of a long process of grammaticalization of the original Proto-Uralic lative (Korhonen 1996:222-224). This process is likely to have been as follows: Proto-Uralic had no genitive, but it did have a lative case marked by *-n, still visible in the Finnish illative -hVn and the Mari dative -lan, etc. This semantic case must have quickly acquired a new dative value which can be observed in many Finno-Ugric languages. It must still have been present in Old Finnish, where -n was often used like the modern allative, and has reached modern Finnish in the constructions described in part 3 of this paper.

At some stage, certainly after the Ugric and Permian branches had split off, the lative-dative must have begun to be applied to possessors, not only in the possessive construction (as today in Mordvin and Mari) but also in adnominal contexts. According to Korhonen (ibid.), "it is possible that the dative (or the lative in the dative function) started to be used also as an adnominal case in the possessive function if the possessivity was emphasized, or if the referent of the possessive attribute was animate, human, definite, or pronominal. Otherwise, the case of the possessive was the nominative. According to this scenario, the [evolution] would have been similar to that in Hungarian, where the dative with suffix -nak/-nek has also taken the function of a genitive."

In its adnominal use, the genitive of possession deriving from the lative-dative must ultimately have been desemanticized and become a simple dependency marker, i.e. a structural case. In this form, it now appears in an irreducible range of contexts in Finnish, as has been seen in part 2. In contrast, the uses presented in this section, which are relics of what the case marked by -n originally was before it became grammaticalized, are losing ground to the locative cases, as might be expected. This process has reached its end in the possessive construction, as Finnish uses only the adessive and not the -n case (see part 4).

There are two features that support the likelihood of the second scenario.

First of all, as Korhonen (ibid.) points out, the line of development [lative > dative > genitive] is quite natural from a typological perspective. In addition, the thesis that structural cases come from the grammaticalization of semantic ones, and these ultimately from adpositions, has been widely accepted for some time (see for example Lehmann 1985:304).

The possessive construction

In the Finnish possessive construction, the possessor, i.e. the entity whose personal ambit is said to include the entity designated as the thing possessed, is an NP bearing, not the case marker -n as in Mordvin and Mari, but the external static locative case, the adessive. When the possessor is inanimate, the adessive case is often replaced by the corresponding internal case, the inessive. This contrast is illustrated in (51).

( A superficial look at the Finnish possessive construction might lead to the assumption that it is nothing but a locative inversion. Rather than a transitive structure involving a verb 'have', this construction would then have an initial PP, the verb 'be', and a subject NP in the nominative. The realization of the P head, i.e. the case marking the possessor, would retain its locative sense, and the literal meaning of the construction would be 'at Soand-So is this'. In short, the possessive construction would thus be a subtype of existential sentence, and the structure of the sentences in (51) would be exactly the same as that of the ones in ( 52). This approach yields contradictory results for several manipulations. Let us look first at the manipulations in question and then try to provide an explanation for this situation.

Contra inversion

The first manipulation is pronominalizing the thing possessed. When the thing possessed is a noun, the fact that it takes nominative case proves nothing regarding its syntactic function (see § 2.6). On the other hand, the pronominal form is discriminatory as it must be accusative in this context.

On this basis, it can be concluded that the postverbal constituent is the direct object of a transitive head.

(53) Peka-lla on häne-t.

Pekka-ADE be.3SG she-ACC 'Pekka has her.'

By way of contrast, the inverted subject of an existential sentence can under no circumstances take the accusative. The nominative would be preferred, but the resulting sentence is not fully acceptable since the inverted subject of existential sentences is supposed to be indefinite, as in the example *kadulla on hänet vs. ?kadulla on hän '?there is he in the street'.

The second manipulation changes the order of the two constituents with respect to the verb. When applied to an existential sentence, this operation clearly changes the way in which the information is distributed (and the definiteness of the subject in translation), but the sentence has approximately the same meaning content. Thus, kadulla on auto 'there is a car in the street' contrasts with the non-existential sentence auto on kadulla At this point, the conclusion can be drawn that not only is the possessive construction syntactically transitive, but furthermore its possessive sense is not just the sum of the meaning of a static locative case ('at So-and-So') and the verb of existence ('is this'). Instead, the possessive interpretation arises from a specific relationship existing between these two constituents in a specific, apparently non-existential syntactic structure.

'
The third manipulation is more complex but equally telling. It is based on the contrast shown in (55). In (55a), the subject qualifies as antecedent of the possessive suffix on the locative complement. In (55b), a locative inversion, the initial locative complement cannot qualify as antecedent to the same suffix on the inverted subject, and the sentence is therefore illformed. The explanation for this contrast is the fact that Binding Principle A is violated in (55b). Given that possessive suffixes are anaphoric, they must be bound, i.e. c-commanded by a coreferent NP, in their binding domain.

(55a) respects this principle: the NP subject locally c-commands the anaphoric constituent. (55b), by contrast, violates it: since the NP in the locative case is embedded in a PP, it cannot c-command the anaphoric constituent.

(55)a. This being established, the manipulation consists of associating an anaphoric constituent with the thing possessed in the possessive construction. If this construction has the same structure as existential sentences, the possessor must also be embedded in a PP and the result should be ill-formed. Yet as observed by Nikanne (1993:81-83) confirmed by ( 56), the result is well-formed. This means that the possessor (the NP in the locative case) is not embedded in a PP.

(56)a. Kansalais-i-lla i on uusi pääministeri-nsä i .

citizen-PL-ADE be.3SG new.NOM prime.minister.NOM-PX.3SG

'The citizens i have their i new prime minister.' b. Joka kiele-ssä i on oma-t sana-nsa i .

each language-INE be.3SG own-PL.NOM word.PL.NOM-PX.3PL

'Each language i has its i own words.'

We can therefore conclude that in the Finnish possessive construction, not only does the postverbal constituent behave like the object of a nonexistential verb, but the preverbal constituent behaves like the subject of the sentence. The problem then is to determine why this subject is in the locative (see in the next section).

The fourth and last manipulation to be discussed here consists of trying to use the possessive construction in sentences which do not have a possessor in the strict sense. If this construction were a locative inversion, this would in all likelihood be impossible. Indeed, when a language without a verb 'have' uses such a strategy, it does so primarly to express a relationship of ownership, not simply of having in one's possession. This is in fact true of the other Uralic languages (Huumo and Inaba 1997:39-42;Inaba 1998:167-169). Remarkably, however, the Finnish possessive construction admits all the semantic functions of a verb 'have':

( The overall conclusion is thus that, while the forms used in the Finnish possessive construction have the appearance of a locative inversion, the results of submitting this construction to various manipulations suggest a

[SVO] structure where the verbal head has the semantic content of a verb 'have'.

Diachronically speaking, it is likely that the original structure was a locative inversion which has since been reanalyzed. It is a fairly common observation that syntactic relationships, given their immaterial nature, evolve more quickly than morphology, which is naturally conservative.

Should it therefore be assumed that morphology is synchronically unmotivated, that surface forms are only the remains of an earlier syntactic organization? Not necessarily: in the final section of this paper, I will propose an analysis of the possessive construction that synchronically resolves the contradictions set out above.

A transformational analysis

A fairly unsatisfactory way to account for the data synchronically would be to allow for two different homophonous verbs of the form olla, each as a separate lexical entry. One would be the verb 'be' and the other, the verb 'have'. The latter would have the inherent property of assigning locative case to its subject. Since this case is neither structural nor semantic, it will need to be assigned some third status, for instance lexical case, which immediately brings to mind the "quirky subjects" of Icelandic.

There is, however, another solution that is both more economical and more elegant. The starting point, taken from a paper by Benveniste (1966:187-207), is this: the verb 'have' is not or.iginal in the languages where it exists. 'Have' must rather be the spell-out of the verb 'be' plus a prepositional component. In other words, languages cannot be divided into those which have and those which do not have a verb 'have'. There are only languages which incorporate a P head into the verb 'be' (like English, French, etc.) and those which do not (Russian, Hindi, etc.). 18 Given this assumption, both situations might wisely be treated as resulting from syntactic transformations of a single initial structure (see [START_REF] Rouveret | Points de vue sur le verbe "être[END_REF] for references and a positive appraisal of this approach).

What should this structure look like? First of all, insofar as 'be' is an inherently impersonal verb, it can reasonably be assumed that as V head it selects a single argument in complement position. Moreover, this sole argument must surely be a small clause with a P-category head. The subject of this clause, i.e. the specifier of the PP, must be the NP expressing the thing possessed. The predicative P' constituent will then associate the NP expressing the possessor with the P head. How then does this approach help to explain the apparent contradictions in the Finnish data? To answer this question, it suffices to specify to the commonplace that semantic cases must be the manifestation of P heads. As Nikanne (1993:77-81) has clearly shown, this notion in no way implies that semantic cases must themselves be P heads cliticized on a noun. In Finnish, the position of these morphemes in the word and the phenomenon of case agreement immediately falsify this analysis. The hypothesis which best fits the data would be that "the semantic cases are assigned by empty Ps, each of which correspond[s] to exactly one locative case" (ibid.).

Clearly, if this hypothesis is correct, it provides an interesting solution to the problem stated in 4.1. Historically, the Finnish possessive construction must have been a locative inversion generated as in (59). Thus, the derivation for a sentence like Pekalla on auto 'Pekka has a car' must have been as in ( 61) where the P' constituent moves to the beginning of the sentence after the P head has assigned case to the possessor NP.

( Here the P head without phonetic content is incorporated into V after having assigned case to the possessor NP. This operation results in a transitive verb head (which can therefore assign accusative case) with the semantic content of a verb 'have' but no change of form since the P head is empty. Under these circumstances, the complement of P, the possessor NP, must now move to subject position in the sentence whence it can ccommand an anaphoric constituent on the NP for the thing possessed. Its case has no meaning; it is merely the effect of the dependency relationship formed with P at an earlier stage of the derivation.

The value of this kind of analysis is its ability to set up a coherent framework incorporating all the morphological, syntactic, and semantic properties of the Finnish possessive construction. No component is left out.

The cost lies in the use of theoretical tools, such as transformations and phonetically null categories, which may give the impression of being too ponderous. Still, this approach "saves the phenomena" just as well if not better than any other. The mere logical possibility that it might be correct should prevent some apparently immediate conclusions from being drawn, such as the assumption that case inflection progressively loses its motivation as syntax evolves.

Conclusion

Three major points have been put forward in the present paper: (1) the Finnish genitive case cannot be treated as the semantic case of possession, even in a loose sense. It has neither semantic content nor categorial representation; it merely "reflects" certain syntactic dependency relationships among constituents. It is in short a structural case.

(2) As a structural case, the Finnish genitive appears in a wide variety of environments which cannot be subsumed under a common denominator.

There are nevertheless a few contexts where apparently genitival forms are actually relics of a semantic lative-dative case which has been progressively grammaticalized into the genitive. (3) In the possessive construction, while other Uralic languages still use a semantic case with dative sense, Finnish requires a static (adessive or inessive) locative case. Although this construction is apparently a locative inversion, it can be shown to consist of a [SVO] sentence, and an explanatory hypothesis can be produced which accounts for all the data.

Many thanks to Raymond Boyd, Eva Havu, Jukka Havu, Johanna Kuningas, Alain

Rouveret, the two editors of this volume and the two anonymous reviewers for extremely helpful discussion and comments.

2

This paper focusses on official standard Finnish (yleiskieli, the "general language" of the Finnish nation). This standard form is based on the written language (kirjakieli) as developed and codified during the second half of the 19th century using features characteristic of the range of regional dialects. It differs in a number of ways from the standard spoken language (yleispuhekieli). See [START_REF] Sauvageot | L'élaboration de la langue finnoise[END_REF]; [START_REF] Havu | Une langue, une nation: contexte et corpus de codification du finnois moderne[END_REF].

3

It will be impossible to discuss all the issues raised by Table 1 in this paper, but closer attention will be given to a few points, particularly the status of the accusative. The genitive morpheme -n has several allomorphs including -den/-tten and -en on the plural root. With the essive, partitive, inessive, elative, adessive, ablative, and abessive cases, the choice of one or the other of these allomorphs will depend on the principle of vowel harmony. For the illative, the symbol V stands for the closest preceding vowel. The comitative and the instructive are non-productive cases.

4

The glossing in this paper follows the Leipzig Glossing Rules, with the following additions: ABE abessive, ADE adessive, DAT.GEN dative-genitive, ELA elative, ILL illative, INE inessive, PART partitive, PRET preterit, PX possessive suffix.

5

Note that in Finnish a DP can itself be selected by a D head, as in [DP tämä [DP Pekan [AP vanha [NP auto]]]] 'this old car of Pekka's'. For further details on the prenominal genitive in Finnish, see Hakulinen et al. (2004:566-573). For a more developed theoretical discussion of the conditions on genitive case assignment in the Finnish DP, see [START_REF] Brattico | Case distribution and nominalization[END_REF].

6

Another case would be the adjective pehmeä 'soft' in pumpulin pehmeä 'soft as cotton'.

It is nevertheless possible to account for this case by assuming an N-A compound noun; the components are indeed often written as a single word. Regarding the distribution and semantic value of the genitive in compound nouns, see Hakulinen et al. (2004:387-421).

It is interesting to note that the quantifiers paljon and vähän themselves come from a reanalysis of two former nouns in the genitive: paljo(+n) 'abundance, large amount' and vähä(+n) 'small amount'. It is uncertain whether they were assigned genitive case for use as preposed noun modifiers (see § 2.1) or, as Toivainen (1993:122-125) argues, as direct objects of verbs (see § 2.6).

8

In some cases, the adjective in -inen and its preposed genitive complement are reanalyzed as a compound: hyvännäköinen 'lovely' (< 'fine to be seen'), luonnonmukainen 'natural' (< 'matching nature'), samanikäinen 'of the same age', tietyntyyppinen 'of a certain type', etc. 9

See [START_REF] Manninen | Small phrase layers. A study of Finnish manner adverbials[END_REF] for a more detailed theoretical discussion of the conditions for assignment of the genitive in the Finnish PP.

10 There is no room here for even the briefest discussion of the properties of each of the many types of Finnish participial clauses. See [START_REF] Koskinen | Features and categories. Non-finite constructions in Finnish[END_REF] for a detailed theoretical approach to this question.

11 An anonymous reviewer rightly notes that the same construction is acceptable with some inergative verbs (uskon [lapsia leikkivän puistossa] 'I believe there are children playing in the park'), and even more rarely with some transitive verbs. See Itkonen (1985:64-65).

12 These are the essential facts. There are, however, complications in specific cases. (1) In interronegative sentences with injunctive import, the object may not take the partitive: eikö oteta lepohetki? 'let's take a break!' (< 'don't we take a break?'). (2) A small number of atelic verbs (e.g., omistaa 'own', sisältää 'contain', nähdä 'see', tietää 'know', muistaa 'remember'), often called "quasi-resultatives", do not assign the partitive to their objects:

omistan talon 'I own a house'. Conversely, some momentarily telic verbs govern the partitive unless they express the attainment of a resulting state: ammuin lintua 'I shot at the bird' (vs. ammuin linnun 'I shot the bird dead').

(3) Sometimes in dialogue, if it is clear from the context that a (telic) process is to be viewed as perfective, the partitive can be used, and is even more natural, on the object: -kirjoitin sen kirjeen 'I wrote that letter';kuinka kauan kirjoitit sitä? 'how long did it take you to write it?'; -kirjoitin sitä pari tuntia 'I wrote it in a couple of hours'. I thank Jukka Havu and one of the anonymous reviewers for calling my attention to the latter point.

13 See Holmberg (2010) for a theoretical discussion of the issues raised by the syntax of generic sentences.

14 In some varieties of Finnish (child language, eastern dialects), this animacy split would seem also to include given names and the nouns designating immediate kin. In Estonian, it affects only the first and second person pronouns (Mahieu 2008:76-82). 15 In this sentence, the partitive indicates non-attainment of the telos rather than the atelic nature of the VP as in (44a). If the telos had been attained, the object would have been in the genitive, and the modifier would have shifted to the inessive: Pekka luki kirjan tunnissa 'Pekka read the (whole) book in an hour'. 16 See Nikanne (1993:86): "According to the distribution, binding, and predication facts, the locative and other semantic cases seem to form PPs where the NP in the locative cases is embedded by some head. Because we are dealing with PPs, the head is probably a P." It must be stressed that the notion that semantic cases are the manifestation of P heads in no way implies that these cases are themselves Ps cliticized on nouns (see § 4.2).

17 In a transformational approach, the inherently impersonal nature of the verb olla 'be' would suggest that the NP expressing the thing possessed is not directly generated as subject of the sentence but rather as subject of the small clause selected by the verb olla, i.e.

as specifier of the P head. The deep structure of (49a) would then be [VP on [PP auto [P' P Pekan]]].

18 "'Have' is just 'be-at' turned around" (Benveniste 1966:199).

  obvious that the role expressed by an NP in the genitive may be ambiguous out of context or hard to define. In (3a), the genitive NP could be either Patient or Agent; in (3b), either Experiencer or Source; and in (3c), either Theme or Agent or Possessor. In (4), although the NP has only one possible role, it is not one of major roles exemplified in (

  to be determined exactly what the structural configuration is for the definition of the dependency relationship reflected by the prenominal genitive. According to

  eat-PTCP.(t)A Liisa.NOM go-PRET.3SG 'When Pekka had eaten, Liisa went away.' The structure in (29), where the participle marked by -mA-("third infinitive") has the abessive case -ttA, shows that circumstantial clauses are not always used to express temporal relationships. The subject nevertheless remains in the genitive. (29) Lähd-i-n [Peka-n huomaa-ma-tta mitään]. go-PRET-1SG Pekka-GEN notice-PTCP-ABE nothing 'I went away without Pekka noticing anything.'

  NOM) try-1SG remember-INF do-INF exercise-GEN 'I will try to remember to do the exercise.' to remember to do the exercise!'

  -one kilometre.NOM 'Now we will run one kilometre.'

  two people in the car.'

Table 1 :

 1 The traditional analysis of the Finnish case system

	GRAMMATICAL	nominative	Ø	basic form
	CASES			(nimentö)
		accusative	0. -t	object form
			1. -n	(kohdanto)
			2. Ø
		genitive	-n	possession
				(omanto)
	GENERAL	essive	-na ~ -nä	state
	LOCATIVE			(olento)
	CASES	partitive	-(t)a ~ -(t)ä	indefinite quantity
				(osanto)
		translative	-ksi	change of state
				(tulento)

  Thirdly, if the partitive is not required and there is no plural marker, it will suffice that the object be a human pronoun for it to take accusative -t. In all, only seven Finnish lexemes can take this case: the six (intrinsically human) personal pronouns and the human interrogative pronoun kuka

	(34)a. Pekka	tapaa	Virtase-t.
	Pekka.NOM meet.3SG Virtanen-PL.NOM
	'Pekka meets/will meet the Virtanens.'
	b. Pekka	rakens-i	hylly-t.
	Pekka.NOM build-PRET-3SG shelf-PL.NOM
	'Pekka built the shelves.'
	'who?'.
	(35)a. Kene-t	Pekka	tapas-i?
	who-ACC	Pekka.NOM meet-PRET.3SG
	'Who Pekka did meet?'
	b. Pekka	löys-i	minu-t.
	Pekka.NOM	find-PRET.3SG me-ACC
	'Pekka found me.'
	c. Tuo	heidä-t	tänne!
	bring.IMP.2SG	they-ACC	here
	'Bring them here!'
	suggests.

  First of all, the NP can be deleted, as in on kuuma '[the weather] is hot', häntä käy sääliksi 'he is a sorry sight to see, in a pitiful state', or hyvin kävi 'it went well'. It can thus be treated as a predicate modifier. In addition, it is

	b. Minu-n	tule-e	sääli	/	ikävä	hän-tä.
	I-DAT.GEN come-3SG pity.NOM		sorrow.NOM he-PART
	'I feel sorry for him. / I miss him.'
	c. Liisa-n		käv-i	hyvin / hassusti.
	Liisa-DAT.GEN	go-PRET.3SG	well	funnily
	'Things went well for Liisa. / Liisa was unlucky.'
	48)a. Peka-n		ol-i	jano	/ kuuma.
	Pekka-DAT.GEN be-PRET.3SG	thirst.NOM	hot.NOM
	'Pekka was thirsty / hot.'

  and appears sentence-initially at a distance from the NP expressing the thing possessed. The following examples are taken fromHuumo and Inaba (ibid.).

	b. Minu-n	kuol-i		kissa.
	I-DAT.GEN	die-PRET.3SG	cat.NOM
	'My cat died.' (dialectal)
	c. Puhuja-n		men-i-vät		paperi-t	sekaisin.
	Liisa-DAT.GEN go-PRET-3PL paper-PL.NOM	mixed
	'The speaker' papers got mixed up.' (dialectal)
	d. Elmeri-n		putos-i		lompakko	järve-en.
	Elmer-DAT.GEN	fall-PRET.3SG wallet.NOM lake-ILL
	'Elmer's wallet fell into the lake.' (dialectal)
	(50)a. Peka-n		on	auto	rikki.
	Pekka-DAT.GEN be.3SG car.NOM	broken
	'Pekka's car is broken.' (dialectal)

  the car is in the street'. If the possessive construction is a kind of existential sentence, it should behave in the same way, i.e. there should be little to distinguish Pekalla on auto 'Pekka has a car' from another sentence, auto on Pekalla, meaning something like 'the car is Pekka's'. This is not the case,

	(54)a. Auto	on	Peka-lla.
	car.NOM	be.3SG Pekka-ADE
	'the car is at Pekka's place'
	b. Kirja	on	minu-lla.
	book.NOM be.3SG	me-ADE
	'The book is with me.'
	however. Changing the order completely changes the meaning of the
	sentence, which no longer expresses a possessive relationship:

  )a. … [ VP on [ PP auto [ P' P Pekka-]]]

	d. … [ VP on-P i [ PP auto [ P' t i Peka-lla]]]
	e. [ NP Peka-lla] j [ VP on-P i [ PP auto t i t j ]]

b. … [ VP on [ PP auto [ P' P Peka-lla]]] c. … [ VP on [ PP auto [ P' P Peka-lla]]] d. [ P' P Peka-lla] i [ VP on [ PP auto t i ]]

At some point, however, this construction must have been reanalyzed by speakers without any change in the surface form of the utterance, so that a

[SVO] sentence was generated as in (60). This is why Pekalla on auto 'Pekka has a car' appears today to be the outcome of the syntactic derivation in (62). (62)a. … [ VP on [ PP auto [ P' P Pekka-]]] b. … [ VP on [ PP auto [ P' P Peka-lla]]] c. … [ VP on [ PP auto [ P' P Peka-lla]]]


Christian A J Vosshenrich

James P Di

Developmental Programming of Natural Killer and Innate Lymphoid Cells

ILCs include NK cells, nuocytes/NH cells, LTi cells and NKp46+ IL--22+ cells.

ILC rapidly produce cytokines (IL--5, --13, --17A, --22, IFN--γ) required for immunity to infection

Introduction

ILC represent an expanding family of innate effector cells that have critical roles in the generation and maintenance of immunity, especially at mucosal surfaces. Natural Killer (NK) cells can be considered as the founding member of the ILC family, having immunological characteristics that include a lymphoid developmental origin, absence of clonally rearranging antigen receptors, and an activation profile that includes T--bet (Tbx21)--regulated prompt cytokine production (IFN--γ) but generally does not result in long--lasting immunological memory. We know much about the molecular determinants that guide NK cell development and generate these potent innate effector cells in both mouse and man (reviewed in [START_REF] Santo | Natural killer cell developmental pathways: a question of balance[END_REF][START_REF] Blom | Development of human lymphoid cells[END_REF][START_REF] Huntington | Developmental pathways that generate natural-killer-cell diversity in mice and humans[END_REF]). The second ILC family member identified was the Lymphoid Tissue--inducer (LTi) cell that expresses the retinoic acid receptor--related orphan receptor γt (RORγt) and has a determinant role in lymphoid tissue formation during fetal and adult life. In adult mice, RORγt--expressing LTi cells can also promptly produce IL--17 and IL--22 following activation with cytokines such as IL--1β and IL--23 suggesting that LTi cells have additional roles in immune defense (reviewed in [START_REF] Cherrier | Development and function of intestinal innate lymphoid cells[END_REF]).

More recently, other IL--22--producing RORγt + ILC that express natural cytotoxicity receptors have been described in mucosal tissues from mice and man (reviewed in [START_REF] Colonna | Interleukin-22-producing natural killer cells and lymphoid tissue inducer-like cells in mucosal immunity[END_REF]).

Finally, novel ILC subsets that have the capacity to produce high levels of the Th2 cytokines IL--5 and IL--13 were discovered and variably named natural helper cells, nuocytes or innate helper cells (reviewed in [START_REF] Koyasu | Natural helper cells: a new player in the innate immune response against helminth infection[END_REF]). All of these different ILC subsets have common characteristics of lymphoid morphology, independence from the recombinase machinery, and a common developmental dependence for the transcriptional repressor Id2 and for γc cytokines (reviewed in [START_REF] Spits | The expanding family of innate lymphoid cells: regulators and effectors of immunity and tissue remodeling[END_REF]). Recently, a standardized nomenclature was proposed for describing these functionally different ILC subsets: group 1 ILC include NK and other ILC that produce IFNγ and are dependent on T--bet for their development and function; group 2 ILC comprise ILC that produce type 2 cytokines (IL--4, IL--5, IL--9 and IL--13) and are dependent on Gata3 and RORα for their development and function; and group 3 ILC subtypes that produce IL--17 and/or IL--22 and depend on RORγt for their development and function (reviewed in [••8]). This framework clusters cells based primarily on functional characteristics but also on signature transcription factors that drive their cytokine production. Still, functional plasticity is characterized by modifications in cytokine secretion profiles that can result from changes in transcription factor expression. As such, an inter--conversion between different ILC subsets may occur during immune responses or following ILC activation. Nevertheless, this ILC nomenclature may be useful to help understand and define the general principles that guide the development of ILC subsets from hematopoietic precursors.

While these new ILC subsets have generated considerable interest and excitement within the scientific community, remarkable advances in our understanding of the development and functional differentiation of NK cells have as well been recently reported. In this review, we will discuss our current knowledge on the development of NK cells from early hematopoietic precursors in the mouse, focusing on the transcription factors that orchestrate this process and discuss how these developmental pathways may also provide insights in to the developmental biology of other ILC subsets.

A Refined Model for Bone Marrow NK cell Development in the mouse

During hematopoiesis hematopoietic stem cells give rise to progressively more restricted precursor populations that generate lymphoid restricted common lymphoid progenitor (CLP) as well as precursors with restricted myeloid potential (CMP). In the mouse, CLP possess precursor potential for T, B, and NK cell at the single cell level [START_REF] Kondo | Identification of clonogenic common lymphoid progenitors in mouse bone marrow[END_REF], and can give rise to ILC2 at the population [• •10,11] and single cell level (Klein Wolterink and Di Santo, submitted). CLP are lineage marker (Lin --) negative and express of low levels of c--Kit (CD117), Sca1 (Ly6A/E), IL7Rα (CD127) and Flk2/Flt3 (CD135). A decade ago, we reported identification of the earliest murine NK cell committed precursor (NKP) residing within a Lin --population expressing the IL2/15Rβ chain (CD122) [START_REF] Rosmaraki | Identification of committed NK cell progenitors in adult murine bone marrow[END_REF]. The developmental potential of this population was limited to NK cells, but only gave rise to NK cells in vitro with a frequency of one in ten, indicating that the NKP subset was not functionally homogeneous. The fact that only 10% of phenotypically defined NKP had true NK precursor potential meant that mutations strongly affecting NKP development could go unnoticed, while normal NKP numbers might still be present in mice lacking almost all phenotypically defined NKPs. As such, it was difficult to reach definitive conclusions regarding factors that influence NKP homeostasis. While the identification of NKP was an important advance, the pathway between CLP and NKP was still poorly defined.

Recently, two reports have further refined the phenotypic definition of NKP and also provided evidence for an additional NK committed precursor populations that is upstream of NKP. Fathman et al. used in vitro assays and in vivo adoptive transfer experiments to identify NKP [• •13]. They found that all NK cell potential resided in a Lin -- CD27 + CD244 + fraction that included several CD127 + cell subsets. As expected, this included CD135 + CLP, but also included two additional NK cell restricted subsets. Both of these subsets lacked CD135, but they differentially expressed CD122: the CD122 -- subset was designated a pre--NKP, while the second CD122 + subset likely corresponds to a refined definition of our previously identified NKP subset, termed refined NKP (rNKP), that also was shown to contain CD122 + CD127 + cells [START_REF] Rosmaraki | Identification of committed NK cell progenitors in adult murine bone marrow[END_REF][START_REF] Fathman | Identification of the earliest natural killer cell-committed progenitor in murine bone marrow[END_REF][START_REF] Vosshenrich | Roles for common cytokine receptor gamma-chain-dependent cytokines in the generation, differentiation, and maturation of NK cell precursors and peripheral NK cells in vivo[END_REF]. Together, this report would suggest a model where the transition from CLP to NKP that involves sequential down--regulation of CD135, up--regulation of CD122, followed by down--regulation of CD127 (Figure 1). This refined model of early NK cell development should provide a means to further dissect the transcriptional program that accompanies NK cell specification and commitment in the mouse. Along these lines, analysis of Ets--1 mutant mice demonstrated a clear defect in pre--NKP and rNKP cells [• •15], while analysis of Rag2 x γc DKO mice showed a decrease in the CD122 + CD127 + NKP subset but not in its immediate CD122 --CD127 + precursor (Brauner, Vosshenrich and Di Santo; unpublished results).

In a second report, Carotta et al. used an Id2 reporter mouse to identify early NK cell precursor cells in adult bone marrow. They also identified NK cell potential (using in vitro assays on OP9 stromal cells) amongst Lin --CD127 + cell populations that lacked CD135 (i.e. were not CLP) but differentially expressed CD117 and Sca1 [••16]. Both populations lacked CD122 expression but expressed low levels of NKG2D, previously identified on a subset of NKP [14,••16] and were therefore different from previously identified NKP; these cells were referred to as pre--pro NK cells and likely correspond to the pre--NKP described by Fathman [16]. Interestingly, these pre--pro NK cells also appear to phenotypically overlap with a recently identified CD127 + Sca1 hi ILC2 precursor population that also expresses CD25 and T1/ST2

Transcription factors driving generation of NK cell precursors (NKP)

While NKP represent a lymphoid precursor stage that is distinct from T and B cell precursors and has demonstrated NK cell potential, it is not yet shown whether NKP lack potential for other ILC lineages. Similarly, pre--NKP or pre--pro NKP have likewise been shown to give rise to NK cells, but their capacity to generate other ILC subsets has not been excluded. Nevertheless, several TF have been identified that are critical for the development of multiple ILC subsets (including NK cells) but do not overtly affect T or B cell precursor activity. The prime example is that of the transcriptional repressor Id2 that acts (like all Id proteins) to counteract E box TF (E2A, E2--2, HEB) activity. In the absence of Id2, very few NK cells develop and residual cells display maturation defects [23,[START_REF] Boos | Mature natural killer cell and lymphoid tissue-inducing cell development requires Id2-mediated suppression of E protein activity[END_REF]. Importantly, ILC2 and ILC3 subsets (LTi cells, IL--22--producing NKp46 + cells) are equally dependent on Id2 activity for their development [START_REF] Spits | The expanding family of innate lymphoid cells: regulators and effectors of immunity and tissue remodeling[END_REF][START_REF] Spits | Innate lymphoid cells -a proposal for uniform nomenclature[END_REF]. This would place Id2 at an early stage of ILC development, potentially involved in the generation of a common ILC precursor. While earlier analysis of NKP in Id2 --/--mice suggested a normal development of NKP [START_REF] Boos | Mature natural killer cell and lymphoid tissue-inducing cell development requires Id2-mediated suppression of E protein activity[END_REF], a further analysis of rNKP as well as pre--NKP/pre--pro NKP cells in these mice should also be performed. This would provide interesting information on the role of Id2 repressor activity in early ILC precursor development.

Thymocyte selection--associated high mobility group box (Tox) is a second example of a TF that predominantly affects ILC but not T and B cell commitment. Tox deficiency ablates NK cell development and in addition, strongly reduces generation of group ILC3, especially LTi cells, resulting in decreased lymph node and Peyer's patch formation [START_REF] Aliahmad | Shared dependence on the DNA-binding factor TOX for the development of lymphoid tissue-inducer cell and NK cell lineages[END_REF]. Whether Tox is required for the generation of ILC2 or other ILC3 subsets (IL--22--producing NKp46 + cells) is not known. Moreover, the mechanism by which Tox promotes the development of NK and LTi cells is poorly understood and the analysis of pre--NKP/pre--pro NKP cells and rNKP in Tox --/--mice has not been reported.

Several TF affect NK cell generation through a reduction in multiple lymphoid precursor populations; these may include CLP or their downstream committed The TF Tbx21 (encoding T--bet) was initially described as a 'master regulator' of Th1 differentiation and also shown to control IFN--γ production in various T cell subsets.

The initial analysis of NK cell differentiation in T--bet KO mice found several defects [START_REF] Townsend | T-bet regulates the terminal maturation and homeostasis of NK and Valpha14i NKT cells[END_REF],

although most appeared related to the homeostasis of mature NK cells that may be related to regulation of receptors for S1P5 [START_REF] Jenne | T-bet-dependent S1P5 expression in NK cells promotes egress from lymph nodes and bone marrow[END_REF]. Tbx21 is a member of a larger family of TF that also includes the broadly expressed Eomesodermin [START_REF] Naiche | T-box genes in vertebrate development[END_REF]. Functional redundancy between T--box TF has been demonstrated in several cell types and T--bet/Eomes are co-expressed in CD8 + T cells where they have overlapping/redundant roles [START_REF] Intlekofer | Effector and memory CD8+ T cell fate coupled by T-bet and eomesodermin[END_REF][START_REF] Cruz-Guilloty | Runx3 and T-box proteins cooperate to establish the transcriptional program of effector CTLs[END_REF].

Recently The effects of Gata3 ablation on NK cell development include an ablation of hepatic and CD127 + thymic NK cells and a defect in BM and splenic NK cell maturation; the latter involves a reduction in CD11b and CD43 expression on mature NK cells and a decrease in their IFN--γ producing capacity [START_REF] Samson | GATA-3 promotes maturation, IFN-gamma production, and liver-specific homing of NK cells[END_REF][START_REF] Vosshenrich | A thymic pathway of mouse natural killer cell development characterized by expression of GATA-3 and CD127[END_REF]. The loss of IFN--γ was unexpected and indicated that Gata3 could regulate T--bet in NK cells [START_REF] Samson | GATA-3 promotes maturation, IFN-gamma production, and liver-specific homing of NK cells[END_REF], although a role for Gata3-mediated control of Eomes expression can not be ruled out (see below)

Transcription factors driving NK cell maturation

Several TF have been found to impact on the differentiation at later stages of NK cell differentiation. Of these, Eomes appears as a critical factor required for completion of NK cell maturation following DX5 acquisition (stage 4; Figure 1). Interestingly, NK cells lacking Eomes, T--bet or bearing temporal deletions in both genes retained significant functional capacities [• •41] indicating that Eomes/T--bet--independent regulation of NK cell cytotoxicity and cytokine production. In contrast, inducible deletion of Eomes in DX5 + mature NK cells resulted in the appearance of DX5 --NK cells that co--expressed TRAIL; this demonstrates that Eomes is actively required in order to maintain the mature NK cell phenotype. Moreover, these DX5 --NK cells preferentially accumulated in the liver, suggesting that this tissue provides an environment that favors homeostasis of this NK cell subset.

Helios, another zinc--finger TF and member of the Ikaros family is abundantly expressed in immature CD11b --NK cells [START_REF] Narni-Mancinelli | Tuning of natural killer cell reactivity by NKp46 and Helios calibrates T cell responses[END_REF]. Helios over--expression has been associated

with hyper--activated mature NK cells mice carrying 'Noe' mutations in the Ncr1 locus that ablate NKp46 cell surface expression [START_REF] Narni-Mancinelli | Tuning of natural killer cell reactivity by NKp46 and Helios calibrates T cell responses[END_REF]. The proposed link between the absence of cell surface NKp46 availability and the up--regulation of Helios transcript that lead to NK cell hyperactivity remains unclear.

Additional TF have been implicated in the final differentiation of NK cells. In Blimp1 (encoded at Prdm1) acts as transcriptional repressor that regulates the terminal differentiation of B and T cells (reviewed in [START_REF] Nutt | The genetic network controlling plasma cell differentiation[END_REF][START_REF] Xin | Blimp1: driving terminal differentiation to a T[END_REF]). In NK cells, Blimp1

regulates the frequency of terminally differentiated CD27 --CD11b + NK cells. Like Ets--1-deficient NK cells, Blimp1--deficient NK cells are hyper--responsive to IL--15 stimulation.

Blimp1--deficiency might also impact on NK trafficking as Blimp1 was shown to regulate chemokine receptor expression in T cells (reviewed in [START_REF] Xin | Blimp1: driving terminal differentiation to a T[END_REF]). While Blimp1--knockdown in human NK cells resulted in increased IFN--γ production, murine NK cells lacking Blimp1 do not show alterations in IFN--γ production [START_REF] Smith | PRDM1/Blimp-1 controls effector cytokine production in human NK cells[END_REF][START_REF] Kallies | A role for Blimp1 in the transcriptional network controlling natural killer cell maturation[END_REF]. The reason for this species-specific difference is not known but could be related to the presence of Hobit (homolog of Blimp1 in T cells, Znf683) a related TF that is highly expressed in NKT cells [••57].

While Hobit is apparently not expressed in resting wild--type NK cells, its expression (up-regulation?) in the absence Blimp1 could contribute to the attenuated phenotype of Blimp1--deficient NK cells. As such, Hobit might sustain IFN--γ production and cytotoxicity in Prdm1 --/--NK cells.

An extended model for NK cell and other ILC subset development

We In the not so distant past, the transcriptional map of NK cell development consisted of a straight line between the hematopoietic stem cell and the mature NK cell with no defining directional markers. We now have a detailed phenotypic model for the emergence of mature NK cells from hematopoietic precursors that proposes a step--by-step process of commitment to the NK lineage, education to self MHC, and maturation and acquisition of NK cell effector functions. Several key TF that guide this process have been revealed and provide a framework for a better understanding of NK cell differentiation in particular, and of ILC development in general.

  [17]. Whether the pre--pro NK cell populations described by Carotta et al. harbors ILC2 potential or whether the putative ILC2 precursor described by Halim et al. also contains NK cell potential has not been studied [••16,••17]. Potentially, these populations might represent an interface between ILC1 and ILC2 development.

Figure 1 Transcriptional

 1 Figure 1

  progenitors for the B, T, NK and possibly other ILC lineages. This group of TF includes Ikaros and Gfi1 that compromise CLP and more restricted lymphoid precursors ([START_REF] Wang | Selective defects in the development of the fetal and adult lymphoid system in mice with an Ikaros null mutation[END_REF][START_REF] Zeng | Transcription factor Gfi1 regulates self-renewal and engraftment of hematopoietic stem cells[END_REF], Klein Wolterink and Di Santo; unpublished). Another TF that may fall into this category is Ets--1 that has roles in B and T cell lineage development, and also in NK commitment, as recently shown byRamirez et al. [••15]. Interestingly, Ets--1--deficiency did not affect CLP numbers but resulted in the reduction of NK cell committed pre--NKP and rNKP populations that ultimately translated to a 5--10 fold reduction in mature NK cells [••15].Ets--1 targets in mature NK cells include Idb2 (coding for Id2), Tbx21 (T--bet) and Il2rb (CD122), although these targets were not confirmed in NKP. Low levels of Ets--1 are already detectable in LMPP and CLP[START_REF] Dias | E2A proteins promote development of lymphoid-primed multipotent progenitors[END_REF] and therefore precede that of Id2[••15]. This observation suggests that Ets--1 might be upstream of Id2 in the NK lineage--defining program. Still, the NK cell deficiency in Id2 --/--mice is stronger than that of Ets--1 --/--mice that might be due to the fact that Id2 levels are reduced but not ablated in absence of Ets--1. Alternatively, other Ets--family members may compensate in the absence of Ets--1 to maintain Id2 levels. Since Ets--1 controls CD122 mRNA expression in NK cells [••15] and regulates CD127 expression in peripheral T cells[START_REF] Grenningloh | Ets-1 Maintains IL-7 Receptor Expression in Peripheral T Cells[END_REF], Ets--1 may have additional roles in the development of other ILC groups.Transcription factors driving immature NK cells development from NKPBeyond the TF that determine the initial steps in NKP and (possibly) other ILC precursor generation, several TF have been identified that play critical roles in the development of 'immature' NK cells in the bone marrow and other tissues. Immature NK cells can be defined as CD3 --CD122 + NK1.1 + DX5 --and are thought to represent a transient developmental intermediate that can further differentiate giving rise to mature NK cells that circulate in the blood and are detected throughout the organism.One critical TF require for iNK generation is Nfil3/E4bp4, a transcriptional activator/repressor that was initially identified as protein binding the ATF site in the adenovirus E4 promoter[START_REF] Cowell | Transcriptional repression by a novel member of the bZIP family of transcription factors[END_REF]. While Nfil3 is strongly expressed in mature NK cells and their precursors, it is not an NK cell--specific TF, and is expressed in T, B and dendritic cell (DC) subsets, where it regulates production of Th2 cytokines IL--5, IL--10, IL--13 in T cells, IL--12 production from macrophages and TLR--3 induced IL--12 production from CD8α + cDC and is involved in the regulation of Ig germ--line epsilon expression affecting subsequent class switch to IgE (reviewed in[START_REF] Male | E4BP4: an unexpected player in the immune response[END_REF]). In the absence of Nfil3, NK cell homeostasis is strongly reduced and NK cell differentiation is blocked at the iNK cell stage [••[START_REF] Gascoyne | The basic leucine zipper transcription factor E4BP4 is essential for natural killer cell development[END_REF][START_REF] Kamizono | Nfil3/E4bp4 is required for the development and maturation of NK cells in vivo[END_REF][34]. While downstream targets of Nfil3 are not clearly defined, residual levels of Gata3 and Id2 were reduced in Nfil3--deficient lymphoid precursors, suggesting that Nfil3 may regulate these TFs. Whether Nfil3 KO mice have defects in the generation of other ILC subsets has not been reported, although preliminary data indicated normal LN development[START_REF] Santo | A defining factor for natural killer cell development[END_REF] and presence of IL--22 + NKp46 + intestinal ILC3 (Xu, Serafini and Di Santo, unpublished) ruling out a role for Nfil3 in controlling differentiation of all ILC3 subsets. These observations would further suggest that Nfil3 does not regulate Id2 in a global fashion but would rather play a more selective role in development of NK cells and perhaps other IFN--γ--producing ILC1.

  , an interesting study of the specific versus redundant role of T--bet and Eomes in NK cell differentiation was reported [••41]. While T--bet was expressed throughout NK cell development (in iNK and mNK in newborn and adult mice), Eomes expression was more restricted and was clearly absent in DX5 --iNK cells that could be found throughout the body but were conspicuously enriched in the liver [••41]. Previous studies have characterized these DX5 --hepatic NK cells and using adoptive transfer experiments showed that they could give rise to functionally mature NK cells (with up-regulation of DX5 and acquisition of MHC class I--specific Ly49 receptors and effector functions) [42]. In the absence of Eomes, NK cell development was blocked at the DX5 -- iNK cell stage, clearly indicating a role for Eomes in terminal NK cell maturation. The residual Eomes--iNK cells expressed T--bet and the combined deletion of T--bet and Eomes ablated development of all NK cells beyond the NKP stage [••41]. Further analysis of Tbx21 --/--mice demonstrated a defect in the generation of iNK cells, placing T-bet as a critical regulator of the NKP --> iNK transition (Figure 2). The transcriptional targets of T--bet at this stage are not known but may include the NK cell activating receptors Ncr1 and Cd161 (encoding NKp46 and NK1.1, respectively) [••41] that may further complicate the unambiguous identification of T--bet--deficient iNK cells. The TF Gata3 has multiple stage--dependent roles in T--cell development and has also been shown to control multiple aspects of NK cell subset differentiation and more recently, ILC2 differentiation ([43-••47], RKW submitted). Gata3 is a zinc--finger TF that binds a consensus (A/T)GATA(A/G) motif and can deliver activating or repressive transcriptional signals. The critical targets of Gata3 in early lymphoid precursors are not fully defined. In immature thymocytes, Gata3 binds hundreds of distinct loci for which the functional implications are not clear [••22]. Interestingly, one predominant Gata3 target is the retinoic acid receptor RORα that has multiple roles in hematopoietic and non--hematopoietic lineages. The similar loss of ILC2 in Gata3 and RORα deficiencies [••10, ••17, ••46, ••47] suggest that these two TF operate in a sequential fashion (Gata3 --> RORα).

  . The selective impact of Gata3 deletion on thymic versus BM NK cell homeostasis suggests that these two developmental pathways are distinct. Concerning thymic NK cell development, we hypothesize that Gata3 is upregulated in lymphoid precursors that enter the thymic microenvironment; this may involve a Notch--dependent signal, although this does not appear to be essential [•48]. Gata3--expressing lymphoid intrathymic precursors primarily generate T cells, but can give rise to NK cells and ILC2 [••10,44,49]. Gata3 + NK cells that develop within the thymus differ phenotypically and functionally from mature splenic NK cells (higher IFN--γ, CD16 --, few Ly49 receptors); these different attributes may be transiently imposed by the thymic microenvironment. Along these lines, adoptive transfer of thymic NK cells to Rag/γc recipients allows for their further maturation with acquisition of Ly49 receptor repertoires and loss of CD127 (Vosshenrich, Di Santo; unpublished results). Concerning hepatic NK cells, it is tempting to speculate that functions of Gata3, Eomes and T--bet may again be intertwined. In the absence of T--bet, hepatic NK cells, especially the immature DX5 --subset, are decreased in number. The DX5 + subset is also affected but possibly 'rescued' due to Eomes expression [••41] either through local generation of DX5 + NK cells in the liver or from influx of DX5 + NK cells from the bone marrow. In contrast, Gata3 deficiency strongly reduces all hepatic NK cell subsets. While the mechanism behind this defect is not understood, one possibility is that Gata3 controls not only T--bet but also Eomes expression in hepatic NK cells. Further experiments are required to validate this hypothesis.

  addition to its role in the transition from NKP --> iNK cells, Ets--1 also regulates homeostasis of mature NK cells. In the absence of Ets--1, mature NK cells have an activated phenotype with enhanced Helios expression and a hyper--responsiveness to IL--15 [••15]. Runx3 is highly expressed throughout NK cell development and targets of Runx3 include NKp46 and possibly CD122 and members of the Ly49 family [51,52].

  would like to propose a model that takes into account these different observations thus far discussed. It is now documented that CLP can give rise to B, T, NK and ILC2 in vivo; whether CLP are precursors for ILC3 subsets needs to be shown. In contrast, dedicated precursors for ILC subsets that are downstream of CLP are less clearly defined in adult mice. Ample evidence exists for the presence of a NKP that has NK lineage potential, but the existence of a 'common ILC precursor' (ILCp) that can subsequently give rise at the clonal level to ILC1, ILC2 and ILC3 subsets has been proposed [••8] but not clearly documented. Up--regulation of Id2 in CLP would provide a mechanism to restrict CLP to the non--T, non--B cell fate and would be necessary for subsequent ILC subset differentiation (Figure2). If such an ILCp exists, it would then undergo additional transcriptional changes to selectively differentiate towards individual ILC sublineages. Previous studies have identified Notch signals as important for ILC2 and lymphoid--tissue inducer (LTi, an ILC3 subset) cell generation [••58-••60] from multipotent lymphoid precursors. In contrast, NK cells do not apparently require Notch signals [•48,61] to develop from CLP. Thus Notch signals could provide an early mechanism to initiate ILC subset differentiation from ILCp. In this model, ILC2 and ILC3 (at least the LTi cell subset) would more closely resemble T cells in their requirements for Notch. Potential downstream targets for Notch in early T cells include Tcf1, Bcl11b and Gata3; the latter could have a dominant role in the initiation of ILC2 specification and its completion via RORα. A similar mechanism could be operative in the generation of RORγt + ILC3 subsets. Still, sustained Notch signaling appears detrimental for ILC3 homeostasis as it favors T cell development at the expense of ILC3 precursors [••60]. In contrast, these same factors (Notch, Gata3, RORα, RORγt) have little or no apparent impact on 'mainstream' NK cell development in the bone marrow. In contrast, two TF have critical roles at the earliest stages: Nfil3 and T--bet. While these two TF have no obvious ability to interact physically or functionally, their coincident expression and critical roles in the generation of iNK from NKP are clearly demonstrated. Up--regulation of T--bet and Nfil3 in CLP and/or ILCp are likely to be critical in the early stages of commitment to the ILC1 lineage as NKP are generated. What mechanisms might control Nfil3 and/or T--bet expression? Although clear answers are not yet available, there are several hypotheses. First, as yet unidentified TF(s) may link Id2 expression (and loss of E--box activity) with up--regulation of Nfil3 or T--bet. These might be identified through comparison of TF profiles between CLP and pre--NKP. Alternatively, the absence of Notch signaling in ILC precursors may be associated with default expression of Nfil3 or T--bet that can then be stably reinforced by extrinsic signals (cytokines).

Figure 1 .

 1 Figure 1. Stages of NK cell development from CLP in the mouse

Figure 2 .

 2 Figure 2. Schematic view of NK development in the bone marrow and liver and comparison with ILC2 and ILC3 development in the mouse

Acknowledgements

This work was supported by institutional support grants from the Institut Pasteur, Inserm, Ligue National Contre le Cancer and the ANR through the Program 'Blanc' (Gut_ILC).