Reviews in Endocrine & Metabolic Disorders 2002;3:55±63 # 2002 Kluwer Academic Publishers. Manufactured in The Netherlands.
The Ovarian Gonadotropin Receptors in Health and Disease Paul A. Fowler and Ilpo T. Huhtaniemi Department of Obstetrics and Gynaecology, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
Key Words. gonadotropin receptors, luteinizing hormone, folliclestimulating hormone, hypogonodism, precocious puberty, infertility
Introduction The actions of the two gonadotropins, luteinizing hormone (LH) and follicle-stimulating hormone (FSH), are pivotal for normal ovarian function. In both cases these effects are exerted on their target cells thorough speci®c G-protein associated seven transmembrane domain receptors [1±3]. A third pituitary hormone, prolactin (PRL), can also be considered a gonadotropin in some species, due to its direct gonadal action. However, such effects have not been unequivocally demonstrated in humans. The identi®cation of the genes of gonadotropin receptors (R) has made it possible to explore further details in the physiology of their action as well as to unravel the molecular pathogenesis of speci®c types of gonadal dysfunction, caused either by activating or inactivating mutations of gonadotropin receptors. Phenotypic consequences of the human mutations have been corroborated using genetically modi®ed mouse models, i.e., transgenic mice overexpressing LH or FSH, or knockouts of the FSH and LH ligand and receptor genes. The present review summarizes brie¯y the current concepts about physiological function of ovarian gonadotropin receptors, as well as the currently available information on the human gonadotropin receptor mutations as well as the relevant animal models for diseases affecting the function of gonadotropin receptors.
Normal Function of Gonadotropin Receptors Gonadotropin receptor structure and signaling LH (and hCG) and FSH operate through cell-surface Gprotein-coupled receptors with seven transmembrane domains, and the cDNAs of their human forms were cloned early in the last decade [4,5]. Both receptors are unique in having a large extracellular domain which is involved in hormone recognition and binding [6,7]. They also have leucine-rich repeat motifs in this domain with divergent sequences which are important for hormone speci®city [8]. The FSHR and LHR genes consist of 10
and 11 exons respectively: the ®rst 9 and 10 exons encoding the extracellular domains while exons 10 (FSHR) and 11 (LHR) encode the transmembrane and intracellular domains [1,2]. Structural studies of the LHR have been hampered by dif®culties in expressing high af®nity receptors, but the recent development of a soluble hCG±LHR complex [9] suggests that a crystalization strategy may be within reach. Detailed understanding of the LHR structure would have two bene®ts. First, improved understanding of the receptor structure±function relationships and second, the possibility that speci®c LH agonists and antagonists could be developed. These would have tremendous clinical potential. Both LHR and FSHR [10] mRNAs undergo complex alternative splicing, but the functional signi®cance of these phenomena remains uncertain. The PRLR is a member of the cytokine receptor superfamily, and it exists in at least three differentially spliced rodent forms: long, intermediate and short [11], complicated by the occurrence of multiple mRNA transcripts [12]. The PRLR is a transmembrane protein with three structural motifs in the intracellular domain [13] and functions through dimerization of two receptor molecules binding to different ligand sites on PRL itself [14]. This leads to activation of the tyrosine JAK2 kinase and signal transducers and activators of transcription (STAT) proteins, with the receptor therefore acting via the JAKSTAT pathway. MAP kinase and other second messengers are also involved in PRLR signal transduction [15]. Gonadotropin receptor expression in the ovary Ovarian expression of LHR, FSHR and PRLR is summarized in Table 1. The ontogeny of FSHR expression is striking, with no expression in primordial human follicles, expression in 33% of primary and two-layer follicles and 100% expression in multilaminar follicles [16]. This re¯ects the expression of FSHR in growing follicles rather than in the passive primordial reserve, especially since the binding activity of FSHR does not change during the menstrual cycle [17]. To date granulosa cells are the only ovarian cell type to express FSHR [18]. Address correspondence to: Ilpo T. Huhtaniemi.
55
56
Fowler and Huhtaniemi
Table 1. Summary of gonadotropin receptor expression in the ovary
Location Granulosa Theca Stroma CL Cycle phase Early FP Mid FP Late FP Luteal P Developmental stage Primordial Primary Secondary CL
LHR (human)
FSHR (human)
PRLR (rodent)
Cells surrounding large follicles
*
* Present in granulosa cell-derived CL. Based on data from references quoted in the text.
Ovarian LHR expression is limited to the theca interna in antral follicles, but spreads to the granulosa cells in preovulatory follicles [19]. In the corpora lutea (CL) LHR expression increases to peak in the mid-luteal phase and then declines, becoming undetectable in regressing follicles [20]. It is important to note that LHR expression in the CL is not lost during maternal recognition of pregnancy [20,21]. The expression of the different forms of PRLR in the ovary differs. For instance, in the mouse CL of early pregnancy, all four PRLR mRNAs are expressed while only the long form persists to late gestation, although these are also found in the granulosa cells [22]. Different PRLR isoforms are found in the human, and both long and intermediate isoform mRNA transcripts are found in the human ovary. Together with differences in signaling, tissue differences suggest that short and long isoform PRLR may have distinct functions [23], but what those might be remains uncertain. During development in the rodent PRLR expression is well documented [24], but even in a recent review [25], there was no report of PRLR expression in the fetal human ovary. The whole issue of whether PRL is gonadotropic in the human is important. The fact that consistent PRL binding activity in the human and non-human primate ovary has not been convincingly demonstrated [26,27], suggests that the human is unlike the rodent and does not have a reliance upon ovarian PRL action. Gonadotropin receptor function and regulation The simple observation that inherited resistance to LH results in anovulation, but normal follicular maturation indicates that FSH alone is requisite for preantral to
preovulatory follicle development. In contrast, the occurrence of normal puberty in affected individuals shows that only low LH concentrations are required for normal steroidogenesis [28]. LHR are critical for the maintenance of theca, granulosa and luteal cell steroidogenesis, maturation of follicle and oocyte and for ovulation. This role has considerable implications for health and disease. For instance in women with polycystic ovaries, overexpression of LHR is associated with hyperstimulation of theca cells and premature luteinization of granulosa cells [29], even though the steroidogenic enzymes were only over-expressed in the theca cells. Gonadotropin receptor expression in the ovary is in¯uenced by other hormones. For instance in the rodent LHR stability is reduced by exposure to PRL [30], although FSH-induced LHR in the ovary are maintained by LH itself and by FSH [31,32]. Similarly PRL itself may in¯uence the expression of different forms of the PRLR, particularly the long form, and the ratio between PRLR forms may be important in the regulation of events such as luteolysis [33]. Many other factors are also important in regulating ovarian gonadotropin receptor expression. In the rodent, once induced by FSH, LHR expression is maintained by cAMP, and increased by activin while IGF-1 also maintains LHR expression even following interrupted FSH exposure [34]. FSHR expression is also self-regulated [35], operating through the cAMP-PKA pathway for up-regulation, although the PKC pathway may play a role in FSHR down-regulation [36]. Similarly to the LHR, FSHR expression is also regulated by activin, although it has up-and downregulatory effects depending upon dose [4]. The expression of FSHR is regulated by upstream stimulatory factors 1 and 2 [37], which is suggestive in terms of cellspeci®c transcription and FSHR expression. The role of the PRLR in the human ovary is unclear, but in the mouse it has become clear from KO studies [38] that PRL must play an obligatory role in female reproduction supported by PRLR expression patterns in the rat [39]. The luteotropic effects of PRL are well recognized [40] and involve progesterone secretion. The latter requires a luteotropic complex and therefore activation of both the PRLR and LHR is required [41]. Similarly PRL is involved in regulating granulosa cell steroidogenesis in the rat [42] and developmental competence of oocytes in the rabbit [43].
Pathological Gonadotropin Receptor Function The pathologies of gonadotropin receptor function with known etiology are rare, and in most cases due to constitutively activating or inactivating mutations of the
The Ovarian Gonadotropin Receptors in Health and Disease
Fig. 1. Schematic structure and currently known mutations of the human LH receptor. &, inactivating mutations; , activating mutations. The short lines across the peptide chain depict the exon boundaries [3,46,47].
receptor genes. Both activating and inactivating LHR mutations have been described, but the former type seems to cause phenotype only in men. No clearly activating FSHR mutations have yet been characterized. In many cases, no mutations are detected in patients with clear phenotype, and in these cases it is possible that another gene involved in the cascade of gonadotropin signal transduction harbors the mutation. Examples of such cases do not exist yet, but it is likely that they will be detected in the future. Luteinizing hormone receptor (LHR) Activating mutations. The ®rst mutations detected in gonadotropin receptors were those activating constitutively the LHR [44,45], apparently because of their striking phenotype. Interestingly, no female phenotype of these mutations has been described. For the sake of completeness, we also describe brie¯y the male phenotype. It is a syndrome of male-limited gonadotropin-independent precocious puberty, also called testotoxicosis. The detection of point mutations in the LHR gene, which in cell transfections proved to cause constitutive ligand-independent activation of the LH signaling pathway, provided a logical explanation for the molecular pathogenesis of testotoxicosis. Today, a total of 12 activating mutations of the LHR gene have been described (Fig. 1). They all, understandably, are localized
57
in the transmembrane region of the LHR, because this part of the receptor molecule is known to play a crucial role in LH signal transduction. The mutations apparently change conformation of the transmembrane region of the receptor in such a fashion that it assumes, at least partially, activated conformation in the absence of ligand hormone. The functional consequence is premature activation of Leydig cell testosterone production before the normal pubertal age of onset of LH secretion. Despite the clear phenotype in males, no apparent phenotype is known in females with activating LHR mutation. One explanation is that the initiation of LH action in the ovary requires FSH priming and FSHdependent paracrine factors may be needed to induce the LHR responsiveness in theca cells. Therefore, since FSH secretion does not start in these women before the normal age of puberty, the necessary FSH induction can not start prematurely. Another explanation is that because prepubertal theca or granolosa cells do not express the LHR, it does not matter whether there is an activating mutation in the LHR gene. The developmental onset of ovarian LHR expression is an intriguing question, but it may remain unanswered since noninvasive methods to study LHR expression in the prepubertal ovary are not available. However, it is curious why no hyperandrogenism is detected at any age in women expressing constitutively activated LHRÐtheir theca cell androgen production should be elevated due to chronic LH stimulation. There are no animal models for activating gonadotropin receptor mutations. This would require production of a ``knock-in'' mutation in the endogenous LHR gene. The closest animal model so far produced for an activating LHR mutation is a mouse expressing the bovine LHb subunit/hCG C-terminal peptide fusion gene under the bovine common a-subunit promoter (bLHbCTP) [48]. The females in this model have very high levels of circulating LH, and might thus mimic constitutive LHR activation. The female mice are infertile, develop multicystic ovaries and granulosa cell tumors, have elevated estrogen and androgen levels, and develop nephropathy. In addition, the female bLHb-CTP mice become obese after puberty, for a very particular reason. Upon LH overproduction the mice started expressing LHR in their adrenal gland, which then stimulated high corticosterone production and Cushing's syndrome-like phenotype [49]. The adrenal function of men with testotoxicosis, as well as female carriers of the same mutations, might be worth investigating. By and large, however, the LH overexpressing mouse does not seem to represent a close phenocopy of the human LHR activating mutation, since none of the above symptoms have been detected in women with such a mutation. It may be that the receptor mutation brings about milder
58
Fowler and Huhtaniemi
activation of LH action and therefore none of the symptoms develop in female carriers of the activating LHR mutations. Inactivating mutations. Today, close to 20 inactivating LHR mutations have been identi®ed, and they can be subdivided into two categories, i.e., partially or completely inactivating [3]. In the partially inactivating forms, some of the receptor activity remains and therefore the LH-dependent target cell functions are not totally absent. In men, LHR inactivation, depending on severity of the inactivation, causes a wide spectrum of phenotypes, ranging from complete lack of masculinization (46,XY male pseudohermaphroditism) to mild undervirilization in the form of micropenis or perineoscrotal hypospadias [3]. Individuals with the complete form of mutation have female external genitals, low testosterone and high LH levels, but normal FSH, total lack of responsiveness to LH/hCG challenge and absent development of secondary male or female sex characteristics. There is a notable lack of breast development in the affected individuals at the age of puberty, which is the clearest phenotypic difference between this condition and complete androgen insensitivity syndrome (testicular feminization), due to inactivating mutations in the androgen receptor gene. Due to lack of testosterone action in the fetal period, the Wolf®an ductus-derived accessory sex organs ( prostate, seminal vesicles) are totally absent. Also the uterus is missing, because the fetal Sertoli cells produce normal levels of antiMuÈllerian hormone. It is, however, noteworthy that the individuals do have epididymides, which is a sign of minimal autonomous testosterone production and subsequent paracrine action on stabilization of the Wolf®an ductal structures closest to the testis [3]. As expected, upon histological examination the testes contain no mature Leydig cells, and spermatogenesis is totally arrested [28,50]. In vitro studies of function of the mutated receptors have shown a clear correlation between the extent of receptor inactivation and severity of the symptoms [3,51]. Females with LHR inactivation have milder phenotype than males, with normal puberty, primary or secondary amenorrhea, hypoestrogenism, and high LH but normal FSH (reviewed in Themmen and Huhtaniemi [3]). Histological examination of ovarian biopsy samples reveals all stages of follicular development, including primordial follicles, preantral and antral follicles with a well-developed theca cell layer, but no preovulatory follicles or CL [28]. Non-ovulated follicles may give rise to cysts. Upon clinical examination, the patients have small uterus, normal-sized vagina with hyposecretory function and thin walls, as well as decreased bone mass. These symptoms are indicative of low estrogen levels.
These observations strongly support the view that LH is essential for ovulation and suf®cient estrogen production, while follicular development is initially autonomous, and at later stages dependent on intact FSH action. The normal feminization at puberty with inactivating LHR mutation indicates that this process in girls is mainly dependent on FSH. In addition, there are several apparent polymorphisms in the LHR gene [3]. Whether they are genuine polymorphisms, with no phenotypic expression or whether they represent subtle alterations of receptor function, with phenotypic effects when under in¯uence of speci®c modi®er genes, remains to be explored. The phenotype of the LHR knockout mice was recently reported by two laboratories [52,53]. The male knockout mice are indistinguishable from controls at birth, displaying full intrauterine masculinization of their sex organs. This indicates that some non-gonadotropic factors are able to maintain fetal Leydig cell androgen production. In this respect the mouse differs from man, where normal LHR function is vital for prenatal masculinization. However, the LHR knockout male mice totally lacked the postnatal sexual development, which is known to be dependent on LH-stimulated testicular androgen synthesis. Homozygous female knockout mice were infertile, due to poor estrogen synthesis and lack of follicular maturation beyond the early antral stage. In this respect the female knockout mouse is a full phenocopy of women with LHR inactivation. The lack of progression of follicular growth from the antral to preovulatory stage in the knockout mice indicates that LH is important in the ®nal stages of follicular maturation before ovulation. Follicle-stimulating hormone receptor Activating mutations. Only a single allegedly activating mutation of the FSHR has been described [54]. It was detected in a hypophysectomized male who, during testosterone replacement therapy, presented with normal spermatogenesis in spite of undetectable gonadotropins. When the transmembrane domain encoding exon 10 of the FSHR gene was sequenced, a heterozygous Asp567 Gly mutation was found in the third intracellular loop (Fig. 2). The mutant receptor displayed borderline constitutive activity in transfected cells, which was marginal in comparison to the clear 4 10-fold elevation of basal cAMP production with the activating LHR mutations [3]. Thus, it remains open whether this FSHR mutation represents a polymorphism or a functional mutation. However, mutations induced in the FSHR cDNA have shown that activating mutations of this gene are possible [55], and it is probably only a matter of time until such human mutations are detected. Candidate
The Ovarian Gonadotropin Receptors in Health and Disease
59
such as postmenopausal ovarian cancer, ovarian hyperstimulation syndrome and with FSH secreting pituitary adenomas present with cystic and hemorrhagic ovaries [3]. Interestingly, the female phenotypes of the FSH and LH overexpressing mice are very similar (see above). However, the human equivalent to this condition, i.e. activating FSHR mutation in women, still remains to be detected and characterized.
Fig. 2. Schematic structure and currently known mutations of the human FSH receptor. &, inactivating mutations; , activating mutations, *, polymorphisms. The short lines across the peptide chain depict the exon boundaries [3].
diseases, such as premature ovarian failure and twin pregnancies, have yielded negative results [56]. It is also possible that activating FSHR mutations do not have phenotype or that our educated guesses about their nature have been wrong because of other, compensatory, factors. An animal model for activating FSHR mutation would therefore be very useful in predicting the human phenotype. At the moment, there are only transgenic mice overexpressing FSH, which may to some extent predict the phenotype of the elusive activating receptor mutation. Male mice overexpressing the human FSHRb gene had normal testicular differentiation and spermatogenesis [57]; nevertheless, they were infertile, although the cause is not known. Whether a gain-of-function mutation of the FSHR gene would produce a similar phenotype in humans is unlikely, since men with pituitary adenomas secreting large amounts of FSH have no testicular phenotype [58]. Transgenic females overexpressing FSH were also infertile, with highly hemorrhagic and cystic ovaries, and elevated serum testosterone, estradiol and progesterone [57]. No gonadal tumors were found in these mice, indicating that FSH alone is not oncogenic. The infertility of these mice was due to disrupted folliculogenesis and the development of ovarian cysts. Thus they mimicked the human ovaries observed in hyperstimulation and PCOS. Likewise, women with elevated serum FSH levels, in conditions
Inactivating mutations. Only few mutations have so far been identi®ed in the FSHR gene (Fig. 2). The paucity of these mutations, in comparison to those of LHR, may indicate that the phenotype(s) caused by them are less obvious and therefore escape our attention. Alternatively, a selection mechanism may be operative against FSHR gene mutations based on their strong anti-fertility effect, precluding inheritance of the faulty alleles. In the ®rst successful search for loss-of-function FSHR mutations, advantage was taken of the considerable enrichment of mutations for certain recessively inherited disorders in Finland [59]. Upon linkage analysis, a cohort of hypergonadotropic ovarian dysgenesis patients revealed a locus in chromosome 2p that was associated with recessive inheritance pattern of the syndrome. Sequencing of the coding region of the FSHR gene revealed a missense Ala189 Val mutation that segregated perfectly with the phenotype. Ligand binding activity and signal transduction of the mutated receptor were severely reduced. Interestingly, it was recently found that the bulk of the mutated FSHR immunoreactivity appeared to sequester within the cells (A. Rannikko, P. Pakarinen, M. Misrahi and I. Huhtaniemi, unpublished observation). All homozygous female carriers of the Ala189 Val FSHR mutation showed follicles in their ovaries, usually in the primordial stage, but occasionally also at more advanced stages of development [60]. In contrast, a total absence of all follicles, including those at the primordial stage, was observed in other cases of hypergonadotrophic hypogonadism when no FSHR mutation could be detected. Thus, the FSHR mutation phenotype is distinct from the common form of ovarian dysgenesis which is found in Turner's syndrome with streak ovaries and absence of growing follicles. A total of ®ve homozygous males were identi®ed and studied in the Finnish families of the affected women [61]. The only ®nding in these men was their mildly or severely disturbed spermatogenesisÐhowever, none of them was azoospermic. Recently, two pairs of compound heterozygous FSHR mutations were described from France in women with primary or secondary amenorrhea, normal pubertal development and follicular development up to the antral stage (Fig. 2) [62,63]. Two of the mutations, Ile160 Thr and Asp224 Val, present in the extracellular
60
Fowler and Huhtaniemi
domain of the receptor, caused almost complete loss of FSH binding. In accordance, cells expressing these receptor mutants showed absent or marginal cAMP response to FSH stimulation. The other two mutations, Arg573 Cys and Leu601 Val, caused less complete receptor inhibition, displaying clear ligand binding and residual cAMP responses to FSH. Very recent studies have identi®ed two additional mutations, Ala419 Thr in the second transmembrane loop of FSHR (E. Docherty, P. Pakarinen, A. Tiitinen, A. Kiilavouri, I. Huhtaniemi, S. Forrest and K. AittomaÈki, unpublished observation), and Pro346 Arg in the extracellular part of exon 10 [64]. Both of these mutations abolished FSH signal transduction, and in the former mutation this occurred in spite of normal FSH-receptor binding. Despite the rarity of the currently known FSHR mutations there seems to be good correlation of the phenotype with the degree of receptor inactivation, in the same fashion as is found with the larger number of LHR mutations [3]. Patients with the lowest remaining FSHR activity are hypergonadotropic with primary amenorrhea and hypoplastic ovaries, while carriers of less affected mutations present with secondary amenorrhea, normal sized-ovaries and follicular development up to the antral stage, underlining the essential role of FSH in growth and development of the ovarian follicles. It is important that ovaries of patients with the milder forms of mutations may respond to high-dose FSH stimulation [62,63], whereas no response was found with the severe form of receptor inactivation (J. Tapanainen, K. AittomaÈki and I. Huhtaniemi, unpublished observation). Hence, the molecular diagnosis of these rare patients may help in design of rational treatment for their infertility. Knockout models exist for both FSHb and FSHR [65± 67], and the phenotypes of the two models de®cient of FSH action, as well as of humans with inactivating FSHR mutation [59,61], are practically identical. All female mice were infertile, and upon histological examination, their ovaries were small and thin, lacking CL and failing to show follicular development beyond the preantral stage. The vagina was imperforate and the uterus was atrophic. Serum concentrations of FSH and LH were elevated [67]. No effect of PMSG treatment was observed in the knockout mice. In FSHR knockout males, as well as in men with inactivating FSHR mutation, much milder phenotypic effects were seen. They were normally masculinized and fertile, although with reduced testicular size. The testicular inhibin B levels did not differ from those in normal littermates, and the serum concentrations of LH and FSH were elevated. In conclusion, the FSHR knockout mice con®rm that ovarian follicular development does not progress beyond the preantral stage without action of FSH. In the absence of mature follicles, estrogen production remains low,
which causes the atrophy of accessory sex organs and lack of negative feedback regulation of gonadotropin secretion. However, in the male, absent FSH action does not necessarily compromise fertility although testicular size and spermatogenesis are suppressed. One common polymorphism on the FSHR gene has been identi®ed (Fig. 2); the polymorphic allele has two point mutations resulting in two amino acid changes, Thr307 =Asn680 and Ala307 =Ser680 . Both of them exist in the normal population with almost equal allelic frequency. It was recently observed in patients undergoing ovarian hyperstimulation that those homozygous for the Ala307 =Ser680 allele had signi®cantly higher basal FSH levels and needed about a 50% increase in numbers of FSH ampoules administered for successful stimulation [68]. This ®nding is very interesting, indicating that ovarian response to gonadotropins depends on the FSHR genotype. Since both gonadotropin and gonadotropin receptor genes have a number of other polymorphisms [3,69], this raises the question of whether the great variability of gonadotropin levels and reproductive functions in general could be due to phenotypic effects of speci®c combinations of polymorphisms in genes of the gonadotropins and their receptors. Prolactin receptor Due to the widespread expression of the PRLR in diverse tissues, including the rodent ovary [39], knockouts present with multiple defects. However the main ovarian effects are observed in females homozygous for a null mutation of the PRLR gene: sterility, irregular cycles, multiple ovarian abnormalities, including reduction in primary follicle and ovulated oocyte numbers, and failure of trophic support for the CL [24,38]. The signi®cance of these ®ndings for humans is currently unclear.
Conclusions and Future Directions Today, both activating and inactivating mutations of gonadotropin receptor genes are known. Likewise, animal models exist for most of these conditions, both in the form of gonadotropin ligand and receptor knockouts and overexpression of gonadotropin genes. Of the possible permutations in humans, the largest number of cases have been reported for the activating and inactivating LHR mutations, and their phenotypic expression is now relatively well-known. The ®nding that women with activating mutations of LHR seem to have no phenotype is puzzling, and animal models with activating LHR mutation could help in predicting the missing phenotype. Concerning the consequences of FSHR mutations,
The Ovarian Gonadotropin Receptors in Health and Disease
much less is known. Females with inactivating FSHR mutation display the expected lack of follicular development, and the ®ndings are identical with the inactivating FSHR mutations and the FSHb and FSHR knockout mice, and therefore the role of FSH in the female can be considered quite well explored. Since no undisputed activating mutation of the FSHR have yet been found, a mouse model would be useful in prediction of the phenotype which might turn out to be either nonexisting or unexpected.
References 1. Segaloff DL, Ascoli M. The lutropin/chorionic gonadotropin receptor . . . 4 years later. Endocrine Rev 1993;14:324±347. 2. Simoni M, Gromoll J, Nieschlag E. The follicle-stimulating hormone receptor: biochemistry, molecular biology, physiology and pathophysiology. Endocrine Rev 1997;18:739±777. 3. Themmen APN, Huhtaniemi IT. Mutations of gonadotropins and gonadotropin receptors: Elucidating the physiology and pathophysiology of pituitary-gonadal function. Endocr Rev 2000;21:551±583. 4. Minegishi T, Nakamura K, Takakura Y, Ibuki Y, Igarashi M. Cloning and sequence of human FSH receptor cDNA. Biochem Biophys Res Commun 1991;175:1125±1130. 5. Kelton CA, Cheng SVY, Nugent NP, Schweickhardt RL, Rosenthal JL, Overton SA, Wands GD, Kuzeja JB, Luchette CA, Chappel SC. The cloning of human follicle-stimulating hormone receptor and its expression in COS-7, CHO and Y-1 cells. Mol Cell Endocrinol 1992;89:141±151. 6. Tilly JL, Aihara T, Nishimori K, Jia X-C, Billig H, Kowalski KI, Perlas EA, Hsueh AJW. Expression of recombinant human folliclestimulating receptor: Species-speci®c ligand binding signal transduction, and identi®cation of multiple overain mRNA transcripts. Endocrinology 1992;131:799±806. 7. Nagayama Y, Wadsworth HL, Chazenbalk GD, Russo D, Seto P, Rapaport B. Thyrotropin-luteinizing hormone/chorionic gonadotropin receptor extracellular domain chimeras as probes for thyrotropin receptor function. Proc Natl Acad Sci USA 1991;88:902±905. 8. Braun T, Scho®eld PR, Sprengel R. Amino-terminal leucine-rich repeats in gonadotropin receptors determine hormone selectivity. EMBO J 1991;10:1885±1890. 9. Remy J-J, Nespoulous C, Grosclaude J, Grebert D, Couture L, Pajot E, Salesse R. Puri®cation and structural analysis of a soluble human chorionogonadotropin hormone-receptor complex. J Biol Chem 2001;276:1681±1687. 10. Findlay JK, Drummond AE. Regulation of the FSH receptor in the ovary. Trends Endocrinol Metab 1999;10:183±188. 11. Kelly PA, Dijiane J, Edery M. Different forms of the prolactin receptor: Insights into mechanisms of prolactin action. Trends Endocrinol Metab 1992;3:54±59. 12. Davis JA, Linzer DIH. Expression of multiple forms of the prolactin receptor in mouse liver. Mol Endocrinol 1989;3:674±680. 13. Ihle JN, Kerr IM. Jaks and Stats in signalling by the cyotkine receptor superfamily. Trends Genet 1995;11:69±74. 14. Chang W-P, Ye Y, Clevenger CV. Stoichiometric structure-function analysis of prolactin receptor signalling domain by receptor chimeras. Mol Cell Biol 1998;18:896±905.
61
15. Bole-Feysot C, Gof®n V, Edery M, Binart N, Kelly PA. Prolactin and its receptor: Actions, signal transduction pathyways and phenotypes observed in prolactin receptor knockout mice. Endocr Rev 1998;19:225±268. 16. Oktay K, Briggs D, Gosden R. Ontogeny of follicle-stimulating hormone receptor gene expression in isolated human ovarian follicles. J Clin Endocrinol Metab 1997;82:3748±3751. 17. Minegishi T, Tano M, Igarashi M, Rokukawa S, Abe Y, Ibuki Y, Miyamoto K. Expression of follicle-stimulating hormone receptor in human ovary. Eur J Clin Invest 1997;27:469±474. 18. Zheng W, Magid MS, Kramer EE, Chen YT. Follicle-stimulating hormone receptor is expressed in human ovarian surface epithelium and fallopian tube. Am J Pathol 1996;148:47±53. 19. Takao Y, Honda T, Ueda M, Hattori N, Yamada S, maeda M, Fujiwara H, Mori T, Wimalasena J. Immunohistochemical localisation of the LH/hCG receptor in human ovary: hCG enhances cell surface expression of LH/hCG expression on luteinizing granulosa cells in vitro. Mol Hum Reprod 1997;3:569±578. 20. Nishimori K, Dunkel L, Hsueh AJ, Yamoto M, Nakano R. Expression of luteinizing hormone and chorionic gonadotropin receptor messenger ribonucleic acid in human corpora lutea during menstrual cycle and pregnancy. J Clin Endocrinol Metab 1995;80:1444±1448. 21. Duncan WC, McNeilly AS, Fraser HM, Illingworth PJ. Luteinizing hormone receptor in the human corpus luteum: lack of downregulation during maternal recognition of pregnancy. Hum Reprod 1996;11:2291±2297. 22. Clarke DL, Linzer DIH. Changes in prolactin receptor expression during pregnancy in the mouse ovary. Endocrinology 1993;133:224±232. 23. Kline JB, Roehrs H, Clevenger CV. Functional characterisation of the intermediate isoform of the human prolactin receptor. J Biol Chem 1999;274:35461±35468. 24. Ormandy CJ, Camus A, Barra J, Damotte D, Lucas BK, Buteau H, Edery M, Brousee N, Babinet C, Binart N, Kelly PA. Null mutation of the PRL receptor gene produces multiple reproductive defects in the mouse. Genes Dev 1997;11:167±178. 25. Freemark M. Ontogenesis of prolactin receptors in the human fetus: Roles in fetal development. Biochem Soc Trans 2001;29:38±41. 26. McNeilly AS. Prolactin and the corpus luteum. In: Jeffcoate SL, ed. Current Topics in Reproductive Endocrinology, vol 4, The Luteal Phase. John Wiley & Sons, 1985:71±87. 27. Bramley TA, Stirling D, Swanston IA, Menzies GS, McNeilly AS, Baird DT. Speci®c binding sites for gonadotrophin-releasing hormone, LH/chornionic gonadotrophin, low-density lipoprotein, prolactin and FSH in homogenates of human corpus luteum. II. Concentrations throughout the luteal phase of the menstrual cycle and early pregnancy. J Endocrinol 1987;113:317±327. 28. Latronico AC, Anasti J, Arnhold IJP, Mendonca BB, Bloise W, Castro M, Tsigos C, Chrousos GP. Testicular and ovarian resistance to luteinizing hormone caused by inactivating mutations of the luteinizing hormone receptor gene. N Engl J Med 1996;331:507± 512. 29. Jakimiuk AJ, Weitsman SR, Navab A, Magof®n DA. Luteinizing hormone receptor, steroidogenesis acute regulatory protein, steroidogenic enzyme messenger ribonucleic acids are overexpressed in thecal and granulosa cells from polycystic ovaries. J Clin Endocrinol Metab 2001;86:1318±1323. 30. Hirakawa T, Minegishi T, Tano M, Kameda T, Kishi H, Ibuki Y, Mizutani T, Miyamoto K. Effect of prolactin on the expression of luteinizing hormone receptors during cell differentiation in cultured rat granulosa cells. Endocrinology 1999;140:3444± 3451.
62
Fowler and Huhtaniemi
31. Casper RF, Erickson GF. In vitro heteroregulation of LH receptors by prolactin and FSH in rat granulosa cells. Mol Cell Endocrinol 1981;23:161±171. 32. Hsueh AJ, Adashi EY, Jones PB, Welsh TH Jr. Hormonal regulation of the differentiation of cultured ovarian granulosa cells. Endocr Rev 1984;5:76±127. 33. Bowen JM, Telleria CM, Towns R, Keyes PL. Downregulation of the long-form prolactin receptor mRNA during prolactin-induced luteal regression. Eur J Endocrinol 2000;143:285±292. 34. Tsuchiya M, Minegishi T, Kishi H, Tano M, Kameda T, Hirakawa T, Ibuki Y, Mizutani T, Miyamoto K. Control of expression of luteinizing hormone receptor by local factors in rat granulosa cells. Arch Biochem Biophys 1999;367:185±192. 35. LaPolt PS, Tilly JL, Aihara T, Nishimora K, Hsueh AJW. Gonadotropin-induced up- and down-regulation of ovarian follicle-stimulating hormone (FSH) receptor gene expression in immature rats: Effects of pregnant mare's serum gonadotropin, human chorionic gonadotropin, and recombinant FSH. Endocrinol 1992;130:1289±1295. 36. Minegishi T, Tano M, Nakamura K, Igarashi S, Ito I, Shinozaki H, Karino S, Ibuki Y, Miyamoto K. Regulation of follicle-stimulating hormone receptor. Horm Res 1996;46:37±44. 37. Xing W, Sairam MR. Characterisation of regulatory elements of ovine follicle-stimulating hormone (FSH) receptor gene: The role of E-box in the regulation of FSH receptor expression. Biol Reprod 2001;64:579±589. 38. Kelly PA, Binart N, Lucas B, Bouchard B, Gof®n V. Implications of multiple phenotypes observed in prolactin receptor knockout mice. Fron Neuroendocrinol 2001;22:140±145. 39. Clarke DL, Arey BJ, Linzer DI. Prolactin receptor message ribonucleic acid expression in the ovary during the rat estrous cycle. Endocrinol 1993;133:2594±2603. 40. Cecium M, Kerr J, Bartke. Infertility in transgenic mice overexpressing the bovine growth hormone gene: Luteal failure secondary to prolactin de®ciency. Biol Reprod 1995;52:1162±1166. 41. Chedresse PJ, Rajkumar K, Ly H, Murphy BD. Dose response of luteinized porcine granulosa cells in vitro to prolactin: Dependency on pre-exposure to human chorionic gonadotropin. Can J Physiol Pharmacol 1988;66:1337±1340. 42. Krasnow JS, Hickey GJ, Richards JS. Regulation of aromatase mRNA and estradiol biosynthesis in rat ovarian granulosa and luteal cells by prolactin. Mol Endocrinol 1990;4:13±22. 43. Yoshimura Y, Nakamurta Y, Yamada H, Ando M, Ubukata Y, Oda T, Suzuki M. Possible contribution of prolactin in the process of ovulation and oocyte maturation. Horm Res 1991;35:22±32. 44. Kremer H, Mariman E, Otten BJ, Moll GW, Jr., Stoelinga GB, Wit JM, Jansen M, Drop SL, Faas B, Ropers HH, Brunner HG. Cosegregation of missense mutations of the luteinizing hormone receptor gene with familial male-limited precocious puberty. Hum Mol Genet 1993;2:1779±1783. 45. Shenker A, Laue L, Kosugi S, Merendino JJ, Jr., Minegishi T, Cutler GB, Jr. A constitutively activating mutation of the luteinizing hormone receptor in familial male precocious puberty. Nature 1993;365:652±654. 46. Pals-Rylaarsdam R, Brichman W, Duranteau L, Lui G, Monroe J, El-Awady MK. Novel double mutation of the luteinizing hormone receptor in a kindred with familial Leydig cell hypoplasia and male pseudohermaphroditism. Proceedings of the American Endocrine Society, 82nd Annual Meeting, Toronto, Canada. Abstract No. 1378. 47. Latronico AC, Shinozaki H, Guerra GJr, Pereira MA, Lemos Marini SH, Baptista MT, Arnhold IJ, Fanelli F, Mendonca BB, Segaloff DL. Gonadotropin-independent precocious puberty due to luteinizing hormone receptor mutations in Brazilian boys: a novel
48.
49.
50.
51.
52.
53. 54.
55.
56.
57.
58.
59.
60.
61.
constitutively activating mutation in the ®rst transmembrane helix. J Clin Endocrinol Metab 2000;85:4799±4805. Risma KA, Clay CM, Nett TM, Wagner T, Yun J, Nilson JH. Targeted overexpression of luteinizing hormone in transgenic mice leads to infertility, polycystic ovaries, and ovarian tumors. Proc Natl Acad Sci USA 1995;92:1322±1326. Kero J, Poutanen M, Zhang FP, Rahman N, McNicol AM, Nilson JH, Keri RA, Huhtaniemi IT. Elevated luteinizing hormone induces expression of its receptor and promotes steroidogenesis in the adrenal cortex. J Clin Invest 2000;105:633±641. Kremer H, Kraaij R, Toledo SP, Post M, Fridman JB, Hayashida CY, van Reen M, Milgrom E, Ropers HH, Mariman E, Themmen APN, Brunner HG. Male pseudohermaphroditism due to a homozygous missense mutation of the luteinizing hormone receptor gene. Nat Genet 1995;9:160±164. Martens JW, Verhoef-Post M, Abelin N, Ezabella M, Toledo SP, Brunner HG, Themmen AP. A homozygous mutation in the luteinizing hormone receptor causes partial Leydig cell hypoplasia: Correlation between receptor activity and phenotype. Mol Endocrinol 1998;12:775±784. Zhang FP, Poutanen M, Wilbertz J, Huhtaniemi I. Normal prenatal but arrested postnatal sexual development of luteinizing hormone receptor knockout (LuRKO) mice. Mol Endocrinol 2001;15:172± 183. Lei ZM, Mishra S, Zou W, Xu B, Foltz M, Li X, Rao CV. Targeted disruption of luteinizing hormone/human chorionic gonadotropin receptor gene. Mol Endocrinol 2001;15:184±200. Gromoll J, Simoni M, Nieschlag E. An activating mutation of the follicle-stimulating hormone receptor autonomously sustains spermatogenesis in a hypophysectomized man. J Clin Endocrinol Metab 1996;81:1367±1370. Tao YX, Abell AN, Liu X, Nakamura K, Segaloff DL. Constitutive activation of G protein-coupled receptors as a result of selective substitution of a conserved leucine residue in transmembrane helix III. Mol Endocrinol 2000;14:1272±1282. Conway GS, Conway E, Walker C, Hoppner W, Gromoll J, Simoni M. Mutation screening and isoform prevalence of the follicle stimulating hormone receptor gene in women with premature ovarian failure, resistant ovary syndrome and polycystic ovary syndrome. Clin Endocrinol (Oxf ) 1999;51:97±99. Kumar TR, Palapattu G, Wang P, Woodruff TK, Boime I, Byrne MC, Matzuk MM. Transgenic models to study gonadotropin function: the role of follicle-stimulating hormone in gonadal growth and tumorigenesis. Mol Endocrinol 1999;13:851±865. Galway AB, Hsueh AJ, Daneshdoost L, Zhou MH, Pavlou SN, Snyder PJ. Gonadotroph adenomas in men produce biologically active follicle-stimulating hormone. J Clin Endocrinol Metab 1990;71:907±912. AittomaÈki K, Dieguez Lucena JL, Pakarinen P, Sistonen P, Tapanainen J, Gromoll J, Kaskikari R, Sankila E-M, LehvaÈslaiho H, Reyes Engel A, Nieschlag E, Huhtaniemi I, de la Chapelle A. Mutation in the follicle-stimulating hormone receptor gene causes hereditary hypergonadotropic ovarian failure. Cell 1995;82:959±968. AittomaÈki K, Herva R, Stenman UH, Juntunen K, YloÈstalo P, Hovatta O, de la Chapelle A. Clinical features of primary ovarian failure caused by a point mutation in the follicle-stimulating hormone receptor gene. J Clin Endocrinol Metab 1996;81:3722± 3726. Tapanainen JS, Aittomaki K, Min J, Vaskivuo T, Huhtaniemi IT. Men homozygous for an inactivating mutation of the follicle-stimulating hormone (FSH) receptor gene present variable suppression of spermatogenesis and fertility. Nat Genet 1997;15:205±206.
The Ovarian Gonadotropin Receptors in Health and Disease
62. Beau I, Touraine P, Meduri G, Gougeon A, Desroches A, Matuchansky C, Milgrom E, Kuttenn F, Misrahi M. A novel phenotype related to partial loss of function mutations of the follicle stimulating hormone receptor. J Clin Invest 1998;102:1352±1359. 63. Touraine P, Beau I, Gougeon A, Meduri G, Desroches A, Pichard C, Detoeuf M, Paniel B, Prieur M, Zorn JR, Milgrom E, Kuttenn F, Misrahi M. New natural inactivating mutations of the folliclestimulating hormone receptor: Correlations between receptor function and phenotype. Mol Endocrinol 1999;13:1844±1854. 64. Allen L, Achermann JC, Kotlar TJ, Jameson JL, Cheetham TD, Ball SG. A novel loss of function mutation in exon 10 of the FSHreceptor gene causing hypergonadotropic hypogonadism: clinical and molecular characteristics. Proceedings of the American Endocrine Society, 82nd Annual Meeting, Toronto, Canada. Abstract No. 2333. 65. Kumar TR, Wang Y, Lu N, Matzuk MM. Follicle stimulating
66.
67. 68.
69.
63
hormone is required for ovarian follicle maturation but not male fertility. Nat Genet 1997;15:201±204. Dierich A, Sairam MR, Monaco L, Fimia GM, Gansmuller A, LeMeur M, Sassone-Corsi P. Impairing follicle-stimulating hormone (FSH) signaling in vivo: Targeted disruption of the FSH receptor leads to aberrant gametogenesis and hormonal imbalance. Proc Natl Acad Sci USA 1998;95:13612±13617. Abel MH, Wootton AN, Wilkins V, Huhtaniemi I, Knight P, Charlton HM. The effect of a null mutation in the FSH receptor gene on mouse reproduction. Endocrinology 2000;141:1795±1803. Perez Mayorga M, Gromoll J, Behre HM, Gassner C, Nieschlag E, Simoni M. Ovarian response to follicle-stimulating hormone (FSH) stimulation depends on the FSH receptor genotype. J Clin Endocrinol Metab 2000;85:3365±3369. Huhtaniemi I, Jiang M, Nilsson C, Pettersson K. Mutations and polymorphisms in gonadotropin genes. Mol Cell Endocrinol 1999;151:89±94.
