Le bisphénol S (BPS) est largement utilisé comme substitut du Bisphénol A (BPA) et l’exposition humaine au BPS est désormais ubiquitaire. Or, le BPS, à l’instar du BPA, présente un potentiel perturbateur endocrinien, ce qui soulève la question du risque liée à une exposition fœtale au BPS pour la santé humaine. Dans ce contexte, l’objectif de cette thèse est d’évaluer l’exposition fœtale au BPS et de caractériser des biomarqueurs phénotypiques d’exposition fœtale et/ou d’effet du BPS à partir d’une signature stéroïdomique. Une étude toxicocinétique réalisée sur le modèle du fœtus ovin a montré que le transfert materno-fœtal du BPS est faible. Cependant, le BPS et son principal métabolite, le BPS glucuronide, sont lentement éliminés du compartiment fœtal en raison d’un passage placentaire fœto-maternel du BPS limité et de la faible vitesse de réactivation du BPSG en BPS. Il en résulte une exposition fœtale au BPS similaire à celle au BPA, lors d’exposition maternelle répétée. L’étude du transfert placentaire du BPS et du BPSG sur le modèle de placenta humain perfusé a conforté les résultats observés chez le mouton, avec des faibles transferts materno-fœtal et fœto-maternel du BPS, respectivement 10 et 3 fois inférieurs à ceux du BPA. L’exposition maternelle quotidienne au BPS au cours de la gestation chez la brebis n’a pas eu d’impact sur les voies de biosynthèse des androgènes dans l’unité materno-fœtoplacentaire pour les fœtus mâles. Bien que le potentiel d’exposition fœtale du BPS est similaire à celui du BPA, nous n’avons pas mis en évidence d’effets associés à cette exposition / Bisphenol S (BPS) is widely used as a substitute for Bisphenol A (BPA) and human exposure to BPS is now ubiquitous. However, BPS, like BPA, displays an endocrine disrupting potential, raising the issue of the risk of fetal exposure to BPS for human health. In this context, the objective of this thesis is to evaluate the fetal exposure to BPS and to characterize phenotypic biomarkers of fetal exposure and / or effect of BPS from a steroidal signature. A toxicokinetic study carried out on the model of the ovine fetus has shown that materno-fetal transfer of BPS is weak. However, BPS and its major metabolite, BPS glucuronide, are slowly eliminated from the fetal compartment due to the limited feto-maternal placental transfer of BPS and the low rate of reactivation of BPSG to BPS. This results in fetal exposure to BPS similar to BPA at repeated maternal exposure. The study of placental transfer of BPS and BPSG on the model of human perfused placenta reinforced the results observed in sheep, with low materno-fetal and feto-maternal transfers of BPS, respectively 10 and 3 times lower than those of BPA. Daily maternal exposure to BPS during pregnancy in ewes did not impact the androgen biosynthetic pathways in the materno-fetoplacental unit for male fetuses. Although the potential for fetal exposure of BPS is similar to that of BPA, we have not found any effects associated with this exposure.

O Adenoma adrenocortical é frequente em adultos, já o carcinoma é raro e agressivo. Mesmo com critérios padronizados, ainda há dificuldade para diferenciar esses tumores, sendo necessário o estudo de marcadores eficientes na detecção e diferenciação. Por serem raros e com diversas manifestações clínicas, culturas in vitro pode ser uma ferramenta para o estudo de processos que envolvem a doença. Foi realizada a caracterização molecular e funcional de culturas de células de tumores de pacientes. Resultados de PCR Array não mostraram um padrão que diferenciasse as culturas em função dos diagnósticos. Desta análise, 7 oncogenes apresentaram maior expressão e 9 supressores de tumor apresentaram baixa expressão nas culturas. WWOX, FHIT e TP73 foram validados por qPCR e a sugestiva interação entre esses fatores nos tumores adrenocorticais merecem futuras investigações. O potencial funcional das culturas T83-ACC, T36-REC e T7-ACA(P) foram evidenciados, e mostraram que podem ser bons modelos para estudo da ação de hormônios e seus mecanismos. / The adrenocortical adenoma is common in adults, since carcinoma is rare and aggressive. Even with standardized scores, it is still difficult to differentiate these tumors, the study of efficient markers in the detection and differentiation is necessary. Because they are rare and diverse clinical manifestations in vitro cultures can be a tool for the study of disease processes that involve. Molecular and functional characterization of cultured tumor cells of patients was conducted. PCR Array results did not show a pattern that differentiates cultures on the basis of diagnoses. This analysis showed higher expression 7 oncogenes and tumor suppressors 9 showed low expression in cultures. WWOX, FHIT and TP73 were validated by qPCR and suggestive interaction between these factors in adrenocortical tumors deserve further investigation. The functional potential of T83-ACC, T36-REC and T7-ACA(P) cell cultures were found, and shown confirm that they can be good models for studying the action of hormones and their mechanisms.

Pendant la grossesse, les hormones stéroïdes jouent un rôle indispensable dans la régulation des principales manifestations physiologiques telles que la reconnaissance maternelle de la gestation, la réceptivité de l'endomètre, le début du développement embryonnaire ainsi que le maintien de la gestation. Cependant, on sait très peu sur la production de ces hormones et les principaux facteurs des voies intracellulaires impliqués dans le processus de stéroïdogenèse dans le placenta bovin pendant les stades initiaux et plus avancés de la gestation. Par ailleurs, certaines anomalies du placenta chez les bovins suite à une mauvaise production de stéroïdes n'ont pas encore été démontrées. Les objectifs de cette thèse étaient donc de : 1) déterminer la présence et la localisation des principales protéines stéroïdiennes dans le placenta de bovins provenant de gestations de 50 à 120 jours, 2) comparer l'expression placentaire d'une série de gènes et de protéines stéroïdiennes entre une gestation impliquant un transfert de noyaux de cellules somatiques (SCNT) et une gestation non-clonale; 3) étudier l'impact des hormones trophiques et des seconds messagers sur la stéroïdogenèse dans le placenta bovin à 140 +10 jours de gestation. L’utilisation de techniques d’immunohistochimie, d’immunobuvardage et de PCR quantitatif nous a permis d’évaluer la présence d'un large éventail de gènes stéroïdiens (STAR, CYP11A1, HSD3B1, CYP17A1 et SCARB1) qui participent au transport du cholestérol et dans la production de différents types de stéroïdes. Dans cette thèse, nous avons démontré la capacité du placenta bovin d’initier la stéroïdogenèse au début de la gestation et nous avons également déterminé les principales cellules impliquées dans ce processus. Nous avons constaté que les tissus maternels expriment les principaux marqueurs de stéroïdogenèse suggérant une plus grande capacité stéroïdogénique que les tissus fœtaux. En outre, un modèle d'expression des protéines complémentaires stéroïdogéniques entre la caroncule et le cotylédon a été observé, indiquant que la stéroïdogenèse placentaire exige une communication cellule à cellule entre les cellules de la mère et du fœtus. Après avoir démontré les principales cellules impliquées dans la synthèse des hormones stéroïdiennes dans le placenta bovin en début de gestation, nous avons ensuite étudié les modifications possibles de la stéroïdogenèse dans les tissus SCNT cotylédonaires à 40 jours de gestation. Nous avons identifié d'importantes modifications dans l'expression des gènes STAR, CYP11A1, HSD3B1, CYP17A1, et SULT1E1. Conséquemment, nous postulons que l'expression réduite des gènes stéroïdiens peut provoquer une insuffisance de la biosynthèse des hormones stéroïdiennes, ce qui pourrait contribuer à un développement anormal du placenta et du fœtus dans les gestations SCNT à court ou long terme. Finalement, nous avons développé un modèle efficace de culture d’explants de placentome qui nous a permis d'explorer les mécanismes sous-jacents spécifiques à la stéroïdogenèse placentaire. Nous avons exploré l'effet stimulant des hormones trophiques et différents messagers secondaires sur l'expression de différentes protéines stéroïdogéniques ainsi que le taux de progestérone (P4) dans les explants de placentome. En utilisant les techniques de RIA et de PCR quantitatif, nous avons constaté que même si les analogues de l'hormone lutéinisante (hCG) ont un effet stimulant sur plusieurs gènes stéroïdiens, le calcium ionophore est le principal modulateur dans la synthèse de la P4. Ces résultats suggèrent que dans le placenta bovin, la synthèse de la P4 est modulée principalement par l'afflux de calcium intracellulaire, et apparemment les nucléotides cycliques ne semblent pas contrôler ce processus. En conclusion, cette étude contribue de manière significative à une meilleure compréhension des mécanismes d'entraînement de la synthèse des stéroïdes placentaires au début de la gestation et permet aussi d’apporter de nouveaux éclairages sur l'importance des stéroïdes placentaires dans la régulation du développement du placenta et du fœtus. / During pregnancy, steroid hormones have essential roles in regulating key physiological events such as maternal recognition, endometrial receptivity, early embryonic development, and maintenance of pregnancy. However, very little is known about the production of these hormones nor about the principal factors and intracellular pathways implicated in the steroidogenic process in bovine placenta, during early and advanced pregnancy. In addition, placental abnormalities in cattle following an improper steroid production in bovine placenta have not been yet demonstrated. The aims of this thesis were to: 1) determine the occurrence and localization of the principal steroidogenic proteins in bovine placenta from day 50 to day 120 of pregnancy; 2) compare the placental expression of a series of steroidogenic genes and proteins between somatic cell nuclear transfer (SCNT) pregnancies and non-SCNT gestations; 3) investigate the impact of trophic hormone, and second messengers on steroidogenesis in bovine placenta at 140 +10 days of gestation. Using immunohistochemistry, western blot and qPCR techniques, we evaluated the presence of a wide range of steroidogenic genes (STAR, CYP11A1, HSD3B1, CYP17A1 and SCARB1), that participate in the cholesterol transport and in the production of different types of steroids. In this thesis, we demonstrated the capability of the early bovine placenta to initiate steroidogenesis, and we also determined the principal cells implicated in this process. We found that maternal tissue expresses the principal steroidogenic markers suggesting it has a greater steroidogenic capacity compared to fetal tissue. Moreover, a complementary pattern of steroidogenic protein expression between the caruncle and the cotyledon were found, indicating that placental steroidogenesis requires cell to cell communication between the maternal and fetal cells. Having shown the principal cells involved in the synthesis of steroid hormones in bovine placenta during early pregnancies, we then studied possible alterations in steroidogenesis in cotyledonary tissue in SCNT at 40 days of pregnancy. We identified significant alterations in the expression of STAR, CYP11A1, HSD3B1, CYP17A1 and SULT1E1 transcripts. Therefore, we postulate that reduced expression of steroidogenic genes may cause an insufficient local biosynthesis of steroid hormones, which might contribute to the abnormal placental and fetal development in SCNT gestations at short or long term. Finally, we developed an efficient placentome explants culture model that allowed us to explore the specific mechanisms underlying placental steroidogenesis. We explored the stimulatory effect of trophic hormones and different second messengers on the expression of various steroidogenic proteins and the progesterone levels in placentome explants. By RIA and qPCR techniques, we found that although LH-like hormones (hCG), had a stimulatory effect on multiple steroidogenic genes, the calcium ionophore was the principal modulator in the synthesis of progesterone. These results suggest that in bovine placenta, the synthesis of progesterone is modulated principally by intracellular calcium influx, and cyclic nucleotides do not seem to be controlling this process. In conclusion, these studies significantly contribute to a better understanding of the driving mechanisms of placental steroid synthesis in early gestations and also provide new insights into the importance of placental steroids in the regulation of placental and fetal development.

Enzyme-catalyzed reactions are important to regulate steroidogenesis and nuclear receptor activation. The present investigation examines the role of steroid metabolism catalyzed by CYP7B1 for regulation of hormone receptor activation and the effects of vitamin D on enzymatic regulation of steroidogenesis. The study reports data indicating that CYP7B1 can regulate estrogenic signaling by converting estrogens into inactive or less active metabolites. Similar results were obtained for CYP7B1-mediated metabolism of some androgen receptor ligands, indicating that CYP7B1 can be involved also in the regulation of androgenic signaling. CYP7B1 substrates and metabolites were found to exert androgenic effects in a cell line-specific manner. Furthermore, cell line differences were observed in the expression pattern for androgen receptor comodulators. This thesis reports that 1α,25-dihydroxyvitamin D3 alters the gene expression and enzyme activity of CYP21A2 and CYP17A1 leading to suppressed production of aldosterone, dehydroepiandrosterone and androstenedione in adrenocortical cells. These are novel findings on vitamin D action. A mechanism is reported for the vitamin D-mediated regulation of the CYP21A2 gene. Data indicate that vitamin D receptor interacting repressor (VDIR) and Williams syndrome transcription factor (WSTF) are key comodulators in this novel vitamin D receptor (VDR)-mediated mechanism. Furthermore, the results indicate that altered expression levels of VDIR and WSTF can shift the suppressing effect of vitamin D to a stimulatory effect. Also, epigenetic components were found to be involved in the effects of vitamin D on CYP21A2 transcriptional rate. In addition, a functional vitamin D response element was identified in the CYP21A2 promoter. This study also reports that 1α,25-dihydroxyvitamin D3 affects sex hormone production in a tissue-specific way. Gene expression and enzyme activity of aromatase were found to be downregulated in cells derived from breast, but not in cells derived from prostate and adrenal cortex. The production of estradiol and dihydrotestosterone was altered in a tissue-selective manner following vitamin D treatment. These findings are of importance for the discussion on vitamin D as a potential anti-breast cancer agent.

No description available.

O Adenoma adrenocortical é frequente em adultos, já o carcinoma é raro e agressivo. Mesmo com critérios padronizados, ainda há dificuldade para diferenciar esses tumores, sendo necessário o estudo de marcadores eficientes na detecção e diferenciação. Por serem raros e com diversas manifestações clínicas, culturas in vitro pode ser uma ferramenta para o estudo de processos que envolvem a doença. Foi realizada a caracterização molecular e funcional de culturas de células de tumores de pacientes. Resultados de PCR Array não mostraram um padrão que diferenciasse as culturas em função dos diagnósticos. Desta análise, 7 oncogenes apresentaram maior expressão e 9 supressores de tumor apresentaram baixa expressão nas culturas. WWOX, FHIT e TP73 foram validados por qPCR e a sugestiva interação entre esses fatores nos tumores adrenocorticais merecem futuras investigações. O potencial funcional das culturas T83-ACC, T36-REC e T7-ACA(P) foram evidenciados, e mostraram que podem ser bons modelos para estudo da ação de hormônios e seus mecanismos. / The adrenocortical adenoma is common in adults, since carcinoma is rare and aggressive. Even with standardized scores, it is still difficult to differentiate these tumors, the study of efficient markers in the detection and differentiation is necessary. Because they are rare and diverse clinical manifestations in vitro cultures can be a tool for the study of disease processes that involve. Molecular and functional characterization of cultured tumor cells of patients was conducted. PCR Array results did not show a pattern that differentiates cultures on the basis of diagnoses. This analysis showed higher expression 7 oncogenes and tumor suppressors 9 showed low expression in cultures. WWOX, FHIT and TP73 were validated by qPCR and suggestive interaction between these factors in adrenocortical tumors deserve further investigation. The functional potential of T83-ACC, T36-REC and T7-ACA(P) cell cultures were found, and shown confirm that they can be good models for studying the action of hormones and their mechanisms.

The innate and adaptive immune processes are modulated by hormones including glucocorticoids and by microbiota. The exact mechanisms underlying the microbial and hormonal contributions to this control are not completely clear. Present study is therefore focused to crosstalk between microbiota and de novo biogenesis or local regeneration of glucocorticoids. In particular, the study analysed the effect of commensal microbiota on expression of genes encoding steroidogenic enzymes (Star, Cyp11a1, Hsd3b1, Cyp21a1, Cyp11b1) and regeneration of glucocorticoids (Hsd11b1) in adrenal glands, colon, spleen and mesenteric lymph nodes using conventional and germ-free mice. The expression of all 5 components of steroidogenesis was identified only in the adrenal gland and colon, whereas the lymphoid organs expressed predominantly Star, Cyp11a1 and Hsd3b1 indicating the ability to produce only progesterone but not corticosterone. Microbiota decreased the expression of Star in all studied tissues but the expression of other genes was insensitive to microbiota or did not respond homogenously depending on the tissue and gene. Hsd11b1 expression was upregulated by microbiota in the spleen but not in other tissues. Similarly, the in vitro treatment of immune cells isolated from mesenteric lymph nodes by microbial...

Cortisol is a glucocorticoid produced by the zona fasciculata (ZF) of the adrenal cortex. Traditionally, cortisol production and release was seen as being regulated strictly by adrenocorticotropic hormone (ACTH). While this is true of baseline cortisol levels and in response to acute mental stress, the picture is somewhat more complicated in other situations.Interleukin-6 (IL-6) contributes to the maintenance of cortisol levels in situations of prolonged immune or inflammatory stress. AMP activated protein kinase (AMPK) was investigated as a possible mediator of the action of IL-6 or as an independent actor in raising cortisol levels in response to hypoxemic or hypoglycemic stress.5-aminoimidazole-4-carboxamide 1-b-D-ribofuranoside (AICAR) was used to activate AMPK. Bovine ZF tissue fragments were exposed to AICAR alone and together with a known AMPK inhibitor, compound C. Protein or mRNA was then extracted from these tissue fragments. As an indicator of overall steroidogenic activity, these extracts were tested using RT-PCR and western blot assays for relative protein and mRNA levels of steroidogenic acute regulatory (StAR) protein, steroidogenic factor-1 (SF-1), and dosage sensitive sex reversal adrenal hypoplasia congenita gene on the X chromosome, gene 1 (DAX-1). Also a reporter gene assay was performed on H295R cells with a transfected StAR promoter.In bovine ZF tissue fragments, AICAR caused a significant increase of StAR protein and mRNA and SF-1 protein with a decrease of DAX-1 protein in a dose and time dependant manner. DAX-1 mRNA was shown to decrease in response to AICAR administration in a dose dependant manner. AICAR induced increases in StAR protein and SF-1 protein, and the attendant decrease in DAX-1 protein were all shown to be reduced by administration of compound C. This demonstrated that in this situation AICAR is acting through AMPK. When IL-6 was given with compound C the levels of StAR, SF-1, and DAX-1 were significantly reduced from samples treated with IL-6 alone. AICAR exposure also increased StAR promoter activity in a dose and time dependant manner. This AMPK induced increase in steroidogenic activity provides a possible mechanism for increased cortisol during hypoxia and hypoglycemia, and a possible mediator for IL-6 in the ZF.

Le récepteur nucléaire orphelin facteur stéroïdogénique 1 (SF-1 ou NR5A1) est un modulateur indispensable du développement surrénal et gonadique et qui joue un rôle dans la détermination du sexe, le développent hypothalamique, la fonction hypophysaire et la stéroïdogénèse. Toutefois, les études sur SF-1 dans le milieu de la biologie de la reproduction portent majoritairement sur des modèles embryonnaires ou de mammifères immatures. L’objectif principal de cette thèse était de déterminer le rôle de SF-1 dans les évènements clés de la fonction reproductrice chez les mâles et femelles matures. Ce facteur de transcription est exprimé dans différents organes, principalement ceux de l’axe hypothalamo-hypophyso-gonadique, et dans divers types cellulaires des gonades. Nous avons donc généré 4 modèles de souris knockout conditionnels (cKO) en utilisant les allèles Cre-recombinase et flox de SF-1 (SF-1f/f) afin d’identifier son rôle dans les différentes populations cellulaires des testicules et ovaires de souris matures. Dans la première étude, nous avons présenté une analyse des souris femelles du modèle cKO du récepteur de la progestérone (PRCre/+;Nr5a1f/f), où la suppression de SF-1 est spécifique aux cellules gonadotropes de l’hypophyse et aux cellules ovariennes de type granulosa suite au déclenchement du signal ovulatoire ainsi que les cellules lutéales du corps jaune. Cette étude a révélé de nouveaux rôles in vivo de SF-1 durant l’ovulation et la lutéinisation, tout en suggérant que SF-1 est un médiateur de la synthèse et sécrétion des gonadotrophines. Les femelles PRCre/+;Nr5a1f/f cKO étaient infertiles principalement en raison de l’importante réduction de FSH et LH sécrété dans la circulation, causé par le phénotype hypophysaire. Afin de contourner cette dysfonction hypophysaire, des traitements de gonadotrophines exogènes ainsi que des transplantations d’ovaires nous ont permis de démontrer que SF-1 régule la transcription de gènes impliqués dans l’expansion du cumulus ainsi que la rupture de follicules pour induire l’ovulation. De plus, nous avons montré que l’absence de SF-1 dans les ovaires de souris matures peut mener à l’infertilité, indépendamment du phénotype hypophysaire. D’autre part, nos trouvailles indiquent que, malgré la basse expression de SF-1 dans le corpus luteum chez la souris, sa déplétion dans les cellules lutéales conditionnée par recombinase Cre inhibe la production de progestérone. Aucun phénotype reproductif a été observé chez les souris PRCre/+;Nr5a1f/f cKO mâles. La deuxième étude a démontré le rôle essentiel de SF-1 dans la fonction du testicule mature. La souris mâle P450 17α-hydroxylase (Cyp17Cre/+;Nr5a1f/f) cKO, où la suppression de SF-1 est spécifique aux cellules de Leydig, était fertile malgré la taille réduite de ses testicules, la malformation de ses tubes séminifères, la perturbation de la spermiogénèse, ainsi que la réduction d’expression de gènes de la stéroïdogénèse. Bien que les mâles aromatase (Cyp19Cre/+;Nr5a1f/f) cKO, supprimant SF-1 dans les cellules de Sertoli, étaient fertiles et démontraient des capacités reproductives similaires aux mâles contrôle, les souris Cyp17Cre/++Cyp19Cre/+; Nr5a1f/f cKO (dKO) étaient soit infertiles ou montrait une fertilité affaiblie. La dysgénésie sévère du cordon testiculaire ainsi que la spermatogénèse perturbée chez la souris dKO étaient causées par la déplétion simultanée de SF-1 chez les cellules de Leydig et Sertoli, suggérant que les cellules de Sertoli peuvent compenser pour l’absence de SF-1 dans les cellules de Leydig et vice versa. Ces données démontrent que SF-1 est requis pour une stéroïdogénèse testiculaire et une spermatogénèse ainsi qu’une fertilité normale, bien que savoir si la régulation de ces fonctions par SF-1 est directe ou indirecte reste à élucider. De façon intéressante, les femelles des trois lignées cKO étudié dans ce deuxième article étaient fertiles et la sous expression de SF-1 dans les cellules ovariennes de type granulosa ou de la thèque a produit des effets mineurs sur leur fonction reproductive. En somme, la recherche présentée dans cette thèse contribue à l’avancement des connaissances sur SF-1 et son rôle dans la régulation d’événements reproductifs cruciaux dans l’hypophyse, l’ovaire et le testicule de souris matures. Les lignes de souris produites dans ce projet vont servir d’outil indispensable pour élucider les mécanismes de régulation de SF-1 sur la fonction gonadique and présenter de nouvelles avenues de recherches pour ce récepteur orphelin. / The orphan nuclear receptor steroidogenic factor-1 (SF-1 or NR5A1) is an indispensable modulator of adrenal and gonadal development, playing key roles in sex determination, hypothalamic development, pituitary function and steroidogenesis. Yet, studies to date of SF-1 in reproductive biology mostly focus on embryonic and immature mammalian models. The overall objective of this thesis was to determine the role of SF-1 in key events of mature male and female mouse reproductive function. This transcription factor is expressed in a variety of organs, mainly those of the hypothalamic-pituitary-gonadal axis, as well as in multiple cell types of the gonads. Therefore, we generated four conditional KO (cKO) mouse models employing Cre-recombinase and floxed alleles of SF-1 (SF-1f/f) to identify its role in different cell types of the testes and ovaries of mature mice. Our first study presents an analysis of female mice from the progesterone receptor (PRCre/+;Nr5a1f/f) cKO model, where SF-1 depletion is specific to gonadotropes in the pituitary gland as well as granulosa cells of the peri-ovulatory follicle and luteal cells of the corpus luteum. This research highlighted new in vivo roles for SF-1 in ovulation and luteinization, and provided further evidence that SF-1 is a mediator of gonadotropin synthesis and secretion. PRCre/+;Nr5a1f/f cKO females were infertile, due in large part to the reduced secretion of FSH and LH, caused by the pituitary phenotype. Exogenous gonadotropin treatments and ovarian transplantation experiments allowed us to circumvent the pituitary dysfunction to demonstrate that SF-1 in granulosa cells regulates the transcription of cumulus expansion and follicle rupture genes to induce ovulation. In addition, we showed that the absence of SF-1 in ovaries of mature mice can lead to female infertility, independent of the pituitary phenotype. Moreover, the data showed that, though SF-1 expression is reduced in mouse corpus luteum, its Cre-mediated depletion in luteal cells abrogates progesterone production. No reproductive phenotype was observed in PRCre/+;Nr5a1f/f cKO males. Results from our second study demonstrated that SF-1 plays an essential role in mature testicular function. The P450 17α-hydroxylase (Cyp17Cre/+;Nr5a1f/f) cKO male mouse, where the SF-1 depletion is specific to Leydig cells, were fertile, though showed reduced testis size with disrupted seminiferous tubules and impaired spermiogenesis, in addition to reduced expression of steroidogenic genes. While the aromatase (Cyp19Cre/+;Nr5a1f/f) cKO males were fertile and showed reproductive capacities comparable to control males, the Cyp17Cre/++Cyp19Cre/+; Nr5a1f/f cKO (dKO) model were either infertile or showed significantly impaired fertility. The dKO males displayed severe testis cord dysgenesis and impaired spermatogenesis caused by the depletion of SF-1 in both Leydig and Sertoli cells, suggesting that Sertoli cells can compensate for the absence of SF-1 in Leydig cells and vice versa. These data provide strong evidence that SF-1 is required for normal testicular steroidogenesis, spermatogenesis and male fertility, though whether the regulation of these functions is direct or indirect remains to be elucidated. Interestingly, the females of the three cKO mouse lines studied in this second article were fertile and the depletion of SF-1 in granulosa cells of antral follicles or in theca cells produced minor effects on their steroidogenic capacities. Collectively, the research presented in this thesis contributes to advance our understanding of the role of SF-1 in the regulation of essential reproductive events in the pituitary, ovary and testis of mature mouse gonads. The mouse lines generated for this project will serve as valuable tools to elucidate the mechanisms underlying SF-1 regulation of gonad function and present novel directions for the investigation of this nuclear receptor.

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