A typical clinical cis-diamminedichloroplatinum (II) (cisplatin) dosing regimen consists of repeated cycles of five to seven daily low dose treatments followed by a one to two week recovery period. While effective, this dosing structure results in a prolonged, and sometimes permanent, infertility in men. Undifferentiated spermatogonia, including spermatogonial stem cells (SSCs), are theoretically capable of repopulating the seminiferous tubules after exposure has ceased. It is proposed that an altered spermatogonial environment during recovery from the initial treatment cycle may drive an increase in SSC mitotic cell activity, rendering the SSC pool increasingly susceptible to cisplatin-induced cell death from subsequent cycles. The undifferentiated spermatogonia population and niche of the adult mouse (C57/BL/6J) were examined during the recovery period of a clinically-relevant course of one and two cycles of 2.5 mg/kg/d of intraperitoneal cisplatin and were compared to mice receiving an equivalent cumulative dose in a single cycle (5.0 mg/kg/d) and vehicle treated controls. Histological examination of the testicular epithelium revealed an increase in the disorganization of spermatogenesis correlating with the number of exposure cycles. Quantification of TUNEL positive cells showed an increase in apoptotic germ cells early in the recovery period in mice exposed to cisplatin compared to control animals. Immunohistochemical (IHC) examination of Foxo1 (undifferentiated spermatogonia marker) showed an increase in the undifferentiated spermatogonia population late in the recovery period in mice exposed to one cycle of 2.5 mg/kg/d, but not following two cycles of 2.5 mg/kg/d. Analysis of BrdU incorporation after dosing indicated a decrease in mitotic activity of early germ cells immediately after cisplatin exposure followed by a return to basal levels by the conclusion of the initial recovery period. No such rebound was observed during the second recovery period. IHC investigation of glial cell line-derived neurotrophic factor (GDNF), a recognized SSC niche factor, revealed an increase in production along the basal Sertoli cell membrane throughout the recovery period in all treatment groups. Taken together, these data establish that the impact of cisplatin exposure on the functional stem cell pool and niche correlates with: (1) the number of dosing cycles; (2) mitotic activity of early germ cells; and (3) alterations in the basal Sertoli cell GDNF expression levels after cisplatin-induced testicular injury. / text

Les Chondrichtyens sont des espèces d’intérêt de par leur position phylogénétique à la base des Vertébrés. Au cours de cette thèse réalisée sur un petit requin, la petite roussette, l’étude des protéines Nanos, essentielles pour le maintien de la lignée germinale chez les Ostéichtyens, a mis en évidence la présence de deux protéines Nanos1 (1A et 1B) chez les Chondrichtyens, résultant d’une duplication du gène en amont des Gnathostomes. Chaque paralogue a révélé des profils d’expression spécifiques suggérant une spécification génique. De plus, la niche des spermatogonies souches (SSCs) a été mieux caractérisée et de nouveaux marqueurs de pluripotence tels que SSEA4 et Sox2 ont été détectés dans les SSCs potentielles chez cette espèce. Une culture primaire enrichie en spermatogonies de la zone germinative a montré une hétérogénéité d’expression des facteurs de SSC analysés (GFRα1, SSEA4, POU2, Nanos1A, Nanos1B, c-Kit), suggérant une hétérogénéité des cellules souches et/ou des progéniteurs. Afin de valider le caractère souche de ces cellules en culture, un test fonctionnel de transplantation a été initié. Le développement de cette technologie, pour la première fois chez un Chondrichtyen, ouvre de nouvelles perspectives en termes de préservation de ces espèces. Enfin, la recherche de facteurs à potentiel thérapeutique au niveau testiculaire chez la petite roussette a permis l’identification d’un peptide capable de réguler la glycémie et l’insulinémie de souris présentant un diabète de type 2, mais son mode d’action reste à explorer. L’ensemble des résultats confirme l’intérêt de la petite roussette pour l’étude évolutive de la niche germinale, essentielle au maintien de la gamétogenèse, et la recherche de molécules à potentiel thérapeutique. / Chondrichthyes are species of interest because of their phylogenetic position at the base of the Vertebrates. In this thesis, based on a small shark, the small spotted dogfish, the study of Nanos proteins, essential for the maintenance of the germ line in Osteichthyes, showed the presence of two Nanos1 proteins (1A and 1B) in Chondrichthyes, resulting from a gene duplication upstream of the Gnathostomata. Each paralog revealed specific expression profiles suggesting a gene specification. In addition, the spermatogonial stem cells (SSCs) niche was better characterized and new pluripotency markers such as SSEA4 and Sox2 were detected in potential SSCs in this species. A primary culture of the germinative zone enriched in spermatogonia showed a heterogeneity of expression of the analysed SSC factors (GFRα1, SSEA4, POU2, Nanos1A, Nanos1B, c-Kit), suggesting heterogeneity of stem cells and / or progenitors. In order to validate the stemness potential of these cells in culture, a functional transplantation test was initiated. The development of this technology, for the first time in a Chondrichthyes, opens new perspectives in terms of preservation of these species. Finally, the search of potential therapeutic factors in the dogfish testis led to the identification of a peptide able to regulate blood glucose and insulin levels in mice presenting type 2 diabetes, but its mode of action remains to be explored. All the results confirm the interest of the small spotted dogfish for the evolutionary study of the germinal niche, essential to the maintenance of gametogenesis, and the search for molecules with therapeutic potential.

Yes / The spermatogonial stem cells (SSCs) are the only germline stem cells in adults that are responsible for the transmission of genetic information from mammals to the next generation. SSCs play a very important role in the maintenance of progression of spermatogenesis and help provide an understanding of the reproductive biology of future gametes and a strategy for diagnosis and treatment of infertility and male reproductive toxicity. Androgens/oestrogens are very important for the suitable maintenance of male germ cells. There is also evidence confirming the damaging effects of oestrogen-like compounds on male reproductive health. We investigated the effects in vitro, of diethylstilbestrol (DES) on mouse spermatogonial stem cells separated using Staput unit-gravity velocity sedimentation, evaluating any DNA damage using the Comet assay and apoptotic cells in the TUNEL assay. Immunocytochemistry assays showed that the purity of isolated mouse spermatogonial cells was 90%, and the viability of these isolated cells was over 96%. Intracellular superoxide anion production (O2−) in SSCs was detected using p-Nitro Blue Tetrazolium (NBT) assay. The viability of cells after DES treatment was examined in the CCK8 (cell counting kit-8) cytotoxicity assay. The results showed that DES-induced DNA damage causes an increase in intracellular superoxide anions which are reduced by the flavonoid, quercetin. Investigating the molecular mechanisms and biology of SSCs provides a better understanding of spermatogonial stem cell regulation in the testis.

A espermatogênese em mamíferos é um processo sustentado pela auto-renovação e diferenciação de células-tronco espermatogoniais (SSCs). O estudo destas células oferece um excelente modelo para o melhor entendimento da biologia das células-tronco adultas e dos mecanismos que controlam as funções das SSCs. Além do potencial biomédico para estudos sobre infertilidade em diferentes espécies, as SSC possuem uma aplicação promissora na biotecnologia para a produção de animais transgênicos. Assim, o objetivo deste trabalho foi responder à pergunta: "SSCs bovinas LacZ+ podem integrar-se aos túbulos seminíferos de bezerros pré-púberes da raça Nelore após transplante autólogo?" Para isso, bezerros Nelore de 5 meses de idade (n=16) foram submetidos a uma orquiectomia unilateral para o isolamento de células espermatogoniais por digestão enzimática. Após o plaqueamento diferencial, as células foram transduzidas com um vetor lentiviral contendo a sequencia do gene marcador LacZ. Para isso, os animais foram aleatoriamente alocados em um dos quatro grupos experimentais: LacZ+/PKH26+, LacZ+/PKH26-, LacZ-/PKH26+, LacZ-/PKH26-. Após 60 h do início do cultivo in vitro, as células espermatogoniais foram transplantadas autologamente para o mediastino do testículo remanescente por injeção guiada por ultrassonografia. O testículo transplantado foi removido cirurgicamente após 45 dias e amostras de tecido foram submetidas a reação com x-gal para verificação da integração de células espermatogoniais transgênicas aos túbulos seminíferos. Células espermatogoniais foram isoladas e cultivadas in vitro com sucesso. Contudo, não foi possível obter uma população pura de SSCs por plaqueamento diferencial. Embora tenha sido eleito o transplante de células espermatogoniais e não de SSCs somente, sabe-se que também foram transplantadas SSCs, pois a caracterização das células isoladas demonstrou a expressão dos marcadores de SSCs ITGA6, GFRa-1, PGP 9.5 e afinidade pela lectina DBA. Crioseções de amostras de tecido testicular coradas com x-gal permitiram a observação de células transgênicas em 8 de 8 animais que receberam células LacZ+. Contudo, todas as células transgênicas observadas estavam situadas no interstício. Concluindo, não foi possível observar a integração das células transgênicas transplantadas aos túbulos seminíferos do testículo receptor após 45 dias do transplante autólogo utilizando a técnica de injeção intratesticular de células espermatogoniais LacZ+ no mediastino de bezerros pré-púberes da raça Nelore. / Mammalian spermatogenesis is sustained by self renewal and differentiation of spermatogonial stem cells (SSCs). The study of these cells provides a model to better understand adult stem cell biology and the mechanisms that control SSC functions. Besides the biomedical potential to perform studies of infertility in many species, SSCs hold a promising biotechnological application at animal transgenesis. In this manner, the goal of this study was to answer the question: "Can LacZ+ bovine SSCs be integrated into seminiferous tubule of prepubertal Nelore bulls subjected to autologous transplantation?" Hence, 5 months old bulls (n=16) were hemicastrated and spermatogonial cells were isolated by a two step enzymatic digestion procedure. After differential plating, cells were transduced with a lentivirus vector carrying the LacZ reporter gene sequence. Animals were randomly allocated in four experimental groups: LacZ+/PKH26+, LacZ+/PKH26-, LacZ-/PKH26+, LacZ-/PKH26-. After 60 h of the onset of in vitro culture, spermatogonial cells were autologously transplanted to the remaining testes by an ultrasound guided needle injection at the testis mediastinum. The transplanted testes were surgically removed after 45 days and testicular tissue samples were subjected to x-gal staining to assess the integration of transgenic spermatogonial cells to seminiferous tubule. Spermatogonial cells were successfully isolated and in vitro cultured. However, it was not possible to obtain a SSC enriched population of cells by differential plating. Although it was decided by the transplant of spermatogonial cells instead of pure SSCs only, it was detected the expression of SSC marker genes ITGA6, PGP9.5, GFR-1 and the affinity for DBA by the isolated cells. Cryosections of x-gal stained testicular tissue samples allowed the observation of transgenic cells in 8 out of 8 animals that received LacZ+ cells. However, all transgenic cells observed were located at the interstitial space. In conclusion, it was not possible to observe the integration of the transplanted transgenic cells into seminiferous tubule of prepubertal Nelore bulls subjected to autologous transplantation using an ultrasound guided needle injection at the testis mediastinum, after 45 days of transplant.

A espermatogênese em mamíferos é um processo sustentado pela auto-renovação e diferenciação de células-tronco espermatogoniais (SSCs). O estudo destas células oferece um excelente modelo para o melhor entendimento da biologia das células-tronco adultas e dos mecanismos que controlam as funções das SSCs. Além do potencial biomédico para estudos sobre infertilidade em diferentes espécies, as SSC possuem uma aplicação promissora na biotecnologia para a produção de animais transgênicos. Assim, o objetivo deste trabalho foi responder à pergunta: "SSCs bovinas LacZ+ podem integrar-se aos túbulos seminíferos de bezerros pré-púberes da raça Nelore após transplante autólogo?" Para isso, bezerros Nelore de 5 meses de idade (n=16) foram submetidos a uma orquiectomia unilateral para o isolamento de células espermatogoniais por digestão enzimática. Após o plaqueamento diferencial, as células foram transduzidas com um vetor lentiviral contendo a sequencia do gene marcador LacZ. Para isso, os animais foram aleatoriamente alocados em um dos quatro grupos experimentais: LacZ+/PKH26+, LacZ+/PKH26-, LacZ-/PKH26+, LacZ-/PKH26-. Após 60 h do início do cultivo in vitro, as células espermatogoniais foram transplantadas autologamente para o mediastino do testículo remanescente por injeção guiada por ultrassonografia. O testículo transplantado foi removido cirurgicamente após 45 dias e amostras de tecido foram submetidas a reação com x-gal para verificação da integração de células espermatogoniais transgênicas aos túbulos seminíferos. Células espermatogoniais foram isoladas e cultivadas in vitro com sucesso. Contudo, não foi possível obter uma população pura de SSCs por plaqueamento diferencial. Embora tenha sido eleito o transplante de células espermatogoniais e não de SSCs somente, sabe-se que também foram transplantadas SSCs, pois a caracterização das células isoladas demonstrou a expressão dos marcadores de SSCs ITGA6, GFRa-1, PGP 9.5 e afinidade pela lectina DBA. Crioseções de amostras de tecido testicular coradas com x-gal permitiram a observação de células transgênicas em 8 de 8 animais que receberam células LacZ+. Contudo, todas as células transgênicas observadas estavam situadas no interstício. Concluindo, não foi possível observar a integração das células transgênicas transplantadas aos túbulos seminíferos do testículo receptor após 45 dias do transplante autólogo utilizando a técnica de injeção intratesticular de células espermatogoniais LacZ+ no mediastino de bezerros pré-púberes da raça Nelore. / Mammalian spermatogenesis is sustained by self renewal and differentiation of spermatogonial stem cells (SSCs). The study of these cells provides a model to better understand adult stem cell biology and the mechanisms that control SSC functions. Besides the biomedical potential to perform studies of infertility in many species, SSCs hold a promising biotechnological application at animal transgenesis. In this manner, the goal of this study was to answer the question: "Can LacZ+ bovine SSCs be integrated into seminiferous tubule of prepubertal Nelore bulls subjected to autologous transplantation?" Hence, 5 months old bulls (n=16) were hemicastrated and spermatogonial cells were isolated by a two step enzymatic digestion procedure. After differential plating, cells were transduced with a lentivirus vector carrying the LacZ reporter gene sequence. Animals were randomly allocated in four experimental groups: LacZ+/PKH26+, LacZ+/PKH26-, LacZ-/PKH26+, LacZ-/PKH26-. After 60 h of the onset of in vitro culture, spermatogonial cells were autologously transplanted to the remaining testes by an ultrasound guided needle injection at the testis mediastinum. The transplanted testes were surgically removed after 45 days and testicular tissue samples were subjected to x-gal staining to assess the integration of transgenic spermatogonial cells to seminiferous tubule. Spermatogonial cells were successfully isolated and in vitro cultured. However, it was not possible to obtain a SSC enriched population of cells by differential plating. Although it was decided by the transplant of spermatogonial cells instead of pure SSCs only, it was detected the expression of SSC marker genes ITGA6, PGP9.5, GFR-1 and the affinity for DBA by the isolated cells. Cryosections of x-gal stained testicular tissue samples allowed the observation of transgenic cells in 8 out of 8 animals that received LacZ+ cells. However, all transgenic cells observed were located at the interstitial space. In conclusion, it was not possible to observe the integration of the transplanted transgenic cells into seminiferous tubule of prepubertal Nelore bulls subjected to autologous transplantation using an ultrasound guided needle injection at the testis mediastinum, after 45 days of transplant.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21166号 / 農博第2292号 / 新制||農||1061(附属図書館) / 学位論文||H30||N5140(農学部図書室) / 京都大学大学院農学研究科応用生物科学専攻 / (主査)教授 今井 裕, 教授 久米 新一, 准教授 南 直治郎 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Ao longo da vida reprodutiva dos machos adultos, espermatozoides são formados pelas células-tronco espermatogoniais (SSCs, do inglês spermatogonial stem cells) por um processo conhecido como espermatogênese. O cultivo in vitro de SSCs abriu novas possibilidades para a transgenia, no entanto os protocolos requerem a adição de fatores de crescimento, o que encarece a manutenção dessas células por um tempo prolongado, fazendo da criopreservação de SSCs uma alternativa para esse problema. O fenótipo molecular de células-tronco espermatogoniais tem sido objeto de estudo nas últimas décadas. Uma das moléculas mais estudadas como marcador na caracterização de espermatogônias é a alfa-6 integrina. Baseado nestas informações, a seguinte hipótese foi proposta: SSCs que apresentam maior expressão de alfa-6 integrina são mais eficientes para modificações genéticas e colonização de túbulos seminíferos. Para testar essa hipótese, as SSCs murinas foram dissociadas de testículos de camundongos com 8 a 11 dias de idade. Essas células foram cultivadas in vitro, caracterizadas quanto sua morfologia, congeladas e incubadas com anticorpo anti-alfa-6 integrina para a purificação das SSCs por separação celular ativada por fluorescência (FACS). Células testiculares foram geneticamente modificadas com a inserção do gene marcador LacZ e o transplante através dos ductos eferentes foi padronizado. As Células germinativas testiculares foram dissociadas e cultivadas in vitro, porém a viabilidade foi aquém da desejada, inviabilizando as etapas de transformação, transplante e posterior avaliação histológica. Usando o marcador molecular alfa-6 integrina foi possível separar populações de células germinativas testiculares por FACS e a expressão gênica de ITGα6, GFRα1, Oct-4 e Thy-1 foi detectada por RT-PCR quantitativo. Em conclusão, não foi possível comprovar a eficiência de transdução e colonização em túbulos seminíferos por células-tronco espermatogoniais selecionadas com alfa-6 integrina. / Throughout the reproductive life of adult males, spermatozoa are formed from spermatogonial stem cells (SSCs) by a process known as spermatogenesis. The in vitro culture of SSCs created new possibilities for transgenesis, however the protocols require addition of growth factors, which increases the maintenance costs of these cells for a prolonged time, making of the cryopreservation of SSCs an alternative for this problem. The molecular phenotype of spermatogonial stem cells have been target of studies in recent decades. One of the most studied marker molecule in the characterization of spermatogonia is integrin alpha-6. Based on these informations, the following hypothesis was proposed: SSCs that show increased expression of integrin alpha-6 are more efficient for genetic modification and colonization of seminiferous tubules. In order to test this hypotesis, murine SSCs were dissociated from testes of 8 to 11 days old mice. These cells were in vitro cultured, characterized based on its morphology, frozen and incubated with anti-integrin alpha-6 antibody for the purification of SSCs by activated cell sorting fluorescence (FACS). Testicular cells were genetically modified with the insertion of the marker gene LacZ and transplantation through the efferent ducts was standardized. The testicular germ cells were dissociated and in vitro cultured, however viability was below expected, precluding the steps of transformation, transplantation and subsequent histological evaluation. Using molecular marker integrin alpha-6 it was possible to separate testicular germ cell populations by FACS and gene expression of ITGα6, GFRα1, Oct-4 and Thy-1was detected by quantitative RT-PCR. In conclusion, it was not possible to prove the efficiency of transduction and colonization in the seminiferous tubules by spermatogonial stem cells selected with alpha 6 integrin.

Ao longo da vida reprodutiva dos machos adultos, espermatozoides são formados pelas células-tronco espermatogoniais (SSCs, do inglês spermatogonial stem cells) por um processo conhecido como espermatogênese. O cultivo in vitro de SSCs abriu novas possibilidades para a transgenia, no entanto os protocolos requerem a adição de fatores de crescimento, o que encarece a manutenção dessas células por um tempo prolongado, fazendo da criopreservação de SSCs uma alternativa para esse problema. O fenótipo molecular de células-tronco espermatogoniais tem sido objeto de estudo nas últimas décadas. Uma das moléculas mais estudadas como marcador na caracterização de espermatogônias é a alfa-6 integrina. Baseado nestas informações, a seguinte hipótese foi proposta: SSCs que apresentam maior expressão de alfa-6 integrina são mais eficientes para modificações genéticas e colonização de túbulos seminíferos. Para testar essa hipótese, as SSCs murinas foram dissociadas de testículos de camundongos com 8 a 11 dias de idade. Essas células foram cultivadas in vitro, caracterizadas quanto sua morfologia, congeladas e incubadas com anticorpo anti-alfa-6 integrina para a purificação das SSCs por separação celular ativada por fluorescência (FACS). Células testiculares foram geneticamente modificadas com a inserção do gene marcador LacZ e o transplante através dos ductos eferentes foi padronizado. As Células germinativas testiculares foram dissociadas e cultivadas in vitro, porém a viabilidade foi aquém da desejada, inviabilizando as etapas de transformação, transplante e posterior avaliação histológica. Usando o marcador molecular alfa-6 integrina foi possível separar populações de células germinativas testiculares por FACS e a expressão gênica de ITGα6, GFRα1, Oct-4 e Thy-1 foi detectada por RT-PCR quantitativo. Em conclusão, não foi possível comprovar a eficiência de transdução e colonização em túbulos seminíferos por células-tronco espermatogoniais selecionadas com alfa-6 integrina. / Throughout the reproductive life of adult males, spermatozoa are formed from spermatogonial stem cells (SSCs) by a process known as spermatogenesis. The in vitro culture of SSCs created new possibilities for transgenesis, however the protocols require addition of growth factors, which increases the maintenance costs of these cells for a prolonged time, making of the cryopreservation of SSCs an alternative for this problem. The molecular phenotype of spermatogonial stem cells have been target of studies in recent decades. One of the most studied marker molecule in the characterization of spermatogonia is integrin alpha-6. Based on these informations, the following hypothesis was proposed: SSCs that show increased expression of integrin alpha-6 are more efficient for genetic modification and colonization of seminiferous tubules. In order to test this hypotesis, murine SSCs were dissociated from testes of 8 to 11 days old mice. These cells were in vitro cultured, characterized based on its morphology, frozen and incubated with anti-integrin alpha-6 antibody for the purification of SSCs by activated cell sorting fluorescence (FACS). Testicular cells were genetically modified with the insertion of the marker gene LacZ and transplantation through the efferent ducts was standardized. The testicular germ cells were dissociated and in vitro cultured, however viability was below expected, precluding the steps of transformation, transplantation and subsequent histological evaluation. Using molecular marker integrin alpha-6 it was possible to separate testicular germ cell populations by FACS and gene expression of ITGα6, GFRα1, Oct-4 and Thy-1was detected by quantitative RT-PCR. In conclusion, it was not possible to prove the efficiency of transduction and colonization in the seminiferous tubules by spermatogonial stem cells selected with alpha 6 integrin.

No description available.

Fxrα est le récepteur nucléaire des acides biliaires, exprimé majoritairement dans le foie, l'intestin, les reins et les glandes surrénales. L'intérêt pour ce dernier est devenu croissant au cours des dernières années, de part le rôle central qu'il joue dans le contrôle de l'homéostasie du cholestérol, des acides biliaires, des triglycérides ou encore du glucose. Plus récemment, Fxrα ainsi que ses ligands, les acides biliaires, ont été localisés dans le testicule, soulevant la question du rôle potentiel de Fxrα dans cet organe, et plus généralement dans la fonction de reproduction mâle. Mais les études menées à ce sujet restent jusqu'à présent peu nombreuses, et focalisées sur son implication dans le contrôle du métabolisme des stéroïdes : l'activation in vivo de Fxrα par un agoniste synthétique conduit ainsi chez l'adulte à court terme à une répression de la stéroïdogenèse. Outre son rôle dans le contrôle de l'activité endocrine des cellules de Leydig, l'impact de l'activation in vivo de Fxrα sur la physiologie plus globale du testicule n'a jamais été abordé à ce jour. De telles études seraient pourtant pertinentes étant donné que Fxrα est ciblé pour le traitement de pathologies métaboliques telles que la dyslipidémie ou le diabète. Dans ce contexte, l'objectif de ce travail de thèse était d'étudier le rôle de Fxrα dans la physiologie et la pathophysiologie du testicule, en s'appuyant sur l'analyse d'un modèle murin dont le gène codant Fxrα a été invalidé. Nos résultats démontrent que : 1) la perte de Fxrα prédispose le testicule à une sur-mortalité des cellules germinales dans un contexte pathologique de cholestase ; 2) la sur-activation de la signalisation Fxrα au cours de la puberté conduit à un défaut de la différenciation germinale, associée à une altération de la fonction endocrine du testicule ; 3) outre la régulation de la stéroïdogenèse dans les cellules de Leydig, Fxrα participe au contrôle des fonctions sertoliennes et de la prolifération et / ou différenciation des cellules germinales souches. L'ensemble de ces données définissent Fxrα comme un nouvel acteur impliqué dans le contrôle de la physiologie testiculaire et devraient être prises en considération quant-à l'utilisation de molécules agonistes et / ou antagonistes de Fxrα dans le cadre du traitement de pathologies métaboliques. / Fxrα is the bile acid nuclear receptor, predominantly expressed in liver, intestine, kidney and adrenal glands. In recent years, interest in Fxrα has been increasing due to its central role in the control of cholesterol, bile acids, triglycerides or glucose homeostasis. More recently, Fxrα and its ligands, bile acids, have been detected in the testis pointing out its potential involvement in this tissue and more widely in the male reproductive functions. However, the few studies on this topic focused essentially on Fxrα involvement in the control of steroids metabolism. Indeed, activation of Fxrα in vivo with a synthetic agonist leads to short-term steroidogenesis repression in the adult. In vivo the impact of alteration of Fxrα signaling on the global testis physiology has never been explored so far. Such studies would be pertinent considering that Fxrα is a target for the treatment of metabolic diseases such as dyslipidemia or diabetes. In this context, the aim of my work was to study the implication of Fxrα in testis physiology and physiopathology by analyzing a knock out mouse model for Fxrα. Our results show that: 1) the loss of Fxrα increase germ cell mortality in the testis in a disease context of cholestasis ; 2) over-activation of Fxrα signaling during puberty leads to germ cell differentiation defects, associated with an alteration of testis endocrine function ; 3) besides steroidogenesis control in Leydig cell, Fxrα is involved in Sertoli cell functions and spermatogonial stem cell proliferation and/or differentiation. Taken together, these data define Fxrα as a new actor involved in the control of testis physiology, and should be taken into consideration regarding the use of Fxrα agonistic or antagonistic ligands for the treatment of metabolic diseases.