Premature ovarian Insufficiency (POI) is the cessation of the ovarian function before the age of 40, defined by high serum gonadotrophins, low estradiol and amenorrhea for at least 4 months. The etiology may be iatrogenic after a surgery, chemotherapy or radiotherapy treatment, environmental, autoimmune or genetic. However, in most of the cases the cause remains unknown. Clinical and family studies suggest a strong heritability of age at menopause and POI, but the number of genetic causes and genes identified to be involved in human POI remains very small. In POI patients, the two crucial functions of the ovary, hormonal secretion and reproduction, are absent. In the last decades, however, new advances in assisted reproduction techniques have allowed the possibility of carrying pregnancies to POI women, thanks to oocyte donation. The aim of this study was to identify new genetic factors implicated in the development of POI women and to analyse the reproductive possibilities and outcome of women with a genetic cause of POI. For the first part of the study, the DNA of a cohort of POI women recruited in the Fertility Clinic of the Hôpital Erasme of the Université Libre de Bruxelles was used to sequence five candidate genes (FSHR, GDF9, BMP15, AMH and AMHR2) known to be implicated in the ovarian folliculogenesis. The most important findings were two very rare variants and one unknown variant in the AMH gene. The functional study performed with these variants suggested a diminished function of the mutant protein. Furthermore, one of the variants was found in the mother of one of the patients, who was also diagnosed of POI at 32 years old. These arguments strongly suggest that a defective AMH could play a role in the development of POI. This is supported by previous studies with knock out mice models, which show an earlier depletion of the ovarian follicle pool due to a faster recruitment of the primordial follicles that constitute the ovarian reserve. The sequencing of the BMP15 gene led to the identification of two new variants not identified among controls but not predicted to be deleterious. Interestingly, one variant previously reported in POI women and predicted to be deleterious for the protein function, was found in a Sub-Saharan African POI patient as well as in our control cohort. This variant was already studied functionally and shown to have a reduced biological activity. However, we identified this variant in 6% of the Sub-Saharan African control population, which suggests that this is a more prevalent variant in the African genotype and raises up the importance of the ethnicity when studying genetic variants.The sequencing of the other genes (FSHR, GDF9 and AMHR2) did not lead to any association with POI.In the second part of the study, 24 women with Turner syndrome and POI were analysed in terms of reproductive, obstetrical and perinatal outcome after oocyte donation. This specific group of patients was chosen because of their specific systemic anomalies that could interfere with pregnancy outcome and because very few reports have been published on this subject. In the 23 patients finally transferred, the pregnancy rate was similar to that obtained after oocyte donation in other cohorts. There was a miscarriage rate of 23% and a rate of complications of pregnancy as high as 50%, mainly caused by pregnancy-induced hypertensive diseases. Four women at risk of genetic POI were included in the fertility preservation program in order to vitrify their oocytes. Three of them have already vitrified successfully their oocytes but none of them has yet used them.Oocyte vitrification represents a new hope for those women with genetic risk of POI to be able to carry a pregnancy with their own oocytes.In conclusion, three variants of the AMH gene could be implicated in the development of POI as demonstrated by the reduced in vitro bioactivity of the variants and the familial segregation of the cases. Since then, it sounds plausible to propose AMH sequencing in the case of familial POI and secondary amenorrhea.In the BMP15 gene, 2 new variants were predicted to be tolerated. A potentially deleterious variant of the BMP15 gene (L148P) previously associated to POI, was also found in 6% of the Sub-Saharan African controls which suggests that it is a common variant in the African ethnic. No clear association was found between the other tested candidate genes and our POI cohort.Regarding Turner’s Syndrome pregnancies, we can conclude that they are high-risk pregnancies that need of a multidisciplinary follow-up before and during pregnancy.Oocyte cryopreservation represents a new tool to be offered to women at risk of genetic POI to preserve their fertility, but not without previous genetic counselling. / Doctorat en Sciences médicales (Médecine) / info:eu-repo/semantics/nonPublished

Este estudo teve como objetivo geral a análise do gene FMR1 (Fragile X Mental Retardation gene 1) quanto a sua relação com a insuficiência ovariana primária (Fragile X-related Primary Ovarian Insufficiency, FXPOI). No Capítulo I, apresentamos revisão da literatura sobre FXPOI. A pré-mutação do gene FMR1 constitui a mais frequente causa genética de predisposição para menopausa precoce e entre os casos familiais, cerca de 10% estão associados à pré-mutação do gene FMR1. Entretanto, pouco se conhece sobre a expressão do gene no ovário de mamíferos e os mecanismos pelos quais a pré-mutação causa POI permanecem desconhecidos. O Capítulo II apresenta os resultados do estudo da expressão do gene FMR1 nos ovários adultos, humano e murino. As enormes dificuldades inerentes à obtenção e ao estudo de células germinativas femininas nos levaram a estudar células da granulosa humana (HGC), que são de fácil obtenção, como subprodutos de procedimentos de fertilização in vitro. Também estudamos a expressão do Fmr1 em células da granulosa de camundongos da linhagem CD1 (MGC), coletadas nos ovidutos, após estimulação da ovulação. As células da granulosa interagem intensamente com os ovócitos durante a foliculogênese, transmitindo sinais através do ovário e apoiando o crescimento e a maturação dos ovócitos durante as últimas fases do crescimento folicular. É, portanto, possível que alterações celulares induzidas pela pré-mutação do gene FMR1 nas HGC afetem o crescimento folicular, a taxa de ovulação e a fecundidade. Padronizamos os protocolos de isolamento e de cultivo das HGC do fluido folicular e confirmamos a origem das células isoladas pela expressão de marcadores de HGC, por RT-PCR, e pela natureza lipídica dos grânulos citoplasmáticos, pela coloração com o corante lipofílico DiI. Demonstramos, por RT-PCR que as HGC isoladas do líquido folicular expressam o mRNA do FMR1. Em camundongos, também por RT-PCR, evidenciamos a expressão do mRNA do Fmr1 em ovócitos e nas MGC, coletados do oviduto após hiper-estimulação da ovulação. Por hibridação in situ de RNA em HCG cultivadas, detectamos o mRNA do FMR1 disperso no citoplasma e no núcleo, concentrado em regiões cujas características indicaram ser nucléolos. Essa mesma distribuição foi observada em fibroblastos cultivados. Essa provável localização nucleolar sugere que o transcrito do FMR1, nessas células, constitua ribonucleoproteínas mensageiras, para seu direcionamento do nucléolo para sítios citoplasmáticos específicos, onde ocorre sua tradução. Verificamos, por Western blotting, que as HGC expressam, em níveis elevados, isoformas da FMRP, com massa molecular entre 60 e 95 kDa. Determinamos a localização subcelular da FMRP nas HGC e da Fmrp nas MGC, por imunocoloração. Os sinais de hibridação foram visualizados dispersos, em grânulos finos, no citoplasma das HGC e das MGC, de maneira semelhante ao padrão de distribuição da proteína em neurônios. Nos filopódios das MGC, observamos marcação concentrada em alguns pontos, de forma semelhante ao padrão, previamente descrito, de distribuição da Fmrp em espinhas dendríticas de neurônios de hipocampo de rato, constituindo grânulos de RNA, que promovem o transporte de mRNA e controlam a tradução. O padrão de distribuição semelhante entre neurônios e MGC pode refletir similaridade da função da Fmrp nos dois tecidos. A indução de estresse oxidativo nas HGC por tratamento com arsenito sódico, levou a proteína a deixar de ter distribuição citoplasmática difusa e passar a fazer parte de grânulos de estresse perinucleares, colocalizando-se com TIA-1, marcador dessas estruturas. Resultados semelhantes foram anteriormente obtidos em células HeLa e no hipocampo de rato. Esses resultados apoiam a hipótese de que a FMRP participa do mecanismo transitório de parada da tradução após estresse. No Capítulo III, descrevemos nossas tentativas para obtenção de linhagem de células tronco embrionárias (ESC) de camundongo knockin (KI) quanto a pré-mutação do gene Fmr1. Para a obtenção de embriões KI, fêmeas selvagens (WT; linhagem C57) foram cruzadas com machos KI (linhagem C57/BL6) e fêmeas KI foram cruzadas com machos WT. Pretendíamos comparar a expressão do gene Fmr1 na linhagem de ESC KI e linhagem de ESC WT, inclusive durante a diferenciação Não tivemos sucesso, o que pode ser atribuído às dificuldades inerentes à obtenção de ESC. No acompanhamento dos primeiros quatro dias do desenvolvimento in vitro dos embriões, alterações de clivagem e parada de desenvolvimento foram mais frequentemente observadas nos embriões obtidos de fêmeas KI. Entretanto as taxas médias de sobrevivência de ovócitos para blastocistos e de embriões com 8 a 16 células para blastocistos não diferiram estatisticamente entre as fêmeas KI e selvagens; a grande variabilidade entre o número de blastocistos obtidos por fêmea e o pequeno número delas nos grupos KI (seis) e selvagem (sete) indicam que esses resultados devem ser interpretados com cautela. A análise da proteína Fmrp nos blastocistos, por imunocoloração, mostrou distribuição provavelmente citoplasmática, com padrão granular de marcação, sendo as granulações mais frequentes nos blastocistos de fêmeas WT, porém mais grosseiras nos blastocistos de fêmeas KI. Esse conjunto de dados é sugestivo de efeito da pré-mutação do gene Fmr1 em fêmea murina sobre o início do desenvolvimento de seus embriões. Esse aspecto necessita investigação mais aprofundada / This study aimed at investigating the FMR1 gene (Fragile X Mental Retardation gene 1), regarding its relationship with primary ovarian insufficiency (Fragile X-related Primary Ovarian Insufficiency, FXPOI). In Chapter I, we present a literature review on FXPOI. The FMR1 premutation is the most frequent genetic cause of predisposition to premature ovary insufficiency (POI) and, among the POI familial cases, about 10% are associated with the FMR1 gene premutation. However, little is known about the gene expression in the mammal ovary, and the mechanisms by which the premutation causes POI remain unknown. Chapter II presents the study of the FMR1 gene expression in the human and murine adult ovaries. The enormous difficulties inherent in obtaining and studying female germ cells led us to study human granulosa cells (HGC), which are easily obtained as byproducts of in vitro fertilization procedures. We also studied the FMR1 expression in granulosa cells of mice of the CD1 strain (MGC), collected from the oviducts after ovulation induction. Granulosa cells interact functionally with oocytes during folliculogenesis, transmitting signals through the ovary and supporting growth and maturation of oocytes during the later stages of follicular growth. It is, therefore, possible that cellular changes induced by the FMR1 premutation in HGCs affect follicular growth, ovulation rate and fecundity. We standardized protocols for isolation and culture of HGCs obtained from follicular fluid and confirmed the origin of the isolated cells by the expression of HGC markers, using RT-PCR, and by the lipid nature of the cytoplasmic granules, as demonstrated by the staining with the lipophilic dye DiI. We demonstrated, by RT-PCR, that HGCs isolated from follicular fluid express the FMR1 mRNA. In mice, also by RT-PCR, we detected the Fmr1 mRNA in oocytes and in the MGCs, collected from the oviduct after ovulation hyperstimulation. Using RNA in situ hybridization on cultured HCGs, we detected the FMR1 mRNA dispersed in the cytoplasm and, in the nucleus, concentrated in regions whose features indicated to be nucleoli. This same distribution was observed in cultured fibroblasts. This probable nucleolar localization of the FMR1 transcript in these cells suggests that it constitutes messenger ribonucleoproteins for further targeting to specific cytoplasmic sites where translation occurs. We verified, by Western blotting, that HGCs express high levels of the main FMRP isoforms, with molecular mass between 60 and 95 kDa. We determined the FMRP subcellular localization in HGCs and that of Fmrp in MGCs, by immunostaining. The hybridization signals were seen scattered in fine granules in the cytoplasm of both HGCs and MGCs, in a pattern of distribution similar to that observed in neurons. In the MGC filopodia, the protein labeling was concentrated at some sites, similar to the previously described pattern of Fmrp distribution in neuronal dendritic spines of rat hippocampus, where it is part of RNA granules, promoting mRNA transport and translation control. The similar distribution pattern between neurons and MGC may reflect the similarity of FMRP function in both tissues. The induction of oxidative stress in the HGC by treatment with sodium arsenite led the protein to leave its diffuse cytoplasmic distribution to become part of perinuclear stress granules, co-localized with TIA-1, a marker of these structures. Similar results were previously obtained in HeLa cells and in rat hippocampus. These results support the hypothesis that FMRP participates in the mechanism of the transient translation arrest after stress. In Chapter III, we describe our attempts to obtain an embryonic stem cell line (ESC) from knock-in mice (KI) for the FMR1 premutation. To obtain KI embryos, wild females (WT, strain C57) were crossed with males KI (strain C57/BL6), and KI females were crossed with WT males. We planned to compare the expression of the fmr1 gene in the ESCs from the KI and WT strains, including during differentiation. We did not succeed in obtaining an ESC KI line, which can be attributed to difficulties inherent to the procedure. At follow-up of the first four days of in vitro development of embryos, changes in cleavage and developmental arrest were more frequently observed in embryos obtained from KI females. Meanwhile, the average survival rates of oocytes to blastocysts, and 8-16 cell embryos to blastocysts were not statistically different between the KI and WT females. The great variability among the numbers of blastocysts obtained per female and the small size of the KI (six females) and WT (seven females) groups indicate that these results should be interpreted with caution. Immunostaining analysis of the Fmrp in blastocysts showed a probably cytoplasmic distribution, with a granular pattern of labeling, the grains being more common in blastocysts from WT females, but coarser in blastocysts from KI females. These data are suggestive that the Fmr1 premutation in murine females affects the early development of their embryos. This aspect needs further investigation

Este estudo teve como objetivo geral a análise do gene FMR1 (Fragile X Mental Retardation gene 1) quanto a sua relação com a insuficiência ovariana primária (Fragile X-related Primary Ovarian Insufficiency, FXPOI). No Capítulo I, apresentamos revisão da literatura sobre FXPOI. A pré-mutação do gene FMR1 constitui a mais frequente causa genética de predisposição para menopausa precoce e entre os casos familiais, cerca de 10% estão associados à pré-mutação do gene FMR1. Entretanto, pouco se conhece sobre a expressão do gene no ovário de mamíferos e os mecanismos pelos quais a pré-mutação causa POI permanecem desconhecidos. O Capítulo II apresenta os resultados do estudo da expressão do gene FMR1 nos ovários adultos, humano e murino. As enormes dificuldades inerentes à obtenção e ao estudo de células germinativas femininas nos levaram a estudar células da granulosa humana (HGC), que são de fácil obtenção, como subprodutos de procedimentos de fertilização in vitro. Também estudamos a expressão do Fmr1 em células da granulosa de camundongos da linhagem CD1 (MGC), coletadas nos ovidutos, após estimulação da ovulação. As células da granulosa interagem intensamente com os ovócitos durante a foliculogênese, transmitindo sinais através do ovário e apoiando o crescimento e a maturação dos ovócitos durante as últimas fases do crescimento folicular. É, portanto, possível que alterações celulares induzidas pela pré-mutação do gene FMR1 nas HGC afetem o crescimento folicular, a taxa de ovulação e a fecundidade. Padronizamos os protocolos de isolamento e de cultivo das HGC do fluido folicular e confirmamos a origem das células isoladas pela expressão de marcadores de HGC, por RT-PCR, e pela natureza lipídica dos grânulos citoplasmáticos, pela coloração com o corante lipofílico DiI. Demonstramos, por RT-PCR que as HGC isoladas do líquido folicular expressam o mRNA do FMR1. Em camundongos, também por RT-PCR, evidenciamos a expressão do mRNA do Fmr1 em ovócitos e nas MGC, coletados do oviduto após hiper-estimulação da ovulação. Por hibridação in situ de RNA em HCG cultivadas, detectamos o mRNA do FMR1 disperso no citoplasma e no núcleo, concentrado em regiões cujas características indicaram ser nucléolos. Essa mesma distribuição foi observada em fibroblastos cultivados. Essa provável localização nucleolar sugere que o transcrito do FMR1, nessas células, constitua ribonucleoproteínas mensageiras, para seu direcionamento do nucléolo para sítios citoplasmáticos específicos, onde ocorre sua tradução. Verificamos, por Western blotting, que as HGC expressam, em níveis elevados, isoformas da FMRP, com massa molecular entre 60 e 95 kDa. Determinamos a localização subcelular da FMRP nas HGC e da Fmrp nas MGC, por imunocoloração. Os sinais de hibridação foram visualizados dispersos, em grânulos finos, no citoplasma das HGC e das MGC, de maneira semelhante ao padrão de distribuição da proteína em neurônios. Nos filopódios das MGC, observamos marcação concentrada em alguns pontos, de forma semelhante ao padrão, previamente descrito, de distribuição da Fmrp em espinhas dendríticas de neurônios de hipocampo de rato, constituindo grânulos de RNA, que promovem o transporte de mRNA e controlam a tradução. O padrão de distribuição semelhante entre neurônios e MGC pode refletir similaridade da função da Fmrp nos dois tecidos. A indução de estresse oxidativo nas HGC por tratamento com arsenito sódico, levou a proteína a deixar de ter distribuição citoplasmática difusa e passar a fazer parte de grânulos de estresse perinucleares, colocalizando-se com TIA-1, marcador dessas estruturas. Resultados semelhantes foram anteriormente obtidos em células HeLa e no hipocampo de rato. Esses resultados apoiam a hipótese de que a FMRP participa do mecanismo transitório de parada da tradução após estresse. No Capítulo III, descrevemos nossas tentativas para obtenção de linhagem de células tronco embrionárias (ESC) de camundongo knockin (KI) quanto a pré-mutação do gene Fmr1. Para a obtenção de embriões KI, fêmeas selvagens (WT; linhagem C57) foram cruzadas com machos KI (linhagem C57/BL6) e fêmeas KI foram cruzadas com machos WT. Pretendíamos comparar a expressão do gene Fmr1 na linhagem de ESC KI e linhagem de ESC WT, inclusive durante a diferenciação Não tivemos sucesso, o que pode ser atribuído às dificuldades inerentes à obtenção de ESC. No acompanhamento dos primeiros quatro dias do desenvolvimento in vitro dos embriões, alterações de clivagem e parada de desenvolvimento foram mais frequentemente observadas nos embriões obtidos de fêmeas KI. Entretanto as taxas médias de sobrevivência de ovócitos para blastocistos e de embriões com 8 a 16 células para blastocistos não diferiram estatisticamente entre as fêmeas KI e selvagens; a grande variabilidade entre o número de blastocistos obtidos por fêmea e o pequeno número delas nos grupos KI (seis) e selvagem (sete) indicam que esses resultados devem ser interpretados com cautela. A análise da proteína Fmrp nos blastocistos, por imunocoloração, mostrou distribuição provavelmente citoplasmática, com padrão granular de marcação, sendo as granulações mais frequentes nos blastocistos de fêmeas WT, porém mais grosseiras nos blastocistos de fêmeas KI. Esse conjunto de dados é sugestivo de efeito da pré-mutação do gene Fmr1 em fêmea murina sobre o início do desenvolvimento de seus embriões. Esse aspecto necessita investigação mais aprofundada / This study aimed at investigating the FMR1 gene (Fragile X Mental Retardation gene 1), regarding its relationship with primary ovarian insufficiency (Fragile X-related Primary Ovarian Insufficiency, FXPOI). In Chapter I, we present a literature review on FXPOI. The FMR1 premutation is the most frequent genetic cause of predisposition to premature ovary insufficiency (POI) and, among the POI familial cases, about 10% are associated with the FMR1 gene premutation. However, little is known about the gene expression in the mammal ovary, and the mechanisms by which the premutation causes POI remain unknown. Chapter II presents the study of the FMR1 gene expression in the human and murine adult ovaries. The enormous difficulties inherent in obtaining and studying female germ cells led us to study human granulosa cells (HGC), which are easily obtained as byproducts of in vitro fertilization procedures. We also studied the FMR1 expression in granulosa cells of mice of the CD1 strain (MGC), collected from the oviducts after ovulation induction. Granulosa cells interact functionally with oocytes during folliculogenesis, transmitting signals through the ovary and supporting growth and maturation of oocytes during the later stages of follicular growth. It is, therefore, possible that cellular changes induced by the FMR1 premutation in HGCs affect follicular growth, ovulation rate and fecundity. We standardized protocols for isolation and culture of HGCs obtained from follicular fluid and confirmed the origin of the isolated cells by the expression of HGC markers, using RT-PCR, and by the lipid nature of the cytoplasmic granules, as demonstrated by the staining with the lipophilic dye DiI. We demonstrated, by RT-PCR, that HGCs isolated from follicular fluid express the FMR1 mRNA. In mice, also by RT-PCR, we detected the Fmr1 mRNA in oocytes and in the MGCs, collected from the oviduct after ovulation hyperstimulation. Using RNA in situ hybridization on cultured HCGs, we detected the FMR1 mRNA dispersed in the cytoplasm and, in the nucleus, concentrated in regions whose features indicated to be nucleoli. This same distribution was observed in cultured fibroblasts. This probable nucleolar localization of the FMR1 transcript in these cells suggests that it constitutes messenger ribonucleoproteins for further targeting to specific cytoplasmic sites where translation occurs. We verified, by Western blotting, that HGCs express high levels of the main FMRP isoforms, with molecular mass between 60 and 95 kDa. We determined the FMRP subcellular localization in HGCs and that of Fmrp in MGCs, by immunostaining. The hybridization signals were seen scattered in fine granules in the cytoplasm of both HGCs and MGCs, in a pattern of distribution similar to that observed in neurons. In the MGC filopodia, the protein labeling was concentrated at some sites, similar to the previously described pattern of Fmrp distribution in neuronal dendritic spines of rat hippocampus, where it is part of RNA granules, promoting mRNA transport and translation control. The similar distribution pattern between neurons and MGC may reflect the similarity of FMRP function in both tissues. The induction of oxidative stress in the HGC by treatment with sodium arsenite led the protein to leave its diffuse cytoplasmic distribution to become part of perinuclear stress granules, co-localized with TIA-1, a marker of these structures. Similar results were previously obtained in HeLa cells and in rat hippocampus. These results support the hypothesis that FMRP participates in the mechanism of the transient translation arrest after stress. In Chapter III, we describe our attempts to obtain an embryonic stem cell line (ESC) from knock-in mice (KI) for the FMR1 premutation. To obtain KI embryos, wild females (WT, strain C57) were crossed with males KI (strain C57/BL6), and KI females were crossed with WT males. We planned to compare the expression of the fmr1 gene in the ESCs from the KI and WT strains, including during differentiation. We did not succeed in obtaining an ESC KI line, which can be attributed to difficulties inherent to the procedure. At follow-up of the first four days of in vitro development of embryos, changes in cleavage and developmental arrest were more frequently observed in embryos obtained from KI females. Meanwhile, the average survival rates of oocytes to blastocysts, and 8-16 cell embryos to blastocysts were not statistically different between the KI and WT females. The great variability among the numbers of blastocysts obtained per female and the small size of the KI (six females) and WT (seven females) groups indicate that these results should be interpreted with caution. Immunostaining analysis of the Fmrp in blastocysts showed a probably cytoplasmic distribution, with a granular pattern of labeling, the grains being more common in blastocysts from WT females, but coarser in blastocysts from KI females. These data are suggestive that the Fmr1 premutation in murine females affects the early development of their embryos. This aspect needs further investigation