RESUMO
Dax1 is an orphan nuclear receptor expressed in both Leydig and Sertoli cells of the testis. Mutation of DAX1 in humans causes adrenal failure and hypogonadotropic hypogonadism. Targeted mutagenesis of Dax1 in mice reveals a primary gonadal defect characterized by overexpression of aromatase and cellular obstruction of the seminiferous tubules and efferent ductules, leading to germ cell death and infertility. Transgenic expression of DAX1 under the control of the müllerian-inhibiting substance promoter, which is selectively expressed in Sertoli cells, improves fertility but does not fully correct the histological abnormalities in the testes of Dax1 knockout (Dax1KO) mice. We therefore hypothesized that Dax1 may also play a crucial role in other somatic cells of the testis, namely the Leydig cells. A 2.1-kilobase fragment of the murine LH receptor 5'-promoter (LHR-DAX1) was used to generate transgenic mice that selectively express DAX1 in Leydig cells. Expression of the LHR-DAX1 transgene caused no observable phenotype in wild-type mice but improved fertility when expressed in Dax1KO males (rescue [RS]). Although testicular size was not increased in LHR-DAX1 RS animals, aromatase expression was restored to normal levels, and sperm production was increased. Testicular pathology was only slightly improved in RS mice compared to Dax1KO animals. Taken together with the result of previous studies of DAX1 expression in Sertoli cells, we conclude that the testis phenotype of Dax1KO mice reflects the combined effects of Dax1 deficiency in both Sertoli and Leydig cells.
Assuntos
Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/metabolismo , Fertilidade/fisiologia , Células Intersticiais do Testículo/metabolismo , Receptores do Ácido Retinoico/deficiência , Receptores do Ácido Retinoico/metabolismo , Proteínas Repressoras/metabolismo , Animais , Aromatase/metabolismo , Receptor Nuclear Órfão DAX-1 , Proteínas de Ligação a DNA/genética , Feminino , Fertilidade/genética , Humanos , Tamanho da Ninhada de Vivíparos , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Tamanho do Órgão , Fenótipo , Gravidez , Regiões Promotoras Genéticas , Receptores do LH/genética , Receptores do Ácido Retinoico/genética , Proteínas Repressoras/genética , Células de Sertoli/metabolismo , Contagem de Espermatozoides , Testículo/metabolismo , Testículo/patologiaRESUMO
Two nuclear receptors, dosage-sensitive sex reversal adrenal hypoplasia congenita, critical region on the X chromosome gene-1 (Dax-1) and steroidogenic factor-1 (SF-1), are required for adrenal development and function. In vitro assays suggest that Dax-1 represses SF-1 mediated transcription. In this study, we generated SF-1(+/-): Dax-1(-/Y) mice to examine the role of Dax-1 in SF-1-dependent steroidogenesis in vivo. While the SF-1 expression was impaired in SF-1(+/-) mice, there was no change in Dax-1 expression in SF-1(+/-) mice and no change in SF-1 expression in Dax-1(-/Y) mice. SF-1(+/-) mice had small adrenal glands with adrenal hypoplasia and cellular hypertrophy. The loss of Dax-1 in SF-1(+/-): Dax-1(-/Y) mice reversed the decreased adrenal weight and histological abnormalities observed in SF-1(+/-) mice. SF-1(+/-) mice had elevated ACTH and the lowest corticosterone following restraint stress. In contrast, Dax-1(-/Y) mice had elevated corticosterone and decreased ACTH. Adrenal responsiveness (ACTH/corticosterone) was highest in Dax-1(-/Y) mice, intermediate in WT and SF-1(+/-): Dax-1(-/Y) mice, and lowest in SF-1(+/-) mice. In accordance with these findings, ACTH stimulation testing resulted in the highest levels of corticosterone in the Dax-1(-/Y) mice. Protein levels of P450c21 and the ACTH receptor were increased in Dax-1(-/Y) mice and intermediate in SF-1(+/-): Dax-1(-/Y) mice following chronic food deprivation. These results are consistent with a model in which Dax-1 functions to inhibit SF-1-mediated steroidogenesis in vivo.
