RESUMO
Members of the Iroquois B (IrxB) homeodomain cluster genes, specifically Irx3 and Irx5, are crucial for heart, limb and bone development. Recently, we reported their importance for oocyte and follicle survival within the developing ovary. Irx3 and Irx5 expression begins after sex determination in the ovary but remains absent in the fetal testis. Mutually antagonistic molecular signals ensure ovary versus testis differentiation with canonical Wnt/ß-catenin signals paramount for promoting the ovary pathway. Notably, few direct downstream targets have been identified. We report that Wnt/ß-catenin signaling directly stimulates Irx3 and Irx5 transcription in the developing ovary. Using in silico analysis of ATAC- and ChIP-Seq databases in conjunction with mouse gonad explant transfection assays, we identified TCF/LEF-binding sequences within two distal enhancers of the IrxB locus that promote ß-catenin-responsive ovary expression. Meanwhile, Irx3 and Irx5 transcription is suppressed within the developing testis by the presence of H3K27me3 on these same sites. Thus, we resolved sexually dimorphic regulation of Irx3 and Irx5 via epigenetic and ß-catenin transcriptional control where their ovarian presence promotes oocyte and follicle survival vital for future ovarian health.
Assuntos
Epigênese Genética/fisiologia , Gônadas/embriologia , Proteínas de Homeodomínio/genética , Fatores de Transcrição/genética , Via de Sinalização Wnt/fisiologia , beta Catenina/metabolismo , Animais , Diferenciação Celular/genética , Células Cultivadas , Embrião de Mamíferos , Feminino , Regulação da Expressão Gênica no Desenvolvimento , Gônadas/metabolismo , Proteínas de Homeodomínio/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos ICR , Camundongos Transgênicos , Ovário/embriologia , Ovário/metabolismo , Caracteres Sexuais , Diferenciação Sexual/genética , Testículo/embriologia , Testículo/metabolismo , Fatores de Transcrição/metabolismoRESUMO
Healthy development of ovarian follicles depends on appropriate interactions and function between oocytes and their surrounding granulosa cells. Previously, we showed that double knockout of Irx3 and Irx5 (Irx3/5 DKO) in mice resulted in abnormal follicle morphology and follicle death. Further, female mouse models of individual Irx3 or Irx5 knockouts were both subfertile but with distinct defects. Notably, the expression profile of each gene suggests independent roles for each; first, they are colocalized in pre-granulosa cells during development that then progresses to include oocyte expression during germline nest breakdown and primordial follicle formation. Thereafter, their expression patterns diverge between oocytes and granulosa cells coinciding with the formulation and maturation of intimate oocyte-granulosa cell interactions. The objective of this study was to investigate the contributions of Irx5 and somatic cell-specific expression of Irx3 during ovarian development. Our results show that Irx3 and Irx5 contribute to female fertility through different mechanisms and that Irx3 expression in somatic cells is important for oocyte quality and survival. Based on evaluation of a series of genetically modified mouse models, we conclude that IRX3 and IRX5 collaborate in the same cells and then in neighboring cells to foster a healthy and responsive follicle. Long after these two factors have extinguished, their legacy enables these intercellular connections to mature and respond to extracellular signals to promote follicle maturation and ovulation.