RESUMO
The ubiquitously expressed Polycomb Group protein Yin-Yang1 (YY1) is believed to regulate gene expression through direct binding to DNA elements found in promoters or enhancers of target loci. Additionally, YY1 contains diverse domains that enable a plethora of protein-protein interactions, including association with the Oct4/Sox2 pluripotency complex and Polycomb Group silencing complexes. To elucidate the in vivo role of YY1 during gastrulation, we generated embryos with an epiblast specific deletion of Yy1. Yy1 conditional knockout (cKO) embryos initiate gastrulation, but both primitive streak formation and ingression through the streak is severely impaired. These streak descendants fail to repress E-Cadherin and are unable to undergo an appropriate epithelial to mesenchymal transition (EMT). Intriguingly, overexpression of Nodal and concomitant reduction of Lefty2 are observed in Yy1 cKO embryos, suggesting that YY1 is normally required for proper Nodal regulation during gastrulation. Furthermore, definitive endoderm is specified but fails to properly integrate into the outer layer. Although anterior neuroectoderm is specified, mesoderm production is severely restricted. We show that YY1 directly binds to the Lefty2 locus in E7.5 embryos and that pharmacological inhibition of Nodal signaling partially restores mesoderm production in Yy1 cKO mutant embryos. Our results reveal critical requirements for YY1 during several important developmental processes, including EMT and regulation of Nodal signaling. These results are the first to elucidate the diverse role of YY1 during gastrulation in vivo.
Assuntos
Transição Epitelial-Mesenquimal/genética , Gastrulação/genética , Proteína Nodal/genética , Transdução de Sinais/genética , Fator de Transcrição YY1/genética , Animais , Sequência de Bases , Benzodioxóis/farmacologia , Relação Dose-Resposta a Droga , Embrião de Mamíferos/embriologia , Embrião de Mamíferos/metabolismo , Feminino , Regulação da Expressão Gênica no Desenvolvimento/efeitos dos fármacos , Camadas Germinativas/embriologia , Camadas Germinativas/metabolismo , Imidazóis/farmacologia , Imuno-Histoquímica , Hibridização In Situ , Fatores de Determinação Direita-Esquerda/genética , Fatores de Determinação Direita-Esquerda/metabolismo , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Microscopia de Fluorescência , Proteína Nodal/metabolismo , Ligação Proteica , Piridinas/farmacologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Transdução de Sinais/efeitos dos fármacos , Fatores de Tempo , Técnicas de Cultura de Tecidos , Fator de Transcrição YY1/metabolismoRESUMO
The multifaceted polycomb group gene Yin-Yang1 (Yy1) has been implicated in a variety of transcriptional regulatory roles both as an activator and silencer of gene expression. Here we examine the role of Yy1 during oocyte growth by conditional deletion of the locus in the growing oocyte. Our results indicate that YY1 is required for oocyte maturation and granulosa cell expansion. In mutant oocytes, we observe severely reduced expression of both Gdf9 and Bmp15, suggesting a mechanism underlying the failure of granulosa cell expansion. Consequently, we observe infertility, failure of estrus cycling, and altered reproductive hormone levels in mutant females. Additionally, we find that YY1-deficient oocytes exhibit altered levels of several oocyte-specific factors, including Pou5f1, Figla, Lhx8, Oosp1, and Sohlh2. These results document YY1's involvement in folliculogenesis and ovarian function in the mouse and indicate that YY1 is required specifically in the oocyte for oocyte-granulosa cell communication.