RESUMEN
During early embryogenesis in amniotic vertebrates, the gonads differentiate into either ovaries or testes. The first cell lineage to differentiate gives rise to the supporting cells: Sertoli cells in males and pre-granulosa cells in females. These key cell types direct the differentiation of the other cell types in the gonad, including steroidogenic cells. The gonadal surface epithelium and the interstitial cell populations are less well studied, and little is known about their sexual differentiation programs. Here, we show the requirement of the homeobox transcription factor gene TGIF1 for ovarian development in the chicken embryo. TGIF1 is expressed in the two principal ovarian somatic cell populations: the cortex and the pre-granulosa cells of the medulla. TGIF1 expression is associated with an ovarian phenotype in estrogen-mediated sex reversal experiments. Targeted misexpression and gene knockdown indicate that TGIF1 is required, but not sufficient, for proper ovarian cortex formation. In addition, TGIF1 is identified as the first known regulator of juxtacortical medulla development. These findings provide new insights into chicken ovarian differentiation and development, specifically cortical and juxtacortical medulla formation.
Asunto(s)
Pollos/genética , Genes Homeobox , Proteínas de Homeodominio/genética , Ovario/embriología , Proteínas Represoras/genética , Animales , Diferenciación Celular , Linaje de la Célula/genética , Embrión de Pollo , Embrión de Mamíferos/metabolismo , Femenino , Regulación del Desarrollo de la Expresión Génica , Técnicas de Silenciamiento del Gen , Gónadas/metabolismo , Proteínas de Homeodominio/metabolismo , Masculino , Ovario/citología , Ovario/metabolismo , Proteínas Represoras/metabolismo , Células de Sertoli/metabolismo , Procesos de Determinación del Sexo/genética , Diferenciación Sexual/genética , Testículo/metabolismoRESUMEN
Although the genetic triggers for gonadal sex differentiation vary across species, the cell biology of gonadal development was long thought to be largely conserved. Here, we present a comprehensive analysis of gonadal sex differentiation, using single-cell sequencing in the embryonic chicken gonad during sexual differentiation. The data show that chicken embryonic-supporting cells do not derive from the coelomic epithelium, in contrast to other vertebrates studied. Instead, they derive from a DMRT1+/PAX2+/WNT4+/OSR1+ mesenchymal cell population. We find a greater complexity of gonadal cell types than previously thought, including the identification of two distinct sub-populations of Sertoli cells in developing testes and derivation of embryonic steroidogenic cells from a differentiated supporting-cell lineage. Altogether, these results indicate that, just as the genetic trigger for sex differs across vertebrate groups, cell lineage specification in the gonad may also vary substantially.
