Opposing Pathways in Mammalian Sex Determination

描述（由申请人提供）：性腺形成为双电位原基，可以发育成睾丸或卵巢。随着它的发展，它揭示了细胞命运的显著可塑性和精细平衡的信号机制，这些机制竞争建立雄性或雌性途径。y连锁基因Sry通过启动支持细胞命运决定和睾丸索形态组织来控制男性性别决定。在过去的十年里，人们对睾丸形态发生的下游调控途径有了很多了解。然而，对于Sry如何启动这一过程知之甚少。现有数据表明，Sry的瞬时表达控制了支持细胞前体的细胞命运决定，从而导致Sox9在整个支持细胞谱系中的稳定表达。与此同时，支持体前体开始聚集在生殖细胞周围，上皮化，并经历新生脐带形成的过程。我们的假设是，支持前体细胞的命运决定步骤和间充质向上皮的转变是通过SOX9的稳定表达而在分子上联系起来的。对这一假设的调查将是我们在此资助期间工作的大方向，重点关注四个主要领域。(1)基于我们之前的工作，我们将使用谱系追踪方法来研究Sertoli前体是如何产生并激活Sox9表达的。(2)我们最近发现了Sertoli命运决定过程中拮抗途径竞争的分子证据。利用小鼠突变体，我们将研究相反的信号通路和转录网络如何导致雄性通路的激活和雌性通路的抑制。(3)我们计划通过染色质免疫沉淀试验和M33突变小鼠来确定多梳组染色质重塑蛋白M33如何参与卵巢或睾丸发育途径的建立。(4)我们将利用活体成像、嵌合小鼠、细胞极性和细胞粘附标记、携带cMaf和Mafb突变的小鼠，研究睾丸索是如何形成的，以及通过SOX9和MAP基因之间的相互作用，睾丸索的形成是否与支持细胞分化有关。cMaf和Mafb是果蝇促性腺激素产生的关键家族成员，已知在哺乳动物软骨形成过程中与SOX9相互作用。

DESCRIPTION (provided by applicant): The gonad forms as a bipotential primordium that can develop into a testis or an ovary. As it develops it reveals the remarkable plasticity of cell fate and the finely balanced signaling mechanisms that compete to establish the male or female pathway. A Y-linked gene, Sry, controls male sex determination by initiating both Sertoli cell fate determination and the morphological organization of testis cords. In the past decade, much has been learned about downstream pathways that regulate testis morphogenesis. However, little is known about how Sry initiates this process. Available data suggests that transient expression of Sry controls a cell fate decision in Sertoli cell precursors that leads to the stable expression of Sox9 throughout the Sertoli lineage. Coincident with this process, Sertoli precursors begin to aggregate around germ cells, epithelialize, and undergo a process of de novo cord formation. Our hypothesis is that the fate determination step and the mesenchymal to epithelial transition of Sertoli precursor cells are molecularly linked through stabilized expression of SOX9. Investigation of this hypothesis will be the broad direction of our work during this funding period with emphasis on four main areas of focus. (1) Based on our previous work, we will use a lineage tracing approach to investigate how Sertoli precursors arise and activate Sox9 expression. (2) We have recently found molecular evidence for the competition of antagonistic pathways during Sertoli fate determination. Using mouse mutants, we will investigate how opposing signaling pathways and transcriptional networks result in the activation of the male pathway and the repression of the female pathway. (3) We plan to determine how the polycomb group chromatin remodeling protein, M33, is involved in the establishment of ovarian or testis developmental pathways using chromatin immunoprecipitation assays and M33 mutant mice. (4) We will investigate how testis cords form, and whether cord formation is linked to Sertoli cell differentiation through an interaction between SOX9 and MAP genes using live imaging, chimeric mice, markers of cell polarity and cell adhesion, and mice carrying mutations in cMaf and Mafb, members of a family shown to be critical for gonadogenesis in Drosophila, and known to interact with SOX9 during chondrogenesis in mammals.