SWI/SNF & Yolk Sac Development

哺乳动物卵黄囊在移植后早期胚胎中起着重要的营养作用。卵黄囊的发育对许多基因的时空表达调控高度敏感；然而，关于染色质结构与卵黄囊组织形态发生过程中所需的转录装置之间的关系的研究很少。与增强子或启动子结合的转录激活剂招募染色质·修饰复合体，这些复合体共价修饰N-端组蛋白尾巴或利用ATPase活性来改变核小体的构象和/或位置。因此，启动子采用~开放的“染色质”构型，因此可以启动转录。相反，转录抑制子可以招募类似或相同的复合体到其他基因座，以建立·封闭的染色质配置，从而阻止转录。现有数据表明，这些复合体调节卵黄囊发育的造血性和非造血性，但这些功能是相互独立的。为了证实这一假设，将在造血室特异性地表达8rg1cdna转基因来修复这一缺陷。这些数据将证实这些复合体在卵黄囊内皮细胞中是否起到明显的作用。此外，基于初步数据，我们建议进行实验，以检验在突变背景下下调Fz5(Frizzled5)表达和上调CDH2(e粘附素2)是否会减少WNT信号中的自由J)·catenin的量，以及这种错误调控是否与TGFb途径交叉。这些信号转导通路的失调被认为可以调节卵黄囊的增殖、迁移、分化和凋亡，而这些都是卵黄囊发育的关键步骤。

The mammalian yolk sac provides an important nutritive role in the early postimplantatlon embryo. Yolk sac development is highly sensitive to the regulation of temporal and spatial expression of a number of genes; however, little work has been done on the relationship of chromatin structure and the transcriptional apparatus required specifically during morphogenesis of this tissue. Transcriptional activators bound to enhancers or promoters recruit chromatin·modifying complexes, which covalently modify N-terrninal histone tails or utilize ATPase activity to alter the conformation and/or position of nucleosomes. As a result, promoters adopt an ~open" chromatin configuration so transcription can be initiated. Conversely, transcriptional repressors ean recruit similar or identical complexes to other loci to establish a ·closedchromatin configuration that precludes transcription. Existing data suggest that these complexes regulate both the hematopoietic and non·hematopoietic aspects of yolk sac development but that these functions are independent of one another. To confirm this hypothesis, a 8rg1 cDNA-transgene will be specifically expressed In the hematopoietic compartment to rescue this defect. These data will confirm whether the complexes playa distinguishable role in endothelial cells of the yolk sac. In addition, based on preliminary data, experiments are proposed to test whether down regulation of Fz5 (frizzled 5) expression and upregulation of Cdh2 (eadherin 2) on the mutant background reduces the amount of free J)·catenin for WNT signaling and that this misregulation intersects with the Tgfb pathway. Misregulation of these pathways are known to regulate proliferation, migration, differentiation and apoptosis, all of which are key steps in yolk sac development.