SWI/SNF & Yolk Sac Development

哺乳动物卵黄囊在胚胎着床后早期具有重要的营养作用。卵黄囊发育受多个基因的时空表达调控高度敏感；然而，关于染色质结构与该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子募集染色质修饰复合物，这些复合物共价修饰n端组蛋白尾部或利用atp酶活性改变核小体的构象和/或位置。因此，启动子采用“开放”的染色质结构，从而可以启动转录。相反，转录抑制因子可以招募与其他基因座相似或相同的复合物，以建立一个封闭的染色质结构，从而阻止转录。现有数据表明，这些复合物调节卵黄囊发育的造血和非造血方面，但这些功能彼此独立。为了证实这一假设，一种8rg1基因转基因将在造血室中特异性表达以挽救这一缺陷。这些数据将证实这些复合物是否在卵黄囊内皮细胞中起着可区分的作用。此外，在初步数据的基础上，我们提出了实验来验证突变背景下Fz5（卷曲5）表达下调和Cdh2（粘附素2）表达上调是否会减少WNT信号通路中游离J)·catenin的数量，并且这种错误调节是否与Tgfb通路交叉。已知这些途径的错误调控可调节增殖、迁移、分化和凋亡，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.