TrxG complexes in pancreas endocrine-cell specification

转录调控是胰腺谱系规范和成熟的关键组成部分。尽管如此，参与这一过程的转录因子调控的具体机制尚不清楚。表观遗传因素，包括DNA甲基化和组蛋白修饰是转录调控的中心介质。我们之前的数据表明，内分泌和外分泌谱系承诺所需的许多转录因子需要获得活跃的染色质状态，和/或去除抑制性组蛋白修饰才能表达。我们假设这些变化是由三胸基团（TrxG）配合物催化的。TrxG复合物都含有核心蛋白Ash2l、Dpy30、Rbbp5和Wdr5，这些蛋白对其组装和/或功能至关重要。因此，为了验证我们的假设，即该复合物对于诱导内分泌和外分泌谱系承诺所必需的转录因子是必要的，我们敲除了胰腺祖细胞中的核心成分Dpy30。我们的初步数据表明，在这些小鼠中，胰腺祖细胞进入内分泌和外分泌谱系的特异性严重受损。***基于这些初步数据，我们假设：(a) Dpy30的缺失会损害胰腺多能祖细胞向外分泌祖细胞特异性转变的能力，Dpy30是维持外分泌细胞成熟状态所必需的；(b)内分泌前体中Dpy30的缺失将阻止内分泌前转录因子的正常诱导，(c) TrxG复合物通过与胰腺关键转录因子和/或尚未确定的胰腺内分泌前特异性lncrna的相互作用被募集到顺式调节区域。为了验证这些假设，我们建议在此补助金的五年期限内实现以下目标。***目的1：确定TrxG复合物在内分泌祖细胞规格中的作用。***目的2：确定TrxG复合物在外分泌细胞分化和成熟状态中的作用。***目的3：确定TrxG复合物如何被募集到内分泌和外分泌特异性顺式调控位点。***这些研究将为胰腺祖细胞如何被指定为不同的胰腺内分泌和外分泌细胞类型提供有价值的见解，并确定TrxG复合物在这一过程中的作用。具体来说，这项工作将解决TrxG复合体对于诱导驱动这些细胞类型的发育和维持的转录级联是否必要。**

Transcriptional regulation is a critical component of pancreas lineage specification and maturation. Despite this the specific mechanisms by which transcription factors involved in this process are regulate are not well understood. Epigenetic factors, which include DNA methylation and histone modifications are central mediators of transcriptional regulation. Our previous data indicated that many of the transcription factors necessary for endocrine and exocrine lineage commitment need to gain an active chromatin state, and/or to remove repressive histone modifications to become expressed. We hypothesized that these changes were catalyzed by trithorax group (TrxG) complexes. TrxG complexes all contain the core proteins Ash2l, Dpy30, Rbbp5, and Wdr5 that are critical to their assembly and/or function. Thus to test our hypothesis that this complex was necessary for the induction of transcription factors necessary for endocrine and exocrine lineage commitment we knocked-out the core component Dpy30 in pancreas progenitors. Our preliminary data suggests that in these mice specification of pancreas progenitors into both endocrine and exocrine lineages is severely compromised.***Based on these preliminary data we hypothesize that: (a) Loss of Dpy30 impairs the ability of pancreas multipotent progenitors cells to be specified into exocrine progenitors, and that Dpy30 is necessary for exocrine cells to be maintain their mature state; (b) Loss of Dpy30 in endocrine precursors will prevent the normal induction of proendocrine transcription factors, and (c) that TrxG complexes are recruited to the cis-regulatory regions by interactions with pancreas critical transcription factors and/or by as yet unidentified pancreas endocrine progenitor specific lncRNAs. To test these hypotheses, we propose the following objectives over the five-year term of this grant.***Objective 1: To determine the role of the TrxG complex in endocrine progenitor specification.***Objective 2: To determine the role of the TrxG complex in exocrine cell specification and maturation state.***Objective 3: To determine how the TrxG complex gets recruited to endocrine and exocrine specific cis-regulatory loci.***These studies will provide valuable insight into how pancreas progenitors become specified into the different pancreas endocrine and exocrine cell types, and determine the role of the TrxG complex in this process. Specifically, this work will address whether the TrxG complex is necessary to allow the induction of the transcriptional cascades that drive the development and maintenance of these cell types. **