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的具体调控机制还不是很清楚。表观遗传因子，包括DNA甲基化和组蛋白修饰，是转录调控的中心媒介。我们以前的数据表明，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)络合物催化的。TrxG复合体都含有对其组装和/或功能至关重要的核心蛋白Ash21、Dpy30、Rbbp5和WDR5。因此，为了验证我们的假设，即这种复合体是诱导内分泌和外分泌谱系承诺所必需的转录因子所必需的，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，胰腺前体细胞同时进入内分泌和外分泌谱系的规范受到了严重损害。*基于这些初步数据，我们假设：(A)Dpy30的缺失削弱了胰腺多能祖细胞被指定为外分泌前体细胞的能力，并且Dpy30是外分泌细胞维持其成熟状态所必需的；(B)内分泌前体中Dpy30的缺失将阻止正常诱导前内分泌转录因子，以及(C)TrxG复合体通过与作为关键转录因子的胰腺和/或尚未被鉴定为胰腺内分泌前体特异性的lncRNAs的相互作用而被招募到顺式调节区。为了验证这些假说，我们提出了以下五年的资助目标。*目标1：确定TrxG复合体在内分泌前体细胞规范中的作用。*目标2：确定TrxG复合体在外分泌细胞规范和成熟状态中的作用。*目标3：确定TrxG复合体如何被招募到内分泌和外分泌特定的顺式调节基因座。*这些研究将提供有价值的洞察力，了解胰腺前体如何被指定为不同类型的胰腺内分泌和外分泌细胞，并确定TrxG复合体在这一过程中的作用。具体地说，这项工作将解决TrxG复合体是否必要，以允许诱导转录级联反应，从而驱动这些细胞类型的发育和维持。**

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. **