Regulation of pancreatic cell fate

描述（由申请人提供）：糖尿病是一个日益严重的健康问题，在世界各地。目前正在进行重要的研究工作，以了解和预防1型和2型糖尿病的发病机制，这两种糖尿病都导致功能性胰岛素产生β细胞的逐渐丧失。特别是，许多研究人员正在探索利用胚胎和成体干细胞或无关的体细胞群体作为产生胰岛素的β细胞的替代来源的方法。许多这些方法正在取得进展;然而，大量功能齐全的β细胞的有效生产尚未实现，主要是由于我们对调节正常胰腺发育的机制的不完全理解。我们已经确定Nkx2.2作为小鼠中确定的胰岛细胞群的特化和分化的关键调节因子。值得注意的是，已经确定了人类患者中的NKX2.2无效突变;胰腺缺陷类似于在NKX2.2无效小鼠中观察到的缺陷，证实了我们的研究对于了解人类胰腺发育和疾病的重要性。我们已经证实，Nkx2.2功能作为一个转录激活因子和阻遏物，以调节胰腺细胞的规格和胰岛细胞的身份。特别是，我们鉴定并表征了Nkx2.2的许多新靶点，包括必需的胰岛细胞特异性调节剂， NeuroD和Arx。我们还确定Nkx2.2是一个大型阻遏物复合物的一部分，该复合物在胚胎和成人中维持β细胞的身份。我们的新的初步数据表明，Nkx2.2的功能上游的神经生成素3+内分泌前体群体，以调节他们的分化潜力。此外，我们已经确定Nkx2.2通过其NK 2特异性结构域（SD）结构域与维持DNA甲基转移酶DNMT 1物理相互作用，以介导胰岛中启动子和细胞特异性DNA甲基化。最后，我们已经证明，Nkx2.2介导几个不同的基本功能，在胚胎和成人胰腺，通过不同的细胞特异性活动。本申请的目的是进一步剖析Nkx2.2介导的调控和表观遗传事件，这些事件对于胰岛细胞特化、维持胰岛细胞身份和β细胞功能至关重要。具体目标1： 确定神经生成素3+内分泌前体群体的分化潜力是如何调节的。在具体目标2中，我们将确定Nkx2.2如何启动和维持胰岛细胞的身份，并介导成人β细胞的成熟和功能。在具体目标3中，我们将确定Nkx2.2功能如何与DNA甲基化交叉，以在胰岛中发挥不同的细胞特异性调节功能。我们的长期目标是了解指定和维持功能性胰岛细胞类型的交叉转录和表观遗传调控程序。

DESCRIPTION (provided by applicant): Diabetes mellitus is an escalating health problem throughout the world. Significant research efforts are currently underway to understand and prevent the pathogeneses of Type 1 and Type 2 diabetes, which both lead to the gradual loss of functional insulin-producing beta cells. In particular, many researchers are exploring methods to exploit embryonic and adult stem cells or unrelated somatic cell populations as alternative sources of insulin-producing beta cells. Progress is being made with many of these approaches; however, the efficient production of large numbers of fully functional beta cells has not yet been achieved, primarily due to our incomplete understanding of the mechanisms regulating normal pancreas development. We have identified Nkx2.2 as a critical regulator of the specification and differentiation of defined islet cell populations in mice. Notably, NKX2.2 null mutations in human patients have been identified; the pancreatic defects resemble those seen in Nkx2.2 null mice, confirming the importance of our studies for also understanding human pancreas development and disease. We have verified that Nkx2.2 functions as a transcriptional activator and repressor to regulate pancreas cell specification and islet cell identity. In particular, we identified and characterized many novel targets of Nkx2.2, including the essential islet cell specific regulators, NeuroD and Arx. We have also determined that Nkx2.2 is part of a large repressor complex that maintains beta cell identity in the embryo and in the adult. Our new preliminary data suggests that Nkx2.2 functions upstream of the Neurogenin3+ endocrine precursor population to regulate their differentiation potentials. Furthermore, we have determined that Nkx2.2 physically interacts with the maintenance DNA methyltransferase DNMT1 through its NK2-specific domain (SD) domain to mediate promoter- and cell-specific DNA methylation in the islet. Finally, we have demonstrated that Nkx2.2 mediates several distinct essential functions in the embryonic and adult pancreas through differential cell-specific activities. The goal of this application is to futher dissect the Nkx2.2 mediated regulatory and epigenetic events that are essential for islet cell specification, maintenance of islet cell identity and beta cell function. In Specific Aim 1 we will determine how the differentiation potential of Neurogenin3+ endocrine precursor populations is regulated. In Specific Aim 2 we will determine how Nkx2.2 initiates and maintains islet cell identity, and mediates adult beta cell maturation and function. In Specific Aim 3 we will determine how Nkx2.2 functions intersect with DNA methylation to exert distinct cell-specific regulatory functions in the pancreatic islet. Our long-term goal is to understand the intersecting transcriptional and epigenetic regulatory programs that specify and maintain functional islet cell types.