Regulation of pancreatic cell fate

描述(申请人提供)：糖尿病是世界范围内一个日益严重的健康问题。目前正在进行重大的研究工作，以了解和预防1型和2型糖尿病的发病机制，这两种疾病都会导致产生胰岛素的β细胞功能逐渐丧失。特别是，许多研究人员正在探索利用胚胎和成人干细胞或无关的体细胞群作为产生胰岛素的β细胞的替代来源的方法。其中许多方法正在取得进展；然而，由于我们对调节正常胰腺发育的机制的不完全了解，大量全功能β细胞的高效生产尚未实现。我们已经确定Nkx2.2是确定的小鼠胰岛细胞群体的规范和分化的关键调节因子。值得注意的是，已经在人类患者中发现了NKX2.2零突变；胰腺缺陷与Nkx2.2零突变小鼠的胰腺缺陷相似，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作为转录激活和抑制因子来调节胰腺细胞的特性和胰岛细胞的特性。特别是，我们确定并鉴定了Nkx2.2的许多新靶点，包括基本的胰岛细胞特异性调控因子， 神经病和阿克斯。我们还确定Nkx2.2是一个大型抑制物复合体的一部分，该复合体在胚胎和成人中维持β细胞的特性。我们新的初步数据表明，Nkx2.2在Neurogenin3+内分泌前体种群的上游发挥作用，调节其分化潜能。此外，我们已经确定Nkx2.2通过其NK2特异性结构域(SD)与维持DNA甲基转移酶DNMT1物理上相互作用，以介导胰岛中启动子和细胞特异性的DNA甲基化。最后，我们已经证明了Nkx2.2通过不同的细胞特异性活动在胚胎和成年胰腺中介导了几种不同的基本功能。这项应用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规范、维持胰岛细胞特性和β细胞功能是必不可少的。在具体目标1中，我们将 确定Neurogenin3+内分泌前体群体的分化潜能是如何调节的。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特性，并调节成年β细胞的成熟和功能。在具体目标3中，我们将确定Nkx2.2的功能如何与DNA甲基化相交，从而在胰岛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.