Regulation of pancreatic islet cell fate

描述(申请人提供)：1型和2型糖尿病都会导致产生胰岛素的β细胞功能逐渐丧失。在尝试开发治疗糖尿病的方法时，重要的研究工作现在集中在从胚胎干细胞(ES)或成人干细胞/祖细胞群体的替代来源中产生具有功能的替代来源的β细胞。这项建议的目的是了解胚胎发育过程中β细胞分化和成熟的调节。这些研究将使我们能够确定有效区分功能贝塔细胞和替代细胞来源所必需的实验条件。我们已经确认Nkx2.2是特定胰岛细胞群规范和分化的关键调节因子；Nkx2.2对所有产生胰岛素的β细胞和大多数产生胰高血糖素的α细胞的形成都是必不可少的。我们还确定，在没有内源性Nkx2.2的情况下，Nkx2.2抑制物衍生物足以区分所有α细胞和少量未成熟的β细胞。在分子水平上，挽救的贝塔细胞与ES细胞分化方案中产生的无功能的贝塔细胞相似。另一方面，Nkx2.2阻遏物衍生物在成年β细胞中的错误表达下调了正常情况下由Nkx2.2激活的晚期转录靶点，并导致β细胞功能中断。基于这些发现，我们假设Nkx2.2在不同类型的胰岛细胞和不同发育阶段的胰岛细胞中都发挥抑制和激活作用，以促进胰岛细胞类型的规范和成熟。此外，我们认为Nkx2.2的功能是通过其不同的蛋白质结构域实现的。了解Nkx2.2如何发挥作用来指定胰岛细胞的发育，对于将其用作指导β细胞分化的工具至关重要。本提案中的研究将确定何时以及在哪些细胞类型中不同的Nkx2.2功能对于胰岛细胞类型规范是关键的。此外，我们还将确定在这些发育过程中调节Nkx2.2活性的Nkx2.2蛋白的功能结构域。综上所述，这一应用的重点是了解β细胞分化的调节。这项拟议的研究将阐明调控胰岛细胞分化的最早分子机制，并将提供额外的生物学工具来操纵来自不同细胞来源的功能性β细胞的分化，以达到治疗目的。公共卫生相关性：糖尿病是一个日益严重的世界性健康问题，其原因是产生胰岛素的β细胞功能逐渐丧失。这项研究将阐明胰岛细胞类型分化的调控。这项研究将促进我们从各种细胞来源促进β细胞分化的能力，以便为细胞替代疗法提供大量的胰岛β细胞池。

DESCRIPTION (provided by applicant): Type 1 and Type 2 diabetes both lead to the gradual loss of functional insulin-producing beta cells. In attempts to develop therapies to treat diabetes, significant research efforts are now focused on generating alternative sources of functioning beta cells from embryonic stem (ES) cells or alternative sources of adult stem/progenitor cell populations. The goal of this proposal is to understand the regulation of beta cell differentiation and maturation during embryonic development. These studies will allow us to define the experimental conditions that are necessary to efficiently differentiate functional beta cells from alternative cell sources. We have identified Nkx2.2 as a critical regulator of the specification and differentiation of defined islet cell populations; Nkx2.2 is essential for the formation of all insulin-producing beta cells and most glucagon-producing alpha cells. We have also determined that, in the absence of endogenous Nkx2.2, an Nkx2.2 repressor derivative is sufficient to differentiate all alpha cells and a small number of immature beta cells. At the molecular level, the rescued beta cells are similar to the non-functional beta cells generated in ES cell differentiation protocols. Alternatively, misexpression of the Nkx2.2 repressor derivative in adult beta cells down- regulates late transcriptional targets that are normally activated by Nkx2.2 and leads to the disruption of beta cell function. Based on these findings, we hypothesize that Nkx2.2 functions both as a repressor and activator in the different pancreatic cell types and at different stages of islet cell development to promote islet cell type specification and maturation. Furthermore, we propose that the function of Nkx2.2 is through its different protein domains. Understanding how Nkx2.2 functions to specify islet cell development will be essential for using it as a tool to direct the differentiation of beta cells. The studies in this proposal will define when and in which cell types the different Nkx2.2 functions are critical for islet cell-type specification. In addition, we will identify the functional domains of the Nkx2.2 protein that modulate Nkx2.2 activity during these developmental processes. In summary, this application is focused on understanding the regulation of beta cell differentiation. The proposed studies will elucidate the earliest molecular mechanisms that regulate islet cell differentiation and will provide additional biological tools to manipulate the differentiation of functional beta cells from alternative cell sources for therapeutic purposes. PUBLIC HEALTH RELEVANCE: Diabetes is a growing world health problem that results from the gradual loss of functional insulin producing beta cells. The proposed research will elucidate the regulation of pancreatic islet cell type differentiation. This research will facilitate our ability to promote beta cell differentiation from a variety of cell sources in order to provide large pools of islet beta cells for cell replacement therapies.