Mechanisms of Pancreatic Beta Cell Specification

描述(由申请人提供)：维持葡萄糖稳态对我们的健康至关重要，如果维持不了，就会导致糖尿病。尽管目前的治疗方案是每天注射几次胰岛素，但糖尿病患者的血糖水平仍然波动很大，使糖尿病成为美国第六大死亡原因。胰岛素注射的替代方法包括尝试开发一种治疗糖尿病的细胞疗法，方法是从人类胚胎干细胞(HESCs)产生分泌胰岛素的？-细胞，或者通过将其他类型的细胞重新编程为？-细胞。然而，尽管在将hESCs分化为胰岛素表达细胞方面取得了一些成功，但这些细胞表达多种激素，并不能逆转糖尿病。从其他细胞来源产生真正有功能的？-细胞的主要瓶颈是缺乏关于？-细胞是如何被指定的知识。我们观察到，转录因子Nkx6.1在内分泌前体细胞中的有条件的、稳定的激活引入了？细胞命运偏差，并不利于向非？细胞胰岛细胞类型的分化。此外，我们发现Nkx6.1是维持成年小鼠细胞特异性基因表达程序所必需的。根据这一建议进行的研究将：(A)确定指定？-细胞并抑制替代内分泌细胞命运的分子线索；(B)直接测试Nkx6.1是否能在体内将非？细胞胰岛细胞重新编程为？-细胞；(C)从基因上剖析Nkx6.1控制的基因调控网络在成人？-细胞命运维持、增殖和功能调节中的作用。从这些研究中获得的知识将有助于设计策略来解决hESC来源的内分泌细胞中的混合内分泌谱系模式，并将其他类型的细胞重新编程为完全功能的？细胞。

DESCRIPTION (provided by applicant): Maintenance of glucose homeostasis is central to our health and its failure results in diabetes mellitus. Despite current treatment regimens of several insulin injections per day, blood glucose levels still fluctuate significantly in diabetic patients, making diabetes the sixth leading cause of death in the United States. Alternative approaches to insulin injections include attempts to develop a cell therapy for diabetes by producing insulin- secreting ?-cells from human embryonic stem cells (hESCs) cells or by reprogramming other cell types into ?- cells. However, despite some success to differentiate hESCs into insulin-expressing cells, these cells express multiple hormones and are not capable of reversing diabetes. The main bottleneck for generating true functional ?-cells from other cell sources is the paucity of knowledge of how ?-cells are specified. We observed that conditional, stable activation of the transcription factor Nkx6.1 in endocrine progenitors introduces a ?-cell fate bias and disfavors differentiation into non-?-cell islet cell types. Moreover, we found that Nkx6.1 is required to maintain expression of ?-cell-specific programs of gene expression in adult mice. Research under this proposal will (a) define the molecular cues that specify ?-cells and repress alternative endocrine cell fates, (b) directly test whether the Nkx6.1 can reprogram non-?-cell islet cells into ?-cells in vivo and (c) genetically dissect the gene regulatory network controlled by Nkx6.1 in the regulation of adult ?-cell fate maintenance, proliferation and function. Knowledge gained from these studies will help devise strategies to resolve mixed endocrine lineage patterns in hESC-derived endocrine cells and to reprogram other cell types into fully functional ?-cells.