Growth Versus Differentiation in Human Beta Cells

但前提是。 许多类型的细胞在生长和分化之间表现出相反的关系。这种联系是 尤其是在β细胞中。β细胞的有丝分裂指数很低，体外生长刺激会导致 然而，胰岛素基因表达的快速关闭，控制这种表达的分子机制是 人们对此知之甚少。 在过去的资助期间，使用来自人类内分泌胰腺的细胞系进行的研究 导致了一种假设，即正向和负向作用的bHLH转录之间的平衡 因子在控制β细胞的增殖和分化中起着核心作用。正向作用bHLH 内分泌胰腺中的因子包括Ngn3和NeuroDI。此处提供的初步数据 证明了这些因素诱导了另外两个正作用的bHLH因子，Hes6和AtohS，两者都不是 之前在内分泌胰腺中发现了这种物质。 Hes6是一种bHLH因子，它抑制Notch信号，Notch信号控制胰腺的形态发生和 内分泌分化。Hes6被发现在胰岛特异表达，Hes6突变小鼠 患上糖尿病，内分泌细胞增殖率增加，也许最有趣的是， 自发形成新的胰腺小叶。Hes6在内分泌胰腺中的作用将被继续研究 在转基因小鼠中使用细胞系模型和谱系分析。 Atohs是一种神经源性bHLH因子，在神经元和胶质细胞之间的谱系决定中发挥作用。 细胞的命运。和Hes6一样，它是由Ngn3和NeuroDI诱导的。虽然没有可用的抗体，但RT-PCR 证明它在胰岛细胞中表达，而在非内分泌细胞中不表达。因此，它是一个强有力的候选者 在内分泌细胞分化中发挥作用。为了追求这一发现，AtohS的下游目标将 被确定了。最后，为了更好地了解控制胰岛素基因表达的途径 已经对β细胞、小分子文库进行了筛选，以寻找调节胰岛素启动子活性的化合物。 为了确定这些化合物的作用机制，将获得生化和遗传数据 并使用生物信息学方法进行整合以进行路径分析。

PROVIDED. Many cell types exhibit an inverse relationship between growth and differentiation. This linkage is particularly strong in beta-cells. Beta-cells have a low mitotic index, and growth stimulation in vitro results in rapid shut off of insulin gene expression, However, the molecular mechanism by which this is controlled is poorly understood. During the past funding period, studies using cell lines developed from the human endocrine pancreas have led to the hypothesis that the balance between positively and negatively acting bHLH transcription factors plays a central role in controlling beta-cell proliferation and differentiation. Positively acting bHLH factors in the endocrine pancreas include Ngn3 and NeuroDI. Preliminary data presented here demonstrates that these factors induce two other positively acting bHLH factors, Hes6 and AtohS, neither of which had previously been identified in the endocrine pancreas. Hes6 is a bHLH factor that inhibits Notch signaling, which controls pancreatic morphogenesis and endocrine differentiation. Hes6 was found to be specifically expressed in islets, and Hes6 mutant mice developed diabetes, had an increased rate of endocrine cell proliferation, and perhaps most interestingly, spontaneously formed new pancreatic lobules. The role of Hes6 in the endocrine pancreas will be pursued using both cell line models and lineage analysis in transgenic mice. AtohS is a neurogenic bHLH factor that plays a role in the lineage decision between neuronal and glial cell fates. Like Hes6, it was induced by Ngn3 and NeuroDI. Although no antibody is available, RT-PCR demonstrated that it is expressed in islet but not in non-endocrine cells. Thus, it is a strong candidate for playing a role in endocrine cell differentiation. To pursue that finding, the downstream targets of AtohS will be ascertained. Finally, to understand better the pathways that control insulin gene expression in the beta-cell, small molecule libraries have been screened for compunds that modulate insulin promoter activity. To determine the mechanism by which those compounds act, biochemical and genetic data will be acquired and integrated using a bioinformatic approach to pathway analysis.