HNF6 Function in the Pancreatic Endocrine Lineage

描述（由申请人提供）：虽然胰岛移植显示出作为1型糖尿病长期治疗的前景，但可用供体组织的供应有限。因此，确定调节胰岛分化和功能的因素至关重要，目的是从胰腺或胚胎干细胞中产生可再生的胰岛供应。HNF 6转录因子对内分泌分化和胰岛功能至关重要。HNF 6在发育过程中在整个胰腺中表达，但在出生前，随着胰岛的形成，内分泌细胞中的HNF 6被永久下调。HNF 6-/-小鼠内分泌分化延迟，内分泌细胞较少，胰岛结构异常，并患有糖尿病。HNF 6激活了关键的前内分泌转录因子ngn 3的表达（ngn 3突变小鼠缺乏所有胰腺内分泌细胞）。HNF 6基因敲除的结果表明，HNF 6的功能对于正常的内分泌发育是必不可少的，但不能区分HNF 6是否仅在内分泌发育的最早阶段需要激活ngn 3，或者HNF 6是否在整个内分泌发育过程中持续发挥作用以促进内分泌细胞的终末分化。本研究的目的是阐明HNF 6在胰岛内分泌发育中的作用。使用小鼠HNF 6可以上调或灭活条件下，我们将分析HNF 6的作用，在规范，增殖和分化的胰腺细胞的内分泌谱系。为了剖析HNF 6在内分泌前体增殖和分化中的作用，将使用可逆诱导的内分泌特异性转基因在不同发育时间点激活HNF 6表达。我们将确定是否HNF 6过表达在早期胚胎阶段刺激增加规格和/或分化的内分泌前体和发育窗口期间，HNF 6可以影响内分泌规格。使用细胞类型特异性和可诱导的Cre-lox策略，HNF 6基因将在内分泌发育途径沿着不同阶段选择性失活，包括：祖细胞特化、增殖、内分泌细胞类型的多样化和终末分化。这些研究将确定HNF 6在内分泌谱系发育中起关键作用的胚胎阶段，即HNF 6仅在内分泌特化的早期阶段需要，还是在胚胎发生期间持续需要用于终末分化和获得成熟功能。

DESCRIPTION (provided by applicant): While islet transplantation shows promise as a long-term treatment for Type 1 diabetes, the supply of available donor tissue is limiting. It is thus critical to identify factors that regulate islet differentiation and function, with the goal of generating a replenishable supply of islets from pancreatic or embryonic stem cells. The HNF6 transcription factor is critical for endocrine differentiation and islet function. HNF6 is expressed throughout the pancreas during development, but becomes permanently down-regulated in endocrine cells just before birth, as islets are forming. HNF6 -/- mice have delayed endocrine differentiation, fewer endocrine cells, abnormal islet architecture, and diabetes. HNF6 activated expression of the critical proendocrine transcription factor, ngn3 (ngn3 mutant mice lack all pancreatic endocrine cells). The results of the global HNF6 knockout demonstrate that HNF6 function is essential for normal endocrine development, but can not distinguish whether HNF6 is required only at the earliest stages of endocrine development to activate ngn3, or whether HNF6 functions continuously throughout endocrine development to promote terminal differentiation of endocrine cells. The goal of this proposal is to elucidate the role of HNF6 during islet endocrine development. Using mice in which HNF6 can be either up-regulated or inactivated conditionally, we will analyze the role of HNF6 in specification, proliferation, and differentiation of pancreatic cells to the endocrine lineage. To dissect the role of HNF6 in endocrine precursor proliferation and differentiation, HNF6 expression will be activated at different developmental time points, using a reversibly inducible endocrine-specific transgene. We will determine whether HNF6 over-expression during early embryonic stages stimulates increased specification and/or differentiation of endocrine precursors and the developmental window during which HNF6 can affect endocrine specification. Using cell type-specific and inducible Cre-lox strategies, the HNF6 gene will be selectively inactivated at different stages along the pathway of endocrine development including: progenitor specification, proliferation, diversification of endocrine cell types, and terminal differentiation. These studies will determine the embryonic stage(s) during which HNF6 plays a critical role in the development of the endocrine lineage, i.e. is HNF6 needed only at early stages of endocrine specification, or is it required continuously during embryogenesis for terminal differentiation and acquisition of mature function.