HNF6 Function in the Pancreatic Endocrine Lineage

描述（由申请人提供）：虽然胰岛移植有望作为1型糖尿病的长期治疗方法，但可用的供体组织供应有限。因此，确定调节胰岛分化和功能的因素是至关重要的，目的是从胰腺或胚胎干细胞中产生可补充的胰岛供应。HNF6转录因子对内分泌分化和胰岛功能至关重要。HNF6在整个胰腺发育过程中表达，但在出生前，随着胰岛的形成，在内分泌细胞中永久下调。HNF6 -/-小鼠出现内分泌分化延迟、内分泌细胞减少、胰岛结构异常和糖尿病。HNF6激活了关键的内分泌前转录因子ngn3的表达（ngn3突变小鼠缺乏所有胰腺内分泌细胞）。全球敲除HNF6的结果表明，HNF6的功能对正常内分泌发育至关重要，但无法区分HNF6是否仅在内分泌发育的早期阶段激活ngn3，还是HNF6在整个内分泌发育过程中持续发挥作用，促进内分泌细胞的终末分化。本研究的目的是阐明HNF6在胰岛内分泌发育中的作用。利用HNF6有条件上调或失活的小鼠，我们将分析HNF6在胰腺细胞向内分泌谱系分化、增殖和分化中的作用。为了分析HNF6在内分泌前体增殖和分化中的作用，我们将使用一种可逆诱导的内分泌特异性转基因，在不同的发育时间点激活HNF6的表达。我们将确定HNF6在胚胎早期的过表达是否会刺激内分泌前体的增加和/或分化，以及HNF6影响内分泌调节的发育窗口期。通过细胞类型特异性和可诱导的Cre-lox策略，HNF6基因将在内分泌发育的不同阶段选择性失活，包括：祖细胞特化、增殖、内分泌细胞类型多样化和终末分化。这些研究将确定HNF6在内分泌谱系发育中起关键作用的胚胎阶段，即HNF6是仅在内分泌规范的早期阶段才需要，还是在胚胎发生过程中持续需要HNF6以实现最终分化和成熟功能的获得。

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.