Mechanisms regulating hepatic specification and differentiation in zebrafish

描述（由申请人提供）： 有人认为，肝脏和腹胰腺起源于共同的祖细胞，并共享一些发育特征。当在小鼠胚胎组织外植体系统中通过阻断信号（如成纤维细胞生长因子（Fgfs）和骨形态发生蛋白（Bmps））阻止肝脏诱导过程时，培养的内胚层开启了一种基因Pdx 1，该基因通常在前肠内胚层（包括胃，十二指肠和胰腺）中表达，但不在肝脏中表达。这些表达Pdx 1的内胚层外植体的进一步孵育导致胰腺内分泌和外分泌细胞的出现，表明腹侧内胚层具有产生多种组织的潜力，包括肝脏和胰腺。这项研究的总体目标是阐明机制调节肝脏规格和可塑性，并随后分化使用斑马鱼作为主要的模式生物。首先，我将通过对Wnt 2bb和Bmp 2b信号以及Hedgehog和Bmp 2b信号进行更详细的谱系追踪分析和功能丧失和获得上位性分析，研究Bmp 2b如何调节肝脏与胰腺的命运决定。其次，我将研究叉头盒和同源盒转录因子如何在Bmp 2b信号下游发挥作用，以调节肝脏与胰腺的命运决定。将进行表达分析以及内胚层特异性功能丧失和获得实验。第三，我将对大规模诱变筛选的4种突变体进行详细的表征。它们在内胚层器官的生长和分化中表现出特定的缺陷。一旦确定了优先顺序，将对潜在的分子病变进行广泛的分析，如表达模式分析和功能丧失和获得研究。我希望通过一系列的实验，我能回答肝和胰腺是如何从共同的祖细胞发育到获得它们独特的和重叠的功能的基本问题。 公共卫生相关性：肝病是美国和世界范围内死亡的主要原因。一般来说，它反映了对损伤的慢性反应，其中修复和再生导致瘢痕形成和/或瘤形成。通常，修复和再生在成年重演胚胎发育。因此，了解发展的机制对预防和治疗慢性损伤和肝癌有直接的意义。

DESCRIPTION (provided by applicant): It has been suggested that the liver and the ventral pancreas originate from common progenitors and share several developmental features. When the liver induction process was prevented in a mouse embryonic tissue explant system by blockig [sic] signals such as Fibroblast growth factors (Fgfs) and Bone morphogenetic proteins (Bmps), the cultured endoderm turned on a gene, Pdx1, that normally expressed in the foregut endoderm [sic], including the stomach, duodenum and pancreas, but not in the liver. Further incubation of these Pdx1 expressing endodermal explants led to the appearance of pancreatic endocrine and exocrine cells, suggesting that the ventral endoderm has the potential to give rise to multiple tissues, including the liver and pancreas. The overall goal of this research proposal is to elucidate mechanisms regulating liver specification and its plasticity, and subsequent differentiation using zebrafish as the main model organism. First, I will investigate how Bmp2b regulates liver versus pancreatic fate decision by performing more detailed lineage tracing analysis ad [sic] loss- and gain-of-function epistatic analysis of Wnt2bb and Bmp2b signaling as well as Hedgehog and Bmp2b signaling. Second, I will investigate how Forkhead box and Homeobox transcription factors function downstream of Bmp2b signaling to regulate liver versus pancreatic fate decision. Expression analysis as well as endoderm-specific loss-and gain-of-function experiments will be performed. Third, I will perform detailed characterization of 4 mutants from large scale mutagenesis screening. They show specific defects in the growth and differentiation of endodermal organs. Once prioritized, identification of the underlying molecular lesion will be followed by extensive analysis, such as expression pattern analysis and loss-and gain-of-function studies. I expect I can answer the fundamental question how the liver and pancreas develop from common progenitors to acquire their unique and overlapping function with series of these experiments. PUBLIC HEALTH RELEVANCE: Liver disease is a major cause of death in the United States and world wide. In general it reflects a chronic response to injury, in which repair and regeneration lead to scarring and/or neoplasia. Often, repair and regeneration in the adult recapitulate embryonic development. Thus, understanding the mechanisms of development has direct implications for prevention and treatment of chronic injury and liver cancer.