HEPATOCYTE NUCLEAR FACTORS IN LIVER REGENERATION

肝脏是为数不多的能够完全 因毒素、病毒等造成的细胞损伤而自我再生 感染或组织切除。这项提议的长期目标是 了解增殖和肝细胞特异性的作用 转录因子在肝脏再生过程中介导复制。 肝细胞特异性基因表达的转录调控依赖于 多个DNA结合位点的组合相互作用 独特的肝细胞核因子(HNF)。肝的再生 损伤后涉及肝细胞增殖的平衡 加上持续表达所需的肝细胞特异性基因 动态平衡，同时减少细胞的转录- 可能干扰肝细胞复制的特定基因。虽然 这种转录下降的机制仍然存在。 未经鉴定，切割的同源结构域HNF-6蛋白很可能是 因为它是为数不多的肝细胞特异性转录之一 在肝脏再生过程中表达降低的因子。 此外，一些潜在的hnf-6靶基因在 肝再生，其中几种可能抑制肝细胞复制。 将产生一种降低HFN-6基因的转基因小鼠系 可以防止肝脏再生过程中的表达。我们将使用这些 小鼠测试未减弱的HFN-6表达是 抑制肝脏再生。即刻早期基因表达 在肝再生过程中诱导的已知的是介导肝细胞 进入细胞周期的G1期。然而， 肝细胞晚期的转录调控机制 复制还没有完全被理解。进一步研究 肝细胞周期进程中的转录过程 再生，我们将改变有翼螺旋的肝细胞表达 HNF-3/叉头同源11(HfH-11)基因。HFH-11是候选者之一 转录因子参与细胞周期进程，因为它的 在肝细胞时期，表达被短暂地重新激活 增殖，推测HfH-11结合部位存在于细胞内。 C-myc、c-myb、转化生长因子α、细胞周期蛋白B1和 细胞周期蛋白D1。我们将产生具有有条件靶向HFH的小鼠- 11成人肝细胞基因破坏与肝再生的研究 这些小鼠将使我们能够检验HfH-11 表达是肝细胞复制所必需的。函数的增益 建议在转基因小鼠中进行研究，以检验早产儿 肝再生过程中HfH-11在肝细胞中的表达 肝细胞增殖期细胞周期动力学改变。评估 这些转基因小鼠在肝肿瘤中形成肝结节 推广模式将允许我们调查是否连续 肝细胞表达hfH-11可增加肝细胞癌的发生率 肝细胞癌。对转录机制的理解 哪些调节肝脏再生的物质可以让我们识别出 在肝纤维化和肝纤维化期间可能被破坏的通路 肝硬变。

The liver is one of the few adult organs capable of completely regenerating itself in response to cellular injury from toxins, viral infections or tissue removal. The long term goal of this proposal is to understand the role of proliferation- and hepatocyte-specific transcription factors mediating replication during liver regeneration. Transcriptional regulation of hepatocyte-specific gene expression relies on combinatorial interaction of multiple DNA binding sites by several distinct hepatocyte nucleus factors (HNF). Regeneration of the liver following injury involves a balance between hepatocyte proliferation plus sustained expression of hepatocyte-specific genes required for homeostasis and simultaneously diminishing the transcription of cell- specific genes that may interfere with hepatocyte replication. Although the mechanisms involved in this transcriptional decline remain uncharacterized, the cut-homeodomain HNF-6 protein is likely to be involved because it is one of the few hepatocyte-specific transcription factors whose expression is reduced during liver regeneration. Furthermore, a number of potential HNF-6 target genes decline during liver regeneration, several of which may inhibit hepatocyte replication. A transgenic mouse line will be generated in which decreased HFN-6 expression during liver regeneration can be prevented. We will use these mice to test the hypothesis that undiminished HFN-6 expression is inhibitory to liver regeneration. The immediate early gene expression that is induced during liver regeneration is known to mediate hepatocyte progression into the G1 stage of the cell-cycle. However, the transcriptional mechanisms mediating the later stages of hepatocyte replication are not completely understood. To further examine transcriptional processes underlying cell cycle progression during liver regeneration, we will alter hepatocyte expression of the winged helix HNF-3/fork head homolog-11 (HFH-11) gene. HFH-11 is a candidate transcription factor involved in cell cycle progression because its expression is transiently reactivated during the period of hepatocyte proliferation, and putative HFH-11 binding sites are present in cell- cycle regulatory genes such as c-myc, c-myb, TGFalpha, cyclin B1 and cyclin D1. We will generate mice possessing a conditional targeted HFH- 11 gene disruption in adult hepatocytes and liver regeneration studies with these mice will allow us to test the hypothesis that HFH-11 expression is necessary for hepatocyte replication. Gain of function studies in transgenic mice are proposed to examine whether premature hepatocyte expression of HFH-11 during liver regeneration results in altered cell cycle kinetics of proliferating hepatocytes. Assessment of these transgenic mice for development of liver nodules in a liver tumor promotion model will allow us to investigate whether continuous hepatocyte expression of HFH-11 increases the incidence of hepatocellular carcinoma. An understanding of transcriptional mechanisms which mediate liver regeneration may allow us to identify regulatory pathways that are potentially disrupted during liver fibrosis and cirrhosis.