Regulation of Kidney-Specific Gene Expression

描述(申请人提供)：本次竞争性续签申请的目的是继续我们正在进行的关于肝细胞核因子-1β(β)及其在调节肾脏特异基因表达和囊性肾脏疾病中的作用的研究。Hnf-1β是一种DNA结合的转录因子，调节肾脏和其他上皮器官中组织特异性基因的表达。Hnf-1β突变可导致肾脏发育异常，包括肾发育不全、发育不良、囊性发育不良和肾小球疾病。为了揭示这些异常的发病机制，我们培育了突变小鼠，它们的表型与受影响的人类相似。在转基因小鼠中，肾脏特异性失活hnf-1β或表达显性-阴性突变体hnf-1β会导致肾囊肿和肾功能衰竭。对这些突变小鼠的分析表明，hnf-1β调节编码纤毛蛋白的基因的转录，这些基因与人类囊性肾脏疾病有关。这些发现表明，hnf-1β在肾脏囊性和发育性疾病中起核心作用。为了进一步阐明hnf-1β的功能，拟议的研究有两个特定的目标。第一个目的是了解hnf-1β是如何调节Wnt信号的。初步研究表明，hnf-1β调控参与WnT信号转导的基因，抑制hnf-1β会导致wnT途径异常激活，这可能是导致包囊形成的原因。将在突变小鼠、培养细胞和器官培养中进行研究，以阐明Wnt信号激活的机制。第二个目标是确定肾脏中受hnf-1β调控的microRNA的特征。除了蛋白质编码基因外，hnf-1β还调节microRNAs的表达，microRNAs是一种小的非编码RNA，调节转录后基因的表达。这些发现揭示了一条新的途径，通过该途径，hnf-1β调节组织特异性基因表达和肾脏发育。将研究受hnf-1β调控的两个microRNAs家族的功能，并鉴定它们的靶基因转录产物。总之，拟议的研究将促进我们对正常肾脏发育的理解，揭开hnf-1β突变是如何导致肾脏疾病的，并确定肾脏囊性和发育性疾病的潜在治疗靶点。

DESCRIPTION (provided by applicant): The purpose of this competitive renewal application is to continue our ongoing studies on hepatocyte nuclear factor-1β (HNF-1β) and its roles in the regulation of kidney-specific gene expression and cystic kidney diseases. HNF-1β is a DNA-binding transcription factor that regulates tissue-specific gene expression in the kidney and other epithelial organs. Mutations of HNF-1β produce renal developmental abnormalities including renal agenesis, hypoplasia, cystic dysplasia, and glomerulocystic kidney disease. To unravel the pathogenesis of these anomalies, we have produced mutant mice that develop phenotypes similar to affected humans. Kidney-specific inactivation of HNF-1β or expression of dominant-negative mutant HNF-1β in transgenic mice produces kidney cysts and renal failure. Analysis of these mutant mice has revealed that HNF-1β regulates the transcription of genes encoding ciliary proteins that are involved in human cystic kidney diseases. These findings demonstrate that HNF-1β plays a central role in cystic and developmental diseases of the kidney. To further elucidate the functions of HNF-1β, the proposed studies have two specific aims. The first aim is to understand how HNF-1β regulates Wnt signaling. Preliminary studies have shown that HNF-1β regulates genes that are involved in Wnt signaling, and inhibition of HNF-1β results in abnormal activation of the Wnt pathway, which may underlie cyst formation. Studies will be performed in mutant mice, cultured cells, and organ culture to elucidate the mechanism of activation of Wnt signaling. The second aim is to characterize microRNAs that are regulated by HNF-1β in the kidney. In addition to protein-coding genes, HNF-1β regulates the expression of microRNAs, which are small non-coding RNAs that regulate post-transcriptional gene expression. These findings have revealed a novel pathway by which HNF-1β regulates tissue-specific gene expression and kidney development. The functions of two families of microRNAs that are regulated by HNF-1β will be studied, and their target mRNA transcripts will be identified. Collectively, the proposed studies will advance our understanding of normal kidney development, unravel how mutations of HNF-1β produce kidney diseases, and identify potential therapeutic targets for cystic and developmental diseases of the kidney.