Histone Deacetylases and Kidney Development

描述（由申请人提供）：越来越多的证据表明，染色质结构和功能的改变会诱导基因表达的特异性和显著变化。组蛋白去乙酰化酶（hdac）是一类进化上保守的酶，它能从组蛋白中去除乙酰基团，使核小体紧密，从而阻止DNA结合蛋白接近DNA。此外，hdac与组蛋白甲基转移酶和其他组蛋白修饰剂一起，创造了一个由转录抑制因子或激活因子读取的“表观遗传密码”。组蛋白乙酰化在癌症、免疫紊乱和胚胎发育中起重要作用。在小鼠中，HDAC1和HDAC2基因的靶向失活导致胚胎致死性，妨碍了肾脏发育的分析。本提案的总体目的是阐明HDAC1/2的肾脏谱系特异性功能。我们的初步数据表明，HDAC 1和HDAC2以发育调节的方式在发育中的肾脏的两个腔室，后肾间质（MM）和输尿管芽（UB）中表达。后肾HDAC活性的药理抑制可诱导基因表达的谱系特异性和时间依赖性变化，损害后肾增殖，并引发过早分化。因此，我们提出HDAC1和HDAC 2在肾脏发育的表观遗传控制中发挥重要作用：1)在MM中，HDAC1/2是维持Eya1和Foxd1基因表达以及MM细胞存活和更新所必需的；2)在UB中，HDAC1/2维持顶端Ret+/Wnt11+细胞池，抑制末端分化程序。我们将使用多种遗传和生化方法，以及器官型和细胞培养系统，以实现以下具体目标：1)阐明在后肾发育过程中依赖hdac的发育过程和谱系特异性形态发生途径；2)确定HDAC1/2对Gdnf-Ret-Wnt11通路调控的贡献；2)确定MM和UB谱系中hdac敏感基因调控网络。该结果将为器官发生的表观遗传控制提供新的见解，并具有重要的临床意义，因为肾脏发育异常是婴儿和儿童慢性肾衰竭的主要原因。公共卫生相关性：在4岁以下儿童中，高达40%的慢性肾衰竭是由肾脏和尿路先天性畸形造成的。除了DNA序列的突变外，肾脏发育异常可能是由于“表观遗传密码”的改变造成的，表观遗传密码位于细胞核中包裹DNA的蛋白质中。由短暂的环境暴露（如毒素、药物、病毒感染）引起的表观遗传密码的稳定改变可以在不改变DNA序列的情况下破坏胎儿基因表达。因此，了解肾脏发育的表观遗传调控可能为治疗或预防肾脏和尿路畸形和肾衰竭开辟新的途径。

DESCRIPTION (provided by applicant): Mounting evidence indicates that alterations in chromatin structure and function induce specific and significant changes in gene expression. Histone deacetylases (HDACs) are an evolutionarily conserved class of enzymes which remove acetyl groups from histones and compacts the nucleosome and thus prevents access of DNA-binding proteins to DNA. Moreover, HDACs, along with histone methyltransferases and other histone modifiers, create an "epigenetic code" that is read by transcriptional repressors or activators. Histone acetylation plays important roles in cancer, immune disorders and embryonic development. In the mouse, targeted inactivation of HDAC1 and HDAC2 genes causes embryonic lethality precluding the analysis of kidney development. The overall aim of this proposal is to elucidate the nephric lineage-specific functions of HDAC1/2. Our preliminary data indicate that HDAC 1 and HDAC2 are expressed in both compartments of the developing kidney, the metanephric mesenchyme (MM) and ureteric bud (UB), in a developmentally regulated manner. Pharmacological inhibition of metanephric HDAC activity induces lineage-specific and time-dependent changes in gene expression, compromises metanephric proliferation, and provokes premature differentiation. We therefore propose that HDAC 1 and HDAC 2 perform essential roles in the epigenetic control of kidney development: 1) in the MM, HDAC1/2 are required for maintained expression of the Eya1 and Foxd1 genes as well as survival and renewal of MM cells; 2) in the UB, HDAC1/2 maintain the pool of tip Ret+/Wnt11+ cells and repress the terminal differentiation program. We will use a variety of genetic and biochemical approaches, together with organotypic and cell culture systems, to conduct the following specific aims: 1) Elucidate the developmental processes and lineage-specific morphogenetic pathways that are dependent on HDACs during metanephric development; 2) Determine the contribution of HDAC1/2 to the regulation of the Gdnf-Ret-Wnt11 pathway; and 2) Identify HDAC-sensitive gene regulatory networks in the MM and UB lineages. The results will provide new insights into the epigenetic control of organogenesis and have important clinical implications as abnormal renal development is the leading cause of chronic renal failure in infants and children. PUBLIC HEALTH RELEVANCE: Congenital malformations of the kidney and urinary tract account for up to 40% of chronic kidney failure in children less than 4 years of age. In addition to mutations in the DNA sequence, abnormal kidney development may result from alterations in the "epigenetic code" which lies in the proteins around which the DNA is wrapped in the nucleus of the cell. Stable alterations in the epigenetic code resulting from transient environmental exposures (e.g., toxins, drugs, viral infections) can disrupt fetal gene expression without altering the DNA sequence. Thus, understanding the epigenetic regulation of kidney development may open new avenues to the treatment or prevention of kidney and urinary tract malformations and kidney failure.