Frequent long-range epigenetic silencing of protocadherin gene clusters on chromosome 5q31 in Wilms' tumor.
Frequent long-range epigenetic silencing of protocadherin gene clusters on chromosome 5q31 in Wilms' tumor.
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DOI：
10.1371/journal.pgen.1000745
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发表时间：
2009-11
期刊：
影响因子：
4.5
通讯作者：
Malik K
中科院分区：
文献类型：
--
作者：
Dallosso AR;Hancock AL;Szemes M;Moorwood K;Chilukamarri L;Tsai HH;Sarkar A;Barasch J;Vuononvirta R;Jones C;Pritchard-Jones K;Royer-Pokora B;Lee SB;Owen C;Malik S;Feng Y;Frank M;Ward A;Brown KW;Malik K
肾母细胞瘤（WT）是一种儿科肾脏肿瘤，由于胎儿发育程序失败而引起。在大多数WT中缺乏可识别的突变表明WT中经常涉及表观遗传畸变。因此，我们进行了一个全基因组的WT启动子超甲基化的分析，并确定在染色体5 q31的超甲基化跨越800个碱基（kb）和超过50个基因。甲基化基因都属于α-、β-和γ-原钙粘蛋白（PCDH）基因簇（分别为人类基因组组织命名法PCDHA@、PCDHB@和PCDHG@）。这表明长距离表观遗传沉默（LRES）发生在发育肿瘤以及成人肿瘤中。亚硫酸氢盐聚合酶链反应分析显示PCDH高甲基化是在所有肾母细胞瘤亚型中发现的常见事件。高甲基化与肿瘤中PCDH表达降低一致。WT前体病变未显示PCDH高甲基化，表明在恶性进展期间发生从头PCDH高甲基化。PCDH结构域的离散边界由组蛋白修饰的突变界定; LRES侧翼的未甲基化基因与结构域内甲基化基因不存在的允许标记相关。沉默的基因用非允许的组蛋白3赖氨酸9二甲基化标记。对胚胎鼠肾和分化中的大鼠后肾间充质细胞的表达分析表明，Pcdh表达受发育调节，Pcdhg基因在胚基细胞中表达。重要的是，我们发现PCDH负调控经典Wnt信号传导，因为短干扰RNA诱导的PCDHG@编码蛋白的减少导致β-连环蛋白升高，β-连环蛋白/T细胞因子（TCF）报告活性增加，以及Wnt靶基因的诱导。相反，PCDH的过度表达会抑制β-连环蛋白/TCF报告基因活性，并且还会抑制软琼脂中癌细胞的集落形成和生长。因此，PCDH是调节在发育和疾病中至关重要的调节途径（例如经典Wnt信号传导）的候选肿瘤抑制剂。人体组织和器官的发育需要细胞仔细调节蛋白质的产生。蛋白质允许健康身体所需的许多不同结构的生长和发育。在许多疾病中，包括一些癌症，由于蛋白质的正常生产发生变化，组织和器官不能正常发育。这里介绍的工作表明，在肾母细胞瘤（一种儿童肾癌）中，可能是正常肾脏生长和发育所必需的大量相关蛋白质没有正常产生。这是由于它们的生产在癌细胞内被关闭。我们展示了这些被称为原钙粘蛋白的蛋白质本身如何改变其他已知在正常生长和癌症中重要的蛋白质的功能。因此，我们的研究增加了我们对原钙粘蛋白在正常生长中的重要性以及改变原钙粘蛋白如何导致疾病（如癌症）的理解。
Wilms' tumour (WT) is a pediatric tumor of the kidney that arises via failure of the fetal developmental program. The absence of identifiable mutations in the majority of WTs suggests the frequent involvement of epigenetic aberrations in WT. We therefore conducted a genome-wide analysis of promoter hypermethylation in WTs and identified hypermethylation at chromosome 5q31 spanning 800 kilobases (kb) and more than 50 genes. The methylated genes all belong to α-, β-, and γ-protocadherin (PCDH) gene clusters (Human Genome Organization nomenclature PCDHA@, PCDHB@, and PCDHG@, respectively). This demonstrates that long-range epigenetic silencing (LRES) occurs in developmental tumors as well as in adult tumors. Bisulfite polymerase chain reaction analysis showed that PCDH hypermethylation is a frequent event found in all Wilms' tumor subtypes. Hypermethylation is concordant with reduced PCDH expression in tumors. WT precursor lesions showed no PCDH hypermethylation, suggesting that de novo PCDH hypermethylation occurs during malignant progression. Discrete boundaries of the PCDH domain are delimited by abrupt changes in histone modifications; unmethylated genes flanking the LRES are associated with permissive marks which are absent from methylated genes within the domain. Silenced genes are marked with non-permissive histone 3 lysine 9 dimethylation. Expression analysis of embryonic murine kidney and differentiating rat metanephric mesenchymal cells demonstrates that Pcdh expression is developmentally regulated and that Pcdhg@ genes are expressed in blastemal cells. Importantly, we show that PCDHs negatively regulate canonical Wnt signalling, as short-interfering RNA–induced reduction of PCDHG@ encoded proteins leads to elevated β-catenin protein, increased β-catenin/T-cell factor (TCF) reporter activity, and induction of Wnt target genes. Conversely, over-expression of PCDHs suppresses β-catenin/TCF-reporter activity and also inhibits colony formation and growth of cancer cells in soft agar. Thus PCDHs are candidate tumor suppressors that modulate regulatory pathways critical in development and disease, such as canonical Wnt signaling. The development of tissues and organs in the human body requires carefully regulated production of proteins by cells. Proteins permit the growth and development of the many varied structures required for a healthy body. In many diseases, including some cancers, tissues and organs fail to develop as they should due to the normal production of proteins being changed. The work presented here shows that in Wilms' tumor, a childhood cancer of the kidney, a large group of related proteins that are likely necessary for growth and development of a normal kidney are not produced properly. This is due to their production being switched off within the cancer cells. We show how these proteins, known as protocadherins, can themselves alter the function of other proteins already known to be important in normal growth and cancer. Thus our study increases our understanding of how protocadherins are important in normal growth and of how altering protocadherins may lead to disease, such as cancer.
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