Discovery of the BMPR1A promoter and germline mutations that cause juvenile polyposis
Discovery of the BMPR1A promoter and germline mutations that cause juvenile polyposis
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DOI：
10.1093/hmg/ddq396
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发表时间：
2010-12-01
影响因子：
3.5
通讯作者：
Howe, James R.
中科院分区：
文献类型：
--
作者：
Calva-Cerqueira, Daniel;Dahdaleh, Fadi S.;Howe, James R.
幼年性息肉病（JP）是一种常染色体显性错构瘤性息肉病综合征，受影响的个体易患结直肠癌和上消化道癌。45%的JP患者有涉及SMAD4和BMPR1A编码区的突变或缺失，但其他病例的遗传基础尚不清楚。我们着手在一个大型家族中鉴定JP基因，该家族有10个受影响的成员，没有SMAD4或BMPR1A编码序列突变或缺失。我们发现了一个种系缺失分离在所有受影响的成员，映射119 kb的上游编码区的BMPR1A的多重连接依赖性探针扩增和比较基因组杂交。为了进一步了解BMPR1A的基因组结构，我们从淋巴母细胞系和正常结肠组织中进行了5' RACE，其揭示了四个非编码（NC）外显子和两个推定的启动子。对该缺失片段的进一步分析表明，该缺失片段长度为12 433 bp，包括一个启动子和一个NC外显子。通过荧光素酶测定评估每个启动子和缺失构建体的活性，并分析较强启动子序列在没有SMAD4或BMPR1A改变的JP患者中的变化。65例JP先证者中共有6例发现有影响该启动子的突变。通过ELISA检测，所有先证者的BMPR1A蛋白减少，所有启动子突变，但一个导致荧光素酶活性显着降低相对于野生型启动子报告。我们的结论是，我们已经确定了BMPR1A的启动子，其中突变可能是多达10%的未知突变的JP病例的原因。
Juvenile polyposis (JP) is an autosomal dominant hamartomatous polyposis syndrome where affected individuals are predisposed to colorectal and upper gastrointestinal cancer. Forty-five percent of JP patients have mutations or deletions involving the coding regions of SMAD4 and BMPR1A, but the genetic basis of other cases is unknown. We set out to identify the JP gene in a large kindred having 10 affected members without SMAD4 or BMPR1A coding sequence mutations or deletions. We found a germline deletion segregating in all affected members, mapping 119 kb upstream of the coding region of BMPR1A by multiplex ligation-dependent probe amplification and comparative genomic hybridization. To further understand the genomic structure of BMPR1A, we performed 5' RACE from lymphoblastoid cell lines and normal colon tissue, which revealed four non-coding (NC) exons and two putative promoters. Further analysis of this deletion showed that it encompassed 12 433 bp, including one promoter and NC exon. The activities of each promoter and deletion constructs were evaluated by luciferase assays, and the stronger promoter sequence analyzed for changes in JP patients without SMAD4 or BMPR1A alterations. A total of 6 of 65 JP probands were found to have mutations affecting this promoter. All probands examined had diminished BMPR1A protein by ELISA, and all promoter mutations but one led to significantly reduced luciferase activity relative to the wild-type promoter reporter. We conclude that we have identified the promoter for BMPR1A, in which mutations may be responsible for as many as 10% of JP cases with unknown mutations.