Revertant mosaicism:: partial correction of a germ-line mutation in COL17A1 by a frame-restoring mutation
Revertant mosaicism:: partial correction of a germ-line mutation in COL17A1 by a frame-restoring mutation
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DOI：
10.1172/jci4338
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发表时间：
1999-05-01
影响因子：
15.9
通讯作者：
Yancey, KB
中科院分区：
文献类型：
--
作者：
Darling, TN;Yee, C;Yancey, KB
泛发性萎缩性良性大疱性表皮病是一种常染色体隐性遗传的表皮下水疱病，以COL 17 A1无效突变为典型。在1个大型亲属中，受影响的个体是COL 17 A1，4003 delTC中2-bp缺失的纯合子，这导致下游提前终止密码子，无义介导的mRNA衰减和XVII型胶原合成的废除。有趣的是，这些患者中的1例，虽然表型相同，她受影响的兄弟姐妹，显示局灶性表达的XVII型胶原蛋白在表皮基底膜的模式，提示回复嵌合。当对随机获得的表皮细胞、口腔粘膜细胞和外周血细胞的研究未能确定这种明显的嵌合现象的遗传基础时，潜在回复突变表皮细胞的微观亚群（即，那些覆盖在含有XVII型胶原的基底膜上的）用激光捕获显微切割选择性分离。对这些细胞的DNA和RNA的分析揭示了第二个突变，4080 insGG，在COL 17 A1的1个等位基因上。这个2-bp的插入纠正了临近提前终止密码子的阅读框架，对抗了无义介导的mRNA衰变，并允许患者角质形成细胞在体内和体外产生蛋白质。这些研究阐明了人类中一种新形式的回复嵌合体的分子基础。
Generalized atrophic benign epidermolysis bullosa is an autosomal recessive subepidermal blistering disease typified by null mutations in COL17A1. In 1 large kindred, affected individuals were homozygous for a 2-bp deletion in COL17A1, 4003delTC, which resulted in a downstream premature termination codon, nonsense-mediated mRNA decay, and abrogation of type XVII collagen synthesis. Interestingly, 1 of these patients, although phenotypically identical to her affected siblings, showed focal expression of type XVII collagen in epidermal basement membrane in a pattern suggestive of revertant mosaicism. When studies of randomly obtained epidermal, oromucosal, and peripheral blood cells failed to identify the genetic basis of this apparent mosaicism, microscopic subpopulations of potentially revertant epidermal cells (i.e., those overlying basement membrane containing type XVII collagen) were selectively isolated using laser capture microdissection. Analysis of DNA and RNA from these cells revealed a second mutation, 4080insGG, on 1 allele of COL17A1. This 2-bp insertion corrected the reading frame just proximal to the premature termination codon, countered nonsense-mediated mRNA decay, and allowed protein production by patient keratinocytes in vivo and in vitro. These studies elucidate the molecular basis of a novel form of revertant mosaicism in humans.