Novel mechanism of revertant mosaicism in Dowling-Meara epidermolysis bullosa simplex
Novel mechanism of revertant mosaicism in Dowling-Meara epidermolysis bullosa simplex
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DOI：
10.1046/j.0022-202x.2003.22129.x
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发表时间：
2004-01-01
影响因子：
6.5
通讯作者：
McLean, WHI
中科院分区：
文献类型：
--
作者：
Smith, FJD;Morley, SM;McLean, WHI
严重的Dowling-Meara型单纯大疱性表皮松解症是由角蛋白5和14的显性负突变引起的，这两种蛋白在表皮基底角化细胞中特异性表达。在Dowling-Meara型单纯大疱性表皮松解症患者中最常见的突变是K14基因外显子1的错义突变R125C。作为正在进行的基因治疗计划的一部分，我们从一个已知携带R125C突变的散发性病例中获得了一个原代角化细胞细胞系。利用角化细胞mRNA对K14全长cDNA进行测序。出乎意料的是，在K14中发现了第二个突变：R125C突变上游的一个杂合1bp插入突变（242insG）。这种移码突变在下游立即产生一个过早终止密码子，从而使显性负等位基因无效。第二种突变仅存在于角质形成细胞的DNA中，而不存在于淋巴细胞DNA中。这个病例代表了一种新的逆转录嵌合机制，是“自然基因疗法”的一个例子。
The severe Dowling-Meara form of epidermolysis bullosa simplex is caused by dominant-negative mutations in keratins 5 and 14, which are specifically expressed in the basal keratinocytes of the epidermis. The most common mutation in the Dowling-Meara form of epidermolysis bullosa simplex patients is the missense mutation R125C in exon 1 of the K14 gene. We made a primary keratinocyte cell line from a sporadic case known to carry the R125C mutation as part of an ongoing gene therapy initiative. The full-length K14 cDNA was sequenced using keratinocyte mRNA. Unexpectedly, a second mutation was identified in K14: a heterozygous 1 bp insertion mutation (242insG) upstream of the R125C mutation. This frameshift mutation creates a premature termination codon immediately downstream, thereby nullifying the dominant-negative allele. The second mutation was only present in DNA derived from keratinocytes and was absent from lymphocyte DNA. This case represents a novel mechanism of revertant mosaicism and is an example of "natural gene therapy".