Two novel mutations and evidence for haploinsufficiency of the ADAR gene in dyschromatosis symmetrica hereditaria
Two novel mutations and evidence for haploinsufficiency of the ADAR gene in dyschromatosis symmetrica hereditaria
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DOI：
10.1111/j.1365-2133.2006.07133.x
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发表时间：
2006-04-01
影响因子：
10.3
通讯作者：
Zhang, X
中科院分区：
文献类型：
--
作者：
Liu, Q;Jiang, L;Zhang, X
遗传性皮肤色素异常症（DSH，MIM 127400）是一种显性遗传性皮肤病，与编码双链RNA特异性腺苷脱氨酶的阿达尔基因突变有关。我们以前报道了两个新的阿达尔突变（p.Q513 X和p.R916 W），并证实了阿达尔在中国DSH患者中的作用。阿达尔基因突变可能是DSH的致病机制之一。目的检测两个中国DSH家系的阿达尔基因突变，探讨杂合子阿达尔基因突变的致病机制。通过限制性酶切分析进一步证实突变。结果在A、B家系中分别发现一个小缺失（c.1555delT，p.C519fs）和一个错义突变（c.3116A > G，p.K1039R）。在携带p.Q513X或p.C519fs的个体中，cDNA片段测序表明突变等位基因的mRNA表达几乎完全丧失，实时定量RT-PCR显示阿达尔表达降低约50%。然而，在错义p.R916 W突变的患者中发现了相同丰度的野生型和突变型cDNA序列，而没有阿达尔表达的降低。这些结果表明无义突变p.Q513X和移码突变p.C519fs可能通过无义介导的mRNA降解产生无效等位基因。结论在中国DSH患者中发现两种新的阿达尔突变。获得了阿达尔单倍不足作为DSH分子发病机制的证据。
Background Dyschromatosis symmetrica hereditaria (DSH, MIM 127400) is a dominantly inherited skin disease associated with mutations in ADAR, the gene that encodes a double-stranded RNA-specific adenosine deaminase. We previously reported two novel ADAR mutations (p.Q513X and p.R916W) and confirmed the role of ADAR in Chinese patients with DSH. Both haploinsufficiency and a dominant-negative effect have been suggested as the potential mechanism by which ADAR mutations cause DSH.Objectives To identify ADAR mutations in two additional Chinese DSH families and to obtain insight into the pathogenic mechanism of heterozygous ADAR mutations.Methods For mutation detection, all ADAR exons and their flanking intronic sequences were amplified and sequenced. Mutations were further confirmed by restriction analysis. Direct sequencing of cDNA fragments produced by reverse transcription-polymerase chain reaction (RT-PCR) and real-time quantitative RT-PCR were used to examine the expression of ADAR in peripheral lymphocytes isolated from affected individuals.Results A small deletion, c.1555delT (p.C519fs), and a missense mutation, c.3116A > G (p.K1039R), were found in families A and B, respectively. In individuals carrying p.Q513X or p.C519fs, sequencing of cDNA fragments indicated almost total loss of mRNA expression from the mutant alleles, and real-time quantitative RT-PCR showed an approximately 50% reduction of ADAR expression. However, equal abundance of the wild-type and mutant cDNA sequences without reduction of ADAR expression was found in a patient with the missense p.R916W mutation. These results suggest that both the nonsense p.Q513X and frameshift p.C519fs mutations have generated null alleles probably by nonsense-mediated mRNA decay.Conclusions Two novel ADAR mutations were found in Chinese patients with DSH. Evidence for ADAR haploinsufficiency as a mechanism underlying the molecular pathogenesis of DSH was obtained.