Exome sequencing identification of a GJB1 missense mutation in a kindred with X-linked spinocerebellar ataxia (SCA-X1)
Exome sequencing identification of a GJB1 missense mutation in a kindred with X-linked spinocerebellar ataxia (SCA-X1)
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DOI：
10.1093/hmg/ddt282
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发表时间：
2013-11-01
影响因子：
3.5
通讯作者：
Gibbs, Richard A.
中科院分区：
文献类型：
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作者：
Caramins, Melody;Colebatch, James G.;Gibbs, Richard A.
我们在一个最初临床诊断为SCA-X1的大型家族中进行了基因鉴定和分子表征项目。该家系在表现共济失调的同时，还具有一些独特的外周神经系统特征。X染色体上的牵连区域使用单倍型划分。通过阵列比较基因组杂交排除大的缺失和重复。在两名受影响的受试者中进行外显子组测序。然后通过桑格测序证实单个鉴定的X染色体候选变体在所有受影响的、携带者和未受影响的家族成员中适当地共分离。通过与dbSNP进行比较，并过滤1000个基因组项目中的1个次要等位基因频率，证实该变体是新的，并且不存在于NHLBI外显子组测序项目或NHLBI HGSC的本地数据库中。随后对转染细胞进行功能实验以评估变体的体外生物学效应。所鉴定的变体由连接蛋白32/间隙连接β 1基因中先前未鉴定的非同义变体GJB 1 p.P58S组成。采用桑格测序的分离研究证实了所有受影响个体和一名已知携带者中存在该变体，而未受影响成员中不存在该变体。功能研究证实，p.P58 S变体减少了间隙连接斑块的数量和大小，但差距连接的电导不受影响。两种X连锁共济失调与遗传基因座有关，其中第一种最近在分子水平上得到了表征。这代表了第二个具有X连锁共济失调分子特征的家族，并且是具有显性和永久性共济失调表型的先前未报告的GJB 1突变的第一例，尽管先前已报告了不同的CNS缺陷。由于存在中枢和外周神经异常，该家系的表型也相对独特。因此，具有独特特征的其他X连锁SCA也可能代表其他已知神经实体的可变表型表达。
We undertook a gene identification and molecular characterization project in a large kindred originally clinically diagnosed with SCA-X1. While presenting with ataxia, this kindred also had some unique peripheral nervous system features. The implicated region on the X chromosome was delineated using haplotyping. Large deletions and duplications were excluded by array comparative genomic hybridization. Exome sequencing was undertaken in two affected subjects. The single identified X chromosome candidate variant was then confirmed to co-segregate appropriately in all affected, carrier and unaffected family members by Sanger sequencing. The variant was confirmed to be novel by comparison with dbSNP, and filtering for a minor allele frequency of 1 in 1000 Genomes project, and was not present in the NHLBI Exome Sequencing Project or a local database at the BCM HGSC. Functional experiments on transfected cells were subsequently undertaken to assess the biological effect of the variant in vitro. The variant identified consisted of a previously unidentified non-synonymous variant, GJB1 p.P58S, in the Connexin 32/Gap Junction Beta 1 gene. Segregation studies with Sanger sequencing confirmed the presence of the variant in all affected individuals and one known carrier, and the absence of the variant in unaffected members. Functional studies confirmed that the p.P58S variant reduced the number and size of gap junction plaques, but the conductance of the gap junctions was unaffected. Two X-linked ataxias have been associated with genetic loci, with the first of these recently characterized at the molecular level. This represents the second kindred with molecular characterization of X-linked ataxia, and is the first instance of a previously unreported GJB1 mutation with a dominant and permanent ataxia phenotype, although different CNS deficits have previously been reported. This pedigree has also been relatively unique in its phenotype due to the presence of central and peripheral neural abnormalities. Other X-linked SCAs with unique features might therefore also potentially represent variable phenotypic expression of other known neurological entities.