Exome Sequencing Identifies a REEP1 Mutation Involved in Distal Hereditary Motor Neuropathy Type V
Exome Sequencing Identifies a REEP1 Mutation Involved in Distal Hereditary Motor Neuropathy Type V
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DOI：
10.1016/j.ajhg.2012.05.007
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发表时间：
2012-07-13
影响因子：
9.8
通讯作者：
Auer-Grumbach, Michaela
中科院分区：
文献类型：
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作者：
Beetz, Christian;Pieber, Thomas R.;Auer-Grumbach, Michaela
远端遗传性运动神经病（dHMNs）是一组影响下运动神经元的神经退行性疾病。在一个三代中同时存在常染色体显性dHMN和dHMN V型（dHMN/dHMN-V）的家族中，我们通过桑格测序排除了已知与dHMN表型相关的所有基因中的突变，并通过连锁分析确定了三个潜在的基因座。两个受影响个体的全外显子组测序揭示了连接区域内的单个候选变体，即，REEP 1中的剪接位点改变（c.304-2A>G）。小基因测定证实剪接受体功能的完全丧失和框内外显子5的跳跃。预测所得mRNA以正常水平表达，并编码内部缩短的蛋白质（p.102_139del）。REEP 1功能丧失突变先前已在显性遗传性痉挛性截瘫（HSP）中被鉴定，HSP是一种与上运动神经元病理学相关的疾病。与我们的临床遗传学数据一致，我们表明REEP 1在下运动神经元中也强烈表达。在细胞系中外源性过表达后，我们观察到p.102_139del的亚细胞定位缺陷，其不同于已知的HSP相关错义突变c.59C>A（p.Ala20Glu）。此外，我们表明p.102_139del而不是p.Ala20Glu招募atlastin-1，即，REEP 1结合伴侣之一，改变定位位点。这些数据证实了HSP中REEP 1突变的功能丧失性质，并表明REEP 1相关的dHMN中存在不同的机制。
The distal hereditary motor neuropathies (dHMNs) are a heterogeneous group of neurodegenerative disorders affecting the lower motoneuron. In a family with both autosomal-dominant dHMN and dHMN type V (dHMN/dHMN-V) present in three generations, we excluded mutations in all genes known to be associated with a dHMN phenotype through Sanger sequencing and defined three potential loci through linkage analysis. Whole-exome sequencing of two affected individuals revealed a single candidate variant within the linking regions, i.e., a splice-site alteration in REEP1 (c.304-2A>G). A minigene assay confirmed complete loss of splice-acceptor functionality and skipping of the in-frame exon 5. The resulting mRNA is predicted to be expressed at normal levels and to encode an internally shortened protein (p.102_139del). Loss-of-function REEP1 mutations have previously been identified in dominant hereditary spastic paraplegia (HSP), a disease associated with upper-motoneuron pathology. Consistent with our clinical-genetic data, we show that REEP1 is strongly expressed in the lower motoneurons as well. Upon exogeneous overexpression in cell lines we observe a subcellular localization defect for p.102_139del that differs from that observed for the known HSP-associated missense mutation c.59C>A (p.Ala20Glu). Moreover, we show that p.102_139del, but not p.Ala20Glu, recruits atlastin-1, i.e., one of the REEP1 binding partners, to the altered sites of localization. These data corroborate the loss-of-function nature of REEP1 mutations in HSP and suggest that a different mechanism applies in REEP1-associated dHMN.