Overexpression of KLC2 due to a homozygous deletion in the non-coding region causes SPOAN syndrome
Overexpression of KLC2 due to a homozygous deletion in the non-coding region causes SPOAN syndrome
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DOI：
10.1093/hmg/ddv388
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发表时间：
2015-12-15
影响因子：
3.5
通讯作者：
Santos, Silvana
中科院分区：
文献类型：
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作者：
Melo, Uira S.;Macedo-Souza, Lucia I.;Santos, Silvana
SPOAN综合征是一种神经退行性疾病，主要特征为痉挛性截瘫、视神经萎缩和神经病变（SPOAN）。受影响的患者从 15 岁起就必须坐轮椅，并出现进行性关节挛缩和脊柱畸形。 SPOAN 患者的视力也低于正常，继发于明显非进行性先天性视神经萎缩。十年前，一个潜在的致病基因被定位在 11q13。在这里，我们对 SPOAN 衍生的样本进行了新一代测序。虽然全外显子组测序未能识别致病突变，但全基因组测序可以检测到位于 KLC2 基因非编码上游区域的纯合 216 bp 缺失 (chr11.hg19:g.66,024,557_66,024,773del)。对来自 SPOAN 患者的成纤维细胞和运动神经元进行的表达测定显示 KLC2 过度表达。 216 bp 缺失构建体中的荧光素酶测定证实了基因报告基因的过度表达，与野生型相比，表达量从 48% 到 74% 不等。斑马鱼中 klc2 的敲低和过度表达显示出轻度至重度的卷尾表型，这表明存在神经肌肉疾病。由非编码区的小缺失引起的基因过度表达是一种新机制，据我们所知，以前从未在隐性条件下报道过这种机制。尽管 KLC2 上调的分子机制仍有待揭示，但这样的例子增加了非编码区在人类病理学中的重要性。
SPOAN syndrome is a neurodegenerative disorder mainly characterized by spastic paraplegia, optic atrophy and neuropathy (SPOAN). Affected patients are wheelchair bound after 15 years old, with progressive joint contractures and spine deformities. SPOAN patients also have sub normal vision secondary to apparently non-progressive congenital optic atrophy. A potential causative gene was mapped at 11q13 ten years ago. Here we performed next-generation sequencing in SPOAN-derived samples. While whole-exome sequencing failed to identify the causative mutation, whole-genome sequencing allowed to detect a homozygous 216-bp deletion (chr11. hg19:g. 66,024,557_66,024,773del) located at the non-coding upstream region of the KLC2 gene. Expression assays performed with patient's fibroblasts and motor neurons derived from SPOAN patients showed KLC2 overexpression. Luciferase assay in constructs with 216-bp deletion confirmed the overexpression of gene reporter, varying from 48 to 74%, as compared with wild-type. Knockdown and overexpression of klc2 in Danio rerio revealed mild to severe curly-tail phenotype, which is suggestive of a neuromuscular disorder. Overexpression of a gene caused by a small deletion in the non-coding region is a novel mechanism, which to the best of our knowledge, was never reported before in a recessive condition. Although the molecular mechanism of KLC2 up-regulation still remains to be uncovered, such example adds to the importance of non-coding regions in human pathology.