Autosomal recessive ataxia

常染色体隐性共济失调
  • 文章类型: Case Reports
    这项研究的目的是鉴定两名婴儿发作患者中与常染色体隐性遗传(AR)罕见脊髓小脑共济失调(SCA)表型相关的可能基因和突变,来自一个近亲家庭.使用全基因组SNP筛查,自合性映射,靶向Sanger测序和nextgen测序,家庭隔离分析,和全面的神经面板,我们在SPTBN2中发现了一个新的突变。接下来,我们利用来自不同物种的氨基酸的多重序列比对以及蛋白质数据库(PDB#1WYQ和1WJM)提供的晶体结构来模拟突变位点及其对β-III-血影蛋白的影响。最后,我们使用各种生物信息学分类器来确定错义变异的致病性。作为常规患者护理的一部分,对患者进行了全面的临床和诊断检查,包括放射学检查。在外显子2中检测到的纯合错义变体(c.1572C>T;p.R414C)在家庭中完全隔离,在大型种族队列以及公开可用的数据集中不存在。我们的综合靶向测序方法没有揭示两名患者中任何其他可能的候选变异或突变。两名男性兄弟姐妹表现出延迟的运动里程碑以及认知和学习障碍。脑MRI显示,在3岁和6.5岁时,中线下椎的孤立性小脑萎缩更为明显。β-III-血影蛋白的氨基酸序列比对表明,414处的精氨酸在各种物种中高度保守,并且位于第一个血影蛋白重复结构域的末端。包容性生物信息学分析预测该变体将具有破坏性并引起疾病。除了新的突变,我们还对以前报道的突变进行了简短的文献综述,并对病例进行了临床比较.我们的研究回顾了以前报道的SPTBN2突变和病例。此外,新的突变,p.R414C,与SPTBN2相关的常染色体隐性遗传性共济失调的婴儿发作形式有关。以前,在人类中很少报道SPTBN2隐性突变。动物模型尤其是β-III-/-小鼠模型提供了对早期协调和步态缺陷的见解,提示功能丧失。预计在接下来的几年中,文献中会出现更多的隐性SPTBN2突变。
    The objective of this study was the identification of likely genes and mutations associated with an autosomal recessive (AR) rare spinocerebellar ataxia (SCA) phenotype in two patients with infantile onset, from a consanguineous family. Using genome-wide SNP screening, autozygosity mapping, targeted Sanger sequencing and nextgen sequencing, family segregation analysis, and comprehensive neuropanel, we discovered a novel mutation in SPTBN2. Next, we utilized multiple sequence alignment of amino acids from various species as well as crystal structures provided by protein data bank (PDB# 1WYQ and 1WJM) to model the mutation site and its effect on β-III-spectrin. Finally, we used various bioinformatic classifiers to determine pathogenicity of the missense variant. A comprehensive clinical and diagnostic workup including radiological exams were performed on the patients as part of routine patient care. The homozygous missense variant (c.1572C>T; p.R414C) detected in exon 2 was fully segregated in the family and absent in a large ethnic cohort as well as publicly available data sets. Our comprehensive targeted sequencing approaches did not reveal any other likely candidate variants or mutations in both patients. The two male siblings presented with delayed motor milestones and cognitive and learning disability. Brain MRI revealed isolated cerebellar atrophy more marked in midline inferior vermis at ages of 3 and 6.5 years. Sequence alignments of the amino acids for β-III-spectrin indicated that the arginine at 414 is highly conserved among various species and located towards the end of first spectrin repeat domain. Inclusive bioinformatic analysis predicted that the variant is to be damaging and disease causing. In addition to the novel mutation, a brief literature review of the previously reported mutations as well as clinical comparison of the cases were also presented. Our study reviews the previously reported SPTBN2 mutations and cases. Moreover, the novel mutation, p.R414C, adds up to the literature for the infantile-onset form of autosomal recessive ataxia associated with SPTBN2. Previously, few SPTBN2 recessive mutations have been reported in humans. Animal models especially the β-III-/- mouse model provided insights into early coordination and gait deficit suggestive of loss-of-function. It is expected to see more recessive SPTBN2 mutations appearing in the literature during the upcoming years.
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