痉挛型截瘫76型(SPG76)是由钙蛋白酶1(CAPN1)突变引起的遗传性痉挛型截瘫(HSP)的一种亚型。我们的研究描述了由于各种CAPN1突变而导致的三个患有痉挛性共济失调的家族的表型和遗传特征,并进一步探讨了这两个新突变的发病机理。三名患者分别为48岁、39岁和48岁,分别。患者1和3来自近亲家庭,而患者2是零星的。体格检查显示高张力,反射亢进,和Babinski下肢的体征.患者2和3还患有构音障碍和抑郁症。通过全外显子组测序鉴定CAPN1突变,其次是Sanger测序和家庭内共分离分析。进一步探索新鉴定的突变的功能检查。在患者1中检测到两个纯合突变(c.213dupG,p.D72Gfs*95)和患有HSP的患者3(c.1729+1G>A),分别。患者2具有复合杂合突变c.853C>T(p。R285X)和c.1324G>A(p。G442S)。Western印迹显示p.D72Gfs*95的分子量小于WT和p.G442S。体外,野生型钙蛋白酶-1主要位于细胞质中,并通过免疫染色与微管蛋白共定位。然而,p.D72Gfs*95和p.G442S异常形成胞内聚集,与微管蛋白几乎没有共定位。在这项研究中,我们确定了三例SPG76,由于四种不同的CAPN1突变,表现为下肢痉挛和共济失调,有或没有延髓受累和情绪障碍。其中,本文首先确定了c.213dupG和c.1324G>A。进一步总结了全球报道的SPG76病例的基因型-表型相关性。
Spastic paraplegia type 76 (SPG76) is a subtype of hereditary spastic paraplegia (HSP) caused by
calpain-1 (CAPN1) mutations. Our study described the phenotypic and genetic characteristics of three families with spastic ataxia due to various CAPN1 mutations and further explored the pathogenesis of the two novel mutations. The three patients were 48, 39, and 48 years old, respectively. Patients 1 and 3 were from consanguineous families, while patient 2 was sporadic. Physical examination showed hypertonia, hyperreflexia, and Babinski signs in the lower limbs. Patients 2 and 3 additionally had dysarthria and depression. CAPN1 mutations were identified by whole-exome sequencing, followed by Sanger sequencing and co-segregation analysis within the family. Functional examination of the newly identified mutations was further explored. Two homozygous mutations were detected in patient 1 (c.213dupG, p.D72Gfs*95) and patient 3 (c.1729+1G>A) with HSP, respectively. Patient 2 had compound heterozygous mutations c.853C>T (p.R285X) and c.1324G>A (p.G442S). Western blotting revealed the p.D72Gfs*95 with a smaller molecular weight than WT and p.G442S. In vitro, the wild-type
calpain-1 is mostly located in the cytoplasm and colocalized with tubulin by immunostaining. However, p.D72Gfs*95 and p.G442S abnormally formed intracellular aggregation, with little colocalization with tubulin. In this study, we identified three cases with SPG76, due to four various CAPN1 mutations, presenting lower limb spasticity and ataxia, with or without bulbar involvement and emotional disorder. Among these, c.213dupG and c.1324G>A are first identified in this paper. The genotype-phenotype correlation of the SPG76 cases reported worldwide was further summarized.