Xiaobo Li1, Zhengmao Hu1, Lei Liu1, Yongzhi Xie1, Yajing Zhan1, Xiaohong Zi1, Junling Wang1, Lixiang Wu1, Kun Xia1, Beisha Tang1, Ruxu Zhang2. 1. From the Department of Neurology, the Third Xiangya Hospital (X.L., L.L., Y.X., X.Z., R.Z.), State Key Laboratory of Medical Genetics (Z.H., J.W., K.X., B.T.), and Department of Physiology, Xiangya School of Medicine (X.L., L.W.), Central South University, Changsha, PR China. 2. From the Department of Neurology, the Third Xiangya Hospital (X.L., L.L., Y.X., X.Z., R.Z.), State Key Laboratory of Medical Genetics (Z.H., J.W., K.X., B.T.), and Department of Physiology, Xiangya School of Medicine (X.L., L.W.), Central South University, Changsha, PR China. zhangruxu@vip.163.com.
Abstract
OBJECTIVE: To identify the underlying genetic cause in a consanguineous Chinese family segregating distal hereditary motor neuropathy (dHMN) in an autosomal recessive pattern. METHODS: We used whole-exome sequencing and homozygosity mapping to detect the genetic variant in 2 affected individuals of the consanguineous Chinese family with dHMN. RNA analysis of peripheral blood leukocytes and immunofluorescence and immunoblotting of stable cell lines were performed to support the pathogenicity of the identified mutation. RESULTS: We identified 3 shared novel homozygous variants in 3 shared homozygous regions of the affected individuals. Sequencing of these 3 variants in family members revealed the c.151+1G>T mutation in SIGMAR1 gene, which located in homozygous region spanning approximately 5.3 Mb at chromosome 9p13.1-p13.3, segregated with the dHMN phenotype. The mutation causes an alternative splicing event and generates a transcript variant with an in-frame deletion of 60 base pairs in exon 1 (c.92_151del), and results in an internally shortened protein σ1R(31_50del). The proteasomal inhibitor treatment increased the intracellular amount of σ1R(31_50del) and led to the formation of nuclear aggregates. Stable expressing σ1R(31_50del) induced endoplasmic reticulum stress and enhanced apoptosis. CONCLUSION: The homozygous c.151+1G>T mutation in SIGMAR1 caused a novel form of autosomal recessive dHMN in a Chinese consanguineous family. Endoplasmic reticulum stress may have a role in the pathogenesis of dHMN.
OBJECTIVE: To identify the underlying genetic cause in a consanguineous Chinese family segregating distal hereditary motor neuropathy (dHMN) in an autosomal recessive pattern. METHODS: We used whole-exome sequencing and homozygosity mapping to detect the genetic variant in 2 affected individuals of the consanguineous Chinese family with dHMN. RNA analysis of peripheral blood leukocytes and immunofluorescence and immunoblotting of stable cell lines were performed to support the pathogenicity of the identified mutation. RESULTS: We identified 3 shared novel homozygous variants in 3 shared homozygous regions of the affected individuals. Sequencing of these 3 variants in family members revealed the c.151+1G>T mutation in SIGMAR1 gene, which located in homozygous region spanning approximately 5.3 Mb at chromosome 9p13.1-p13.3, segregated with the dHMN phenotype. The mutation causes an alternative splicing event and generates a transcript variant with an in-frame deletion of 60 base pairs in exon 1 (c.92_151del), and results in an internally shortened protein σ1R(31_50del). The proteasomal inhibitor treatment increased the intracellular amount of σ1R(31_50del) and led to the formation of nuclear aggregates. Stable expressing σ1R(31_50del) induced endoplasmic reticulum stress and enhanced apoptosis. CONCLUSION: The homozygous c.151+1G>T mutation in SIGMAR1 caused a novel form of autosomal recessive dHMN in a Chinese consanguineous family. Endoplasmic reticulum stress may have a role in the pathogenesis of dHMN.
Authors: Marta Garcia-Miralles; Michal Geva; Jing Ying Tan; Nur Amirah Binte Mohammad Yusof; Yoonjeong Cha; Rebecca Kusko; Liang Juin Tan; Xiaohong Xu; Iris Grossman; Aric Orbach; Michael R Hayden; Mahmoud A Pouladi Journal: JCI Insight Date: 2017-12-07