BACKGROUND Limb-girdle muscular dystrophies (LGMDs) are large group of heterogeneous genetic diseases, having a hallmark feature of muscle weakness. Pathogenic mutations in the gene encoding the giant skeletal muscle protein titin (TTN) are associated with several muscle disorders, including cardiomyopathy, recessive congenital myopathies and limb-girdle muscular dystrophy (LGMD) type10. The phenotypic spectrum of titinopathies is expanding, as next generation sequencing (NGS) technology makes screening of this large gene possible. AIM This study aimed to identify the pathogenic variant in a consanguineous Pakistani family with autosomal recessive LGMD type 10. METHODS DNA from peripheral blood samples were obtained, whole exome sequencing (WES) was performed and several molecular and bioinformatics analysis were conducted to identify the pathogenic variant. TTN coding and near coding regions were further amplified using PCR and sequenced via Sanger sequencing. RESULTS Whole exome sequencing analysis revealed a novel homozygous missense variant (c.98807G > A; p.Arg32936His) in the TTN gene in the index patients. No heterozygous individuals in the family presented LGMD features. The variant p.Arg32936His leads to a substitution of the arginine amino acid at position 32,936 into histidine possibly causing LGMD type 10. CONCLUSION We identified a homozygous missense variant in TTN, which likely explains LGMD type 10 in this family in line with similar previously reported data. Our study concludes that WES is a successful molecular diagnostic tool to identify pathogenic variants in large genes such as TTN in highly inbred population.

中文翻译：

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TTN基因的纯合子错义变体导致常染色体隐性隐性环带型肌营养不良症（10型）。

背景技术肢带型肌营养不良症（LGMD）是一大类异质性遗传疾病，具有肌肉无力的特征。编码巨型骨骼肌蛋白titin（TTN）的基因中的致病性突变与几种肌肉疾病有关，包括心肌病，隐性先天性肌病和四肢腰肌营养不良（LGMD）类型10。随着下一代测序（NGS）技术使筛查这种大基因成为可能，滴眼病的表型范围正在扩大。目的本研究旨在鉴定常染色体隐性LGMD 10型近亲巴基斯坦家庭的致病变异。方法从外周血样本中获得DNA，进行了完整的外显子组测序（WES），并进行了一些分子和生物信息学分析以鉴定病原体。使用PCR进一步扩增TTN编码区和近编码区，并通过Sanger测序进行测序。结果整个外显子组测序分析显示，在索引患者的TTN基因中有一个新的纯合错义变体（c.98807G> A； p.Arg32936His）。该家族中没有杂合子个体具有LGMD特征。变体p.Arg32936His导致32,936位的精氨酸氨基酸替换为组氨酸，可能导致LGMD类型10。结论我们鉴定了TTN中的纯合错义变体，这可能解释了该家族中LGMD类型10，与之前报道的相似数据。