Analysis of clinical, pathological and genetic features of 3 patients with limb girdle muscular dystrophy type 2A caused by non-canonical splice site mutations in the CAPN3 gene
10.3760/cma.j.cn113694-20230912-00154
- VernacularTitle:CAPN3基因非经典剪接位点突变致肢带型肌营养不良2A型患者3例的临床、肌肉病理和遗传学特点分析
- Author:
Guangyu WANG
1
;
Haoyang LIU
;
Xiaoqing LYU
;
Chuanzhu YAN
;
Pengfei LIN
Author Information
1. 山东大学齐鲁医院神经内科，济南 250012
- Keywords:
Muscular dystrophies, limb-girdle;
Biopsy;
Mutation;
CAPN3 gene
- From:
Chinese Journal of Neurology
2023;56(12):1341-1348
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the clinical, pathological and genetic features of 3 cases of limb-girdle muscular dystrophy 2A (LGMD2A) caused by non-canonical splice site mutations in the CAPN3 gene. Methods:For the 3 LGMD2A patients admitted to Qilu Hospital of Shandong University from July 2016 to July 2018 were selected as the subjects. Clinical data were collected, whole exome sequencing was conducted, and the candidate variants were verified by Sanger sequencing. Total RNA was extracted from the skeletal muscle tissue of 3 probands and effects of splicing mutations on pre-mRNA splicing in the CAPN3 gene were verified by reverse-transcription polymerase chain reaction. Total protein was extracted from the muscle tissue of the probands and expression level of calpain 3 protein was detected by Western blotting. Results:All the 3 probands presented muscle weakness in upper and lower limbs, and muscle weakness in proximal limbs was more severe. Muscle biopsies all indicated myogenic impairment. Genetic sequencing showed proband 1 carried compound heterozygous c.2185-14T>G and c.2305C>T (p.R769W) mutations in the CAPN3 gene, proband 2 carried compound heterozygous c.1193+30G>A and c.2069_2070delAC (p.H690Rfs *9) mutations, and proband 3 carried homozygous c.1194-9A>G mutations in the CAPN3 gene. Splicing assay showed the c.2185-14T>G mutation located in intron 20 induced retention of the entire intron 20, the c.1193+30G>A mutation in intron 9 induced retention of the first 31 nucleotides of intron 9, and the c.1194-9A>G mutation in intron 9 induced retention of the last eight nucleotides of intron 9. Western blotting revealed deficiency of calpain 3 protein in skeletal muscle of proband 1 and proband 2. Conclusions:The clinical manifestation of LGMD2A is muscle weakness predominantly in proximal limbs, and the muscle pathology is mostly characterized by myogenic impairment.Moreover, aberrant splicing of pre-mRNA caused by non-canonical splice site mutations plays a pathogenic role in this disease.
