Targeted Next-generation Sequencing Reveals a Homozygous Nonsense Mutation in CAPN3 that Causes Limb-girdle Muscular Dystrophy Type 2A First in Vietnam

Abstract

Limb-girdle muscular dystrophy (LGMD) is a genetically heterogeneous entity characterized by progressive wasting of the shoulder and pelvic-girdle muscles. Diagnosing particular types of LGMD is still challenging, especially in developing countries, with targeted next-generation sequencing (NGS) emerging as the most advanced diagnostic tool. Here, a 15-year-old Vietnamese girl with proximal muscle weakness was examined for genetic cause via targeted NGS using the AmpliSeq Inherited Disease Ready-to-Use Panel on the Ion Torrent Personal Genome Machine of the detected nucleotide changes, a mutation in exon 3 of CAPN3 was considered to be the responsible mutation. In the readpile-ups, only T was observed at the 424th nucleotide, while only C was observed in the normal sample. The c.424 C>Ttransition in CAPN3 shifted glutamine to a stop codon at the 142nd amino acid residue (p.Q142X). The homozygous c.424C>T genotype was confirmed via XspI restriction enzyme digestion using polymerase chain reaction-amplified product from the index case encompassing exon 3.The patient was concluded to be autosomal recessive LGMD type 2A. XsaIdigestion of 100 control Vietnamese genomes disclosed one carrier of this mutation. Thus, LGMD type 2Awas first diagnosed in Vietnam, a developing country, via targeted NGS, avoiding invasive muscle biopsy.