Severe MDC1A congenital muscular dystrophy due to a splicing mutation in the LAMA2 gene resulting in exon skipping and significant decrease of mRNA level

Genet Test. 2007 Fall;11(3):199-207. doi: 10.1089/gte.2006.0517.

Abstract

Congenital muscular dystrophies (CMDs) are a clinically and genetically heterogeneous group of neuromuscular disorders, with autosomal recessive inheritance. We report a patient with severe congenital muscular dystrophy and total deficiency in the laminin alpha2 chain. Genetic analyses showed a linkage to the MDC1A locus for the patient's family, and DNA sequencing revealed in the propositus of a new homozygous mutation in the donor splice site of intron 58 of the LAMA2 gene. RT-PCR experiments performed on total RNA from a patient's muscle biopsy showed a complete skipping of exon 58 in LAMA2 cDNA and a significant decrease in the LAMA2 mRNA level. This exon skipping altered the open reading frame of the mutant transcript and generated a premature termination codon (PTC) within exon 59, which potentially elicits the nonsense mRNA to degradation by NMD (nonsense-mediated mRNA decay). However, the residual exon 58-lacking mRNA could potentially be translated, and the resulting truncated alpha2 chain would lack its LG4 and LG5 domains that are involved in binding with alpha-dystroglycan. These results demonstrate the utility of mRNA analysis to understand the mutation primary impact and the disease phenotype in the patients.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Child, Preschool
  • Codon, Terminator
  • Exons*
  • Genetic Linkage
  • Humans
  • Laminin / genetics*
  • Male
  • Molecular Sequence Data
  • Muscular Dystrophies / congenital*
  • Muscular Dystrophies / genetics*
  • Mutation*
  • RNA Splice Sites
  • RNA Splicing*
  • RNA, Messenger / metabolism*

Substances

  • Codon, Terminator
  • Laminin
  • RNA Splice Sites
  • RNA, Messenger
  • laminin alpha 2