Mutations in the integrin α7 gene cause congenital myopathy

The basal lamina of muscle fibers plays a crucial role in the development and function of skeletal muscle. An important laminin receptor in muscle is integrin α7β1D. Integrin β1 is expressed throughout the body, while integrin α7 is more muscle-specific. To address the role of integrin α7 in human muscle disease, we determined α7 protein expression in muscle biopsies from 117 patients with unclassified congenital myopathy and congenital muscular dystrophy by immunocytochemistry. We found three unrelated patients with integrin α7 deficiency and normal laminin α2 chain expression. To determine if any of these three patients had mutations of the integrin α7 gene, ITGA7, we cloned and sequenced the full-length human ITGA7 cDNA, and screened the patients for mutations. One patient had splice mutations on both alleles; one causing a 21-bp insertion in the conserved cysteine-rich region, and the other causing a 98-bp deletion. A second patient was a compound heterozygote for the same 98-bp deletion, and had a 1- bp frame-shift deletion on the other allele. A third showed marked deficiency of ITGA7 mRNA. Clinically, these patients showed congenital myopathy with delayed motor milestones. Our results demonstrate that mutations in ITGA7 are involved n a form of congenital myopathy.