Identification of a novel mutant transcript of laminin α2 chain gene responsible for muscular dystrophy and dysmyelination in dy^2J mice

Abstract

Murine dystrophia muscularis-2J (dy2J) is an autosomal recessive disorder characterized by muscular dystrophy and dysmyelination of peripheral nerve. Biochemical characterization of dy2J mice revealed the expression of a mutant laminin alpha 2 chain with a smaller molecular weight in the basal lamina of striated muscle and peripheral nerve. DNA sequencing of the alpha 2 chain cDNA amplified by RT-PCR from dy2J mice identified a novel and predominant transcript with a 171 base in-frame deletion. We also confirmed an underlying splice donor site mutation in the alpha 2 chain gene of the dy2J mouse. Translation of this variant transcript would result in the expression of a truncated alpha 2 chain having a 57 amino acid deletion (residues 34-90) and a substitution of Gln91Glu in the N-terminal domain VI, which is presumed to be involved in self-aggregation of laminin heterotrimers. Thus, the mutant alpha 2 chain could disrupt the formation of the laminin network and lead to muscle cell degeneration. Our results provide a molecular basis of muscular dystrophy and dysmyelination of peripheral nerve.

Basement Membranes: Cell Scaffoldings and Signaling Platforms

“…Polymerization defects are implicated in a number of developmental abnormalities. The dy2J dystrophic mouse, possessing an in-frame deletion within the laminin a2LN domain, is characterized by attenuated muscle sarcolemmal and Schwann cell endoneurial basement membranes, muscle degeneration/regeneration and peripheral nerve amyelination (Sunada et al 1995a;. Missense-mutations of the a2 and a1 LN domains have been found to cause a mild neuromuscular and retinal defects respectively, the latter associated with a partial reduction in the ability of the LN domain to bind to its bLN and gLN partners (Patton et al 2008;Edwards et al 2010).…”

Electrotransfer of naked DNA in the skeletal muscles of animal models of muscular dystrophies

“…Spontaneous animal models have been described for the most frequent form, Duchenne muscular dystrophy (DMD), [1][2][3] and also for the occidental form of congenital muscular dystrophy (CMD). [4][5][6][7][8][9][10][11] These models have helped the investigations of potential therapeutic avenues, including the recent approaches based on gene transfer. In skeletal muscle, transduction efficacy is largely dependent on the development of a vector or vehicle that can selectively and efficiently deliver a gene to target cells with minimal toxicity.…”

“…28,29 The dystrophia muscularis dy/dy and dy 2J /dy 2J mice are animal models for the occidental form of CMD. [4][5][6][7][8][9][10] Both murine and human diseases share common clinical, histological and genetic features, among which are the generalized and progressive alteration of the muscular tissue. The number of fibers is decreased and their diameter is greatly variable.…”

“…The difference between these models may be related to the expression of a truncated, but partially functional protein in the dy 2J /dy 2J mouse. 9,10 .Using these animal models, we addressed some issues specific to dystrophic muscle: is transduction of skeletal muscle fibers efficient in animal models of muscular dystrophies using reporter plasmids, and does muscle dystrophy hamper efficacy? Does the transfer of therapeutic genes induce the expression of functional proteins in these suffering muscles in vivo?…”

Myoblast transplantations lead to the expression of the laminin α2 chain in normal and dystrophic (dy/dy) mouse muscles

“…The milder allelic variant, the dy 2J /dy 2J mouse model, 20 has an identified mutation on the laminin ␣2 chain gene which leads to the synthesis of a truncated protein. 21,22 Two knock-out mouse models have been described recently. 23,24 We have shown previously that the transplantation of primary mouse muscle cell cultures partially restored laminin ␣2 chain expression in dy/dy mice.…”