Expression of mouse agrin in normal, denervated and dystrophic muscle.

Agrin is a heparan sulfate proteoglycan that is required for the development of postsynaptic specializations at the neuromuscular junction. An alternatively spliced isoform of agrin that lacks this activity is found in basement membranes of several tissues including embryonic muscle. Overexpression of a miniaturized form of this agrin isoform ameliorates the severe muscle dystrophy of laminin alpha2-deficient mice, a mouse model for merosin-deficient congenital muscle dystrophy. Several lines of evidence indicate that this amelioration is based on the high-affinity binding of the mini-agrin to the laminins and to alpha-dystroglycan. Here, we used antibodies raised against mouse agrin to evaluate protein expression in adult muscle of normal and dystrophic mice. We find that expression of agrin in non-synaptic region varies greatly between different muscles in wild-type mice and that its levels are altered in dystrophic muscle.