Exon 3 was targeted with a point mutation changing residue 1343 in the coding region from C to T (c.1343C>T). This results in a P448L (p.Pro448Leu) substitution in the translated peptide. An FRT and loxP site flanked neomycin resistance gene cassette that was inserted into intron 2 was removed through cre-mediated recombination. This allele mimics a mutation found in certain human congenital muscular dystrophies (MDC1C) patients. In mice carrying this allele, muscle and heart cells lack glycosylation of alpha-dystroglycan.