Site-directed mutagenesis of codon 179 (exon 5; older nomenclature is S156C) resulted in a serine to cysteine substitution. A floxed neomycin selection cassette inserted into intro 4 was excised via the in vitro expression of cre recombinase. Sequence analysis showed that a normal sized transcript detected by Northern blot and RT-PCR analyses contained the desired missense mutation. Western blot analysis of ECM protein extracts confirmed proper translation of the mutant transcript.