A lacZ-neo was inserted into the Wisp3 locus, replacing exons3-5 and creating a null allele. The allele resulted in a fusion protein that has Beta-gal activity under the endogenous promoter. The Wisp3 protein is truncated immediately after the IGFBP domain, and lacks the vWF, TSP and C-terminal domains. RT-PCR of cartilage from mutants showed a lack of wild-type transcript. Beta-gal activity was confirmed in cells transfected with a vector expressing the Wisp3-lacZ fusion protein. (J:94500)