To verify that this was the causative mutation in gw71, we performed an in vitro activity assay for the protein using wild-type and mutant atp7a. Fibroblasts from patients with Menkes disease which lack functional ATP7A were transfected with tyrosinase in combination with either wild-type or mutant zebrafish atp7a created via site-directed mutagenesis of the wild-type cDNA. Here, TYR is linked to Menkes disease.