Although PKP2 dominant mutations have been associated with arrhythmogenic right ventricular cardiomyopathy in humans [9] an intronic or intergenic mutation is unlikely to account for the Python phenotype as all human PKP2 mutations found to date occur in the coding region or splice sites which are not mutated in Python mice, the homozygous phenotype for the null Pkp2 mutation is very different from the Python homozygote [10] and Pkp2 mRNA level is not altered in Python hearts as judged by microarray analysis (data not shown) suggesting no disease-causing non-coding regulatory changes. The gene discussed is PKP2; the disease is Arrhythmogenic right ventricular dysplasia.