Of the significant SNPs in the Chr 5 QTL region, missense variants in Myo18b are the most likely candidates for predisposition to cardiac dilation, considering the widely acknowledged role of Myo18b in myofibril assembly and myopathies.38–40,53 However, none of these are unique to CAST and B6—the only two strains displaying significant founder effects for the LVD trait (see Table S5). This evidence concerns the gene CAST and myopathy.