The known contribution of Fzd8 to canonical β-catenin signaling and the WNT pathway15 is a likely mechanism to explore and potentially assign to the variant Fzd8. By contrast, the hypertrophic cardiomyopathy that we identified in Leprotl1-mutant mice suggests functions of this gene in addition to its known role in growth (that is, GH in the liver) and metabolism16. This evidence concerns the gene FZD8 and hypertrophic cardiomyopathy.