TNNI3K and hydrops fetalis: Recently, a correlation was reported between mononuclear cardiomyocyte frequency, CM proliferation, post-MI outcome, and expression of Tnni3k across strains of the Hybrid Mouse Diversity Panel.62 However, Tnni3k genetic ablation had no effect on cardiac function or response to injury,62 and in the current study no correlation was observed between MI-induced HF phenotype in CC RI strains and Tnni3k locus polymorphisms or mRNA expression levels (Supplementary Fig. S2).