In contrast to the reported data for pressure-overload-induced heart failure and dilated cardiomyopathy, where Na+/Ca2+ exchanger 1 (NCX1) and Ca2+-calmodulin-dependent protein kinase II delta (CaMKIIδ) are typically upregulated33,34, we found that both Ncx1 and Camk2d gene expression was significantly decreased in both Fxn-cKO males (–58% for Ncx1 and -49% Camk2d) and females (–50% for Ncx1 and -25% for Camk2d) (Fig. 6g, h). Here, FXN is linked to heart failure.