HCN4 and hydrops fetalis: This is consistent with early termination of spontaneous membrane depolarizations observed in Hcn4:shJph2 SANCs that failed to trigger AP,34 akin to our observations in Cav-3KO (Fig. 3A) and HF mice (Fig. 6E) during caveolae-mediated LCR-to-AP uncoupling.