Reduced inter-cluster distances and increased ‘fragmentation’ of CRUs (increased number of individual RyR2 clusters per CRU) are also observed in HF (Kolstad et al., 2018; Sheard et al., 2019), with all of these remodeling properties associated with pro-arrhythmic Ca2+ handling of RyR2 (Louch et al., 2013; Walker et al., 2015). The gene discussed is RYR2; the disease is hydrops fetalis.