CAMK2G and hydrops fetalis: Increased RyR colocalization with the cell surface in HF may compensate for t-tubule loss by facilitating surface Ca2+ release, similar to enhanced surface Ca2+ release in neonatal sheep atrial cells with sparse t-tubules.49 How RyR redistribution occurs in this study is unknown, but decreased RyR abundance (as reported in the atria in HF50) alters RyR cluster structure,51 as does CAMKII,52 which is increased in the sheep atria in HF.19 Thus, these factors may play a role in the altered RyR distribution we report.