Plays an essential role in heart function and development by regulating the organization and function of the sarcoplasmic reticulum in cardiomyocytes. Expressed in embryos 48 to 96 hours post-fertilization (at protein level) (PubMed:32075961). Expressed in both ventricular and atrial cardiomyocytes (at protein level) (PubMed:32075961). The short lumenal loops between transmembrane domains 1 and 2 and between transmembrane domains 3 and 4 may impart a wedge-like configuration, thus deforming membranes. 60% of embryos die 7 days post-fertilization (PubMed:32075961). Embryos have cardiac developmental defects including a lack of cardiac looping and atrio-ventricular conduction defects with dysynchronous beating rhythms (PubMed:32075961). Increase in RTN4 protein expression levels (PubMed:32075961). Morpholino knockdown causes apparent sarcoplasmic reticulum membrane vacuolization in ventricular tissue along with structural discontinuity between sarcomeres (PubMed:32075961). Belongs to the DP1 family.