Required for myofibril assembly and outgrowth of the cardiac chambers in the developing heart (PubMed:27217161). Appears to be catalytically inactive, showing no activity against O-acetyl-ADP-ribose (By similarity). Expressed in heart (at protein level) (PubMed:27217161). A short form is detected in both heart and tadpole tail (at protein level) (PubMed:27217161). Expressed in embryos, juveniles and adults. Onset of embryonic expression coincides with early myocardial differentiation (PubMed:27217161). Expression is detected in cardiac tissue from stage 29 with the greatest concentration found in regions of actively growing chamber myocardium (PubMed:27217161). At stage 40, highly expressed in the left and right lateral sides marking the growing atrial chambers with lower levels in the dorsal atrial roof (PubMed:27217161). Morpholino knockdown results in defective embryonic cardiogenesis with hearts forming small ventricles that do not beat (PubMed:27217161). Defective endocardial maturation with endocardial cells showing a rounded morphology and no clear lumen forming in the heart (PubMed:27217161). Myofibril assembly is disrupted in the developing ventricle, preventing ventricle outgrowth (PubMed:27217161). Belongs to the ADP-ribosylglycohydrolase family. Although it belongs to the ADP-ribosylglycohydrolase family, lacks metal-binding and substrate-binding residues, suggesting that it has no hydrolase activity.