Only a few SENP2 nulls could be recovered after E11.5 but were significantly underdeveloped (Figure 1A‐D) and exhibited heart deformities including pericardial effusion, missing atrioventricular (AV) cushion (Figure 1E,F), and myocardial thinning (Figure 1G,H). Here, SENP2 is linked to pericardial effusion.