Mutations in MINDBOMB 1 (MIB1), encoding an E3 ubiquitin ligase of the NOTCH signaling pathway, cause left ventricular noncompaction cardiomyopathy (LVNC) in mice and humans, increasing the risk of arrhythmia and left ventricular dysfunction. Here, MIB1 is linked to Left ventricular noncompaction cardiomyopathy.