TTN and familial atrial fibrillation: The remaining patients without an identified pathogenic MYBPC3 or MYH7 variant had mutations in ABCC9, SGCD, TTN, CSRP3, and PLN. Variants in ABCC9, which encodes an ATP-sensitive K+ channel, have been implicated in familial atrial fibrillation, sporadic DCM, and hypertrichotic osteochondrodysplasia.