biostudies-literatureRuijmbeek CWThe Sonderforschungsbereich/Transregio 23The CRC-1213Dutch Heart Foundatione168247https://www.ebi.ac.uk/biostudies/studies/S-EPMC10544232biostudies-literatureUnknown8(17)Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the funcJCI insightBiallelic variants in FLII cause pediatric cardiomyopathy by disrupting cardiomyocyte cell adhesion and myofibril organization.PMC10544232Project B01Project C0803-003-2020-T062Tessadori FPestel JAl-Hassnan ZNvan Slegtenhorst MAIdrees HKeller Lvan Ham TJAlmesned Aden Bersselaar LMVVerhagen JMStainier DYHousley MPReischauer SHousley Fder Linde HCVLai JKDalinghaus MWillemsen RRuijmbeek CWBakkers JPiesker JfalseBiallelic variants in FLII cause pediatric cardiomyopathy by disrupting cardiomyocyte cell adhesion and myofibril organization.Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the func2023-01-01T00:00:00Z2023 Sep2026-05-29T01:49:15.138Z2025-04-19T23:49:34.631ZS-EPMC105442323756159110.1172/jci.insight.168247