Tubulin tyrosine ligase variant perturbs microtubule tyrosination, causing hypertrophy in patient-specific and CRISPR gene-edited iPSC-cardiomyocytes

Hypertrophic cardiomyopathy (HCM) is a hereditary heart condition characterized by either preserved or reduced ejection fraction without any underlying secondary causes. The primary cause of HCM is sarcomeric gene mutations, which account for only 40%-50% of the total cases. Here, we identified a pathogenic missense variant in tubulin tyrosine ligase (TTL p.G219S) in a patient with HCM. We used clinical, genetics, computational, and protein biochemistry approaches, as well as patient-specific and CRISPR gene-edited induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs), to demonstrate that the TTL pathogenic variant results in a reduced enzymatic activity and the accumulation of detyrosinated tubulin leading to the disruption of redox signaling, ultimately leading to HCM. Our findings highlight - for the first time to our knowledge - the crucial roles of the TTL variant in cardiac remodeling resulting in disease.