https://doi.org/10.1007/s00392-025-02625-4
1Medizinische Hochschule Hannover Kardiologie und Angiologie Hannover, Deutschland; 2Universitätsklinikum Hamburg-Eppendorf Zentrum für Experimentelle Medizin, Experimentelle Herz-Kreislaufforschung Hamburg, Deutschland; 3Medizinische Hochschule Hannover Molekulare und Translationale Kardiologie Hannover, Deutschland; 4Medizinische Hochschule Hannover Institut für Molekular- und Zellphysiologie Hannover, Deutschland; 5Medizinische Hochschule Hannover Institut für Pathologie Hannover, Deutschland; 6Medizinische Hochschule Hannover Zentrale Forschungseinrichtung Elektronenmikroskopie Hannover, Deutschland
Background: Cardiomyocyte mitochondria serve multiple roles in regulating cardiac function and distribute along sarcomeres during physiological development. Mitochondrial motility is mediated by Ras Homolog Family Member T (RHOT) 1 and RHOT2, which couple mitochondria to kinesin and dynein motors. We sought to test the hypothesis that RHOT protein expression and mitochondrial motility are required for mitochondrial positioning during cardiomyocyte development.
Methods: We generated mice with cardiomyocyte-specific deletion of Rhot1 and Rhot2 (cRhot1/2-KO) to determine the impact of mitochondrial motility on cardiomyocyte maturation. Contractile function was determined by transthoracic echocardiography. Mitochondrial motility was determined by a kinesin-1 single molecule motility assay, mitochondrial respiratory capacity was determined in isolated mitochondria. Mitochondrial localization and ATP production were assessed by confocal microscopy and following adenoviral expression of the FRET-based ATP biosensor ATeam. Cardiac ultrastructure was assessed by electron micrographs.
Results: Mitochondria isolated from cRhot1/2-KO hearts exhibited impaired motility in the presence of preserved respiratory capacity with pyruvate and palmitoyl-carnitine each combined with malate as substrates. cRhot1/2-KO mice developed age-dependent heart failure and fatal cardiomyopathy with the majority of mice dying by the age of 40 weeks. Electron micrographs, confocal microscopy, and FRET-based measurements revealed sarcomere disarray and perinuclear accumulation of mitochondria and ATP production.
Conclusion: Mitochondrial motility, mediated by RHOT proteins, is required for mitochondrial positioning during cardiomyocyte development and links spatial ATP production to structural and functional maturation of the developing heart.