Sarcomeric perturbations of myosin motors lead to dilated cardiomyopathy in genetically modified MYL2 mice

Abstract

SignificanceDilated cardiomyopathy (DCM) is a progressive heart disease with no current cure, often culminating in heart transplantation. Transgenic D94A (aspartic acid-to-alanine) mice carrying a novel DCM-causative mutation in the MYL2 gene, encoding the cardiac myosin regulatory light chain, were created and investigated by echocardiography and invasive hemodynamic and molecular structural and functional assessments. Our data show that hypocontractile myosin motors and structural perturbations at the level of sarcomeres trigger aberrant functional remodeling in D94A hearts and the development of DCM, which closely follows the clinical phenotype. Left ventricular chamber dilation and decreased ejection fraction, observed in D94A hearts, were indicative of systolic dysfunction, a hallmark of DCM. Our study suggests that MYL2 may be considered a therapeutic target for dilated cardiomyopathy.

Slow‐twitch skeletal muscle defects accompany cardiac dysfunction in transgenic mice with a mutation in the myosin regulatory light chain

“…Tandem (The Global Proteome Machine Organization; https://www.thegpm.org/TANDEM/index.html). The relative amount of human protein was determined by the amount of human-specific peptide (AGGANSN) relative to the total amount of mouse (IEGGSSN) and human-specific RLC peptides (21).…”

“…The strips were then transferred to a fresh pCa8/ 50% glycerol, v/v (storage solution) mixed with 1% Triton X-100 (MilliporeSigma, Burlington, MA, USA) for 24 h at 4°C. Finally, the fibers were transferred to a fresh storage solution and kept at 220°C for 5-10 d (19)(20)(21). Before the experiment, muscle bundles were dissected into strips of ;1.5 mm in length and ;100 mm in diameter, attached to a Güth force transducer, freshly skinned in pCa 8 solution with 1% Triton X-100 (;30 min), rinsed thoroughly in pCa 8 solution, and their sarcomere length adjusted to 2.1-2.3 mm.…”

“…The force-pCa measurements were performed at 21°C in solutions of increasing Ca 2+ concentrations from pCa 8 to 4, each containing the ATP regeneration system. The force-pCa curves were analyzed by using the Hill equation, and the maximal tension (pCa 4) was expressed in kilonewton per square meters with the crosssectional area assumed to be circular (19)(20)(21).…”

“…Equatorial X-ray diffraction patterns were collected from freshly skinned left ventricular PMs and SOL muscle strips mounted in a X-ray chamber using the small angle instrument on the BioCAT beamline 18-D at the Advanced Photon Source, Argonne National Laboratory (Argonne, IL, USA) as previously described (20,21). The following mice were used for measurements in PMs: WT, 6M and 14F (5-7 mo old); and R58Q, 4M and 11F (4-8 mo old).…”

“…It is positioned at the head-rod junction of the myosin heavy chain (MHC) and, together with the myosin essential light chain, stabilizes the a-helical neck region of the myosin head (13). To address the mechanisms responsible for triggering cardiac disease, several RLC mutations have been investigated in humanized mouse models expressing the human ventricular RLC mutant proteins (14)(15)(16)(17)(18)(19)(20)(21). This study focuses on the R58Q (arginine-to-glutamine) mutation shown by population studies to cause HCM and sudden cardiac death that occurred in families of various ethnic origins (5)(6)(7).…”