Perturbation of the titin/MURF1 signaling complex is associated with hypertrophic cardiomyopathy in a fish model and in human patients

Abstract

Hypertrophic cardiomyopathy (HCM) is a hereditary disease characterized by cardiac hypertrophy with diastolic dysfunction. Gene mutations causing HCM have been found in about half of HCM patients, while the genetic etiology and pathogenesis remain unknown for many cases of HCM. To identify novel mechanisms underlying HCM pathogenesis, we generated a cardiovascular-mutant medaka fish, non-spring heart (nsh), which showed diastolic dysfunction and hypertrophic myocardium. The nsh homozygotes had fewer myofibrils, disrupted sarcomeres and expressed pathologically stiffer titin isoforms. In addition, the nsh heterozygotes showed M-line disassembly that is similar to the pathological changes found in HCM. Positional cloning revealed a missense mutation in an immunoglobulin (Ig) domain located in the M-line–A-band transition zone of titin. Screening of mutations in 96 unrelated patients with familial HCM, who had no previously implicated mutations in known sarcomeric gene candidates, identified two mutations in Ig domains close to the M-line region of titin. In vitro studies revealed that the mutations found both in medaka fish and in familial HCM increased binding of titin to muscle-specific ring finger protein 1 (MURF1) and enhanced titin degradation by ubiquitination. These findings implicate an impaired interaction between titin and MURF1 as a novel mechanism underlying the pathogenesis of HCM.

MuRF1/TRIM63, Master Regulator of Muscle Mass

“…Moreover, very recent data showed that missense mutations in a titin Ig domain located in the M line-A-band transition zone of titin disrupted sarcomeres and led to HCM both in medaka fish and in humans [181]. In vitro studies revealed that these mutations increased the binding of MuRF1 [181].…”

Case Report: Two New Cases of Autosomal-Recessive Hypertrophic Cardiomyopathy Associated With TRIM63-Compound Heterozygous Variant

“…While not rare in some forms of HCM, restrictive phenotype had a malign prognosis in pediatric and adult patients with HCM ( Maskatia et al, 2012 ; Li et al, 2020 ). In TRIM63 -associated HCM, restrictive dysfunction could reflect the altered molecular interaction of MuRF1 with titin ( Higashikuse et al, 2019 ). There is a MuRF1-binding site in titin adjacent to the titin kinase domain.…”

“…There is a MuRF1-binding site in titin adjacent to the titin kinase domain. Mutations of this region lead to hypertrophy and diastolic dysfunction in the medaka fish experimental model and Japanese patients with HCM associated with TRIM63 ( Higashikuse et al, 2019 ). In addition, mutations of the titin MuRF1-binding site lead to the expression shift to the stiffer titin isoforms, increased titin binding to MuRF1, and enhanced titin degradation through ubiquitination.…”

“…In cardiac myocytes, overexpression of MuRF1 enhances susceptibility to heart failure in response to pressure overload, and its activation prevents cardiac hypertrophy ( Arya et al, 2004 ; Willis et al, 2009 ). MuRF1 targets include sarcomere contractile, structural proteins, and signaling molecules ( Witt et al, 2005 ; Polge et al, 2011 ; Chen et al, 2012 ; Maejima et al, 2014 ; Polge et al, 2018 ; Higashikuse et al, 2019 ; Bulatov et al, 2018 ). The involvement of TRIM63 in various pathological processes has been documented in several experimental and functional studies ( Chen et al, 2012 ; Su et al, 2014 ; Olivé et al, 2015 ; Salazar-Mendiguchía et al, 2020 ).…”

Shared Molecular Mechanisms of Hypertrophic Cardiomyopathy and Its Clinical Presentations: Automated Molecular Mechanisms Extraction Approach

“…Titin and titin-related molecules were found to be important in the intersection of myocardial stiffness and HCM. Higashikuse et al (2019) suggested that titin mutations in HCM families can be incorporated into the sarcomere and impair TRIM63 (MURF1) binding, resulting in abnormal sarcomere stiffness [ 60 ].…”