title: Increased myofilament Ca2+ sensitivity and diastolic dysfunction as early consequences of Mybpc3 mutation in heterozygous knock-in mice.
abstract: Hypertrophic cardiomyopathy (HCM) is frequently caused by mutations in MYBPC3 encoding cardiac myosin-binding protein C (cMyBP-C). The mechanisms leading from gene mutations to the HCM phenotype remain incompletely understood, partially because current mouse models of HCM do not faithfully reflect the human situation and early hypertrophy confounds the interpretation of functional alterations. The goal of this study was to evaluate whether myofilament Ca(2+) sensitization and diastolic dysfunction are associated or precede the development of left ventricular hypertrophy (LVH) in HCM. We evaluated the function of skinned and intact cardiac myocytes, as well as the intact heart in a recently developed Mybpc3-targeted knock-in mouse model carrying a point mutation frequently associated with HCM. Compared to wild-type, 10-week old homozygous knock-in mice exhibited i) higher myofilament Ca(2+) sensitivity in skinned ventricular trabeculae, ii) lower diastolic sarcomere length, and faster Ca(2+) transient decay in intact myocytes, and iii) LVH, reduced fractional shortening, lower E/A and E'/A', and higher E/E' ratios by echocardiography and Doppler analysis, suggesting systolic and diastolic dysfunction. In contrast, heterozygous knock-in mice, which mimic the human HCM situation, did not exhibit LVH or systolic dysfunction, but exhibited higher myofilament Ca(2+) sensitivity, faster Ca(2+) transient decay, and diastolic dysfunction. These data demonstrate that myofilament Ca(2+) sensitization and diastolic dysfunction are early phenotypic consequences of Mybpc3 mutations independent of LVH. The accelerated Ca(2+) transients point to compensatory mechanisms directed towards normalization of relaxation. We propose that HCM is a model for diastolic heart failure and this mouse model could be valuable in studying mechanisms and treatment modalities.
authors.affiliation: INSERM U974, Institut de Myologie, Paris, France.
authors.forename: Bodvaël
authors.initials: B
authors.lastname: Fraysse
authors.forename: Florian
authors.initials: F
authors.lastname: Weinberger
authors.forename: Sonya C
authors.initials: SC
authors.lastname: Bardswell
authors.forename: Friederike
authors.initials: F
authors.lastname: Cuello
authors.forename: Nicolas
authors.initials: N
authors.lastname: Vignier
authors.forename: Birgit
authors.initials: B
authors.lastname: Geertz
authors.forename: Jutta
authors.initials: J
authors.lastname: Starbatty
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Krämer
authors.forename: Catherine
authors.initials: C
authors.lastname: Coirault
authors.forename: Thomas
authors.initials: T
authors.lastname: Eschenhagen
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Kentish
authors.forename: Metin
authors.initials: M
authors.lastname: Avkiran
authors.forename: Lucie
authors.initials: L
authors.lastname: Carrier
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002312:Cardiomyopathy, Hypertrophic / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology*; D002352:Carrier Proteins / Q000235:genetics*; D003971:Diastole; D004452:Echocardiography; D055879:Gene Knock-In Techniques; D023061:Gene Order; D006352:Heart Ventricles / Q000378:metabolism / Q000503:physiopathology; D006579:Heterozygote; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism; D009210:Myofibrils / Q000378:metabolism*; D000099163:Myosin Binding Protein C
chemical_list: D002118:Calcium; D002352:Carrier Proteins; D000099163:Myosin Binding Protein C