Increased myofilament Ca²⁺ sensitivity and diastolic dysfunction as early consequences of Mybpc3 mutation in heterozygous knock-in mice

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• 作者：Bodvaë ; l Fraysse^a ; ^b ; ¹ ; Florian Weinberger^c ; ¹ ; Sonya C. Bardswell^d ; ¹ ; Friederike Cuello^d ; Nicolas Vignier^a ; ^b ; Birgit Geertz^c ; Jutta Starbatty^c ; Elisabeth Kr&auml ; mer^c ; Catherine Coirault^a ; ^b ; Thomas Eschenhagen^c ; Jonathan C. Kentish^d ; Metin Avkiran^d ; Lucie Carrier^a ; ^b ; ^c ; ^{l.carrier@uke.de}
• 关键词：cMyBP-C ; cardiac myosin-binding protein C ; cTnI ; cardiac troponin I ; CSQ ; calsequestrin ; HCM ; hypertrophic cardiomyopathy ; Het ; heterozygous Mybpc3-targeted knock-in mice ; KI ; homozygous Mybpc3-targeted knock-in mice ; KO ; homozygous Mybpc3-targeted knock-
• 刊名：Journal of Molecular and Cellular Cardiology
• 出版年：2012
• 出版时间：June, 2012
• 年：2012
• 卷：52
• 期：6
• 页码：1299-1307
• 全文大小：1220 K

文摘

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 Ca²⁺ 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 Ca²⁺ sensitivity in skinned ventricular trabeculae, ii) lower diastolic sarcomere length, and faster Ca²⁺ 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 Ca²⁺ sensitivity, faster Ca²⁺ transient decay, and diastolic dysfunction. These data demonstrate that myofilament Ca²⁺ sensitization and diastolic dysfunction are early phenotypic consequences of Mybpc3 mutations independent of LVH. The accelerated Ca²⁺ 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.