title: Correcting diastolic dysfunction by Ca2+ desensitizing troponin in a transgenic mouse model of restrictive cardiomyopathy.
abstract: Several cardiac troponin I (cTnI) mutations are associated with restrictive cardiomyopathy (RCM) in humans. We have created transgenic mice (cTnI(193His) mice) that express the corresponding human RCM R192H mutation. Phenotype of this RCM animal model includes restrictive ventricles, biatrial enlargement and sudden cardiac death, which are similar to those observed in RCM patients carrying the same cTnI mutation. In the present study, we modified the overall cTnI in cardiac muscle by crossing cTnI(193His) mice with transgenic mice expressing an N-terminal truncated cTnI (cTnI-ND) that enhances relaxation. Protein analyses determined that wild type cTnI was replaced by cTnI-ND in the heart of double transgenic mice (Double TG), which express only cTnI-ND and cTnI R193H in cardiac myocytes. The presence of cTnI-ND effectively rescued the lethal phenotype of RCM mice by reducing the mortality rate. Cardiac function was significantly improved in Double TG mice when measured by echocardiography. The hypersensitivity to Ca(2+) and the prolonged relaxation of RCM cTnI(193His) cardiac myocytes were completely reversed by the presence of cTnI-ND in RCM hearts. The results demonstrate that myofibril hypersensitivity to Ca(2+) is a key mechanism that causes impaired relaxation in RCM cTnI mutant hearts and Ca(2+) desensitization by cTnI-ND can correct diastolic dysfunction and rescue the RCM phenotypes, suggesting that Ca(2+) desensitization in myofibrils is a therapeutic option for treatment of diastolic dysfunction without interventions directed at the systemic beta-adrenergic-PKA pathways.
authors.affiliation: Department of Basic Science, College of Biomedical Science, Florida Atlantic University, Boca Raton, FL 33431, USA.
authors.forename: Yuejin
authors.initials: Y
authors.lastname: Li
authors.forename: Pierre-Yves Jean
authors.initials: PY
authors.lastname: Charles
authors.forename: Changlong
authors.initials: C
authors.lastname: Nan
authors.forename: Jose Renato
authors.initials: JR
authors.lastname: Pinto
authors.forename: Yingcai
authors.initials: Y
authors.lastname: Wang
authors.forename: Jingsheng
authors.initials: J
authors.lastname: Liang
authors.forename: Gang
authors.initials: G
authors.lastname: Wu
authors.forename: Jie
authors.initials: J
authors.lastname: Tian
authors.forename: Han-Zhong
authors.initials: HZ
authors.lastname: Feng
authors.forename: James D
authors.initials: JD
authors.lastname: Potter
authors.forename: J-P
authors.initials: JP
authors.lastname: Jin
authors.forename: Xupei
authors.initials: X
authors.lastname: Huang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D002313:Cardiomyopathy, Restrictive / Q000503:physiopathology*; D003971:Diastole; D004452:Echocardiography; D005260:Female; D006801:Humans; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics*; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology*; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D019210:Troponin I / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D019210:Troponin I; D002118:Calcium