Abstract 843: Restrictive Cardiomyopathy Linked cTnI Mutation (K178E) Causes Severe Heart Failure and Early Mortality

Abstract

Multiple mutations in cardiac troponin I (cTnI) have been linked to the development of restrictive cardiomyopathy (RCM) in human patients. Among them, K178E mutation has the worst clinical phenotype. K178E mutation may influence the inhibitory function through actin binding since previous studies have shown that amino acids number 173–181 bind to actin and increase the inhibitory effect of TnI. We modeled the mutation of lysine 178→glutamate (K178E) in human cTnI by cardiac specific expression of the mutated protein (cTnI 179Glu in mouse sequence) in transgenic mice. Multiple lines were generated with varying degrees of expression to establish a dose relationship. Increased resting tension in isolated cardiac myocytes and decreased myofibrillar compliance were the main manifestations in cellular function measurements. In vivo cardiac function measured by high-resolution ultrasonic imaging and Doppler echocardiography revealed a significant diastolic dysfunction characterized with decrease of left ventricular end diastolic dimension (LVEDD), decreased cardiac ejection fraction (EF) and left ventricular faction of shortening (FS) as well as a decreased cardiac output (CO). Doppler measurements showed a restrictive left ventricular filling pattern, i.e. reversed E/A ratio; decreased deceleration time (DT); decreased isovolumic relaxation time (IVRT). Enlarged left and right atria was a dramatic sign, which was observed in most of the transgenic mice, and was developed early and fast (at age of 2–3 weeks). Severely affected lines developed a pathology similar to that observed in human restrictive cardiomyopathy patients who carry the same mutation and with a high early mortality. Our data indicate the causality of this mutation for diastolic dysfunction and heart failure and provide a useful animal model for further understanding the thin filament structure-function relationships and the physiological function of triponin in cardiac contraction and relaxation. (Supported by NIH GM073621 and AHA0715116B) This research has received full or partial funding support from the American Heart Association, AHA Greater Southeast Affiliate (Alabama, Florida, Georgia, Louisiana, Mississippi, Puerto Rico & Tennessee).