The in vivo and in vitro functional enhancement of DKO mice demonstrates that enhancing the sarcomeric contractility can be cardioprotective in HF characterized by reduced cardiac output, such as in cases of DCM.
To determine whether myocardial inflammation is associated with cardiac dysfunction in dilated cardiomyopathy (DCM) caused by MYBPC3 mutation, we used the well-characterized cMyBP-C<sup>(t/t)</sup> mouse model of DCM at 3months of age.
To determine whether oxidative stress markers were elevated in MYBPC3-mutated cardiomyopathies, a previously characterized 3-month-old mouse model of dilated cardiomyopathy (DCM) expressing a homozygous MYBPC3 mutation (cMyBP-C((t/t))) was used, compared to wild-type (WT) mice.
As a result, 7 novel mutations (MYPN, p.E630K; TNNT2, p.G180A; MYH6, p.R1047C; TNNC1, p.D3V; DES, p.R386H; MYBPC3, p.C1124F; and MYL3, p.D126G), 3 variants of uncertain significance (RBM20, p.R1182H; MYH6, p.T1253M; and VCL, p.M209L), and 2 known mutations (MYH7, p.A26V and MYBPC3, p.R160W) were revealed to be associated with DCM.
One variant (D145E) that was previously reported in association with hypertrophic cardiomyopathy and that produced results in vivo in this study consistent with prior hypertrophic cardiomyopathy functional studies was found associated with the MYBPC3P910T rare variant, likely contributing to the observed DCM phenotype.
Differences were observed in the frequency of splice site and frame-shift mutations in the gene MYBPC3, which occurred more frequently (P< 0.02, P< 0.001, respectively) in HCM than in DCM, suggesting that cardiac myosin-binding protein C haploinsufficiency predisposes to hypertrophy rather than to dilation.
Thereto, phosphorylation of the two main target proteins of the beta-adrenergic receptor pathway, troponin I (cTnI) and myosin binding protein C (cMyBP-C) was analysed in different parts in the free left ventricular wall of end-stage failing HCM and DCM patients and donors obtained during transplant surgery.
A group of 99 unrelated adult patients with DCM (familial n=27, sporadic n=72) were screened for the following genes: cardiac beta-myosin heavy chain, cardiac myosin-binding protein C (MYBPC3), regulatory and essential myosin light chains, alpha cardiac actin, alpha tropomyosin, cardiac troponin T, cardiac troponin I, cardiac troponin C, dystrophin, and lamin A/C.
In order to detect novel mutations we screened the sarcomeric protein genes beta-myosin heavy chain (MYH7), myosin-binding protein C (MYBPC3), troponin T (TNNT2), and alpha-tropomyosin (TPM1) in 46 young patients with DCM.