Abstract
Hypertrophic cardiomyopathy (HCM) is a myocardial disorder, with complications including heart failure, thromboemboli and sudden death. Human and feline HCM (fHCM) are clinically comparable, thus fHCM may serve as a spontaneous animal model. fHCM in Maine Coon (MC) cats is associated with the p.A31P mutation in the cMyBP-C protein. The mutation is located in the cMyBP-C C0-domain which is known to interact with actin. The presence and levels of the wild type and mutated protein in heart tissue from mutant and wild type MC cats were examined by SDS-PAGE and mass spectrometry (MS). Quantitative yeast-2-hybrid (Y2H) protein-protein interaction analysis was used to assess the effect of the mutation on C0C1/actin interaction. The NMR-based structure of the C0 domain was used to calculate the energetic consequence of replacing alanine with a proline residue. In the homozygous MC cat, the mutated cMyBP-C protein was present, and cMyBPC-C levels were not reduced compared to that of the wild type cat. However, the interaction of actin with mutant cMyBP-C C0C1 was reduced compared to that of wild type. This may be because the substitution of the alanine with proline in position 31 was energetically highly unfavorable and resulted in only one hydrogen bond within the anti-parallel beta-strand compared to two hydrogen-bonds for alanine, possibly destabilizing the structure of the actin-interacting domain. The p.A31P mutation is present in cardiac tissue and the most likely pathogenic mechanism is interference with contractility by reducing binding of the C0C1 domain of cMyBP-C to actin.
Highlights
Hypertrophic cardiomyopathy (HCM) is a primary structural disorder of the myocardium; characterized by left ventricular hypertrophy and clinical complications ranging from no symptoms to sustained palpitation, heart failure and sudden cardiac death 1
We examined the effect of the p.A31P amino acid substitution on the interaction between the cardiac myosin binding protein-c (cMyBP-C) C0C1 domain and actin using quantitative b-galactosidase assays in a yeast-two-hybrid (Y2H) system and by in silico molecular modeling
After normalizing of the cMyBP-C protein (Figure 1—band three) to the bands of myomesin, α-actinin 2 and troponin T (Figure 1—bands two, six and 12, respectively) no differences in the protein level of cMyBP-C were seen between the mutant and the wild type cMyBP-C form, the p.A31P mutation does not appear to result in haploinsufficiency of cMyBP-C in the heart
Summary
Hypertrophic cardiomyopathy (HCM) is a primary structural disorder of the myocardium; characterized by left ventricular hypertrophy and clinical complications ranging from no symptoms to sustained palpitation, heart failure and sudden cardiac death 1. HCM has a prevalence of 0.2% 1 , the prevalence in cats is unknown, it may be as high as 9% 26.3% in some predisposed breeds including the Maine Coon (MC) breed 2,3. Feline HCM (fHCM) is the most commonly diagnosed cardiac disease in cats and has been described as an excellent spontaneous animal model for human HCM, as it mimics the clinical characteristics of human disease e.g. risk of heart failure, cardiac arrhythmia and sudden death 4-6. Within the MC breed, fHCM is frequently associated with a p.A31P substitution in the sarcomeric protein cardiac myosin binding protein-c (cMyBP-C), encoded by the feline MYBPC3 gene 6,7.
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