From Mice to Men: How Animal Models Help Us to Understand Hypertrophic Cardiomyopathy

April 11, 2023

Hypertrophic cardiomyopathy (HCM) is a heart muscle disorder that affects around one in every 500 people[1]. It causes the walls of the left ventricle, the heart's primary pumping chamber, to thicken and stiffen. This lowers the amount of blood that can be pumped out to the rest of the body with each heartbeat. Pathogenic mutations in the gene encoding myosin-related proteins are usually responsible for HCM. Some people, however, may develop HCM later in life as a result of other factors such as high blood pressure or aging[2].

Symptoms of HCM include chest pain, shortness of breath, palpitations, dizziness, and fainting. Some people may have no symptoms and go about their lives normally, while others may have serious complications such as heart failure or sudden cardiac death. HCM is, in fact, the leading cause of sudden cardiac death in those under the age of 35[1]. In clinic, it can be divided into obstructive and non-obstructive HCM based on hemodynamic features. Physical examination, electrocardiogram (ECG), echocardiography (echo), and cardiac magnetic resonance imaging (MRI) are all useful diagnostic tools for HCM.


Figure 1: Thick heart muscle reduces blood flow to the aorta[1]

Early epidemiological research has revealed that the prevalence of HCM in the general adult population ranged from 0.16% to 0.23%, with an average of 0.20%. HCM phenotypes that were previously undiagnosed or easily ignored can now be reliably detected, thanks to the advancement of cardiac imaging technologies, which predict that the true prevalence rate can reach 1 in 200 individuals (0.5%). Hypertrophic cardiomyopathy typically manifests in early adulthood or late adolescence, however, a small percentage of patients have an earlier or later onset.

MYH7 (encoding β-myosin heavy chain, the major monomer of human left ventricular myosin heavy chain dimers) and MYBPC3 (encoding cardiac myosin binding protein C) mutations are the most frequent causes of HCM, accounting for roughly 80% to 90% of all sarcomere mutations in HCM patients. Aside from MYBPC3, the majority of sarcomere mutations that cause HCM are missense mutations, whereas more than half of MYBPC3 pathogenic mutations are insertions, deletions or splicing site mutations, resulting in truncated protein expression or partial or complete loss of gene function.

Although MYH7 is one of the high-frequency pathogenic genes associated with HCM in humans, when utilizing animal models to study HCM caused by MYH7 mutations, researchers typically choose Myh6 (encoding α-myosin heavy chain) as the target rather than the direct homologous Myh7 gene. This is because MYH7 expression is low in adult rodents, including mice, and it is less involved in the formation of left ventricular myosin heavy chain dimers, whereas Myh6 is the predominant subtype in adult rodents' left ventricles[3]. Additionally, the human MYH7 protein shares more than 92% sequence identity with the mouse MYH6 protein. Thus, most human pathogenic MYH7 mutations can be modeled by mutations in Myh6 in mice, allowing for the construction of comparable animal models. Researchers have shown promising findings using mouse models with Myh6 mutations to investigate the efficacy of the small molecule inhibitor MYK-461[4] to treat HCM in humans.


GemPharmatech used gene editing technology to modify the Myh6 and Mybpc3 genes in C57BL/6JGpt mice to obtain the Myh6 R404Q point mutant mouse model (No. T051403) and the Mybpc3 knockout mouse model (No. T027708), respectively.


Figure 2: Thickened left ventricle and increased cardiac systolic function in Myh6 R404Q +/- mice.

Compared with wild-type control mice, 5-month-old Myh6 R404Q +/- mice showed significant reductions in LVID;d, LVID;s, LVESV, and LVEDV and significant increases in LVPW;d, LVPW;s, LVAW;s, EF, and FS. These findings indicate that Myh6 R404Q +/- mice exhibit left ventricular wall thickening, decreased ventricular volume, and enhanced cardiac contractile function, suggesting that they possess a phenotype similar to human hypertrophic cardiomyopathy (HCM) and can be used as a mouse model for HCM research.


Figure 3: Dilated and thickened ventricles in Mybpc3 KO -/- mice

Compared to wild-type mice and Mybpc3 KO +/- mice, 2-month-old Mybpc3 KO -/- mice had significant increases in left ventricular diameter (LVID;d, LVID;s), diastolic ventricular wall (LVPW;d, LVAW;d), and ventricular volume (LVESV, LVEDV), while cardiac contractile function parameters (EF and FS) showed significant decreases. These results indicated that Mybpc3 -/- mice exhibit a phenotype of myocardial hypertrophy and dilated cardiomyopathy, accompanied by some degree of cardiac dysfunction.


All in all, the Myh6 R404Q mice developed by GemPharmatech exhibit a phenotype of myocardial hypertrophy and enhanced cardiac contractile function, while Mybpc3 KO mice exhibit a phenotype of myocardial dilation and hypertrophy and congenital heart failure. Both of these mouse models can be used as models for hypertrophic cardiomyopathy, but due to their different phenotypes, their applications will also differ.



2. Marian AJ. Molecular Genetic Basis of Hypertrophic Cardiomyopathy. Circ Res. 2021 May 14;128(10):1533-1553.

3. Ntelios D, Meditskou S, Efthimiadis G, Pitsis A, Zegkos T, Parcharidou D, Theotokis P, Alexouda S, Karvounis H, Tzimagiorgis G. α-Myosin heavy chain (MYH6) in hypertrophic cardiomyopathy: Prominent expression in areas with vacuolar degeneration of myocardial cells. Pathol Int. 2022 May;72(5):308-310.

4. Green EM, Wakimoto H, Anderson RL, Evanchik MJ, Gorham JM, Harrison BC, Henze M, Kawas R, Oslob JD, Rodriguez HM, Song Y, Wan W, Leinwand LA, Spudich JA, McDowell RS, Seidman JG, Seidman CE. A small-molecule inhibitor of sarcomere contractility suppresses hypertrophic cardiomyopathy in mice. Science. 2016 Feb 5;351(6273):617-21.