Insights and Challenges of Multi-Scale Modeling of Sarcomere Mechanics in cTn and Tm DCM Mutants—Genotype to Cellular Phenotype

Dewan, Sukriti; McCabe, Kimberly J.; Regnier, Michael; McCulloch, Andrew D.

doi:10.3389/fphys.2017.00151

Cited by 9 publications

(6 citation statements)

References 130 publications

(254 reference statements)

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“…interactions between the force-generating molecular motor myosin and the thin filament. TNNT2 is one of the most frequently mutated genes in DCM (28,29). There have been several excellent model systems developed to better understand aspects of the disease caused by this mutation (30)(31)(32)(33)(34); however, the connection between the molecular mutation and the cellular phenotype seen in humans remains unclear.…”

Section: Significancementioning

confidence: 99%

Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy

Clippinger

Cloonan

Greenberg

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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Familial dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death and a major indicator for heart transplant. The disease is frequently caused by mutations of sarcomeric proteins; however, it is not well understood how these molecular mutations lead to alterations in cellular organization and contractility. To address this critical gap in our knowledge, we studied the molecular and cellular consequences of a DCM mutation in troponin-T, ΔK210. We determined the molecular mechanism of ΔK210 and used computational modeling to predict that the mutation should reduce the force per sarcomere. In mutant cardiomyocytes, we found that ΔK210 not only reduces contractility but also causes cellular hypertrophy and impairs cardiomyocytes’ ability to adapt to changes in substrate stiffness (e.g., heart tissue fibrosis that occurs with aging and disease). These results help link the molecular and cellular phenotypes and implicate alterations in mechanosensing as an important factor in the development of DCM.

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Section: Significancementioning

confidence: 99%

Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy

Clippinger

Cloonan

Greenberg

et al. 2019

Proc. Natl. Acad. Sci. U.S.A.

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“…Troponin-T is a subunit of the troponin complex, which, together with tropomyosin, regulates the calcium-dependent interactions between the force-generating molecular motor myosin and the thin filament. TNNT2 is one of the most frequently mutated genes in DCM (28, 29). There have been several excellent model systems developed to better understand aspects of the disease caused by this mutation (30–34).…”

Section: Introductionmentioning

confidence: 99%

Disrupted Mechanobiology Links the Molecular and Cellular Phenotypes in Familial Dilated Cardiomyopathy

Clippinger¹,

Cloonan²,

Greenberg³

et al. 2019

Preprint

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27Familial dilated cardiomyopathy (DCM) is a leading cause of sudden cardiac death and a 28 major indicator for heart transplant. The disease is frequently caused by mutations of 29 sarcomeric proteins; however, it is not well understood how these molecular mutations 30 lead to alterations in cellular organization and contractility. To address this critical gap in 31 our knowledge, we studied the molecular and cellular consequences of a DCM mutation 32 in troponin-T, DK210. We determined the molecular mechanism of DK210 and used 33 computational modeling to predict that the mutation should reduce the force per 34 sarcomere. In mutant cardiomyocytes, we found that DK210 not only reduces contractility, 35 but also causes cellular hypertrophy and impairs cardiomyocytes' ability to adapt to 36 changes in substrate stiffness (e.g., heart tissue fibrosis that occurs with aging and 37 disease). These results link the molecular and cellular phenotypes and implicate 38 alterations in mechanosensing as an important factor in the development of DCM. 39Results 100 DK210 decreases calcium sensitivity in an in vitro motility assay 101We set out to decipher the molecular mechanism of the DK210 mutation in vitro. 102The molecular effects of cardiomyopathy mutations depend on the myosin isoform (7-9, 103 35-37) and therefore, we used porcine cardiac ventricular myosin (38). Porcine ventricular 104 cardiac myosin (MYH7) is 97% identical to human, while murine cardiac myosin (MYH6) 105 is only 92% identical. Porcine cardiac myosin has very similar biophysical properties to 106 human cardiac myosin, including the kinetics of the ATPase cycle, step size, and 107 sensitivity to load (38-41), making it an ideal myosin for biophysical studies. 108Given the role of troponin-T in thin filament regulation, we first determined whether 109 the DK210 mutation affects calcium-based regulation of myosin binding to thin filaments 110 using an in vitro motility assay (42). Reconstituted thin filaments, consisting of porcine 111 cardiac actin and recombinantly expressed human troponin and tropomyosin, were added 112 to a flow cell coated with porcine cardiac myosin in the presence of ATP. The speed of 113 filament translocation was measured as a function of added calcium. As has been 114 reported previously, the speed of regulated thin filament translocation increased 115 sigmoidally with increasing Ca 2+ concentration (43), ( Figure 1B). Data were fit with the Hill 116 equation to obtain the pCa50 (i.e., the concentration of calcium necessary for half-117 maximal activation). Consistent with previous studies using mouse cardiac, rabbit cardiac, 118 and rabbit skeletal muscle fibers (31, 33, 44), DK210 shows a right-shifted curve (pCa50 119 = 5.7 ± 0.1) compared to the WT (pCa50 = 6.1 ± 0.1; p < 0.0001), meaning more calcium 120 is needed for the same level of activation. This suggests that the mutant could show 121 impaired force production during a calcium transient. 122 7 123 Molecular mechanism of DK210-induced changes in thin filament regulat...

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“…Troponin-T, encoded by TNNT2, is a subunit of the troponin complex that regulates calcium-dependent interactions between thick and thin filaments. TNNT2 is one of the most frequently mutated genes in DCM [39]. A deletion of lysine 210 (∆K210) in troponin-T causes early-onset DCM [40].…”

Section: Genetic Causes Of Dcmmentioning

confidence: 99%

Direct Sarcomere Modulators Are Promising New Treatments for Cardiomyopathies

Tsukamoto

2019

IJMS

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Mutations in sarcomere genes can cause both hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM). However, the complex genotype-phenotype relationships in pathophysiology of cardiomyopathies by gene or mutation location are not fully understood. In addition, it is still unclear how mutations within same molecule result in different clinical phenotypes such as HCM and DCM. To clarify how the initial functional insult caused by a subtle change in one protein component of the sarcomere with a given mutation is critical for the development of proper effective treatments for cardiomyopathies. Fortunately, recent technological advances and the development of direct sarcomere modulators have provided a more detailed understanding of the molecular mechanisms that govern the effects of specific mutations. The direct inhibition of sarcomere contractility may be able to suppress the development and progression of HCM with hypercontractile mutations and improve clinical parameters in patients with HCM. On the other hand, direct activation of sarcomere contractility appears to exert unexpected beneficial effects such as reverse remodeling and lower heart rate without increasing adverse cardiovascular events in patients with systolic heart failure due to DCM. Direct sarcomere modulators that can positively influence the natural history of cardiomyopathies represent promising treatment options.

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Insights and Challenges of Multi-Scale Modeling of Sarcomere Mechanics in cTn and Tm DCM Mutants—Genotype to Cellular Phenotype

Cited by 9 publications

References 130 publications

Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy

Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy

Disrupted Mechanobiology Links the Molecular and Cellular Phenotypes in Familial Dilated Cardiomyopathy

Direct Sarcomere Modulators Are Promising New Treatments for Cardiomyopathies

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