Current Research

The Greenberg lab is interested in contractile systems, with a focus on cardiovascular disease. We have several projects that we are currently pursuing:

​Familial cardiomyopathies:

Familial cardiomyopathies are found in up to 1 in  500 people, and these conditions are the leading cause of sudden cardiac death in young people. In patients with pediatric onset disease, these conditions are especially devastating.  Patients with these diseases show alterations in the structural and mechanical properties of the myocardium. Human genetic studies have shown that the most common cause of familial cardiomyopathies is mutation of the proteins involved in generating and regulating force and power output in the heart; however, it is not well understood how changes at the molecular scale lead to alterations in cardiac contractility at the cellular and tissue levels. We have developed molecular, cellular, and tissue-scale models of these diseases, and we are using computational modeling to link these various scales.  We are applying our newly gained knowledge to design new precision medicine therapies for these diseases.

Representative publications:

Clippinger SR, Cloonan PE, Greenberg L, Ernst M, Stump WT, Greenberg MJ. Disrupted mechanobiology links the molecular and cellular phenotypes in familial dilated cardiomyopathy. Proc Natl Acad Sci U S A. 2019 Sep 3;116(36):17831-17840. doi: 10.1073/pnas.1910962116. Epub 2019 Aug 19. PMID: 31427533; PMCID: PMC6731759.

Clippinger SR, Cloonan PE, Wang W, Greenberg L, Stump WT, Angsutararux P, Nerbonne JM, Greenberg MJ. Mechanical dysfunction of the sarcomere induced by a pathogenic mutation in troponin T drives cellular adaptation. J Gen Physiol. 2021 May 3;153(5):e202012787. doi: 10.1085/jgp.202012787. PMID: 33856419; PMCID: PMC8054178.

Barrick SK, Greenberg L, Greenberg MJ. A troponin T variant linked with pediatric dilated cardiomyopathy reduces the coupling of thin filament activation to myosin and calcium binding. Mol Biol Cell. 2021 Aug 19;32(18):1677-1689. doi: 10.1091/mbc.E21-02-0082. Epub 2021 Jun 23. PMID: 34161147; PMCID: PMC8684737.

Precision medicine for heart failure:

There are multiple pathways that can lead to heart failure, including iron overload, viral infection, and diabetes.  We are trying to understand the mechanisms driving these diseases, and then leverage our mechanistic insights to develop precision medicine therapeutics.  We are part of the Cardiovascular Precision Medicine Research Initiative (CPRi) focused on translating basic science knowledge into precision medicine therapeutics for cardiovascular disease. For more information on this initiative, click here.

Representative publications:

Ezekian JE, Clippinger SR, Garcia JM, Yang Q, Denfield S, Jeewa A, Dreyer WJ, Zou W, Fan Y, Allen HD, Kim JJ, Greenberg MJ, Landstrom AP. Variant R94C in TNNT2-Encoded Troponin T Predisposes to Pediatric Restrictive Cardiomyopathy and Sudden Death Through Impaired Thin Filament Relaxation Resulting in Myocardial Diastolic Dysfunction. J Am Heart Assoc. 2020 Mar 3;9(5):e015111. doi: 10.1161/JAHA.119.015111. Epub 2020 Feb 26. PMID: 32098556; PMCID: PMC7335540.

Papadaki M, Kampaengsri T, Barrick SK, Campbell SG, von Lewinski D, Rainer PP, Harris SP, Greenberg MJ, Kirk JA. Myofilament glycation in diabetes reduces contractility by inhibiting tropomyosin movement, is rescued by cMyBPC domains. J Mol Cell Cardiol. 2022 Jan;162:1-9. doi: 10.1016/j.yjmcc.2021.08.012. Epub 2021 Sep 3. PMID: 34487755; PMCID: PMC8766917.

Woody MS, Greenberg MJ, Barua B, Winkelmann DA, Goldman YE, Ostap EM. Positive cardiac inotrope omecamtiv mecarbil activates muscle despite suppressing the myosin working stroke. Nat Commun. 2018 Sep 21;9(1):3838. doi: 10.1038/s41467-018-06193-2. PMID: 30242219; PMCID: PMC6155018.

Technology development:

Our studies require tools for studying contractility across multiple levels of organization.  We are actively developing tools that enable us to model heart contractility at the molecular, cellular, and tissue levels.  For our molecular studies, we have developed an optical trapping system with force feedback to study the contractility of single motor proteins.  For our cellular studies, we use CRISPR/Cas9 to introduce disease-causing mutations into human stem cells, and then differentiate these stem cells into cardiomyocytes.  We use engineering techniques to study the contractility of single cells and to mimic the electrical and mechanical environments of the heart.  For our tissue level studies, we are generating human engineered heart tissues in microelectromechanical devices. Importantly, these tools will give us an unprecedented understanding of how the heart generates force and power in both health and disease.

Representative publications:

Blackwell T, Stump WT, Clippinger SR, Greenberg MJ. Computational Tool for Ensemble Averaging of Single-Molecule Data. Biophys J. 2021 Jan 5;120(1):10-20. doi: 10.1016/j.bpj.2020.10.047. Epub 2020 Nov 26. PMID: 33248132; PMCID: PMC7820714.

Barrick SK, Clippinger SR, Greenberg L, Greenberg MJ. Computational Tool to Study Perturbations in Muscle Regulation and Its Application to Heart Disease. Biophys J. 2019 Jun 18;116(12):2246-2252. doi: 10.1016/j.bpj.2019.05.002. Epub 2019 May 7. PMID: 31126584; PMCID: PMC6588827.

Molecular motors in health and disease:

Molecular motors power force generation and movement in a wide range of physiological processes including hearing, muscle contraction, and intracellular transport.  The function of these motors is tightly regulated, and dysfunction of these motors can lead to a wide range of diseases.

Representative publications:

Porter JR, Meller A, Zimmerman MI, Greenberg MJ, Bowman GR. Conformational distributions of isolated myosin motor domains encode their mechanochemical properties. Elife. 2020 May 29;9:e55132. doi: 10.7554/eLife.55132. PMID: 32479265; PMCID: PMC7259954.

McAdow J, Yang S, Ou T, Huang G, Dobbs MB, Gurnett CA, Greenberg MJ, Johnson AN. A pathogenic mechanism associated with myopathies and structural birth defects involves TPM2-directed myogenesis. JCI Insight. 2022 Jun 22;7(12):e152466. doi: 10.1172/jci.insight.152466. PMID: 35579956.