Investigating Signaling Mechanisms that Contribute to Cardiomyopathies and Heart Failure
Cardiomyopathies are diseases of the heart that lead to cardiac hypertrophy, impaired left ventricular systolic function, heart failure, and death. Many etiologies cause cardiomyopathies including myocardial infarction that results in scar formation, genetic predisposition related to inherited genetic variants that confer increased risk of developing disease1, and environmental exposures including chemotherapeutic agents. Despite advances in pharmacologic and device-based treatment, ~50% of individuals who have heart failure do not survive beyond five years, highlighting the need for additional therapies. To address this important clinical need, my laboratory’s research focuses on the following areas:
(1) Signaling pathways that cause or modify cardiomyopathies identified in genetic screens of Drosophila. Genetic screens of Drosophila mutants harboring molecularly-defined genomic deficiencies were performed using Optical Coherence Tomography (OCT) to measure cardiac chamber dimensions and function.2-5 These experiments identified mutants that had dilated or hypertrophic cardiomyopathies related to epidermal growth factor receptor and associated downstream signaling molecules. Using a model of Raf-mediated cardiac hypertrophy – a condition associated with types of Noonan syndrome, we identified that Hippo kinase and the transcriptional co-activator, yorkie (yki), produce cardiac hypertrophy, similar to the activation of the EGFR/Ras/Raf pathway.6,7 Additionally, Tgi, the Drosophila orthologue of Vestigial-like 4 (Vgll4), prevented Raf-mediated cardiac hypertrophy. The mammalian orthologues of the Hippo pathway, namely mammalian Ste20-like kinase (MST1/2) and Yes-associated protein 1 (YAP1), influence organ size and can lead to increased myocyte proliferation (hyperplasia) in the embryonic heart. However, the contributions of Raf-mediated signals participate in YAP1/TEAD1 and Vgll4 signaling in mammalian cardiac hypertrophy are unknown. To translate our findings to mammals, including humans, we are investigating these pathways transgenic mice that express a Raf mutation (RafL613V/+ knockin) identified in patients who have Noonan syndrome and cardiac hypertrophy in conjunction with AAV9 that harbor components for the Hippo/YAP pathway.
(2) Mechanisms to induce transient cardiomyocyte proliferation to enhance myocardial regeneration after injury. Postnatally, mouse cardiomyocytes lose the ability to proliferate and transition to bi-nucleation and/or increased polyploidy through a process of endoreplication (also known as endoreduplication). The signals that dictate the fate of cardiomyocytes to proliferate or endoreplicate are unknown. In many cell types, the evolutionarily conserved MuvB/DREAM complex regulates cell proliferation. Lin52 regulates MuvB/DREAM complex activity through the phosphorylation state of a conserved serine (S28), a substrate of dual-specificity tyrosine phosphorylation-regulated kinase 1a (DYRK1A). The phosphorylation of Lin52 S28 is required for the MuvB core repress genes that are expressed in the G1/S phase. The dephosphorylation of Lin52 at S28 allows the MuvB core to interact with transcription factors, including B-Myb, to drive entry into the cell cycle. Thus, the dephosphorylation of S28 of Lin52 can (1) de-repress the expression of gene in G1/S and (2) promote the expression of genes in G2/M – leading to transition of cells from quiescence to proliferation. Importantly, the contributions of Lin52, DYRK1A-mediated phosphorylation of Lin52 S28, and the MuvB/DREAM complex in cardiac growth are unknown and represent potential targets to induce myocardial regeneration after injury. Experiments employing chronic LAD ligation or ischemia-reperfusion MI in αMHC-Cre;CAG-STOP-Fucci2aR (a fluorescence ubiquitin-based cell cycle indicator (Fucci)) mice while genetically and pharmacologically manipulating the MuvB/DREAM complex are being performed to evaluate changes in LV function, scar characteristics, and in vivo cell cycling of cardiomyocytes. These exciting experiments, in conjunction with other transgenic lineage tracing mouse models, have the potential to identify new therapeutic targets to promoter myocardial regeneration after injury.
For the most current list of Dr. Wolf's publications, please click here.
Jeff Saucerman, Department of Biomedical Engineering, UVA
Fred Epstein, Department of Biomedical Engineering, UVA
Thurl Harris, Department of Pharmacology, UVA
Elizabeth McNally, Department of Medicine/Cardiology, Feinberg School of Medicine-Northwestern University
Howard Rockman Lab, Duke University Medical Center
Don Fox Lab, Department of Pharmacology and Cancer Biology: http://www.foxlabduke.com/
1. Wolf, M.J., Noeth, D., Rammohan, C., and Shah, S.H. (2016) Complexities of Genetic Testing in Familial Dilated Cardiomyopathy. Circ. Cardiovasc Genet. 9:95-99. PMCID: PMC5131558.
2. Wolf, M.J., Amerin, H., Izatt, J.A., Choma, M.A., Reedy, M.C., and Rockman, H.A.* (2006) Drosophila as a Model for the Identification of Genes Causing Adult Human Heart Disease. Proc. Natl. Acad. Sci. U.S.A. 103: 1394-9. PMCID: PMC1360529.
3. Yu, L., Lee, T. Lin, N., and Wolf, M.J. (2010) Affecting Rhomboid-3 Function Cause a Dilated Heart in Adult Drosophila. PLoS Genetics 6(5):e1000969. PMCID: PMC2877733.
4. Wolf M.J., Rockman HA. (2011) Drosophila, Genetic Screens, and Cardiac Function. Circ. Res. Sep 16;109(7):794-806. PMCID: PMC3678974.
5. Wolf, M.J. (2012) Modeling Cardiomyopathies in Drosophila. Trends in Cardiovascular Medicine 22(3):55-61. PMCID: PMC3728662.
6. Yu, L., Daniels, J., Glaser, A.E., and Wolf, M.J. (2013) Raf-mediated cardiac hypertrophy in adult Drosophila. Dis Model Mech. 6(4):964-76. PMCID: PMC3701216.
7. Yu, L., Daniels, J.P., Wu, H., and Wolf, M.J. (2015) Cardiac hypertrophy induced by active Raf depends on Yorkie-mediated transcription. Science Signal. 3;8(362):ra13. PMCID: PMC5131564.