Adult mammalian cardiomyocytes are terminally differentiated cells with very limited capabilities to divide, thus, injury to the heart typically causes permanent loss of muscle mass leading to ventricular dysfunction and heart failure. Therefore, a better understanding of how the myocyte cell cycle is controlled should enhance our ability to provide effective therapy for several heretofore-intractable cardiac diseases. Several studies indicate that the cardiomyocyte growth state in the developing heart correlates with regulated shifts in the expression of extracellular matrix and integrin receptors and the ability of these matrices to support myocyte growth in vitro. These data underscore the importance of integrin signaling in regulating both cardiac morphogenesis and the progression of cardiac disease, but how these processes are fine-tuned during the different phases of cardiac growth is unknown. It is clear from our studies completed within the past funding cycle that FAK functions to mediate cardiomyocyte proliferation during development, cardiomyocyte hypertrophy following pressure overload, and cardiomyocyte survival following an ischemic insult. We have also made the interesting discovery that FAK activity is dynamically regulated in the post-natal heart by expression of its endogenous inhibitor, FRNK. Our results demonstrate that FRNK is transiently expressed in the heart with peak levels occurring 5-7 days post-natal (just prior to cell cycle withdrawal) and that cardiac-selective expression of FRNK starting at E10.5 leads to a severe ventricular non-compaction defect and embryonic lethality associated with impaired cardiomyocyte proliferation and impaired coronary plexus formation. Importantly, ventricular cardiomyocyte-specific expression of a super-activatable FAK variant (bMHC-SuperFAK) was able to rescue this phenotype, indicating a cell autonomous role for FAK in regulating these critical functions. Thus, our working hypothesis is that dynamic regulation of FAK signaling is important for the control of cardiomyocyte cell cycle withdrawal during development and perhaps to cell-cycle re-entry in response to cardiac stress. We have generated many genetically modified gain-of-function/loss-of-function mouse models that will allow us to test this hypothesis and to identify the downstream signals that are important for the effects of FAK/FRNK on cardiomyocyte proliferation. In addition, since FAK signaling is regulated by, or required for, the effects of many of the environmental cues that regulate cardiac development and function, we strongly feel that the results from the proposed studies will have broad implications on our understanding of congenital cardiac disease and on the progression heart failure. We will utilize genetically modified mice, established cardiac cell culture models, and samples from a human heart repository to identify FAK-dependent mechanisms that regulate the pathogenesis of congenital and acquired heart disease.

Public Health Relevance

We strive to understand the molecular mechanisms that regulate the ability of heart cells to divide, since strategies to manipulate this function could be efficacious in the context of several congenital heart diseases and heart failure. While heart cells can undergo division during development, alterations of the timing or locale of division can lead to congenital heart disease. Furthermore, these cells lose the ability to divide shortly after birth, thus any damage to the heart can cause irreversible loss of function.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
2R01HL081844-05A1
Application #
7785173
Study Section
Cardiac Contractility, Hypertrophy, and Failure Study Section (CCHF)
Program Officer
Liang, Isabella Y
Project Start
2005-06-15
Project End
2013-12-31
Budget Start
2010-01-05
Budget End
2010-12-31
Support Year
5
Fiscal Year
2010
Total Cost
$331,691
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Pathology
Type
Schools of Medicine
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599
Giudice, Jimena; Taylor, Joan M (2017) Muscle as a paracrine and endocrine organ. Curr Opin Pharmacol 34:49-55
Cheng, Zhaokang; Zhu, Qiang; Dee, Rachel et al. (2017) Focal Adhesion Kinase-mediated Phosphorylation of Beclin1 Protein Suppresses Cardiomyocyte Autophagy and Initiates Hypertrophic Growth. J Biol Chem 292:2065-2079
Lenhart, Kaitlin C; Becherer, Abby L; Li, Jianbin et al. (2014) GRAF1 promotes ferlin-dependent myoblast fusion. Dev Biol 393:298-311
Cheng, Zhaokang; DiMichele, Laura A; Rojas, Mauricio et al. (2014) Focal adhesion kinase antagonizes doxorubicin cardiotoxicity via p21(Cip1.). J Mol Cell Cardiol 67:1-11
Bai, Xue; Lenhart, Kaitlin C; Bird, Kim E et al. (2013) The smooth muscle-selective RhoGAP GRAF3 is a critical regulator of vascular tone and hypertension. Nat Commun 4:2910
O'Neill 4th, Thomas J; Mack, Christopher P; Taylor, Joan M (2012) Germline deletion of FAK-related non-kinase delays post-natal cardiomyocyte mitotic arrest. J Mol Cell Cardiol 53:156-64
Zajac, Britni; Hakim, Zeenat S; Cameron, Morgan V et al. (2012) Quantification of myocyte chemotaxis: a role for FAK in regulating directional motility. Methods Mol Biol 843:111-23
Tandon, Panna; Conlon, Frank L; Taylor, Joan M (2012) ROCKs cause SHP-wrecks and broken hearts. Small GTPases 3:209-12
Medlin, Matt D; Taylor, Joan M; Mack, Christopher P (2012) Quantifying sphingosine-1-phosphate-dependent activation of the RhoGTPases. Methods Mol Biol 874:89-97
Cheng, Zhaokang; DiMichele, Laura A; Hakim, Zeenat S et al. (2012) Targeted focal adhesion kinase activation in cardiomyocytes protects the heart from ischemia/reperfusion injury. Arterioscler Thromb Vasc Biol 32:924-33

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