Congenital cardiac defects affect nearly 1% of all live births and are the most common cause of infant mortality in the United States. Among the most severe forms of congenital heart defects are those involved in outflow tract and interventricular septation, whereas valve anomalies are the most common form of congenital heart defect. The long-term goal of the proposed studies is to define the molecular mechanisms and pathways that control cardiovascular development and underscore these congenital cardiac anomalies. Specifically, this application is focused on the identification of transcriptional pathways and mechanisms that function during the development of the second heart field (SHF) and its derivatives in the OFT and RV. The LIM-homeodomain transcription factor Isl1 and the MADS domain transcription factor MEF2C are essential regulators of SHF development. Recent work has established that the Mef2c gene is a direct transcriptional target of Isl1 in the SHF, forming the basis of a transcriptional pathway in the AHF. However, the upstream transcriptional regulators of the Isl1 gene in the SHF remain undefined in spite of the early, essential role for Isl1 in that lineage. Similarly, the downstream targets of MEF2C are not known, even though Mef2c is required for heart development, and its function is required specifically in the SHF for proper OFT alignment and endocardial cushion remodeling. This proposal will therefore test the hypothesis that MEF2C is required in the SHF to control cell number or migration of SHF-derived cells into the OFT endocardial cushions and that MEF2C is a direct transcriptional activator of Nfatc1 in the endocardial cushions. This is significant since the transcription factor NFATc1 is required for endocardial cushion remodeling and heart valve maturation. This proposal will also test the hypothesis that the expression of the Isl1 gene in the SHF is regulated via a novel modular enhancer that integrates upstream signals to direct expression in cardiovascular progenitors in the anterior lateral mesoderm.
Two specific aims are proposed.
Specific aim one will determine the requirement of MEF2C in OFT alignment and endocardial cushion development by examining the requirement of Mef2c for migration of SHF-derived cells into the heart and for cell proliferation and survival using a conditional knockout approach in mice.
Specific Aim 1 will also determine if Nfatc1 is a direct transcriptional target of MEF2C in the outflow tract endocardial cushions via a conserved, consensus MEF2 site present in the Nfatc1 endocardial- specific enhancer using a transgenic mouse approach.
Specific Aim 2 will identify regulators of Isl1 transcription in the SHF by defining upstream regulators of a novel SHF-specific Isl1 transcriptional enhancer. The goal is to place Isl1 into a transcriptional and signaling pathway, which will provide essential information about the early events controlling heart development and Isl1+ progenitor self-renewal and differentiation.

Public Health Relevance

Heart defects are the most common class of birth defect in the United States, affecting nearly 1% of all newborns. Among the most serious of these defects are the cyanotic lesions, which affect septation of the ventricles and outflow tracts and allow oxygenated and deoxygenated blood to mix. The proposed studies will contribute to the understanding of the molecular pathways and the biochemical and genetic mechanisms controlling heart development. Defining these pathways is essential to determine how to reactivate the genetic programs controlling the development of heart tissue for the purpose of regeneration and repair, tissue engineering, directed differentiation of induced pluripotent cells, and diagnosis and intervention in cardiovascular birth defects.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-CVRS-K (02))
Program Officer
Schramm, Charlene A
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of California San Francisco
Internal Medicine/Medicine
Schools of Medicine
San Francisco
United States
Zip Code
Hua, Lisa L; Vedantham, Vasanth; Barnes, Ralston M et al. (2014) Specification of the mouse cardiac conduction system in the absence of Endothelin signaling. Dev Biol 393:245-54
Ehlers, Melissa L; Celona, Barbara; Black, Brian L (2014) NFATc1 controls skeletal muscle fiber type and is a negative regulator of MyoD activity. Cell Rep 8:1639-48
Robinson, Ashley S; Materna, Stefan C; Barnes, Ralston M et al. (2014) An arterial-specific enhancer of the human endothelin converting enzyme 1 (ECE1) gene is synergistically activated by Sox17, FoxC2, and Etv2. Dev Biol 395:379-89
Parker, Stephen C J; Stitzel, Michael L; Taylor, D Leland et al. (2013) Chromatin stretch enhancer states drive cell-specific gene regulation and harbor human disease risk variants. Proc Natl Acad Sci U S A 110:17921-6
May, Dalit; Blow, Matthew J; Kaplan, Tommy et al. (2012) Large-scale discovery of enhancers from human heart tissue. Nat Genet 44:89-93
Schachterle, William; Rojas, Anabel; Xu, Shan-Mei et al. (2012) ETS-dependent regulation of a distal Gata4 cardiac enhancer. Dev Biol 361:439-49
Lammerts van Bueren, Kelly; Black, Brian L (2012) Regulation of endothelial and hematopoietic development by the ETS transcription factor Etv2. Curr Opin Hematol 19:199-205
Palencia-Desai, Sharina; Kohli, Vikram; Kang, Jione et al. (2011) Vascular endothelial and endocardial progenitors differentiate as cardiomyocytes in the absence of Etsrp/Etv2 function. Development 138:4721-32
Tsuchihashi, Takatoshi; Maeda, Jun; Shin, Chong H et al. (2011) Hand2 function in second heart field progenitors is essential for cardiogenesis. Dev Biol 351:62-9
Rojas, Anabel; Schachterle, William; Xu, Shan-Mei et al. (2010) Direct transcriptional regulation of Gata4 during early endoderm specification is controlled by FoxA2 binding to an intronic enhancer. Dev Biol 346:346-55

Showing the most recent 10 out of 27 publications