Congenital heart defects (CHDs) are the leading non-infectious cause of death in the first year of life; however, the etiology of most lesions is unknown. Hairy-related transcription factors (Hrt1, Hrt2 and Hrt3) are transcriptional repressors that are expressed in the somites, cardiac outflow tract, pulmonary arteries, and have mutually exclusive expression domains in the atria and ventricles. We found that Hrt2 forms a complex with Gata4, a transcription factor necessary for normal human cardiac development, that results in repression of Gata4 transactivation. Hrt2 repression of Gata4 was disrupted by the kinase Akt1. We have also identified mutations in the coding regions of Hrt2 in patients with congenital heart disease that suggest a novel Hrt domain necessary for repression. We hypothesize that (1) Hrt2's negative regulation of Gata4-dependent transactivation is sensitive to a growth signal, and (2) that mutations in Hrt2 found in patients with congenital heart malformations reveal a novel and critical domain for Hrt function during cardiogenesis.
The specific aims to be addressed in this proposal include:
Specific Aim 1 : To elucidate the biologic significance of the Hrt2-Gata4 complex and the mechanism(s) by which Hrt2-mediated repression of GATA-dependent cardiac gene expression is sensitive to Akt1. We will study the functional consequences of Hrt2 on chromatin acetylation of endogenous GATA-dependent cardiac genes and examine the role of the orange domain in mediating Akt1-responsive protein-protein interactions.
Specific Aim 2 : To determine the mechanisms by which clustered human HRT2 mutations found in CHDs affect Hrt2 function. We will conduct detailed in vitro assays to identify co-factors dependent on this novel domain, and we will generate mice harboring these mutations to study their functional consequences in vivo.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Clinical Investigator Award (CIA) (K08)
Project #
5K08HL079260-03
Application #
7234116
Study Section
Special Emphasis Panel (ZHL1-CSR-M (O1))
Program Officer
Commarato, Michael
Project Start
2005-09-05
Project End
2010-05-31
Budget Start
2007-06-01
Budget End
2008-05-31
Support Year
3
Fiscal Year
2007
Total Cost
$104,360
Indirect Cost
Name
University of California San Francisco
Department
Pediatrics
Type
Schools of Medicine
DUNS #
094878337
City
San Francisco
State
CA
Country
United States
Zip Code
94143
Zhu, Jun-Yi; Heidersbach, Amy; Kathiriya, Irfan S et al. (2017) The E3 ubiquitin ligase Nedd4/Nedd4L is directly regulated by microRNA 1. Development 144:866-875
King, Isabelle N; Qian, Li; Liang, Jianping et al. (2011) A genome-wide screen reveals a role for microRNA-1 in modulating cardiac cell polarity. Dev Cell 20:497-510
Kwon, Chulan; Cheng, Paul; King, Isabelle N et al. (2011) Notch post-translationally regulates ?-catenin protein in stem and progenitor cells. Nat Cell Biol 13:1244-51
Ransom, Joshua F; King, Isabelle N; Garg, Vidu et al. (2008) A rare human sequence variant reveals myocardin autoinhibition. J Biol Chem 283:35845-52
Jia, Haibo; King, Isabelle N; Chopra, Sameer S et al. (2007) Vertebrate heart growth is regulated by functional antagonism between Gridlock and Gata5. Proc Natl Acad Sci U S A 104:14008-13