A synchronized heart beat is controlled by pace-making signals of the cardiac conduction system (CCS). Future therapeutic approaches to regeneration or repair of this essential heart tissue after injury or congenital disease would benefit from a clear understanding of the mechanisms that regulate differentiation of the CCS. This project aims to determine for the first time the molecular signals that induce differentiation of the CCS in vivo. Our studies in the embryonic chick heart have shown that: 1) impulse- conducting Purkinje cells differentiate from myocytes during embryogenesis; 2) this conversion of contractile myocytes into conduction cells is induced by local signals derived from developing coronary arteries in vivo; 3) the vascular cytokine, endothelin (ET), induces embryonic myocytes to differentiate into Purkinje cells in vitro; 4) ET-induced Purkinje fiber differentiation is mediated by binding of ET to its G protein-coupled receptors (ETRs) ubiquitously expressed by all myocytes; and 5) Purkinje fiber differentiation is triggered only when ET is proteolyticaly activated from its precursor, big-ET, by the ET-converting enzyme (ECE). Therefore, we hypothesize that a) the ET-signal is a local, instructive cue that recruits myocytes to Purkinje cells; and b) activation of ET-signaling is spatially and temporally confined by ECE-expression in the embryonic heart. In the proposed studies, we will test these hypotheses experimentally.
Our specific aims are to: 1) identify the direct association of ECE expression with Purkinje fiber differentiation in the embryonic heart; 2) establish the inductive function of ET-signals during Purkinje fiber differentiation in vivo; and 3) determine links between the ET-signaling and CCS development in the mouse heart. Our basic strategies are to: 1) determine the timing and location of ECE expression during the CCS development at the both transcriptional and translational levels (Aim 1); 2) generate an ectopic site of activated ET-signaling within embryonic chick hearts (Aim 2); and 3) examine the CCS development in mice null for ET-related genes (Aim 3). The proposed studies will provide the foundation for understanding molecular mechanisms that induce differentiation of the CCS, and may also provide the basis for re-initiating CCS development in the adult heart in the future.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL062175-02
Application #
6184604
Study Section
Cardiovascular and Pulmonary Research A Study Section (CVA)
Program Officer
Wang, Lan-Hsiang
Project Start
1999-04-01
Project End
2003-03-31
Budget Start
2000-04-01
Budget End
2001-03-31
Support Year
2
Fiscal Year
2000
Total Cost
$291,537
Indirect Cost
Name
Weill Medical College of Cornell University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
201373169
City
New York
State
NY
Country
United States
Zip Code
10065
Pennisi, David J; Mikawa, Takashi (2009) FGFR-1 is required by epicardium-derived cells for myocardial invasion and correct coronary vascular lineage differentiation. Dev Biol 328:148-59
Pennisi, David J; Mikawa, Takashi (2005) Normal patterning of the coronary capillary plexus is dependent on the correct transmural gradient of FGF expression in the myocardium. Dev Biol 279:378-90
Ishii, Yasuo; Mikawa, Takashi (2005) Somatic transgenesis in the avian model system. Birth Defects Res C Embryo Today 75:19-27
Hall, Christopher E; Hurtado, Romulo; Hewett, Kenneth W et al. (2004) Hemodynamic-dependent patterning of endothelin converting enzyme 1 expression and differentiation of impulse-conducting Purkinje fibers in the embryonic heart. Development 131:581-92
Xaymardan, Munira; Tang, Lilong; Zagreda, Leze et al. (2004) Platelet-derived growth factor-AB promotes the generation of adult bone marrow-derived cardiac myocytes. Circ Res 94:E39-45
Pennisi, David J; Ballard, Victoria L T; Mikawa, Takashi (2003) Epicardium is required for the full rate of myocyte proliferation and levels of expression of myocyte mitogenic factors FGF2 and its receptor, FGFR-1, but not for transmural myocardial patterning in the embryonic chick heart. Dev Dyn 228:161-72
Hyer, Jeanette; Kuhlman, Julie; Afif, Evelyn et al. (2003) Optic cup morphogenesis requires pre-lens ectoderm but not lens differentiation. Dev Biol 259:351-63
Kelly, Kristine A; Wei, Yan; Mikawa, Takashi (2002) Cell death along the embryo midline regulates left-right sidedness. Dev Dyn 224:238-44
Kanzawa, Nobuyuki; Poma, Clifton P; Takebayashi-Suzuki, Kimiko et al. (2002) Competency of embryonic cardiomyocytes to undergo Purkinje fiber differentiation is regulated by endothelin receptor expression. Development 129:3185-94
Ballard, Victoria L T; Mikawa, Takashi (2002) Constitutive expression of preproendothelin in the cardiac neural crest selectively promotes expansion of the adventitia of the great vessels in vivo. Dev Biol 251:167-77

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