Induction of Purkinje fiber differentiation by coronary arterialization

Induction of Purkinje fiber differentiation by coronary arterialization

^*Department of Cell Biology, Cornell University Medical College, 1300 York Avenue, New York, NY 10021; ^‡Department of Cell Biology and Anatomy, Medical University of South Carolina, 171 Ashley Avenue, Charleston, SC 29425-2204; and ^§Institute of Molecular Medicine and Genetics, Medical College of Georgia, 1120 15th Street, Augusta, GA 30912-2640

Communicated by Setsuro Ebashi, National Institute for Physiological Sciences, Okazaki, Japan (received for review June 7, 1999)

Abstract

A synchronized heart beat is controlled by pacemaking impulses conducted through Purkinje fibers. In chicks, these impulse-conducting cells are recruited during embryogenesis from myocytes in direct association with developing coronary arteries. In culture, the vascular cytokine endothelin converts embryonic myocytes to Purkinje cells, implying that selection of conduction phenotype may be mediated by an instructive cue from arteries. To investigate this hypothesis, coronary arterial development in the chicken embryo was either inhibited by neural crest ablation or activated by ectopic expression of fibroblast growth factor (FGF). Ablation of cardiac neural crest resulted in ≈70% reductions (P < 0.01) in the density of intramural coronary arteries and associated Purkinje fibers. Activation of coronary arterial branching was induced by retrovirus-mediated overexpression of FGF. At sites of FGF-induced hypervascularization, ectopic Purkinje fibers differentiated adjacent to newly induced coronary arteries. Our data indicate the necessity and sufficiency of developing arterial bed for converting a juxtaposed myocyte into a Purkinje fiber cell and provide evidence for an inductive function for arteriogenesis in heart development distinct from its role in establishing coronary blood circulation.

Footnotes

↵ † J.H. and M.J. contributed equally to this work.
↵ ¶ To whom reprint requests should be addressed. E-mail: gourdier{at}musc.edu.
↵ ‖ To whom reprint requests should be addressed. E-mail: tmikaw{at}mail.med.cornell.edu.
Abbreviations:

NC,

neural crest;

FGF,

fibroblast growth factor;

En,

embryonic day n;

β-gal,

β-galactosidase;

anti-SMA,

anti-smooth muscle actin;

Cx42,

connexin 42