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Bidirectional fusion of the heart-forming fields in the developing chick embryo.

Moreno-Rodriguez RA, Krug EL, Reyes L, Villavicencio L, Mjaatvedt CH, Markwald RR

Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, South Carolina 29425, USA. morenor@musc.edu

It is generally thought that the early pre-tubular chick heart is formed by fusion of the anterior or cephalic limits of the paired cardiogenic fields. However, this study shows that the heart fields initially fuse at their midpoint to form a transitory "butterfly"-shaped, cardiogenic structure. Fusion then progresses bi-directionally along the longitudinal axis in both cranial and caudal directions. Using in vivo labeling, we demonstrate that cells along the ventral fusion line are highly motile, crossing future primitive segments. We found that mesoderm cells migrated cephalically from the unfused tips of the anterior/cephalic wings into the head mesenchyme in the region that has been called the secondary heart field. Perturbing the anterior/cranial fusion results in formation of a bi-conal heart. A theoretical role of the ventral fusion line acting as a "heart organizer" and its role in cardia bifida is discussed.

Published 14 December 2005 in Dev Dyn, 235(1): 191-202.
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