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Organogenesis begins with specification of a progenitor cell population, the size of which provides a foundation for the organ's final dimensions. Here, we present a new mechanism for regulating the number of progenitor cells by limiting their density within a competent region. We demonstrate that retinoic acid signaling restricts cardiac specification in(More)
Developing organs acquire a specific three-dimensional form that ensures their normal function. Cardiac function, for example, depends upon properly shaped chambers that emerge from a primitive heart tube. The cellular mechanisms that control chamber shape are not yet understood. Here, we demonstrate that chamber morphology develops via changes in cell(More)
The bioactive lipid sphingosine 1-phosphate (S1P) and its G protein-coupled receptors play critical roles in cardiovascular, immunological, and neural development and function. Despite its importance, many questions remain about S1P signaling, including how S1P, which is synthesized intracellularly, is released from cells. Mutations in the zebrafish gene(More)
Myocardial differentiation is initiated by the activation of terminal-differentiation gene expression within a subset of cells in the anterior lateral plate mesoderm. We have previously shown that shortly after this activation, myocardial cells undergo epithelial maturation [1], suggesting that myocardial differentiation encompasses both molecular and(More)
T-box transcription factors are critical regulators of early embryonic development. We have characterized a novel zebrafish T-box transcription factor, hrT (H15-related T box) that is a close relative of Drosophila H15 and a recently identified human gene. We show that Drosophila H15 and zebrafish hrT are both expressed early during heart formation, in(More)
A conserved endothelin 1 signaling pathway patterns the jaw and other pharyngeal skeletal elements in mice, chicks and zebrafish. In zebrafish, endothelin 1 (edn1 or sucker) is required for formation of ventral cartilages and joints in the anterior pharyngeal arches of young larvae. Here we present genetic analyses in the zebrafish of two edn1 downstream(More)
The genes that control development of embryonic melanocytes are poorly defined. Although transcription factor Ap-2alpha is expressed in neural crest (NC) cells, its role in development of embryonic melanocytes and other neural crest derivatives is unclear because mouse Ap-2alpha mutants die before melanogenesis. We show that zebrafish embryos injected with(More)
Development of a functional organ requires the establishment of its proper size as well as the establishment of the relative proportions of its individual components. In the zebrafish heart, organ size and proportion depend heavily on the number of cells in each of its two major chambers, the ventricle and the atrium. Heart size and chamber proportionality(More)
A quantitative understanding of tissue morphogenesis requires description of the movements of individual cells in space and over time. In transparent embryos, such as C. elegans, fluorescently labeled nuclei can be imaged in three-dimensional time-lapse (4D) movies and automatically tracked through early cleavage divisions up to ~350 nuclei. A similar(More)