ABSTRACT A quantitative description of the molecular networks that sustain morphogenesis is one of the challenges of developmental biology. Specifically, a molecular understanding of the segmentation of the antero-posterior axis in vertebrates has yet to be achieved. This process known as somitogenesis is believed to result from the interactions between a genetic oscillator and a posterior-moving determination wavefront. Here we quantitatively study and perturb the network in zebrafish that sustains this wavefront and compare our observations to a model whereby the wavefront is due to a switch between stable states resulting from reciprocal negative feedbacks of Retinoic Acid (RA) on the activation of ERK and of ERK on RA synthesis. This model quantitatively accounts for the near linear shortening of the post-somitic mesoderm (PSM) in response to the observed exponential decrease during somitogenesis of the mRNA concentration of a morphogen (Fgf8). It also accounts for the observed dynamics of the PSM when the molecular components of the network are perturbed. The generality of our model and its robustness allows for its test in other model organisms.

Quantitative study of the somitogenetic wavefront in zebrafish