A fate map of the epiblast of the early chick embryo.

We have used carbocyanine dyes (DiI and DiO) to generate fate maps for the epiblast layer of the chick embryo between stage X and the early primitive streak stage (stages 2-3). The overall distribution of presumptive cell types in these maps is similar to that described for other laboratory species (zebrafish, frog, mouse). Our maps also reveal certain patterns of movement for these presumptive areas. Most areas converge towards the midline and then move anteriorly along it. Interestingly, however, some presumptive tissue types do not take part in these predominant movements, but behave in a different way, even if enclosed within an area that does undergo medial convergence and anterior movement. The apparently independent behaviour of certain cell populations suggests that at least some presumptive cell types within the epiblast are already specified at preprimitive streak stages.