A neural plate fate map at stage HH4 in the chick: methodology and preliminary data

This paper centers on the design of a perfected methodology for establishing a fate map of the chick neural plate at stages 3d/4, projected upon the closing neural tube (stages 9-11). The principal aim was to saturate the area of interest with overlapping small isochronic and homotopic grafts (100-300 cells), in order to later derive firmer conclusions from the detailed comparisons thus made possible. We used an ocular grid centered on Hensen's node for the localization of the grafts. Chick embryos in New culture were used as donors and hosts, to evade potential differences in intercalation or proliferation behavior between quail and chick cells. Donor tissue was labelled with the non-diffusing fluorescein derivative carboxyfluorescein diacetate succinimidyl ester, later visualized by fluorescence microscopy at various timepoints during survival and by a sensitive whole-mount immunocytochemical protocol after fixation. We present only preliminary data of the ongoing mapping, illustrating well-delimited patches of graft-derived cells which can be identified across the neural/non-neural epiblast continuum, or across the dorsoventral dimension of the neural tube wall.