Fig. 2

Gene expression domains subdivide the anterior neural plate. Dorsal views anterior to the top; (A,B,D) tailbud stage, (C) 1-somite stage; (A) The opl (black) expression domain is contained within the otx2 (red) domain as shown by fluorescence microscopy. The white arrowhead points to the indentation in the opl expression domain. (B) 10-15 embryos were doubly labeled with mRNA probes for otx2 and opl or mar. Gene expression borders were recorded on 10x10 grids representing the reticule in the eyepiece of the microscope. The distances from the midline and the origin (⋆) were measured in individual embryos and average values and standard deviations calculated. Such analysis produced averaged gene expression domains for otx2 (red), opl (blue) and mar (green). The averaged outline of the polster is indicated in black. Error bars indicate standard deviations. (C) opl (red) and pax6 (black) occupy overlapping domains in the anterior neural plate. The posterior portion of the pax6 expression domain overlaps the lateral arms of the mar expression domain (not shown). Cells farther anterior express pax6 less intensely and also express opl. A white arrowhead indicates the region corresponding to the mar protrusion and the indentation in the posterior border of the opl expression domain. (D) Cells of the prechordal plate and median neural plate express the cyclops gene (black). The site of the mar protrusion (white arrowhead) is not distinguished by cyclops gene expression pattern. opl expression is shown in red. Scale bar, 100 μm.