Fig. 1. The anteroposterior position of the five subsets of midline cells at stage 11. Midline precursors were labelled with the fluorescent dyes DiD or DiI (red). The position of the two daughter cells is shown in embryos expressing tau-GFP (green) in the Engrailed domain. (A,B,D,F,H,I,K) Midline siblings at stage 11; (C,E,G,J,L) midline lineages at stage 17. Midline subsets are indicated on the right. (A,B) At stage 11, midline glia are located either in the middle of the segment (A) or anterior to the Engrailed domain (B). (H,I) At stage 11, ventral unpaired median neurons are positioned within the Engrailed domain (H), or posterior to it (I). The three other subsets of midline cells show a reproducible anteroposterior position. In panel A and K only one of the two midline siblings is in focus. Note that the absence of DiI from the nucleus enables cells to be counted. Ventral views, anterior to the left.