Fig. 2.

Different patterns of Nrarp expression in the chick and mouse presomitic mesoderm (PSM). A–K: Nrarp expression analyzed by in situ hybridization in the PSM of (A–F) six Hamburger and Hamilton (HH) stage 11–12 chick embryos and (G–K) five E9.5–E10.5 mouse embryos, which display different patterns of expression. The position of the last somitic border is indicated with a black arrow (or two black arrows when the new border is forming). Rostral is to the top. L: Graphical analysis of cNrarp expression (see the Experimental Procedures section). Each bar along the x-axis represents one embryo. The y-axis represents the extent of gene expression domains along the anteroposterior axis of the PSM, anterior to the top. Darker stripes represent stronger expression domains as compared to lighter bars. The gray rectangle highlights the group of embryos undergoing formation of a new somitic border.