Fig. 1. Expression patterns of LSox5 in the cephalic region of chick embryos. Dorsal views of stage 7 (A), 8 (D), 9 (F) and 10 (G) embryos show the expression of LSox5 mRNA in the neural folds/neural tube, following a pattern compatible with premigratory and migratory cephalic neural crest. Transverse sections of stage7 (B,C) and stage 10 (H,I) embryos show LSox5 expression all along the dorsoventral axis of the neural tube at prosencephalic levels (B,H), and a restriction to the most dorsal region at more caudal levels (C,I). (E) A dorsal view of a stage 8 embryo showing the expression of Slug in territories competent to form neural crest, and its absence from the non-crest producing prosencephalic regions. (J-L) A transverse section of a stage 10 embryo at the hindbrain level labelled with both anti-LSox5 (green) and anti-Slug (red) antibodies. Only a subpopulation of the cells within the neural tube (nt) express both Slug and LSox5, whereas all the migratory cells express both genes. LSox5 expression increases along the cell migratory tracts, while Slug expression diminishes in some migratory cells. (M) A transverse section of a stage 10 embryo at the level of the rostral hindbrain shows that as migration proceeds, LSox5 immunoreactive cells (green) acquire the HNK1 epitope (red). (N) Parasagittal section of a stage 25 embryo showing the proximal segment of the oculomotor nerve. LSox5 expression (green) is high in the precursors of the Schwann cells, where it coincides with the P₀ marker. (O) Section through the ophthalmic lobule of the trigeminal ganglion of an E5.5 (stage 28) embryo double stained for Islet (red) and LSox5 (green). The small nuclei, morphologically associated with satellite glia, express LSox5, while those of the neuroblasts express Islet.