First expressed in embryos at 8.5-9 days in facial and branchial arch mesenchyme, otic vesicles and frontonasal ectoderm around olfactory placodes, a day later expression is seen in the developing forebrain in primordia of the ganglionic eminence and ventral diencephalic regions. In day 12.5 embryos, expressed in the brain and bones, and also in all skeletal structures of midgestation embryos after the first cartilage formation, and expression progressively declines in both brain and skeleton in day 15 embryos. Belongs to the distal-less homeobox family.