Nested expression domains of four homeobox genes in developing rostral brain

Two homeobox genes, Otx1 and Otx2, act with two other previously identified homeobox genes, Emx1 and Emx2, to control development of the rostral brain in mice and are homologous with orthodenticle and empty spiracle genes in Drosophila. Thus some vertebrate and invertebrate homeobox genes are now known to be homologues. The four genes govern expression of several regions of the brain including the telencephalon. The genes' expression domains progress in the sequence Emx1, Emx2, Otx1 and Otx2.