ORTHOPEDIA, A NOVEL HOMEOBOX-CONTAINING GENE EXPRESSED IN THE DEVELOPING CNS OF BOTH MOUSE AND DROSOPHILA

A novel homeobox-containing gene has been identified. Its name, Orthop edia (Otp), exemplifies the homology shared by both the orthodenticle and Antennapedia homeodomains. Otp is highly conserved in evolution. I n mouse, Otp is expressed only in restricted domains of the developing forebrain, hindbrain, and spinal cord. In Drosophila, otp first appea rs at gastrulation in the ectodermal proctodeum and later in the hindg ut, anal plate, and along the CNS. Here, we compare the Otp-, Distal-l ess homeobox 1-(Dlx1-), Orthodenticle homolog 1- (Otx1-), Otx2-, and E mpty spiracles homolog 2-expressing domains. Our results indicate that Otp is expressed along the CNS both in mouse and Drosophila; Otp coul d specify regional identities in the development of the forebrain and spinal cord; transcription of Otp and Dlx1 takes place in alternating hypothalamic regions reminiscent of a segment-like pattern; and the st ructural and functional conservation could correspond to a conserved f unction maintained in evolution.