OTLX2, AN OTX-RELATED HOMEOBOX GENE EXPRESSED IN THE PITUITARY-GLAND AND IN A RESTRICTED PATTERN IN THE FOREBRAIN

The vertebrate nervous system forms by the specification of, successiv ely, neuroepithelial regions and cell groups. One of the proposed majo r histogenetic steps is the subdivision of the neural tube in compartm ents along its caudorostral and dorsoventral axis. This event is refle cted, and may be directed, by the restricted expression of many transc ription factors. Here, we report on the isolation of a new homeobox ge ne of the paired superclass, Otlx2, whose early expression pattern in the mesencephalon and prosencephalon is congruent with proposed neurom eric models of brain morphogenesis. In addition, its late embryonic an d postnatal expression, in clear continuity with the earlier pattern, suggests a role in the neuronal differentiation and the histogenesis o f several prosencephalic and mesencephalic areas. Finally, Otlx2 is ex pressed from the earliest morphogenetic events in the Rathke's pouch, the anlage of the adenohypophysis, an expression site shared by a very close homologue, Otlx1/Ptx1/P-Otx.