COMMITMENT OF CNS PROGENITORS ALONG THE DORSOVENTRAL AXIS OF DROSOPHILA NEUROECTODERM

In the Drosophila embryo, the central nervous system (CNS) develops fr om a population of neural stem cells (neuroblasts) and midline progeni tor cells, Here, the fate and extent of determination of CNS progenito rs along the dorsoventral axis was assayed. Dorsal neuroectodermal cel ls transplanted into the ventral neuroectoderm or into the midline pro duced CNS lineages consistent with their new position. However, ventra l neuroectodermal cells and midline cells transplanted to dorsal sites of the neuroectoderm migrated ventrally and produced CNS lineages con sistent with their origin, Thus, inductive signals at the ventral midl ine and adjacent neuroectoderm may confer ventral identities to CNS pr ogenitors as well as the ability to assume and maintain characteristic positions in the developing CNS. Furthermore, ectopic transplantation s of wild-type midline cells into single minded (sim) mutant embryos s uggest that the ventral midline is required for correct positioning of the cells.