Antp regulates segment-specific survival and morphology in the postembryonic ventral nervous system. Ginna E. Freehling, Danielle R. Alaimo, Kirstin T. Rudd, Anthony R. Cillo, Elizabeth C. Marin. Bucknell University, Lewisburg, PA.

   In the postembryonic ventral nervous system, 25 persisting neuroblasts give rise to the adult-specific secondary neurons, which have been observed to exhibit segment-specific survival and morphology. Several of the Hox genes have been reported to be expressed in the appropriate time and place to regulate these differences: Scr, Antp, Ubx, abdA, and AbdB,. Our previous experiments showed that Ubx is expressed in a segment-, lineage-, and hemilineage-specific manner in the thoracic and anterior abdominal segments. Loss of Ubx function in posterior neuroblast lineages via mitotic recombination at the beginning of larval neurogenesis resulted in transformation to the neuron morphology and survival patterns of their anterior thoracic counterparts. Gain of Ubx function through ectopic expression in anterior thoracic segments caused the neurons to exhibit a posterior transformation phenotype, often but not always leading to cell death. The distinct outcomes we observed implied that Ubx has been co-opted for different and sometimes opposite roles dependent upon the neuronal hemilineage.
    Antp is expressed in an adjacent and at least partially overlapping domain anterior to Ubx in the ventral nervous system. We have characterized the expression pattern of Antp in the 25 lineages and performed gain and loss of function experiments to define the role of this gene in anteroposterior patterning in the ventral nervous system. We are in the process of examining genetic interactions between Ubx and Antp to determine whether any of the earlier effects of manipulating Ubx expression were actually due to changes in Antp expression or activity.