Meeting Abstract

P3.62  Thursday, Jan. 6  Understanding central nervous system development in an annelid: mapping gene expression profiles during early brain formation in Capitella teleta MEYER, NP*; SEAVER, EC; Univ. of Hawaii nmeyer@hawaii.edu

Capitella teleta (formerly Capitella sp. I) is a polychaete annelid whose central nervous system consists of a dorsal anterior brain and a ventral nerve cord with reiterated ganglia. In C. teleta, brain neurogenesis begins at the end of gastrulation with the ingression of single cells from localized areas of anterior ectoderm. This process generates a stratified epithelium consisting of an inner neural layer, which eventually forms the brain. We characterized homologs of several genes that are involved in neurogenesis in other animals, including neural stem cell genes (soxB), neural basic helix loop helix genes (achaete-scute complex, neurogenin, neuroD), neural subtype specification genes (gsx, pax6, runt), and neural differentiation genes (elav, synaptotagmin). During neural precursor ingression, cell divisions are restricted to the apical layer of cells in the anterior ectoderm, while neural differentiation markers are basally localized. Prior to and during neural precursor ingression, homologs of soxB1, achaete-scute complex and neurogenin are apically expressed in the anterior ectoderm, although each has a distinct pattern. Once a stratified neural epithelium is present, neuroD and putative neural subtype markers are expressed basally in the mitotically quiescent neural precursor cells. This suggests that neural subtype patterning may occur after neural precursor cell internalization. By combining the information from gene expression profiles with that from cellular and proliferative analyses, we have begun to generate a more detailed model of the sequential steps of early brain development.