Meeting Abstract

122.1  Monday, Jan. 7  Notch signaling during neural development in the annelid Capitella teleta TOLCHIN, S; MEYER, NP*; Clark Univ. nmeyer@clarku.edu

Central nervous system development begins with fate specification of neural precursor cells, which generate the brain and nerve cord. Comparisons between vertebrates and arthropods have provided important insights into neural development, but studies in spiralians are still lacking. To understand the evolution of nervous systems, we are investigating brain development in the spiralian annelid Capitella teleta. C. teleta has a dorsal anterior brain that has several hundred cells. Brain development begins at the end of gastrulation with the ingression of single cells from localized areas of anterior ectoderm. During ingression, cell divisions are restricted to apical cells in the anterior ectoderm, while neural differentiation markers are basally localized. In both vertebrates and arthropods, proneural bHLH genes and Notch signaling play a role in neural fate specification and differentiation, although their function seems to be somewhat different between organisms. Based on expression of the proneural gene homologs Ct-ash1 and Ct-ngn, and preliminary functional analysis of Ct-ash1, we hypothesize that cells expressing the highest levels of proneural genes ingress and then differentiate into neurons. Furthermore, Ct-notch and Ct-delta are expressed in the region of the developing brain. To test a possible function of Notch signaling in specifying neural fate or in preventing neural differentiation, we treated embryos with the gamma secretase inhibitor DAPT, which blocks cleavage-mediated activation of Notch. Despite apparent phenotypes in other tissues, notably the developing foregut, we did not see a strong phenotype in the developing nervous system. If true, these results would provide an interesting contrast to neural development in other animals.