Meeting Abstract

91.1  Thursday, Jan. 7  Cellular and molecular mechanisms of brain development in the annelid Capitella teleta MEYER, NP*; SEAVER, EC; Kewalo Marine Lab, PBRC, Univ. of Hawaii, Honolulu, HI nmeyer@hawaii.edu

Capitella teleta (formerly Capitella sp. I) is a polychaete annelid whose central nervous system (CNS) consists of a dorsal, anterior brain, circumesophageal connectives and a ventral nerve cord with reiterated ganglia. This organization is similar to many other annelids and structurally resembles the basic arthropod CNS. However, recent phylogenomic data indicates that centralized nervous systems may have evolved independently between these two animal lineages. Much of our understanding of the mechanisms controlling CNS development comes from detailed studies in two of the three major bilaterian clades, ecdysozoans and deuterostomes. Consequently, it is important that we elucidate mechanisms of CNS development in the third bilaterian clade, the lophotrochozoans. To address this, we have assembled a detailed molecular and cellular description of early brain neurogenesis in the lophotrochozoan annelid C. teleta utilizing several different approaches. In C. teleta brain neurogenesis proceeds by the ingression of single cells from the anterior ectoderm to generate a stratified epithelial layer. Cell divisions are apically restricted, while neural differentiation markers are basally localized. Prior to and during neural precursor ingression, a proneural achaete-scute homolog, CapI-ash1, is apically expressed in patches of anterior ectoderm with varying levels of intensity. Furthermore, functional analysis indicates that CapI-ash1 may be involved in fate specification of neural precursors and/or their differentiation, but not ingression. These results suggest that some cellular mechanisms of C. teleta brain neurogenesis are shared with arthropod CNS development, although the function of CapI-ash1 may be more similar to proneural gene function during vertebrate neurogenesis.