Meeting Abstract
Early neural fate specification is relatively well-understood in vertebrate and insect model organisms, where a region of ectoderm receives extrinsic signals to become neural ectoderm. By studying the annelid Capitella teleta we can elucidate to what extent extrinsic versus intrinsic signals are involved in early neural fate specification in other metazoans. So far, only ascidians had been shown to require intrinsic and extrinsic signals to specify neural fate. We hypothesize that in C. teleta the potential to generate brain neural ectoderm is autonomously specified by factors that are asymmetrically segregated to the daughters of the first quartet micromeres (1q), while ventral nerve cord (VNC) neural ectoderm is conditionally specified in daughters of the 2d micromere by extrinsic signaling from surrounding blastomeres. Using mechanical and chemical protocols, we have successfully isolated blastomeres from 2- to 8-cell C. teleta embryos. Isolated blastomeres continue dividing for more than 3 days, enough time to assess neural fate via expression of homologs of proneural and pan-neuronal genes, and by immunohistochemistry. Daughters of isolated C blastomeres (fated to generate the right eye, right brain lobe, and cilia) generate an eye, an adjacent clearing in the tissue that resembles a brain lobe, and cilia. Preliminary results also suggest that daughters of isolated 1q cells express the pan-neuronal gene Ct-elav1, indicating a possible role for neural determinants in C. teleta brain formation. These and future experiments to examine the transcriptomic profile of isolated blastomeres should enable us to identify the type of signaling (intrinsic versus extrinsic) and putative genes involved in early neural specification in spiralians.
