Meeting Abstract

P2.59  Wednesday, Jan. 5  Isolation of genes required for the ingression, patterning, and differentiation of cells that give rise to the larval skeleton in the pencil urchin, Eucidaris tribuloides MILLER, E.; MOORE, D.; ORLOWSKI, S.; TEKELENBURG, S.; ROMANO, L.*; Denison University, Granville, OH romanol@denison.edu

Our lab utilizes the sea urchin as a model system to explore the functional consequence of changes in genes and their cis-regulatory elements during embryonic development. In particular, we are examining genes that are required for development of the larval skeleton. Skeletogenesis is initiated when the micromeres are specified to become the primary mesenchyme cells (PMCs). These cells ingress into the blastocoel and then form two ventrolateral clusters in response to cues from the overlying ectoderm. Finally, the cells secrete a variety of proteins upon their differentiation. We are currently focused on the molecular basis for several differences between the “modern” purple urchin, Strongylocentrotus purpuratus, and the “primitive” pencil urchin, Eucidaris tribuloides. In the purple urchin, the larval skeleton is derived from a fixed number of micromeres that ingress from the vegetal plate in the early gastrula. In the pencil urchin, the larval skeleton is derived from a variable number of micromeres that ingress from the tip of the archenteron in the late gastrula. We have been using RACE PCR to extend partial cDNA sequences from the pencil urchin. Thus far, we have been able to isolate one or more genes involved in ingression (e.g. FoxN2/3), patterning (e.g. VEGF-R), and differentiation (e.g. SM29). We have been confirming the identity of genes through phylogenetic analysis. Ongoing work includes isolating additional genes as well as preparing probes for in situ hybridization. We expect this work will eventually provide critical insight into some of the diversity that exists among different species of echinoderms.