Meeting Abstract

BERN.1  Jan. 5  The Endocrine System just before the Backbone: Genomics of the Spineless SHERWOOD, NM; Univ. of Victoria, BC Canada nsherwoo@uvic.ca

The nature of the endocrine system in animals that evolved just before the vertebrates has been difficult to study. Now, the release of the complete genome for two groups lacking a backbone, amphioxus and tunicates, has revealed the presence of a number of endocrine-related ligands, receptors, enzymes, transcription factors and signaling molecules that are homologous to those in vertebrates. The phylogenetic position of these basal chordates and the simplicity of their genomes before expansion by duplication in the vertebrates suggest that insight into the foundation of vertebrate endocrine-related genes is possible. In a tunicate (Ciona intestinalis), the major endocrine systems isolated and studied are those involved with metabolism and growth (insulin, IGF and their receptor), with reproduction (gonadotropin-releasing hormone, GnRH, and its four receptors), with feeding (CCK/gastrin and its receptor) and with brain-gut-thyroid function (tachykinin and its receptor). In amphioxus (Branchiostoma floridae) the genome is just released but insulin-like peptides, an insulin-IGF receptor and GnRH receptors have been isolated and studied. Although hormones are difficult to identify within the genome, a number of receptors including G-protein-coupled receptors, tyrosine kinase receptors and nuclear receptors have been annotated within the genome. Of equal interest are the endocrine molecules that are not present. One conundrum is the apparent lack of pituitary hormones, classical steroids and their receptors in tunicates, whereas the status of the pituitary and steroids is an open question in amphioxus. The presence of releasing factors such as GnRH in an animal lacking pituitary hormones provides an opportunity to study ancestral and peripheral actions of these neuropeptides.