Meeting Abstract

P3.66  Sunday, Jan. 6  Evolution of the LGR hormone receptor gene family in metazoans AZOFEIFA, J.G.; CHAPPELL, P.; WEIS, V.M.; SCHWARZ, J.A.*; Vassar College; Oregon State University; Oregon State University; Vassar College joschwarz@vassar.edu

Cnidarians exhibit cyclical patterns of gametogenesis and spawning, but it is not clear which genes play roles in establishing and controlling coral reproduction. We hypothesized that selected aspects of the cellular mechanisms used to establish reproductive cycles might be conserved across metazoans. We used a bioinformatic approach to identify cnidarian homologs of a set of vertebrate hormone receptor, hormone synthesis, and circadian and developmental genes. From a set of 15 initial candidate genes we identified unambiguous orthologs of only a handful of genes, with orthology of many of these complicated by gene duplication events through metazoan evolution. For example, the Leucine-Rich Repeat G-Protein Coupled Receptor (LGR) gene family in mammals functions as receptors for the hormones luteinizing hormone (LH) and follicle stimulating hormone (FSH). To get insights into whether cnidarian LGR homologs might play roles in controlling gametogenesis, we aimed to reconstruct the phylogenetic history and structure of the LGR gene family across metazoans. In addition to identifying gene duplication events that produced multiple paralogs of LGR genes in cnidarians, we also report a novel class of LGR from the sea anemone Aiptasia pallida. We also determine that unicellular sister taxa of metazoans lack LGR genes, and that they appear for the first time in early branching metazoans, specifially comb jelly (Mnemiopsis leidyi) and sponge (Amphimedon queenslandica). We have constructed the most comprehensive LGR phylogeny to date, elucidating gene duplication events and selective pressures on the amino acid sequence. Homology modeling of a predicted cnidarian ortholog of the LH/FSH receptor shows a similar protein fold to the human FSH receptor, suggesting a similar function in ligand binding.