Meeting Abstract

27.1  Wednesday, Jan. 5  The Genome of the Ctenophore Mnemiopsis leidyi and its Implications on the History of Animals RYAN, JF*; PANG, K; MORELAND, RT; NGUYEN, A; NISC, ; WOLFSBERG, TG; MULLIKIN, JC; MARTINDALE, MQ; BAXEVANIS, AD; National Human Genome Research Institute (NHGRI), NIH; Univ. of Hawaii; NHGRI, NIH; NHGRI, NIH; NHGRI, NIH; NHGRI, NIH; NHGRI, NIH; Univ. of Hawaii; NHGRI, NIH jfryan@mail.nih.gov

Despite the great strides that have been made in the areas of phylogenomics, and phylogenetics, the early history of animals remains ambiguous. Functional data from non-bilaterian species holds the promise of shedding light on metazoan origins and morphological complexity. However, the ambiguity surrounding the relationships at the base of the animal tree has made it difficult to interpret this functional data. One of the major hurdles has been the absence of whole-genome data from a ctenophore species. Here, we report the results of the sequencing, annotation, and initial analysis of the ~150-megabase genome of the ctenophore, Mnemiopsis leidyi. Many of the crucial elements of the animal genetic toolkit are present in Mnemiopsis, including most of the Wnt signaling pathway components and several homeodomain classes. However, many of the exciting findings stem from missing elements; these include Wnt antagonists, Hox genes, paired domains coupled with homeodomains, and nuclear receptors devoid of zinc-finger DNA-binding domains. These analyses suggest that placozoans, cnidarians, and bilaterians form a clade exclusive of Porifera and Ctenophora that we have named the ParaHoxozoa. Analysis of the presence or absence, and the sequential order, of conserved domains within these lineages are helping to further resolve the relationships of these early-branching lineages. Unraveling the branches at the base of the Metazoa will allow for the identification of genetic elements that were likely present or absent at key branching points in metazoan history. This knowledge, coupled with the steady influx of functional data from these species, will provide important insights into the evolutionary history of animal form, diversity, and complexity.