Meeting Abstract

13.4  Tuesday, Jan. 4  The Genomic Complement of the Ctenophore Nervous System SIMMONS, D*; PANG, K; RYAN, J; BAXEVANIS, A; MARTINDALE, MQ; University of Hawaii; University of Hawaii; Genome Technology Branch, NIH; Genome Technology Branch, NIH; University of Hawaii davidsim@hawaii.edu

Nervous systems are thought to be evolutionarily important to the rise and diversification of metazoans, yet the origin of simple nervous systems remain largely unknown. With respect to recent data on basal metazoan phylogeny, ctenophores can confidently be regarded as the earliest animal with true neurons. Due to their advantageous phylogenetic position, ctenophores provide a good source of comparison to other organisms to determine evolutionarily conserved regulatory modules important in the origins of the nervous system.

Using next generation sequencing, a rough draft of the genome has been generated for the lobate ctenophore, Mnemiopsis leidyi. The genome was searched in silico for a large set of known neural genes. We have identified numerous homologues of these genes, which are known to be important in the development of the nervous system in other animals. We have identified members of the Notch pathway, several transcription factors involved in neuron specification and axon guidance. There is also a large set of genes involved in the synthesis and transport of neurotransmitters. Since genes involved in the post-synaptic scaffold have been shown to be present in sponges, which lack neurons, a comparison with ctenophores is necessary for understanding the evolution of the synapse. Interestingly, some genes present in the sponge genome appear to be lacking in the ctenophore. Additionally, we utilized whole mount in situ hybridization to look at expression of these genes during development and in cydippid larvae. This research into the genomic complement of the ctenophore, Mnemiopsis leidyi, provides new information on the origins and evolution of animal nervous systems.