The long-term goal of this project is a cephalopod model system for studies into mechanisms of embryogenesis, neural development and regeneration. Among animals, human beings are large organisms with disproportionately large brains. Cephalopods, which include squids and octopuses, are the largest non-mammalian organisms and have the largest brains among all invertebrates. They also have a cellular pattern of early embryogenesis that is strikingly similar to that of vertebrates. To study cephalopod development at a mechanistic level requires the identification of a cephalopod species with ready availability, easy husbandry and an embryology permitting experimental manipulation. We have identified such a preparation, the California Two-spot Octopus (O. bimaculoides). An important additional advantage in choosing an octopus for a cephalopod model system is that octopus arms, each of which contains a massive central nervous system, regenerate rapidly after amputation and could serve as a new model in regenerative medicine. To date, we have developed methods for octopus in situ hybridization and immunohistochemistry, engineered an octopus plasmid expression vector and demonstrated gene delivery into octopus embryos and arm tissue. We have also isolated cDNAs for a small panel of octopus developmental regulatory genes by degenerate primer PCR and through plasmid cDNA library sequencing. For O. bimaculoides to be a credible model system will, however, require a much greater depth of information about octopus gene expression and regulation.
The first aim of the proposed work is to develop RNAseq databases for O. bimaculoides using state-of-the-art sequencing technologies and assembly programs.
The second aim i s to apply this transcriptome information about message structure to a concurrent O. bimaculoides genome sequencing project, and to build out a cephalopod community web site (www.cephseq.org) for sharing sequence data. Cephalopod genomes are large and repeat-rich so transcriptome data will be essential for genome assembly and annotation. The generation of these transcriptomic and genomic resources will drive hypothesis-driven research on the molecular and cellular mechanisms of cephalopod development and regeneration.
Among animals, humans are notable for their large size and disproportionately large brains. Experimental approaches to understanding how large animals such as humans develop, and how that development can go awry, require appropriate animal model systems. We propose to generate genomic resources for a new model system, the cephalopod mollusc Octopus bimaculoides, since cephalopods include the largest non-mammalian organisms and have the largest invertebrate brains.