15-P046 Elucidating the genetic basis of scale loss in fish

Gene and whole genome duplications have profoundly shaped the structure and function of the vertebrate genome. Teleost fish, which comprise approximately 50% of all known vertebrate species, have undergone a third round of whole genome duplication (3R) above and beyond the two rounds of whole genome duplication shared by all vertebrates (2R). Most non-teleost vertebrates including tetrapods have 4 Hox gene clusters: HoxA, HoxB, HoxC and HoxD. Teleost models including zebrafish, medaka and pufferfish have been shown to possess 7 clusters including hoxaa, hoxab,hoxba,hoxbb, hoxca, hoxda and either hoxcb (medaka and pufferfish) or hoxdb (zebrafish),as a consequence of whole genome duplication followed by lineage specific loss of an entire hox cluster. This variability in whole hox cluster content between teleost clades is mirrored by equally variable hox gene content across orthologous clusters in different species, highlighting the putatively plastic nature of the teleost genome. The timing, mechanism, and developmental consequences of the duplication and subsequent loss of individual hox genes or whole clusters are currently under investigation. We present data pertaining to the structure, coding and non-coding element content of hoxgene clusters in the African Freshwater Butterflyfish, Pantodon bucholzi, a member of the most basal lineage of teleost fish, the Osteoglossomorpha. Comparative genomic approaches using Pantodon and other model teleost fish are used to reconstruct the ancestral post-3R hoxcomplement and to probe the basis for and developmental consequences of the variable hox gene content in diverse teleost genomes.