15-P015 Non-individualization of Dlx gene expression during teeth and dermal denticles development in the catshark

a massive sequencing approach of a cDNA library, the whole set of Hox genes of the chondrichthyan, Scyliorhinus canicula. We have sequenced seven BAC clones that include all of the HoxA, HoxB and HoxD clusters. The transcriptomic data suggests that no HoxC genes have been maintained in this species. The expression of the posterior Hox genes was studied by insitu hybridization and showed that all the posterior genes of the three catshark Hox clusters are expressed differentially in the posterior part of the body and in the paired fins. Posterior HoxA and D genes were expressed during two temporal phases in both the pectoral and pelvic fin buds, while observing spatial colinearity. Posterior HoxB transcripts were identified only in the pelvic fin buds. Comparing this data with those for other vertebrates (tetrapods and teleosts), we have analyzed Hox code evolution in relation to the evolution of paired appendages in gnathostomes.