Meeting Abstract
P2.66 Sunday, Jan. 5 15:30 Expression of 5’ HoxD paralogs in the paired fins of the actinopterygian Polyodon spathula AUGUSTUS, G.J.*; SIMS, S.E.; TULENKO, F.J.; HUDSON, M.L.; DAVIS, M.C.; Kennesaw State University; Kennesaw State University; Kennesaw State University; Kennesaw State University; Kennesaw State University gaugustu@students.kennesaw.edu
Our previous analyses of gene expression during paired fin patterning in a basal actinopterygian, the North American paddlefish Polyodon spathula revealed an inverted collinear expression of 5’ HoxD genes. This HoxD expression pattern was long considered a developmental hallmark of the autopod and is shown in tetrapods to be controlled by a ‘digit enhancer’ regulatory region. Recently published data confirm the antiquity of this regulatory region in gnathostomes, which together with our previous results in Polyodon demonstrate that aspects of autopod development are primitive to tetrapods and that limb origins entailed only ‘slight’ modifications of ancient patterns of gene expression and their underlying regulatory landscapes. However, direct comparisons of expression data between tetrapods and paddlefish are complicated by the fact that Polyodon exhibits a taxon specific whole genome duplication (WGD), independent of the WGD that occurred in teleosts. In light of the independently duplicated genome in paddlefish, we have further investigated the expression patterns of their 5’ HoxD genes to determine 1) if both “alpha” and “beta” paralogs co-express during paired fin development; and 2) whether differences in the relative timing, position, and/or quantity of expression exist that might suggest subfunctionalization of the two paralog’s roles in paired fin development. A previous study, comparing synonymous and nonsynonymous substitutions rates among the paralogous Polyodon HoxA and HoxD clusters suggested that one of the two HoxA/D clusters may be transcriptionally inactivated, resulting in functional diploidization. We discuss this hypothesis in light of our gene expression results.
