Meeting Abstract

S8.4  Tuesday, Jan. 6  Zebrafish developmental genetics and the mechanisms of dental evolution STOCK, D.W.; University of Colorado, Boulder David.Stock@Colorado.edu

Dentition in fishes exhibits enormous diversity in shape, number, and location of individual teeth. The developmental and genetic mechanisms underlying this diversity are just beginning to be characterized through studies in a variety of taxa. My laboratory is carrying out comparative analyses of tooth development focused on the zebrafish, Danio rerio, because of the unparalleled genetic, molecular, and embryological tools available for the analysis of its development. One of the most distinctive features of dentition in the zebrafish is its restriction to a single pair of elements of the pharyngeal skeleton, the fifth ceratobranchials. Such dentition is characteristic of the order Cypriniformes, to which the zebrafish belongs, and is the result of evolutionary reduction of tooth-bearing locations. To understand the mechanisms of this reduction, we compared oropharyngeal development of the zebrafish and the characiform Mexican blind cave tetra, Astyanax mexicanus. In addition to being among the most closely-related species to the zebrafish retaining oral teeth, A. mexicanus is amenable to many of the same manipulations employed in zebrafish developmental genetics. Comparisons of gene expression between these species and mutant analyses in the zebrafish revealed several candidate genes for involvement in cypriniform dentition reduction. Transgenic and pharmacological manipulation of the expression of some of these genes in the zebrafish and A. mexicanus produced altered numbers of teeth and tooth cusps. These results provide insight into mechanisms of dentition reduction in cypriniforms and the origins and ontogenetic distribution of multicuspid teeth in fishes.