Meeting Abstract

12.1  Sunday, Jan. 4  Developmental Influence in the Evolution of Phalanges KAVANAGH, KD*; JERNVALL, J; TABIN, C; Harvard Medical School and Stony Brook University; University of Helsinki and Stony Brook University; Harvard Medical School kathryn_kavanagh@yahoo.com

Phalanges (finger and toe bones) originate from a single condensation that grows and segments sequentially along each digit, repeatedly deploying the same activator-inhibitor gene networks as each element is formed. The developmental processes involved in determining where joints are positioned, effectively segmenting the developing digit and determining phalanx size, are unknown, however understanding the developmental relationship between sequentially-developing phalanges is essential to modeling the evolution of phalanx size. In this study we evaluate in this system the usefulness of a previous model, the inhibitory cascade, that allows prediction of the evolution of molar tooth proportions (Kavanagh et al., 2007. Nature 449:427-432). Using experimental studies in the chick embryo autopod in combination with comparative studies of vertebrate lineages with hyperphalangy (e.g. cetaceans, ichthyosaurs, birds, amphibians), we are studying the developmental relationship among phalanges during morphogenesis and evolution. We are interested in the timing of formation of elements, growth rates, and the role of inhibition in establishing joint spacing. The adaptive significance of phalangeal morphology will be discussed in the context of the inhibitory cascade model.