Meeting Abstract
The limb has been a classical system for asking questions about evolution and development. It has long been proposed that digit specification was the result of a self-organizing periodic patterning process (Ede & Law, Journal of Theoretical Biology, 1975) – and maybe even a Turing system (Frisch & Newman, Science, 1979). However, evidence for the molecular basis of this pattern has been hard to obtain. Over the last few years we uncovered evidence for the involvement of Hox genes and FGF signaling as key modulators of this process (Sheth et al. Science, 2012), and for Bmp and Wnt signaling to constitute the Turing system itself (Raspopovic et al. Science, 2014). Most recently, we have shown that the same core regulatory circuit is also involved in the patterning of radials in the catshark Scyliorhinus canicula (Onimaru et al. Nature Communications, 2016). Through computer simulations of realistic growing models of the mouse limb bud and the catshark fin bud, we illustrate how this single regulatory circuit can recapitulate the distal skeletal patterns of both species. These data-driven models strengthen previous theoretical proposals that limb skeletal patterns were probably quite flexible during evolution. Fundamental to this flexibility is the self-organising nature of the patterning process. It supports the view that comparing the details of skeletal arrangement across species provides only limited information about evolutionary relationships.
