PL-08 Enhancing mammalian regeneration

One of the crucial issues concerning the evolution of animal form is whether there is any general tendency as to the genetic and molecular mechanisms involved? A vast body of comparative studies has revealed that morphology evolves via changes in the spatial regulation of gene expression during development. So the question of the evolution of form boils down to one concerning the evolution of gene regulation. Changes in the transcription of any individual gene may result from modifications of its cis-regulatory sequences, of the deployment or activity of the transcription factors that act upon these sequences, or both. Understanding the relative contribution of these different mechanisms is thus central to formulating a general understanding of the genetic and molecular mechanisms governing morphological variation and divergence. We have analyzed numerous cases of the gain, loss, and modification of pigmentation patterns in Drosophila as models of morphological evolution. Our results demonstrate how the functional diversification of the modular cis-regulatory elements of various pleiotropic genes contributes to evolutionary novelty and the diversity, while circumventing the pleiotropic effects of coding sequence mutations. We argue that there is now sufficient empirical evidence to support a general genetic theory of morphological evolution which asserts that, under most conditions, changes in cis-regulatory sequences are the much more likely mode of morphological evolution than are changes in coding sequences.