Jerry Coyne has a post up which critiques an extremely breathless review of a new book, Epigenetics Revolution. Overall I agree with the thrust of Coyne’s take. Epigenetics is real, and probably important, but it doesn’t imply that there’s a revolution and that everything that has come before needs to be thrown out. But I was struck by one of Coyne’s asides:
…This study has segued into the new field of “evo devo,” which tries to understand the evolutionary basis of developmental genetics. “Evo devo” itself has, of course, led to its own important discoveries, like the presence and conservation of homeobox genes, the use of the same genes over and over again in forming similar but non-homologous traits (e.g., PAX6 in the formation of fly eyes and vertebrate eyes), and the linear arrangement of genes in some organisms (e.g., Drosophila) that correspond to the linear arrangement of body parts they affect.
Howard Hughes Medical Institute is showing Sean B. Carroll the love today. HHMI named him the next Vice President of Science Education. Since he already has published several popular books I think this turns out to be after the fact recognition of his service in this area. But I noticed in my RSS that HHMI also put out a lavish press release on a paper which just came out by Carroll’s lab, Preexisting Patterns Guide Evolution’s Paintbrush:
One of the enduring mysteries of the animal world is how colored patterns come to adorn different species’ skin, scales, or feathers. Now, a team led by Howard Hughes Medical Institute investigator Sean B. Carroll has discovered how wing spots evolved in a species of polka-dotted fruit fly.
The new studies show that pigment production in the wing is patterned according to the spatial distribution of a molecule that helps sculpt the shape of the body during development. The finding underscores the concept that evolution likes to tinker with existing genetic machinery to evolve new patterns and forms.
Here’s the paper in Nature, Generation of a novel wing colour pattern by the Wingless morphogen:
The complex, geometric colour patterns of many animal bodies have important roles in behaviour and ecology. The generation of certain patterns has been the subject of considerable theoretical exploration, however, very little is known about the actual mechanisms underlying colour pattern formation or evolution. Here we have investigated the generation and evolution of the complex, spotted wing pattern of Drosophila guttifera. We show that wing spots are induced by the Wingless morphogen, which is expressed at many discrete sites that are specified by pre-existing positional information that governs the development of wing structures. Furthermore, we demonstrate that the elaborate spot pattern evolved from simpler schemes by co-option of Wingless expression at new sites. This example of a complex design developing and evolving by the layering of new patterns on pre-patterns is likely to be a general theme in other animals.
In case you don’t know the “back story,” Carroll has gotten into it with other evolutionary biologists such as Jerry Coyne over his interest in particular types of constraints in evolution and development. I’ve heard him be termed the “King of Evo-Devo” in private conversation. What Richard Dawkins did for the “selfish gene” in the 1970s I think Carroll is trying to pull off for gene regulation in this century.
Oh, and by coincidence, I notice that the Sean Carroll has a paper in the current issue of Nature, Infrared images of the transiting disk in the ϵ Aurigae system. You read his take over at his blog.