Keck School of Medicine Events

Keck School of Medicine of USC Research Seminar Series

"Modularity in Development and Evolution of the Head Skeleton"
April 2013
Monday, April 8, 2013
11:30 AM - 1:00 PM
Norris Research Towers Aresty Auditorium
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Charles B. Kimmel, PhD

Professor Emeritus of Biology, Institute of Neuroscience, University of Oregon will be presenting. Dr. Gage Crump will be hosting this event.A light lunch will be served before the Seminar at 11:30 am.
Abstract: Might development constrain or bias the course of evolution? A venerable hypothesis is that some morphologies are 'impossible' - forbidden because of the way that development works. However, we examined the shapes of the four opercular bones in diverse teleosts and found no evidence for forbidden morphologies or developmental constraint. We account for our observed rich shape variation by noting that evolutionary shape changes in discrete regions of bone are dissociable from changes in other regions. Dissociation is a hallmark of modularity, where modules are relatively autonomous developmental building blocks. Modularity should permit evolutionary flexibility, for example modularity can facilitate keeping of functional fits among neighboring bones that are evolving new shapes. His lab tested this hypothesis with stickleback and salmonids, and found that the locations in the skull where evolutionary changes in bone shape occur strikingly predict module boundaries. With zebrafish we find that bone shaping during development occurs in phases. Each phase, or developmental module, is marked by a distinctive pattern of osteoblast arrangement and bone outgrowth, and mutational analyses reveal that separate phases are under separate genetic control. Hence the zebrafish work provides insight about the cellular and developmental genetic basis of skull modularity.

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