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Research gains toehold on skeletal evolution

Posted November 4, 2013

The developmental rules for forming a foot just got a little simpler. New research led by UMass Dartmouth Biology faculty member Dr. Kathryn Kavanagh and Harvard Medical School Professor Cliff Tabin, joined by Professor Uri Alon and Oren Shoval, of Israel’s Weizmann Institute of Science’s Department of Molecular Cell Biology, Akinori Kan of Harvard Medical School’s Department of Genetics, and UMass Dartmouth’s Dr. Benjamin Winslow and graduate student Brian Leary, studied the toe bones, or phalanges, of animals in order to test an idea that has been debated by evolutionary biologists for centuries—that the developmental process itself can guide evolution.

“Most bones in the skeleton evolve relatively independently from other bones, meaning that the size of each bone has freedom to evolve to suit any particular adaptive need. However, the toe bones seemed to be an exception,” said Professor Kavanagh. “We first noticed that phalanges size proportions seemed to vary in predictable ways, from a gradient large-to-small, to a more equal-sized pattern, suggesting some coordination among parts.”

Using chicken embryos as a model, the team used small foil barriers placed in the edge of the developing chick digit to prevent molecular signals from communicating with the still-developing tips. They found that this interference set up a shift in joint positioning that continued to reverberate during the rest of the digit’s development. In contrast, when the barrier was placed in the metatarsal (the major bones of the foot’s sole), only the metatarsal was altered with no reverberation into the phalanges.

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