From Embryos to Evolution: Evo-Devo
@ the Radcliffe Institute, March 5, 2012
Scientists trying to understand the evolutionary past have gained insight from studying embryonic development—a relatively new area of science called evo-devo. Nicole Le Douarin, a pioneer of modern developmental biology, discussed how studying embryonic development sheds light on a key innovation in vertebrate evolution: the emergence of a head and brain. Le Douarin, now an honorary professor at Collège de France, spoke at Radcliffe on March 5 as part of the Dean’s Lecture Series.
Le Dourin made important contributions to developmental biology from the beginning of her career in the 1960s. Catherine Dulac, a former student who is now Higgins Professor of Molecular and Cellular Biology at Harvard Medical School, said that Le Douarin’s remarkable PhD thesis, under the mentorship of French embryologist Etienne Wolff, “is still one of the most highly cited papers on development of the liver and digestive system.”
The rest of her career has focused on the neural crest, a transient formation of cells unique to the developing embryos of vertebrates. Le Douarin said that when she began her work in 1969, very little was known about the role of this elusive structure in development. The neural crest forms at the margins of the neural tube—the embryonic precursor of the brain and spinal cord—but its cells then detach and become migrants, invading nearby tissues. It was difficult for scientists to track these cells as they moved throughout the organism. Le Douarin came up with an ingenious solution, taking advantage of a type of quail with cells that could be stained and visualized under a microscope. She transplanted the neural tube and crest cells of a quail embryo into a chick embryo, allowing her to distinguish the cells as they left their origin for other tissues.
These studies showed that cells wandered even farther than had been known, incorporating themselves into the brain, bones, heart, pigment cells, and other organs and connective tissues. “No part of the body is devoid of cells from the neural crest,” she said.
In 1983, scientists Carl Gans and Glenn Northcutt argued that the neural crest was an evolutionary innovation that led to the “new head” of vertebrates, which had unique features that made it possible to form a brain, sensory organs, skull, and jaws. “It was a change in lifestyle,” Le Douarin said, allowing organisms to become active predators, sensing and seeking prey and attacking them with jaws and teeth.
Le Douarin described subsequent research in her lab on the organization of the neural crest and the molecular signals that determine its influence on tissues. These studies have shown that this small structure plays a critical role in the development of the facial bones and parts of the brain—making it a key player in creating sophisticated organisms.
Courtney Humphries is a freelance writer whose articles have appeared in the Boston Globe, Harvard Magazine, and other publications.