January 24, 2003
On Evolution and Growth, Clues From Birds' Beaks
By THE ASSOCIATED PRESS
Using tiny needles to exchange cells in 36-hour-old bird embryos, scientists
have replaced a duck's flat bill with a quail's pointed beak, and vice
versa. The experiment has uncovered critical factors in the evolution of
birds and may lead to a better understanding of what causes human facial
birth defects like cleft palate.
No matter what the species, beaks derive from similar-looking embryonic
tissue. To find out what makes them turn out so different, researchers at
the University of California at San Francisco switched the neural crest
cells � the cells that give rise to beaks � in the duck and quail embryos.
They let the eggs incubate until they were about 11 days old, halfway to
hatching and large enough to tell what the forming birds' beaks looked like.
The ducks grew quail beaks and the quails grew duck bills, the researchers
report today in the journal Science. In an accompanying review, Dr. Paul A.
Trainor of the Stowers Institute for Medical Research in Kansas City says
the experiments demonstrate that different species' neural crest cells carry
different programs for beak development.
The transplanted cells also altered the way the birds' natural tissues and
even their genes reacted in the presence of the foreign beak, slightly
modifying some surrounding facial features and speeding some gene action,
Dr. Trainor notes. Together, these factors make the cells crucial to beak
evolution.
Dr. Jill A. Helms, an orthopedics researcher who is an author of the new
study, said an understanding of beak development could shed light on human
craniofacial development. If people have an equivalent to the birds'
powerful neural crest cells, surgeons might someday be able to correct a
cleft palate before birth with a transplant of mouth-growing cells.
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