Songbird's DNA may shed light on human speech
Published 4:00 am, Friday, April 2, 2010
The zebra finch, a chatty little songbird that learns his speech from his father and passes it on to his offspring, has long been a model for scientists studying human speech disorders.
Now an international team of researchers has sequenced the zebra finch's entire genome, hoping the secrets of the Australian bird's genes will lead to advances in understanding human speech and learning disorders in problems as varied as autism, strokes, the late stages of Parkinson's disease and even stuttering.
After five years of laborious analysis, the full assortment of the finch's genes is reported today in the journal Nature by scientists who say they have decoded 800 genes involved in the finch's ability to learn his father's songs.
Allison J. Doupe, who is a psychiatrist and a neuroscientist at UCSF, said sequencing the genome of the finch opens up new opportunities to study human disorders involving the nervous system because many of the finch's genes are apparently identical to those in humans.
"Once you know that whole genome, you have a list of the parts in the brain concerned with vocal learning," said Doupe, who was not a member of the sequencing team. "It's amazing how many of the finch's behavioral patterns are like humans, and how many of their genes are also found in the human genome."
Only 4 inches long and weighing less than half an ounce, the zebra finch has a stubby, bright orange beak, black-and-white-striped feathers on its throat and an orange and white mottled breast.
Only the males sing. Like many birds, male and female zebra finches mate for life.
But the zebra finches are unique because they seem to merely babble when they're very young. It's only as they grow that they learn their songs note by note from their fathers. As adults, they pass those same songs on to their male offspring, with only minor variations. And so it goes, from generation to generation.
"We hope that the zebra finch will be a model for us to study what's going on at the molecular level in the brain," Clayton said in an interview.
The bird's entire genome holds roughly a billion units of DNA that carry the code for making proteins - about half the number in the human genome. But one surprise in analyzing its genes, Clayton said, was that the team also discovered large numbers of "noncoding" RNA molecules that apparently influence hundreds of genes to turn on or off as the birds learn to sing.
"It's an unexpected finding that we still don't fully understand," he said.