Friday, April 2, 2010

A finch's decoded genome might help us with speech

By Kim McGuire

When we hear a song for the first time, it often seems like it goes in one ear and out the other, sometimes only few catchy words from a chorus leaving much of an impression.
bullet Hear the sounds of the zebra finch

But when the Australian zebra finch hears its father sing for the first time, those simple melodies activate large, complex gene networks in the bird’s brain, according to new research by an international team of scientists that includes researchers from Washington University and the University of Illinois at Urbana-Champaign.

The findings, published today in the journal Nature, reveal how the team successfully decoded the genome of the zebra finch, only the second bird to have its genetic code completely mapped.

The project provides new insights that will help scientists understand how humans learn language and may someday provide insights into diseases like autism that can inhibit speech, team members say.

"Now we can look deep into the genome, not just at the genes involved in vocal learning, but that the complex ways in which they are regulated," said Richard K. Wilson, the research’s senior author and director of Washington University’s Genome Center. "This information provides clues to how vocal learning occurs at the most basic molecular level in birds and people."

Past research has shown that hundreds of genes light up in the finch’s brain as the bird learns a new song.

The new research show that significantly more genes — about 800 total — are activated by the act of singing.

The team selected the zebra finch for study because songbirds are among few animals that learn how to sing — just like humans. As young birds, the finch "babbles" but eventually learns how to imitate its father.

In contrast, a chicken, the other bird to have its genome sequenced, instinctively knows how cluck. It is not a form of communication learned from other birds.

"There is a functional development parallel between the way a bird learns to sing and a human learns to speak," said David Clayton, a neuroscience professor at the University of Illinois and leader of the group that proposed the genome sequencing project. "The avian brain is quite different in a superficial detail from the mammalian brain or the human brain, but some striking parallels have emerged."

Wes Warren, lead author and genetics professor at Washington University, explained that the zebra finch proved to be the model study organism because they learn to sing in a predictable way over a relatively short span of time and many of their genes are conserved in humans.

Now, scientists can conduct future studies to identify a core set of genes in the finch’s brain and see if any of these are disrupted in people with speech disorders caused stuttering, or stroke and by diseases like autism and Parkinson’s, Warren said.

"It’s just amazing to know that when the finch hears a song, there’s always a gene that corresponds in the brain," he said. "Clearly, that’s going to be even more complex in humans."

Warren said as more animals have their genes sequenced, scientists will be able to draw more comparisons that might yield insight into human development.

Next up for some of the Washington University scientists who participated in the finch project is the sequencing of the parrot genome, which is slated for completion sometime later this year.

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