Newly Decoded Bird Genes May Help Explain Human Speech Disorders
The recently decoded zebra finch genome is expected to give scientists and researchers more insight into human speech disorders and treatment, researchers are reporting.
Researchers have realized that the process by which a young zebra finch learns to sing resembles the process by which a human learns to speak, said molecular biologist David Clayton, a principal investigator in the consortium that recently decoded the zebra finch genome and the principal researcher at the Clayton Laboratory at the University of Illinois at Urbana-Champaign.
In the April 1 issue of the journal Nature, Clayton and an international team of scientists reported: "Like other songbirds, the zebra finch communicates through learned vocalizations, an ability otherwise documented only in humans and a few other animals." They noted that this ability is present in chickens, the only other bird for whom a full genome has been developed.
Clayton added that the zebra finch only learns how to sing during the juvenile period of its life, just like a human learns how to speak a language best before puberty.
The big question however, is how animal models can help cure human disorders and why. “There is the idea of developing animal models for specific diseases or disorders. In the case of speech, we know next to nothing about the genes that are necessary for speech and vocal learning,” Clayton said. “By comparing animals that have this ability like the songbirds and humans, with animals that don't, like chickens and mice, we may be able to decipher the instruction set that is used to build the necessary hardware for speech learning and production.”
Speech learning, Clayton added, involves certain circuits in the brain that can’t be studied directly in humans. In the zebra finch however, the researches have been able to “experimentally record the way neurons fire in the brain during singing, and we can work out the detailed neuroanatomy of the song control system and study how it develops during the song learning period,” he said.
Studying this songbird also has other advantages. "The zebra finch develops in a matter of months whereas it takes a human 20 years to reach adulthood,” Clayton said. “So in the zebra finch we can ask how early experiences or other testing interventions affect how well you copy your father’s song. Each bird learns to copy a song by listening to a tutor, but they don't make an exact copy. Why do some birds copy more accurately than others? We potentially could identify genes associated with that."
“In the long term by taking advantage of the similarity of the genomes, of all the species, we can gain insight into the mechanisms and possibly test therapies for human conditions,” he said.
Clayton hopes that by studying the songbirds, genome specific genes can be identified that are involved in processes, like stuttering. Once that specific gene is targeted then the researches can try to devise ways to manipulate it. Although gene therapy is one theoretical treatment, more conventional drug therapies may emerge once scientists know what the "molecular players" are, he said. Researchers could design or screen for a drug that binds to the defective gene product and in doing so perhaps repair or mitigate the effects of the defective gene, he added.
“You have to learn to speak by listening to others, and your ability to speak is at the center of many social interactions," Clayton said. "Studying how all this works in a model organism may lead to insights about how we learn better, or worse, from our own parents and tutors, or how our social circumstances affect our learning ability, or how our communications abilities affect our social success. In other words, some of the ‘therapies’ or ‘treatments’ could end up being behavioral or social, just as much as some may be ‘biomedical’ or drugs."
Gene Robinson, director of neuroscience at the University of Illinois in Urbana-Champaign, said he hopes that other animals' genomes can serve as models to unravel puzzles in human behavior and disease. "We know that genes in the animals are the same genes in humans. We are all playing with the same deck of cards," he said.
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