Almost all animals that communicate vocally do it by instinct. The zebra finch is one exception: Young males learn their love songs from their fathers. Now a research team reports the identification of 33 genes related to singing in this songbird. Experts say the work harbingers a new era of using powerful genomic tools to probe the biology of vocal learning--and perhaps reveal the secret of why so few animals do it.
Many researchers see parallels between the way birds learn songs and humans learn language. Over the years, they've identified the regions of the zebra finch brain that are involved in song learning and examined the electrical activity of the neurons therein. These studies have yielded many insights into the biological mechanisms of vocal learning, but not at the molecular level.
Hoping to take the next step, a team of 20 researchers led by Kazuhiro Wada and Erich Jarvis at Duke University in Durham, North Carolina, cataloged more than 4000 genes expressed in the zebra finch brain. By attaching snippets of these genes to glass slides, they created DNA microarrays that allowed them to compare gene activity in the brains of zebra finches that sang shortly before being killed with gene activity in zebra finches that weren't singing.
Singing increased the activity of 31 genes and decreased the activity of two, the researchers report in a paper to be published online next week in the Proceedings of the National Academy of Sciences. Although these genes probably represent only about a third of those whose activity is altered during singing, they are surprisingly diverse, with roles in intracellular and synaptic signaling and protein modification and transport, among others, Jarvis says. He speculates that singing depletes neurons of the protein products of these genes--and requires increased gene activity to replace them.
Jarvis and colleagues also showed that they can overexpress genes in the zebra finch brain--a potentially valuable tool for investigating a gene's role in behavior. By manipulating the activity of individual genes, Jarvis eventually hopes to determine which ones are essential for vocal learning. That may give clues to why some species don't have this behavior, he says.
The paper shows that genomic tools for songbird research are getting closer to those for other lab animals, says Fernando Nottebohm, a neuroethologist who studies bird song at Rockefeller University in New York City. It's just a hint of what's to come, adds David Clayton, a geneticist at the University of Illinois, Urbana-Champaign, who's leading a collaborative effort of 16 laboratories working on songbird genomics. A preliminary draft of the zebra finch genome is now being assembled, Clayton says, and much larger DNA libraries and microarrays are in the works: "There's going to be a flood of stuff coming out very soon."