Syndicate content

Songbird Genome Offers Clues to “Learned Vocalizations”

The first genome of a songbird (the male zebra finch), has been sequenced and has revealed secrets of the relatively rare ability to communicate through “learned vocalizations.” This ability has been documented in just a few other animals, including other songbirds, parrots, hummingbirds, bats, whales, and humans. The ability is lacking in chickens, the only other bird to have had its genome sequenced, and is also absent in female zebra finches. The current research indicates that the ability seems to depend, in part, on the extensive involvement of non-coding RNAs (ncRNAs). A major reason the researchers decided to study the zebra finch genome was the male bird's ability to learn complex songs from its father. At first, a fledgling male finch makes seemingly random sounds, much like the babble of human babies. With practice, the young bird eventually learns to imitate its father's song. Once the bird has mastered the family song, it will sing that song for the rest of its life and pass the song on to the next generation. Though female finches do perceive and remember songs, researchers suggest that their inability to learn songs may be due to differences in sex hormones, as well as chromosomal sex differences affecting the brain. The chicken and zebra finch genomes are similar in many ways. Both have approximately one billion DNA base pairs--roughly one-third the size of a human genome. However, researchers discovered that some genes associated with vocal behavior have undergone accelerated evolution in the finch. For example, they found a disproportionately high number of ion channel genes among the 49 genes in the finch genome that are suppressed, or turned off, in response to song. Human ion channel genes have been shown to play key roles in many aspects of behavior, neurological function, and disease. Consequently, the researchers suspect that the evolution of this group of genes in songbirds may be essential for learned vocalization.

While many parts of the genome are engaged during vocal communication, one surprising finding was the extensive involvement of ncRNAs. Analysis of the zebra finch genome sequence suggested that ncRNAs, which have been proposed to contribute to the evolution of greater complexity in humans and other animals, may be a driving force behind learned vocal communication.

"These findings will transform scientific research on the songbird system," said Dr. Story Landis, director of the National Institute of Neurological Disorders and Stroke (NINDS), which provided some of the support for the study. "Although scientists understand much about how songbirds acquire and modify their vocal patterns, the availability of the genome sequence will allow insight into the molecular underpinnings of this natural behavior. This could lead to better understanding of learning and memory, neural development and adaptation, and speech and hearing disorders."

"By comparing the finch genome with the human genome, we should now be able to expand our understanding of learned vocalization in humans. Such information may help researchers who are striving to develop new ways to diagnose and treat communication disorders, such as stuttering and autism," said Dr. Eric Green, director of the National Human Genome Research Institute, which also provided funding for the songbird research.

This work was carried out by scientists at the Washington University School of Medicine and an international team of collaborators, and was published in the April 1, 2010 issue of Nature. The image is courtesy of L. Brian Stauffer, University of Illinois News Bureau. [Press release] [Nature abstract]