For the first time, researchers have sequenced the genome of a songbird, reports an international consortium of researchers (Nature 464, 757–762; 2010). This songbird, the zebra finch, is already an established animal model in several biological fields. Other than songbirds, only a few animals, such as whales and humans, can learn vocalizations. Researchers can now study this songbird's genome to better understand the development of learned vocalizations in songbirds and other animals.

Credit: Theodore Scott

Wesley Warren of the University of Washington in St. Louis, MO, and colleagues sequenced the genome of a male zebra finch (Taeniopygia guttata) and then compared this genome with that of a chicken (Gallus gallus), the only other bird whose genome has been sequenced to date. Chickens, whose lineage diverged from that of the zebra finch about 100 million years ago, cannot learn vocalizations. The researchers found that the genomes of the zebra finch and the chicken were generally similar in structure. However, these birds regulate their sex chromosomes in different ways. As only male zebra finches learn songs, this difference in sex chromosome regulation might be related to the zebra finch's singing behavior.

Further analysis of the zebra finch's genome showed that singing significantly altered the expression of about 800 genes in the zebra finch, causing these genes to be expressed at either higher or lower levels. Another recent research study that analyzed gene expression in the auditory forebrain of the zebra finch had shown that when a bird listened to a song, distinct sets of RNA were expressed in different ways. This RNA expression is involved in the bird's ability to learn. Warren and his team mapped these RNAs onto the zebra finch genome and found that many of these RNAs are non-coding. This suggests that some of these “song-responding” RNAs are modulating the expression of other genes instead of directly producing proteins. Based on phylogenomic comparisons between the genes of the chicken, the zebra finch and several different mammals, the team found evidence that some of the zebra finch genes that are regulated by singing or listening to song are rapidly evolving.

The authors explain that their results suggest that non-coding RNAs could be key links that help the zebra finch learn vocal communication. As the process by which male birds learn to sing is similar to how humans learn to speak, further study of the zebra finch genome could help elucidate the molecular mechanisms by which people learn to speak.