In musicals, characters communicate even mundane information through song. Similarly, some birds use songs to communicate environmental and reproductive information. How do songbirds learn and perform songs? Li et al. report freely available tools to identify genes important in song development and production in a recent article in Proceedings of the National Academy of Sciences.
Only male zebra finches sing. During juvenile development, they learn a template song from their fathers that they copy to develop their own songs. The high vocal center (HVC) brain nucleus is important in learning and producing songs in juvenile and adult zebra finches, respectively.
The authors generated cDNA libraries from zebra finch brains at four developmental time points, from embryonic development through sexual maturity. In all, they identified 9845 cDNA sequences, 5866 of which represented distinct genes. The authors identified most of the sequences in their dataset only once and found few genes represented repeatedly.
Between 30 and 50 days of age, male zebra finches develop their own songs and become independent. The authors calculated the rate of gene discovery for each cDNA library as the percent of genes recovered from the total number of expressed sequence tags. They found the highest rate of gene discovery in the cDNA library from 30- to 50-day-old zebra finches, suggesting that song development induces gene expression.
Gene Ontology analysis showed that different groups of genes were active at different times during zebra finch development. Relative to the other developmental time points, the cDNA library from embryonic zebra finches had the most genes involved in transcription, translation, cell cycle and RNA processing. In contrast, the cDNA library from 1- to 20-day-old zebra finches had the most genes involved in neuron development, apoptosis and cell signaling. Zebra finches reach sexual maturity at 90 days of age. The cDNA library from 60- to 90-day-old zebra finches had the most genes that function at the synapse.
The authors printed cDNA microarrays from the thousands of clones they identified in the zebra finch brain. They found 404 genes upregulated and 408 genes downregulated in HVC relative to the rest of the brain. Many of the genes that were differentially regulated in HVC, including parvalbumin, calmodulin-binding transcription factor and calcineurin, are important in calcium signaling, suggesting that HVC neurons may have different electrophysiological properties relative to other neurons in the zebra finch brain.
Songbirds may use similar genes in song production. Canaries are songbirds that breed seasonally. The canary HVC showed similar regulation of nearly 50% of the genes upregulated, including parvalbumin and calmodulin-binding transcription factor, and downregulated, including reelin and Purkinje cell protein 4, in the zebra finch HVC relative to the rest of the brain. The authors found similar localization patterns of these genes in other nuclei important in song production in both zebra finches and canaries.
The authors have made zebra finch microarrays and an online database of zebra finch expressed sequence tags freely available to the community. Because neurons in HVC are continually replaced even in adulthood, the regulation of genes in HVC may shed some light on mechanisms important in neurogenesis.