This finding suggests that the synaptic transmission machinery differs between mammalian and avian species, although it is not clear if such molecular changes translate into functional modifications at the systems level.ĭuplications of a variety of genes relative to chickens or humans, including growth hormone and caspase-3, the latter of which is associated with the induction of apoptosis, and gene family expansions, including of the PAK3 and PHF7 genes, which are involved in dendritic plasticity and transcriptional regulation, respectively, were also found in the zebra finch genome. Curiously, similarly to chickens, zebra finches lack the synapsin I gene, which encodes a phosphoprotein involved in the regulation of neurotransmitter vesicle availability in pre-synaptic membranes. As detailed by the consortium authors, the genome lacks genes that encode milk, salivary and vomeronasal receptor proteins, similarly to what has been documented for the chicken, a non-vocal-learning avian species whose genome was uncovered 6 years ago. The unveiling of the zebra finch genome also provides exciting insights into the evolution of avian and mammalian species. When comparing hearing-driven transcripts with genes thought to have been positively selected in songbirds, a significant over-representation of genes encoding ion channels was uncovered, consistent with robust and complex expression patterns of ion channel-associated transcripts in stations of the song-control circuit. Overall, these findings highlight the role of microRNAs and non-coding RNAs in the control of gene expression in the songbird brain, in addition to the active regulation of transcription factors and their respective target genes. In fact, many of these targets have been identified for the first time and will now enable researchers to develop testable hypotheses about the gene regulatory interactions that are induced during a learned behavior. Changes in transcription factor expression that occurred early after singing were strongly correlated with later modifications in the expression patterns of groups of their predicted target genes.
#Songbird species series#
By using a microarray platform with oligonucleotides generated as part of this project, the songbird genome consortium was able to uncover a series of transcriptional regulators whose expression was modulated by the act of singing.
Singing behavior also drives robust gene expression programs in structures of the song control system, a specialized brain network required for sensorimotor integration and vocal output. Furthermore, known and novel microRNAs were found to be expressed in the auditory forebrain, and their binding sites were detected in the untranslated regions of regulated genes. When birds were stimulated with playbacks of recorded song, thousands of transcripts were upregulated or downregulated, and analyses of their genomic sequences revealed that roughly two-thirds of the downregulated transcripts were non-coding RNAs. It was found that in the auditory forebrain of animals in silent conditions, approximately 40% of the detected transcripts are non-coding, indicating that regulatory microRNAs may have a central role in brain homeostasis. Here, I review some of the most exciting findings of this pioneering effort.Īuditory experience, a fundamental consequence of social interactions within and across songbird species, had been previously shown to strongly affect gene regulatory events in the auditory forebrain. Furthermore, this initial snapshot of the songbird genome should provide critical insights into fundamental scientific questions, including an array of physiological and evolutionary processes. The annotation and sequence coverage of the zebra finch genome will certainly be refined in the years to come, but the initial endeavor is expected to provide a unique platform for modern genomics research in this organism.
These initiatives, along with new zebra finch genome sequences, have resulted in the complete genome sequenced with 17,475 protein-coding genes identified, as well as regulatory regions and non-coding RNAs. Sequencing the zebra finch genome was initiated in 2005 under the Large Scale Genome Sequencing Program of the National Human Genome Research Institute, leveraging prior work in the research community characterizing the zebra finch brain transcriptome. Now an international consortium has unveiled the genome of the zebra finch ( Taeniopygia guttata, Figure 1), along with a multi-layered analysis of its sequence.
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