Avian model organisms, including songbirds (zebra finches, canaries, starlings), parrots, chicken, quail, and pigeons have contributed much to our understanding of brain function and disorders that affect neural development, function, and cognition. Furthermore, many bird groups are being increasingly recognized as having enlarged brains that are capable of advanced cognitive and learning skills that rival and even surpass those in mammals. Despite these contributions, we still lack a clear understanding of how the molecular brain organization in birds compares to that in mammals, including humans. To address this gap, we utilized resource building funds from the NINDS and NIGMS to develop the Zebra finch Expression Brain Atlas (ZEBrA), currently the largest in situ hybridization database of brain gene expression for any avian species. ZEBrA is a publicly accessible website with a database containing >3,500 high resolution digital images of brain sections from adult male zebra finches that are aligned to a reference histological atlas, and hybridized to reveal the brain-wide expression of >720 genes of relevance for brain development, physiology, plasticity, and vocal learning. Notably, nearly 200 of these genes have been linked to speech and/or neural disorders in humans, and/or constitute shared molecular specializations of analogous brain regions for vocal production and learning in birds and humans. Many expression patterns in ZEBrA have also revealed previously unsuspected subdomains that are not visible with conventional histological techniques, as well as enrichments in discrete nuclei within circuits that underlie specific behaviors (e.g., vocal production and learning). Despite these findings, a quantitative analysis of the ZEBrA database has not yet been performed, which has hindered our ability to perform accurate comparative analyses with similar resources from mammals (e.g. Allen Institute's Mouse Brain Atlas - MBA). We propose here to use image analysis methods to extract equivalent regional gene expression data from both databases. The outcomes in finch will define regional molecular profiles of major brain areas and specialized nuclei of the vocal control and learning circuitry, the latter a cognitive trait of high relevance to human speech and language. The ZEBrA and MBA data will also be compared to derive insights into how avian and mammalian brains relate or diverge molecularly. Such insights will help to further validate the use of avian species as informative model organisms for understanding the molecular basis of brain function and cognitive skills, as well as the genetic basis of brain disorders of high relevance to humans.
Although avian species have long been important model organisms for studying brain structure-function relationships and disorders that affect neural development, cognition, and behavior, a clear understanding of the molecular organization of the avian brain, as it relates to those of mammals, including humans, has been lacking. Here we propose a comprehensive analysis of the Zebra finch Expression Brain Atlas (ZEBrA) with major goals of defining the molecular profiles of major avian brain areas and specialized nuclei of the vocal learning circuitry, and comparing these profiles to those generated for the Allen Institute's Mouse Brain Atlas. Expected outcomes will include a better understanding of similarities and divergences in the molecular brain architecture of birds and mammals, as well as novel insights into the genetic basis of complex traits like speech, language, and related cognitive functions of high relevance to humans.
