FoxP2Expression in Avian Vocal Learners and Non-Learners

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Abstract
Most vertebrates communicate acoustically, but few, among them humans, dolphins and whales, bats, and three orders of birds, learn this trait.FOXP2is the first gene linked to human speech and has been the target of positive selection during recent primate evolution. To test whether the expression pattern ofFOXP2is consistent with a role in learned vocal communication, we cloned zebra finchFoxP2and its close relativeFoxP1and compared mRNA and protein distribution in developing and adult brains of a variety of avian vocal learners and non-learners, and a crocodile. We found that the protein sequence of zebra finch FoxP2 is 98% identical with mouse and human FOXP2. In the avian and crocodilian forebrain,FoxP2was expressed predominantly in the striatum, a basal ganglia brain region affected in patients withFOXP2mutations. Strikingly, in zebra finches, the striatal nucleus Area X, necessary for vocal learning, expressed moreFoxP2than the surrounding tissue at post-hatch days 35 and 50, when vocal learning occurs. In adult canaries,FoxP2expression in Area X differed seasonally; moreFoxP2expression was associated with times when song becomes unstable. In adult chickadees, strawberry finches, song sparrows, and Bengalese finches, Area X expressedFoxP2to different degrees. Non-telencephalic regions in both vocal learning and non-learning birds, and in crocodiles, were less variable in expression and comparable with regions that expressFOXP2in human and rodent brains. We conclude that differential expression ofFoxP2in avian vocal learners might be associated with vocal plasticity.