What role does the singing molecule retinoic acid play during song learning in the zebra finch brain?
Christina Roeske, Doctoral Fellow.
Retinoic acid is primarily known for controlling pattern formation processes during the embryonic development of vertebrates. It is crucial for the development of numerous structures, among them limbs, face, and hindbrain. The idea that retinoic acid also plays a role in learning is relatively new. First evidence came from knockout mice lacking certain retinoic acid receptors. These mice showed poorer spatial learning than their receptor equipped relatives .
That retinoic acid is also important for song learning in the bird brain was suggested for the first time in the course of a gene expression study on the zebra finch brain. A retinoic acid synthesizing enzyme, RalDH, was found to be expressed specifically in parts of the song control system . Interestingly, pharmacological blocking of this enzyme in the song nucleus HVC in juvenile birds lead to impaired song learning. This shows that the retinoic acid signaling pathway is indispensable for normal song learning; however, the mechanisms by which this is achieved remain unclear. I am studying the expression patterns of the different players of the retinoic acid signaling pathway to get a more detailed idea of where exactly retinoic acid is exerting its effect.1. Crandall J, Sakai Y, Zhang J, Koul O, Mineur Y, Crusio WE, McCaffery P (2004) 13-cis-retinoic acid suppresses hippocampal cell division and hippocampal-dependent learning in mice. Proc Natl Acad Sci USA, 2004. 101(14): 5111-5116. 2. Denisenko-Nehrbass NI, Jarvis E, Scharff C, Nottebohm F, Mello CV (2000) Site-Specific Retinoic Acid Production in the Brain of Adult Songbirds. Neuron 27: 359-370