Gene regulatory co-option drives birdsong neural circuit specialization [overexpression snRNA-Seq]

Yet the molecular mechanisms driving motor circuit evolution remain poorly understood. Birdsong, a learned complex motor skill with parallels to human speech, is controlled by a dedicated neural circuit -- the song system -- that is distinguished from nearby sensorimotor regions by molecular, physiological, and connectivity specializations.

By profiling gene expression and chromatin accessibility in the songbird brain, we have found that each projection neuron type in the song system has a molecularly similar sister neuron type in adjacent non-song regions that lacks specialized gene expression and is transcriptionally similar to neurons in the chicken brain. The GRNs controlled by transcription factors \textit{MAFB} and \textit{EMX2}, typically active in fast-spiking interneurons and astrocytes, are specifically active in song-dedicated extratelencephalic projection neurons.