Activation of feedforward wiring in adult hippocampal neurons by the bHLH transcription factor Ascl4

Although evidence indicates that the adult brain retains a considerable capacity for circuit formation, adult wiring has not been broadly considered and remains poorly understood. Here, we investigated wiring activation in adult neurons. Based on bioinformatic analyses on a previously published dataset (GSE161619), we identified the basic-helix-loop-helix (bHLH) transcription factor Ascl4 as a potential regulator of adult wiring and show that the AAV-mediated overexpression of Ascl4 can cell autonomously induce wiring in different types of hippocampal neurons of adult mice. The new axons are mainly feedforward and reconfigure synaptic weights in the hippocampal circuit. Mice with rewired circuits do not display signs of pathology and solve spatial problems equally well as controls. Our results demonstrate reprogrammed connectivity by a single transcriptional factor and provide insights into the regulation of brain connectivity in adults.