Transcription of a plasticity gene is activated by neuronal hyperpolarization

Long term synaptic plasticity requires transcription in response to changes in neuronal activity. While genes induced by neuronal activity have been extensively studied, genes induced by hyperpolarization are largely unknown. We focused on , a Rho1 GEF whose rhythmic expression drives the daily retraction of the projections of LN circadian pacemaker neurons. We found that transcription is repressed by activity and induced by hyperpolarization in LNs – the opposite of typical activity-regulated genes. is repressed by activity-regulated transcriptional factors including Mef2 and Sr (fly Egr-1) and activated by Toy, a Pax6 transcription factor. transcription is also induced by inactivity. Thus and represent a class of genes induced by hyperpolarization.