Project Summary A neuron’s activity history is precisely encoded in its gene expression profile. This molecular encoding is achieved via transcriptional regulatory programs specific to distinct features of activity patterns. In particular, an activating stimulus evokes unique, temporally segregated waves of transcription as a function of its duration. The regulatory mechanisms which orchestrate the transduction of stimuli duration into temporal waves of transcription have been described in heterogenous populations of neuronal cell types. However, whether similar or distinct mechanisms operate to translate activity patterns into specific expression programs in defined neuronal subtypes in vivo is unknown. We have established AFD, a pair of sensory neurons in C. elegans, as a cellular model in which to describe the regulatory pathways that transduce neuronal activity into gene expression changes. Via AFD specific RNA-Seq, we have shown that the duration of temperature experience is encoded in AFD by temporal waves of gene expression reflecting similar waves described in more complex organisms. These temporally regulated gene expression changes are critical for modulating AFD functions. Preliminarily, bioinformatics analyses and experimental manipulations suggest that the CREB transcription factor together with the SPR-4/REST repressor shape the temporal kinetics of temperature- induced upregulation in a subset of genes. The goal of this proposal is to provide a systematic mechanistic description of the molecular pathways by which the duration of temperature experience is encoded in the molecular profile of AFD. Experiments proposed in Aim 1 will employ a multifaceted approach including bioinformatics analyses, experimental deletions, and AFD-specific ATAC-Seq to identify cis-acting regulatory motifs which direct activity-dependent transcription in AFD as a function of stimulus duration, and to determine their role in the epigenetic control of gene expression. In Aim 2