Fig. 1

a. Schematic representation of the experimental flow used by Kim and colleagues. Briefly, cortices were dissected from E16.5 C57BL/6 mouse embryos (far left) and neurons seeded into culture dishes. Neuronal activity was dampened by treatment over night with TTX before depolarizing membranes with KCl. Changes in expression and chromatin were assessed by RNA-seq and ChIP-seq. b. Schematic representation of chromatin state at enhancers and promoters prior to and after KCl treatment. The enhancer and promoter are represented by a tan and green box respectively. Transcription factors and Pol II are indicated. The right facing hooked arrow at the promoter indicates the transcriptional start site. Wavy arrows represent transcripts and their direction of transcription. Below this are stylized representations of ChIP-seq peak profiles for the chromatin modifications H3K4me1 and H3K4me3, the transcription factor NPAS4, co-activator CBP and Pol II. c. Schematic representation showing the impact of the deletion of the Arc promoter on eRNA transcription. Top image shows the wild type Arc enhancer upstream (right side) of the Arc gene locus (left side). Pol II is located at both elements, whereas Serum Response Factor (SRF) is restricted to the enhancer. Bidirectional eRNA transcripts are generated at the enhancer which is represented as the RNA Seq profiles to the far right (black = forward strand; red = reverse strand). The lower image shows the loss of transcripts in the Arc knockout.