Figure 1.

Epigenetic mechanisms regulate cell type-specific gene expression involved in memory storage. Histone modifications, such as acetylation and methylation, regulate gene expression in response to experience (e.g., Mews et al., 2017). Newly developed sequencing technology enables the study of gene expression at the single-cell level and allows insight into the enormous heterogeneity of gene activity profiles within defined neuronal populations. For example, snRNA-seq performed on hippocampal brain tissue enables cluster analysis that groups individual single-cell transcriptomes by subregion and cell type. This approach can identify sets of marker genes whose expression distinguishes any such cluster. Shown is a projection of individual cells following global dimensionality reduction that congregate into clusters representing the hippocampal subregions CA1, CA2, and CA3, the subiculum (SUB1-SUB3), the dentate gyrus (DG), and GABAergic interneurons (GABA). Epigenetic mechanisms also act at the synapse, where microRNAs and lncRNAs regulate the localized translation and stability of mRNA transcripts that encode proteins central to synaptic plasticity (Park et al., 2017; Madugalle et al., 2020).