Histone variant H2BE enhances chromatin accessibility in neurons to promote synaptic gene expression and long-term memory.

Regulation of histones occurs through multiple mechanisms including exchange with histone variants. Unlike canonical histones, variants are replication-independent and therefore accumulate in post-mitotic cells such as neurons. While recent findings link variants to neurological and neuropsychiatric disorders, few are well studied in the context of the brain. H2BE is the single H2B variant found outside germline tissues, yet its expression and effects on chromatin remained unclear. We applied new tools including novel antibodies, biochemical assays, and sequencing approaches to reveal broad H2BE expression in the brain and its role in regulating chromatin structure, neuronal transcription, and mouse behavior. H2BE is enriched at promoters and enhances chromatin accessibility. We further identify a single amino acid driving these accessibility changes. Lastly, we show that H2BE is critical for synaptic gene expression and long-term memory. Together, these data reveal a novel mechanism linking histone variants to chromatin regulation and neuronal function underlying memory.