Epigenetic stability in the adult mouse cortex under conditions of pharmacologically induced histone acetylation

Epigenetic mechanisms regulate cue memory underlying discriminative behavior

The burgeoning field of neuroepigenetics has introduced chromatin modification as an important interface between experience and brain function. For example, epigenetic mechanisms like histone acetylation and DNA methylation operate throughout a lifetime to powerfully regulate gene expression in the brain that is required for experiences to be transformed into long-term memories. This review highlights emerging evidence from sensory models of memory that converge on the premise that epigenetic regulation of activity-dependent transcription in the sensory brain facilitates highly precise memory recall. Chromatin modifications may be key for neurophysiological responses to transient sensory cue features experienced in the "here and now" to be recapitulated over the long term. We conclude that the function of epigenetic control of sensory system neuroplasticity is to regulate the amount and type of sensory information retained in long-term memories by regulating neural representations of behaviorally relevant cues that guide behavior. This is of broad importance in the neuroscience field because there are few circumstances in which behavioral acts are devoid of an initiating sensory experience.

Suberoylanilide hydroxamic acid (SAHA) alleviates the learning and memory impairment in rat offspring caused by maternal sevoflurane exposure during late gestation

Recent studies have shown that sevoflurane can cause long-term neurotoxicity and learning and memory impairment in developing and progressively neurodegenerative brains. Sevoflurane is a widely used volatile anesthetic in clinical practice. Late gestation is a rapidly developing period in the fetal brain, but whether sevoflurane anesthesia during late gestation affects learning and memory of offspring is not fully elucidated. Histone deacetylase 2 (HDAC2) plays an important regulatory role in learning and memory. This study examined the effect of maternal sevoflurane exposure on learning and memory in offspring and the underlying role of HDAC2. The Morris water maze (MWM) test was used to evaluate learning and memory function. Q-PCR and immunofluorescence staining were used to measure the expression levels of genes related to learning and memory. The results showed that sevoflurane anesthesia during late gestation impaired learning and memory in offspring rats (e.g., showing increase of the escape latency and decrease of the platform-crossing times and target quadrant traveling time in behavior tests) and upregulated the expression of HDAC2, while downregulating the expression of the cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) and the N-methyl-D-aspartate receptor 2 subunit B (NR2B) mRNA and protein in the hippocampus of offspring in a time-dependent manner. HDAC2 inhibitor suberoylanilide hydroxamic acid (SAHA) treatment alleviated all of these changes in offspring rats. Therefore, the present study indicates that sevoflurane exposure during late gestation impairs offspring rat's learning and memory via upregulation of the expression of HDAC2 and downregulation of the expression of CREB and NR2B. SAHA can alleviate these impairments.

Variation among intact tissue samples reveals the core transcriptional features of human CNS cell classes

It is widely assumed that cells must be physically isolated to study their molecular profiles. However, intact tissue samples naturally exhibit variation in cellular composition, which drives covariation of cell-class-specific molecular features. By analyzing transcriptional covariation in 7,221 intact CNS samples from 840 neurotypical individuals, representing billions of cells, we reveal the core transcriptional identities of major CNS cell classes in humans. By modeling intact CNS transcriptomes as a function of variation in cellular composition, we identify cell-class-specific transcriptional differences in Alzheimer's disease, among brain regions, and between species. Among these, we show that PMP2 is expressed by human but not mouse astrocytes and significantly increases mouse astrocyte size upon ectopic expression in vivo, causing them to more closely resemble their human counterparts. Our work is available as an online resource ( http://oldhamlab.ctec.ucsf.edu/ ) and provides a generalizable strategy for determining the core molecular features of cellular identity in intact biological systems.