Targeting acetyl-CoA metabolism attenuates the formation of fear memories through reduced activity-dependent histone acetylation

Histone acetylation is a key component in the consolidation of long-term fear memories, which are models for highly resilient and durable memory. Histone acetylation is fueled by acetyl-CoA and recently, nuclear-localized metabolic enzymes that produce this metabolite have emerged as direct and local regulators of histone acetylation. In particular, Acetyl-coA synthetase 2 (ACSS2) mediates histone acetylation in the mouse hippocampus. However, whether ACSS2 regulates long-term fear memory remains to be determined. Here, we show that Acss2 knockout is well-tolerated in mice, yet the Acss2 null mouse exhibits reduced acquisition of long-term fear memory. Loss of Acss2 leads to reductions in both histone acetylation and expression of critical learning and memory-related genes in the dorsal hippocampus, specifically following fear conditioning. Further, systemic administration of blood-brain-barrier (BBB)-permeable Acss2 inhibitors during the consolidation window reduces fear memory formation in mice and rats, and reduces anxiety in a predator-scent-stress (PSS) paradigm. Our findings suggest that nuclear acetyl-CoA metabolism via ACSS2 plays a critical, previously unappreciated role in the formation of fear memories. Included are two separately analyzed experiments that used RNA-seq to examine the transcriptome in the hippocampus from mice on a C57BL6/J background harboring a deletion of the metabolic gene Acss2. Experiment 1 (6 samples) consists of whole hippocampi processed from 3 genotypes (Acss2 WT[reference], Acss2 Het, and Acss2 KO), with two replicates each. All samples were processed together. Experiment 2 (17 samples) consists of 2 genotypes (Acss2 WT, Acss2 KO), 2 conditions (homecage-housed[reference], and fear conditioned). Replicates included are: 5 replicates WT untreated, 3 replicates WT fear conditioned, 5 replicates ACSS2- untreated, 4 replicates ACSS2- fear conditioned.组蛋白乙酰化（Histone acetylation）是长期恐惧记忆巩固过程中的关键环节，而长期恐惧记忆本身便是高稳定性、持久性记忆的研究模型。组蛋白乙酰化的发生依赖乙酰辅酶A（acetyl-CoA）供能，近年来，定位于细胞核内、可合成该代谢物的代谢酶已被证实为组蛋白乙酰化的直接局部调控因子。其中，乙酰辅酶A合成酶2（Acetyl-coA synthetase 2，ACSS2）可介导小鼠海马体中的组蛋白乙酰化。然而，ACSS2是否参与调控长期恐惧记忆仍有待阐明。本研究证实，Acss2基因敲除在小鼠中具有良好耐受性，但Acss2敲除小鼠的长期恐惧记忆获得能力显著下降。Acss2缺失会导致小鼠背侧海马体中的组蛋白乙酰化水平以及关键学习记忆相关基因的表达水平均出现降低，该效应特指于恐惧条件化训练后产生。此外，在记忆巩固窗口期内通过全身给药给予可透过血脑屏障（blood-brain-barrier，BBB）的ACSS2抑制剂，可降低小鼠与大鼠的恐惧记忆形成能力，并在捕食者气味应激（predator-scent-stress，PSS）范式中缓解焦虑样行为。本研究结果表明，经由ACSS2介导的细胞核乙酰辅酶A代谢，在恐惧记忆形成过程中发挥了此前未被认知的关键作用。本数据集包含两项独立分析的实验，均通过RNA测序（RNA-seq）检测了C57BL/6J背景、携带Acss2代谢基因缺失的小鼠海马体转录组。实验1共包含6个样本：分别取自3种基因型（Acss2野生型[Acss2 WT，reference]、Acss2杂合子[Acss2 Het]与Acss2敲除型[Acss2 KO]小鼠的全海马体组织，每种基因型设置2个生物学重复），所有样本同步完成实验处理。实验2共包含17个样本，涉及2种基因型（Acss2 WT与Acss2 KO）以及2种处理条件（笼养对照组[homecage-housed，reference]与恐惧条件化组）。样本分组如下：未处理野生型组5个重复、恐惧条件化野生型组3个重复、未处理Acss2敲除组5个重复、恐惧条件化Acss2敲除组4个重复。