Transcriptomics analysis of the hippocampus in Kdm1a/Kdm5c double-inducible forebrain-specific knockouts

Loss or reduced expression of lysine demethylases (KDMs) is linked to neurodevelopmental disorders and intellectual disability. Given the phenotypic similarities between KDM1A and KDM5C deficient mice, and the convergence of both enzymes in maintaining a repressive state via H3K4 demethylation, we examined their functional interaction using double-inducible, forebrain-specific knockouts (dKDM-ifKOs). These mice showed transcriptional and epigenetic dysregulation beyond the additive effects of individual knockouts, including stronger ectopic expression of non-neuronal genes in hippocampal neurons. Thousands of de novo H3K4me3-enriched regions emerged, indicating synergistic disruption of chromatin regulation. In line with these molecular changes, dKDM-ifKOs displayed more severe behavioral impairments than the single ifKOs, along with altered hippocampal expression of ion channels and increased excitability of CA1 pyramidal neurons. These findings underscore the joint role of ID-linked KDMs in regulating cell-type-specific gene silencing and H3K4 methylation levels to safeguard neuronal identity and responsiveness, as well as cognitive function Kdm1af/f, Kdm5cf/f and CamKIIα-CreERT2 mouse strains have been previously described , they are available at public repositories (Jackson Lab stock #23969; MMRRC stock 066789-UCD; and EMMA EM:02125, respectively). Mice were maintained on a C57BL/6J genetic background. The recombinant protein CreERT2 is dependent on tamoxifen (TMX) administration, and its expression is restricted to principal neurons of the forebrain, where CamKIIα is expressed. CaMKIIα–driven, TMX induced Cre recombination results in the elimination of exons 5 and 6 in Kdm1af/f and exons 11 and 12 in Kdm5cf/f . Mice were 2 to 3-month-old at the time of TMX administration.

赖氨酸去甲基化酶（lysine demethylases, KDMs）的缺失或表达降低，与神经发育障碍及智力障碍密切相关。鉴于KDM1A与KDM5C缺陷小鼠的表型相似，且二者均通过H3K4去甲基化维持染色质抑制状态，我们利用双诱导型前脑特异性敲除小鼠（dKDM-ifKOs）探究了二者的功能互作。该双敲除小鼠的转录与表观遗传失调程度超出了单个敲除的加性效应，具体表现为海马神经元中非神经元基因的异位表达显著增强；同时出现数千个从头富集的H3K4me3区域，提示染色质调控存在协同紊乱。与上述分子变化一致，双诱导型前脑特异性敲除小鼠较单个敲除小鼠表现出更严重的行为缺陷，同时伴随海马离子通道表达异常及CA1锥体神经元兴奋性升高。本研究结果证实，与智力障碍相关的KDMs可协同调控细胞类型特异性基因沉默与H3K4甲基化水平，从而维持神经元特性与响应性，保障认知功能。
Kdm1af/f、Kdm5cf/f及CamKIIα-CreERT2小鼠品系此前已有报道，可通过公共资源库获取（杰克逊实验室库存编号#23969、小鼠资源与研究中心（MMRRC）库存编号066789-UCD，以及欧洲小鼠突变体资源库（EMMA）编号EM:02125）。所有小鼠均维持于C57BL/6J遗传背景。重组蛋白CreERT2的活性依赖于他莫昔芬（tamoxifen, TMX）给药，且其表达仅限于表达CamKIIα的前脑主神经元。由CaMKIIα驱动、他莫昔芬诱导的Cre重组可分别敲除Kdm1af/f小鼠的第5、6外显子与Kdm5cf/f小鼠的第11、12外显子。本研究中，给药他莫昔芬时小鼠年龄为2至3月龄。