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在雷特综合征小鼠模型中,尽管环境丰富化对行为有挽救作用,但前额叶连接仍持续中断。

Persistent Disruptions in Prefrontal Connectivity Despite Behavioral Rescue by Environmental Enrichment in a Mouse Model of Rett Syndrome.

作者信息

Ährlund-Richter Sofie, Harpe Jonathan, Fernandes Giselle, Lam Ruby, Sur Mriganka

机构信息

The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.

出版信息

J Comp Neurol. 2025 Jul;533(7):e70073. doi: 10.1002/cne.70073.

Abstract

Rett syndrome, a neurodevelopmental disorder caused by loss-of-function mutations in the MECP2 gene, is characterized by severe motor, cognitive, and emotional impairments. Some of the deficits may result from changes in cortical connections, especially downstream projections of the prefrontal cortex (PFC), which may also be targets of restoration following rearing conditions such as environmental enrichment that alleviate specific symptoms. Here, using a heterozygous Mecp2 female mouse model closely analogous to human Rett syndrome, we investigated the impact of early environmental enrichment on behavioral deficits and PFC connectivity. Behavioral analyses revealed that enriched housing rescued fine motor deficits and reduced anxiety, with enrichment-housed Mecp2 mice performing comparably to wild-type (WT) controls in rotarod and open field assays. Anatomical mapping of top-down anterior cingulate cortex (ACA) projections demonstrated altered PFC connectivity in Mecp2 mice, with increased axonal density in the somatosensory cortex and decreased density in the motor cortex compared to WT controls. ACA axons revealed shifts in hemispheric distribution, particularly in the medial network regions, with Mecp2 mice exhibiting reduced ipsilateral dominance. These changes were unaffected by enriched housing, suggesting that structural abnormalities in PFC connectivity persist despite behavioral improvements. Enriched housing rescued brain-derived neurotrophic factor (BDNF) levels in the hippocampus but failed to restore BDNF levels in the PFC, consistent with the persistent deficits observed in prefrontal axonal projections. These findings highlight the focal nature of changes induced by reduction of MeCP2 and by exposure to environmental enrichment and suggest that environmental enrichment starting in adolescence can alleviate behavioral deficits in Mecp2 mice without reversing abnormalities in large-scale cortical connectivity.

摘要

雷特综合征是一种由MECP2基因功能丧失突变引起的神经发育障碍,其特征为严重的运动、认知和情感障碍。其中一些缺陷可能源于皮质连接的变化,尤其是前额叶皮质(PFC)的下游投射,这些投射也可能是诸如环境富集等饲养条件改善特定症状后恢复的靶点。在此,我们使用一种与人类雷特综合征极为相似的杂合Mecp2雌性小鼠模型,研究了早期环境富集对行为缺陷和PFC连接性的影响。行为分析表明,丰富饲养环境挽救了精细运动缺陷并减轻了焦虑,在转棒试验和旷场试验中,处于丰富饲养环境的Mecp2小鼠表现与野生型(WT)对照相当。自上而下的前扣带回皮质(ACA)投射的解剖图谱显示,Mecp2小鼠的PFC连接性发生改变,与WT对照相比,体感皮质中的轴突密度增加,运动皮质中的密度降低。ACA轴突显示出半球分布的变化,特别是在内侧网络区域,Mecp2小鼠的同侧优势降低。这些变化不受丰富饲养环境的影响,这表明尽管行为有所改善,但PFC连接性的结构异常仍然存在。丰富饲养环境挽救了海马体中脑源性神经营养因子(BDNF)的水平,但未能恢复PFC中的BDNF水平,这与前额叶轴突投射中观察到的持续缺陷一致。这些发现突出了MeCP2减少和环境富集所诱导变化的局部性质,并表明青春期开始的环境富集可以减轻Mecp2小鼠的行为缺陷,而不会逆转大规模皮质连接性的异常。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/2b24/12269803/9d6549d80c22/CNE-533-e70073-g002.jpg

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