Çalışkan Gürsel, Lacalle Sara Enrile, Kul Emre, Del Ángel Miguel, Zambrano Allison Loaiza, Hukema Renate, Santos Mónica, Stork Oliver
Research Group "Synapto-Oscillopathies", Institute of Biology, Otto-von-Guericke-University, D 39120 Magdeburg, Germany.
Department of Genetics and Molecular Neurobiology, Institute of Biology, Otto-von-Guericke University, D 39120 Magdeburg, Germany.
Brain. 2025 Jun 2. doi: 10.1093/brain/awaf203.
Fragile X-associated tremor/ataxia syndrome (FXTAS) is a late-onset neurodegenerative disorder caused by a preCGG repeat expansion in the FMR1 gene. Individuals with the FMR1 premutation often exhibit neuropsychiatric symptoms before FXTAS onset, leading to the identification of fragile X-associated neuropsychiatric disorders (FXAND). Rodent models of FXTAS show motor impairments, pathological intranuclear inclusions, and heightened anxiety. However, the early onset of neuropsychiatric features and underlying mechanisms remain poorly understood. To address the above issues, we used the doxycycline (dox)-inducible 90CGG mouse model, with transgene activation at two developmental stages: adolescence and young adulthood. Mice were evaluated in a behavioural battery to assess anxiety-like behaviour, exploration, and motor coordination and learning. Next, we conducted a combination of ex vivo extracellular local field potential recordings to measure synaptic physiology and oscillatory activity in the limbic system, particularly in the basolateral amygdala (BLA) and ventral hippocampus (vH) regions. Parvalbumin interneurons and intranuclear inclusions in the amygdala and hippocampus were investigated by immunofluorescence, while mass spectrometry and gene set enrichment were used to identify differentially expressed proteins molecular pathways. Adolescent 90CGG mice displayed early-onset hyperactivity, transitioning to heightened anxiety in young adulthood, coinciding with the accumulation of intranuclear inclusions in the BLA and vH. Electrophysiological analysis revealed augmented gamma oscillations in the vH, emerging during adolescence and persisting in young adulthood. These changes correlated with a reduction in parvalbumin interneurons in these regions, and together likely contribute to enhanced BLA excitability and impaired vH plasticity. Finally, proteomic analysis of the vH revealed altered proteins linked to attention deficit hyperactivity disorder in adolescence and anxiety/depression in adulthood, aligning well with behavioural findings. Importantly, these behavioural, electrophysiological, and cellular alterations were reversible upon transgene inactivation. This study reveals a temporal progression of CGG premutation effects on behaviour, from hyperactivity to heightened anxiety to late onset motor dysfunction. Moreover, these findings provide altered network activity in the limbic system as a putative mechanism in neuropsychiatric features of premutation carriers.
脆性X相关震颤/共济失调综合征（FXTAS）是一种迟发性神经退行性疾病，由FMR1基因中的前CGG重复序列扩增引起。携带FMR1前突变的个体在FXTAS发病前常表现出神经精神症状，从而导致脆性X相关神经精神障碍（FXAND）的发现。FXTAS的啮齿动物模型表现出运动障碍、病理性核内包涵体和焦虑加剧。然而，神经精神特征的早期发作及其潜在机制仍知之甚少。为了解决上述问题，我们使用了强力霉素（dox）诱导的90CGG小鼠模型，在两个发育阶段激活转基因：青春期和成年早期。对小鼠进行行为测试，以评估焦虑样行为、探索行为以及运动协调和学习能力。接下来，我们进行了离体胞外局部场电位记录，以测量边缘系统，特别是基底外侧杏仁核（BLA）和腹侧海马体（vH）区域的突触生理学和振荡活动。通过免疫荧光研究杏仁核和海马体中的小白蛋白中间神经元和核内包涵体，同时使用质谱分析和基因集富集来鉴定差异表达的蛋白质分子途径。青春期的90CGG小鼠表现出早期多动，成年早期转变为焦虑加剧，这与BLA和vH中核内包涵体的积累同时发生。电生理分析显示，vH中的γ振荡增强，在青春期出现并持续到成年早期。这些变化与这些区域小白蛋白中间神经元的减少相关，共同可能导致BLA兴奋性增强和vH可塑性受损。最后，对vH的蛋白质组学分析揭示了与青春期注意力缺陷多动障碍和成年期焦虑/抑郁相关的蛋白质改变，与行为学研究结果高度吻合。重要的是，这些行为、电生理和细胞改变在转基因失活后是可逆的。这项研究揭示了CGG前突变对行为影响的时间进程，从多动到焦虑加剧再到迟发性运动功能障碍。此外，这些发现表明边缘系统中网络活动的改变是前突变携带者神经精神特征的一种潜在机制。
