Cross-frequency coupling analysis in amyotrophic lateral sclerosis as potential biomarker and therapeutic target

肌萎缩性侧索硬化症（ALS）的特点是分别位于大脑皮层和脑干/脊髓的上、下运动神经元（UMN和LMN）退行性变。ALS的诊断主要依靠LMN体征，这在其他疾病中也很常见。此外，评估治疗疗效的金标准仍然主要基于LMN评估，不包括UMN评估。这在一定程度上是因为LMN退行性变可以掩盖UMN的迹象，使得更难以忠实地检测到UMN功能障碍，从而延迟了治疗的开始并限制了临床试验的早期纳入。为了规避这一限制，我们在此建议评估皮质功能障碍（Ct Dysf）以提高ALS的诊断。依靠经颅磁刺激（TMS）和磁共振成像（MRI）的方法揭示了ALS的早期皮质功能障碍，其在LMN症状发作之前与生存负相关，并且不存在于仅针对LMN的疾病中。因此，结合LMN征象，Ct Dysf有助于ALS的诊断和预后。虽然TMS和MRI在常规临床应用中受到限制，但脑电图（EEG）由于其高时间分辨率和最近的方法进步，包括源成像和交叉频率耦合（CFC）评估，有可能满足对Ct Dysf定量和可靠的生物标志物的需求。重要的是，脑电图可以很容易地在患者和动物模型中实施，从而促进多中心研究的转化，为评估更有可能成功的新疗法铺平道路。基于我们的初步数据，我们假设改变的CFC可以作为ALS患者Ct Dysf的早期定量生物标志物。因此，我们聚集了德国和法国的临床前和临床团队，他们在ALS方面具有知名的专业知识，1)测试改变的CFC是否可能代表ALS患者和症状前基因突变携带者Ct Dysf的一种新的早期生物标志物；2)确定ALS小鼠模型中CFC和Ct Dysf改变的时间、空间和细胞起源；3)生成ALS小鼠模型和患者Ct Dysf细胞和突触起源的计算模型。我们预计在ALS患者和症状前突变携带者中发现CFC的显著损伤，这种损伤将随着疾病的发展而恶化，特别是在感觉运动区域，这是ALS患者首先受到影响的区域。同时，我们希望揭示ALS中CFC改变的细胞和电路基础，并生成全脑振荡动力学模型，以便将来通过靶向已识别的细胞类型促进治疗研究。基于我们的临床前和临床团队之前建立的强有力的合作，FrequALS为强有力改进的ALS诊断管道提供了基础，并将揭示新的基于电路的治疗靶点。

Amyotrophic lateral sclerosis (ALS) is characterized by the degeneration of upper and lower motor neurons (UMN & LMN), located in the cerebral cortex, and the brainstem/spinal cord, respectively. ALS diagnosis mostly relies on LMN signs, which are also common to other diseases. In addition, the gold standard to assess therapy efficacy remains primarily based on LMN evaluation, excluding UMN assessment. This is partly because LMN degeneration can mask UMN signs, making it more difficult to faithfully detect UMN dysfunction, which delays treatment initiation and limits early inclusion in clinical trials. To circumvent this limitation, we here propose to evaluate cortical dysfunction (Ct Dysf) to improve ALS diagnosis. Methods relying on transcranial magnetic stimulation (TMS) and magnetic resonance imaging (MRI) revealed early cortical dysfunction in ALS, that precedes the onset of LMN signs, negatively correlates with survival and is not present in diseases that solely target LMN. Thus, in combination with LMN signs, Ct Dysf could help ensure diagnosis and prognosis of ALS. While TMS and MRI are limited in their routine clinical application, electroencephalogram (EEG) has the potential to meet the need for a quantitative and reliable biomarker of Ct Dysf thanks to its high time resolution and recent methodological advances, including source imaging and the assessment of cross-frequency coupling (CFC). Importantly, EEG can be easily implemented in both patients and animal models, thereby facilitating translational multicentric research, paving the way for the assessment of new therapies with a greater chance of success. Based on our preliminary data, we hypothesize that altered CFC can serve as an early and quantitative biomarker of Ct Dysf in ALS. We have thus gathered German and French preclinical and clinical teams with well-known expertise in ALS to 1) test whether altered CFC may represent a novel and early biomarker of Ct Dysf in patients with ALS and presymptomatic gene mutation carriers; 2) determine the temporal, spatial and cellular origins of altered CFC and Ct Dysf in mouse models of ALS and 3) generate computational models of cellular and synaptic origins of Ct Dysf in ALS mouse models and patients. We anticipate finding a significant impairment of CFC in ALS patients and presymptomatic mutation carriers, which will worsen over the course of the disease, particularly in sensorimotor areas, which are the first to be affected in ALS. In parallel, we expect to unravel the cellular and circuit basis of altered CFC in ALS and to generate a whole-brain oscillatory dynamics model, in order to facilitate therapeutic studies by targeting identified cell types in the future. Building on previously established, strong collaborations between our preclinical and clinical teams, FrequALS is thus providing groundwork for a strongly improved ALS diagnostic pipeline and will unravel novel circuit-based therapeutic targets.