Gelot Antoinette-Bernabe, Draia-Nicolau Tangra Ondina, Mathieu Rémi, Silvagnoli Lucas, Watrin Françoise, Cardoso Carlos, Manent Jean-Bernard, de Chevigny Antoine, Represa Alfonso
INMED, INSERM, Aix-Marseille University, Marseille, France.
Neuropathology, Hôpital Trousseau, Assistance Publique-Hôpitaux Parisiens, Sorbonne Université, Paris, France.
Epilepsia. 2025 Jun;66(6):2099-2109. doi: 10.1111/epi.18325. Epub 2025 Feb 20.
Mutations in genes of the mTOR pathway have been identified as a major cause of hemimegalencephaly (HMG), focal cortical dysplasia type II, and tuberous sclerosis, cortical malformations associated with epilepsy. These conditions are characterized at the cellular level by increased size of pyramidal neurons that grow with dysmorphic features and in some cases by the presence of giant balloon cells. Our previous research in tuberous sclerosis has shown that parvalbumin (Pvalb) and calbindin immunoreactive cells in cortical and subcortical tuberal lesions show cytomegalic features, suggesting the involvement of GABAergic cells in mTOR-related pathologies. In the present report, we propose to deepen our understanding of the role of interneurons in mTOR-related cortical malformations by analyzing the maturation of Pvalb neurons in fetal samples of HMG.
We performed immunohistochemical staining of cortical samples from individuals with HMG from 21 gestational weeks to 10 postnatal months. The study focused on Pvalb cells, and pS6 counterstaining was performed to assess the activation of the mTOR pathway. To investigate the pathomechanisms behind the cytomegalic features, we examined mTOR pathway gene expression in Pvalb interneurons and cortical projection neurons using a single-cell transcriptomic atlas of the human neocortex.
Our results revealed cytomegalic features in Pvalb interneurons, indicating abnormal development in HMG patients compared to controls. This phenotype progressively worsened over time, suggesting ongoing developmental abnormalities associated with mTOR dysregulation, which may underlie the pathology of cortical malformations in HMG. Our transcriptomic data revealed similar expression patterns of mTOR and its upstream regulators in both Pvalb and glutamatergic neurons during development, suggesting that mTOR pathway disorders may induce similar phenotypes in both cell types.
The present data suggest that Pvalb interneurons are involved in the development of mTOR-related cortical dysplasia and that they may be a contributor to the clinical phenotype of these patients.
哺乳动物雷帕霉素靶蛋白（mTOR）信号通路相关基因突变已被确定为半侧巨脑症（HMG）、II型局灶性皮质发育不良和结节性硬化症（与癫痫相关的皮质畸形）的主要病因。这些病症在细胞水平上的特征是锥体细胞增大，伴有畸形特征，在某些情况下还存在巨大的气球样细胞。我们之前对结节性硬化症的研究表明，皮质和皮质下结节性病变中表达小白蛋白（Pvalb）和钙结合蛋白的免疫反应性细胞呈现细胞肿大特征，提示γ-氨基丁酸能（GABAergic）细胞参与了mTOR相关的病理过程。在本报告中，我们建议通过分析HMG胎儿样本中Pvalb神经元的成熟情况，加深对中间神经元在mTOR相关皮质畸形中作用的理解。
我们对妊娠21周后至出生后10个月的HMG患者的皮质样本进行了免疫组织化学染色。该研究聚焦于Pvalb细胞，并进行磷酸化核糖体蛋白S6（pS6）复染以评估mTOR信号通路的激活情况。为了研究细胞肿大特征背后的发病机制，我们使用人类新皮质单细胞转录组图谱，检测了Pvalb中间神经元和皮质投射神经元中mTOR信号通路基因的表达。
我们的结果显示Pvalb中间神经元存在细胞肿大特征，表明与对照组相比，HMG患者存在异常发育。这种表型随时间逐渐恶化，提示与mTOR失调相关的持续发育异常，这可能是HMG皮质畸形病理的基础。我们的转录组数据显示，在发育过程中，mTOR及其上游调节因子在Pvalb和谷氨酸能神经元中具有相似的表达模式，提示mTOR信号通路紊乱可能在两种细胞类型中诱导相似的表型。
目前的数据表明，Pvalb中间神经元参与了mTOR相关皮质发育不良的发生发展，并且它们可能是这些患者临床表型的一个促成因素。
