Institut du Cerveau-Paris Brain Institute-ICM, Inserm, CNRS, Sorbonne Université, Paris, France.
AP-HP, Hôpitaux Universitaires La Pitié Salpêtrière-Charles Foix, Department of Neurosurgery, Sorbonne Université, Paris, France.
Neuropathol Appl Neurobiol. 2023 Oct;49(5):e12937. doi: 10.1111/nan.12937.
Mesial Temporal Lobe Epilepsy-associated Hippocampal Sclerosis (MTLE-HS) is a syndrome associated with various aetiologies. We previously identified CD34-positive extravascular stellate cells (CD34+ cells) possibly related to BRAF oncogenic variant in a subset of MTLE-HS. We aimed to identify the BRAF oncogenic variants and characterise the CD34+ cells.
We analysed BRAF oncogenic variant by digital droplet Polymerase Chain Reaction in 53 MTLE-HS samples (25 with CD34+ cells) and nine non-expansive neocortical lesions resected during epilepsy surgery (five with CD34+ cells). Ex vivo multi-electrode array recording, immunolabelling, methylation microarray and single nuclei RNAseq were performed on BRAF MTLE-HS and BRAF mutant non-expansive lesion of hippocampus and/or neocortex.
We identified a BRAF oncogenic variant in five MTLE-HS samples with CD34+ cells (19%) and in five neocortical samples with CD34+ cells (100%). Single nuclei RNAseq of resected samples revealed two unique clusters of abnormal cells (including CD34+ cells) associated with senescence and oligodendrocyte development in both hippocampal and neocortical BRAF mutant samples. The co-expression of the oncogene-induced senescence marker p16 and the outer subventricular zone radial glia progenitor marker HOPX in CD34+ cells was confirmed by multiplex immunostaining. Pseudotime analysis showed that abnormal cells share a common lineage from progenitors to myelinating oligodendrocytes. Epilepsy surgery led to seizure freedom in eight of the 10 patients with BRAF mutant lesions.
BRAF underlies a subset of MTLE-HS and epileptogenic non-expansive neocortical focal lesions. Detection of the oncogenic variant may help diagnosis and open perspectives for targeted therapies.
内侧颞叶癫痫相关海马硬化症（MTLE-HS）是一种与多种病因相关的综合征。我们之前在一部分 MTLE-HS 中发现了可能与 BRAF 致癌变异有关的 CD34 阳性血管外星状细胞（CD34+细胞）。我们旨在鉴定 BRAF 致癌变异体并描述 CD34+细胞。
我们通过数字液滴聚合酶链反应分析了 53 例 MTLE-HS 样本（25 例有 CD34+细胞）和 9 例癫痫手术中切除的非扩张性新皮层病变（5 例有 CD34+细胞）中的 BRAF 致癌变异体。对 BRAF MTLE-HS 和 BRAF 突变的海马和/或新皮层非扩张性病变进行了离体多电极阵列记录、免疫标记、甲基化微阵列和单细胞 RNAseq。
我们在 5 例有 CD34+细胞的 MTLE-HS 样本（19%）和 5 例有 CD34+细胞的新皮层样本（100%）中发现了 BRAF 致癌变异体。切除样本的单细胞 RNAseq 显示，在 BRAF 突变的海马和新皮层样本中，存在两个与衰老和少突胶质细胞发育相关的异常细胞簇（包括 CD34+细胞）。CD34+细胞中致癌基因诱导的衰老标志物 p16 和外脑室下区放射状胶质细胞祖细胞标志物 HOPX 的共表达通过多重免疫染色得到了证实。假时间分析表明，异常细胞具有从祖细胞到髓鞘形成少突胶质细胞的共同谱系。在 10 例 BRAF 突变病变患者中，有 8 例术后癫痫发作得到控制。
BRAF 是 MTLE-HS 和致痫性非扩张性新皮层局灶性病变的一个亚群。检测致癌变异体可能有助于诊断，并为靶向治疗开辟前景。
