Increased expression of Fragile X mental retardation protein in malformative lesions of patients with focal cortical dysplasia.

Abstract

Focal cortical dysplasia (FCD) accounts for nearly half of all cases of medically refractory epilepsy in the pediatric and adult patient populations. This neurological disorder stems from localized malformations in cortical brain tissue due to impaired neuronal proliferation, differentiation, and migration patterns. Recent studies in animal models have highlighted the potential role of the Fragile X mental retardation protein (FMRP) levels in FCD. The purpose of this study was to investigate the status of FMRP activation in cortical brain tissues surgically resected from patients with FCD. In parallel, this study also investigated protein levels within the PI3K/AKT/mTOR and canonical Wnt signaling pathways. Pathologic tissue from malformative lesions of FCD patients with medically refractory epilepsy was compared to relatively normal control non-epileptic tissue from patients with intracranial neoplasms. A series of western blotting assays were performed to assess key proteins in the PI3K/AKT/mTOR, canonical Wnt signaling pathways, and FMRP. There was suppression of S235/236-phosphorylated S6, GSK3α, and GSK3β protein levels in samples derived from FCD patients, compared to non-epileptic controls. FCD samples also had significantly greater levels of total and S499-phosphorylated FMRP. These findings support our hypothesis that malformative lesions associated with FCD are characterized by high levels of FMRP activation along with dysregulation of both PI3K/AKT/mTOR and canonical Wnt signaling. These novel clinical findings extend previous work in animal models, further suggesting a potential unforeseen role of GSK3α and GSK3β in the pathophysiology of FCD and refractory epilepsy.