The Role Of FGF13 In Epilepsy With Malformations Of Cortical Development

Malformations of cortical development(MCD)are a complex and important collection of neurodevelopmental disorders in central nervous system(CNS),which underlie over most of medically refractory childhood seizures.MCD are associated with neurological morbidity,including epilepsy,intellectual disability and motor dysfunction.MCD include multiple developmental malformations,such as focal cortical dysplasia(FCD)and tuberous sclerosis complex(TSC),most of which are medically refractory epilepsy.MCD are considered to be a well-recognized cause of refractory epilepsy and the studies on the mechanisms of epileptogenesis in patients with MCD are of great significance.Cerebral cortical development needs a complex series of highly regulated steps,of which neuronal migration is a key part.MCD have been defined as a “neuronal migration disorder”.Studies have shown that FGF13 controls the polarization and migration of neurons,FGF13 interacts with voltage-gated sodium channels(VGSC).Therefore,we speculate that FGF13 may be involved in the development of epilepsy associated with MCD.In our study,surgical specimens of MCD and MCD model of rat were used to investigate the expression and specific cellular distribution of FGF13 in MCD,to assess the correlations between the FGF13 protein levels and different clinical variables,to clarify the role of FGF13 in the pathogenesis of epilepsy in MCD.Methods:Part 1: We investigated the expression and specific cellular distribution of FGF13 in patients with FCDs and TSC by real-time quantitative PCR,Western blot,immunohistochemistry and Double-Label Immunofluorescence.Also correlations between the FGF13 protein levels and different clinical variables were assessed.Part 2: In utero irradiation model of rats and focal freeze lesions model of rats were created.We also overexpressed FGF13 by local injection of adeno-associated virus(AAV).Western blot and immunohistochemistry were used to investigate the expression and specific cellular distribution of FGF13.Video-electroencephalography(VEEG)was used to observe the behavior and EEG of these rats which were induced epilepsy by penicillin to confirm the role of FGF13 in the refractory epilepsy with MCDs.Results:(1)Expression and cellular distribution of FGF13 in FCDs1.Both the mRNA levels and protein levels of FGF13 were significantly higher in the cortical lesions from patients with FCD than in the control cortices.And the protein levels of FGF13 in FCDs were positively correlated with the frequency of seizures before surgery.2.The immunohistochemical results showed that strong FGF13 immunoreactivity was observed in misshapen cells,including neuronal microcolumns,hypertrophic neurons,dysmorphic neurons,and most balloon cells.Moreover,double-label immunofluorescence analyses confirmed that FGF13 was mainly localized in neurons and nearly absent in glia-like cells.Taken together,FGF13 may play an important role in the epileptic process in patients with FCDs.(2)Expression and cellular distribution of FGF13 in TSC1.Both the mRNA and protein levels of FGF13 were significantly higher in the cortical tubers from patients with TSC than in the control cortices.The protein levels of FGF13 in the TSC samples were positively correlated with the frequency of seizures.2.The immunohistochemical results showed strong FGF13 immunoreactivity in abnormal cells,including dysplastic neurons(DNs)and giant cells(GCs).Moreover,double-label immunofluorescence analyses confirmed that FGF13 was mainly localized in neurons and nearly absent in glia-like cells.Therefore,we speculated that FGF13 may be involved in the epileptogenesis of TSC through abnormal neural circuits in cortical tubers.(3)The role of FGF13 in MCD rat models1.In utero irradiation model of rats(group 1),focal freeze lesions model of rats(group2),overexpressed FGF13 rats(group 3)and normal SD rats(group 0)were created.The protein levels of FGF13 were significantly higher in the cortical lesions from group 1,2 and 3than in the normal control.The immunohistochemical results showed strong FGF13 immunoreactivity in abnormal cells(balloon cells in group 1 and dysplastic neurons in microgyral malformation of group 2).2.The results of behavior and EEG showed that Video-electroencephalography(VEEG)was used to observe the behavior and EEG of these rats which were induced epilepsy by penicillin to confirm the role of FGF13 in the refractory epilepsy with MCDs.The spikes in these three groups were significantly increased compared with group 0.And the onset times were shorter in all these three groups than group 0.Our findings suggest that FGF13 may play an important role in the epileptic process in MCDs and provide a new basis for understanding refractory epilepsy epileptogenicity and pathogenesis.Conclusion:It can be inferred that FGF13 may be involved in the pathological process of epilepsy associated with MCDs.