Synaptic Vesicle Protein 2A Protein Research Articles

Analysis of Differential Expression of Synaptic Vesicle Protein 2A in the Adult Rat Brain

Synaptic vesicle protein 2A (SV2A), which plays an important role in the pathophysiology of epilepsy, is a unique vesicular protein recognized as a pharmacological target of anticonvulsant drugs. Furthermore, SV2A is a potential synaptic density marker, as it is ubiquitously expressed throughout the brain in all nerve terminals independently of their neurotransmitter content. Due to the growing interest in this protein, we thoroughly analyzed SV2A levels, expression patterns and colocalization in both excitatory and inhibitory synapses among different brain structures in healthy rats. In addition, we discuss the main semiquantitative methodologies used to study SV2A because these techniques might represent powerful tools for evaluating synaptic changes associated with brain disorders. Our results showed that the SV2A expression levels differed among the analyzed structures, and a positive correlation between the SV2A mRNA copy number and protein level was observed by Western blot. In addition, immunohistochemistry demonstrated slight but consistent asymmetrical SV2A levels in different laminated structures, and SV2A expression was increased by up to 40% in some specific layers compared to that in others. Finally, triple immunofluorescence revealed strong SV2A colocalization with GABAergic terminals, mainly around the principal cells, suggesting that SV2A primarily participates in this inhibitory system in different rat brain structures. Although the SV2A protein is considered a good candidate marker of synaptic density, our data show that changes in its expression in pathological processes must be viewed as not only increased or decreased synapse numbers but also in light of the type of neurotransmission being affected.

Anxiety-like features and spatial memory problems as a consequence of hippocampal SV2A expression.

The Synaptic Vesicle Protein 2A (SV2A) is a transmembrane protein whose presence is reduced both in animal models and in patients with chronic epilepsy. Besides its implication in the epileptic process, the behavioural consequences of the changes in its expression remain unclear. The purpose of our research is to better understand the possible role(s) of this protein through the phenotype of cKO (Grik4 Cre+/-, SV2A lox/lox) mice, male and female, which present a specific decrease of SV2A expression levels in the hippocampal glutamatergic neurons but without any epileptic seizures. In this study, we compare the cKO mice with cHZ (Grik4 Cre+/-, SV2A lox/+) and WT (Grik4 Cre+/+, SV2A lox/lox) mice through a battery of tests, used to evaluate different features: the anxiety-related features (Elevated Plus Maze), the locomotor activity (Activity Chambers), the contextual fear-related memory (Contextual Fear Conditioning), and the spatial memory (Barnes Maze). Our results showed statistically significant differences in the habituation to a new environment, an increase in the anxiety levels and spatial memory deficit in the cHZ and cKO groups, compared to the WT group. No statistically significant differences due to the genotype appeared in the spontaneous locomotor activity or the fear-linked memory. However, sexual differences were observed in this last feature. These results highlight not only an important role of the SV2A protein in the cognitive and anxiety problems typically encountered in epileptic patients, but also a possible role in the symptomatology of other neurodegenerative diseases, such as the Alzheimer’s disease.

Differential expression of SV2A in hippocampal glutamatergic and GABAergic terminals during postnatal development

The function of synaptic vesicle protein 2A (SV2A) has not been clearly identified, although it has an essential role in normal neurotransmission. Changes in SV2A expression have been linked to several diseases that could implicate an imbalance between excitation and inhibition, such as epilepsy. Although it is known that SV2A expression is necessary for survival, SV2A expression and its relationship with γ-aminobutyric acid (GABA) and glutamate neurotransmitter systems along development has not been addressed. This report follows SV2A expression levels in the rat hippocampus and their association with glutamatergic and GABAergic terminals along postnatal development. Total SV2A expression was assessed by real time PCR and western blot, while immunofluorescence was used to identify SV2A protein in the different hippocampal layers and its co-localization with GABA or glutamate vesicular transporters. SV2A was dynamically regulated along development and its association with GABA or glutamate transporters varied in the different hippocampal layers. In the principal cells layers (granular and pyramidal), SV2A protein was preferentially localized to GABAergic terminals, while in the hilus and stratum lucidum SV2A was associated mainly to glutamatergic terminals. Although SV2A was ubiquitously expressed in the entire hippocampus, it established a differential association with excitatory or inhibitory terminals, which could contribute to the maturation of excitatory/inhibitory balance.

Differential expression of synaptic vesicle protein 2A after status epilepticus and during epilepsy in a lithium-pilocarpine model

Synaptic vesicle protein 2A (SV2A) has become an attractive target of investigation because of its role in the pathophysiology of epilepsy; SV2A is expressed ubiquitously throughout the brain in all nerve terminals independently of their neurotransmitter content and plays an important but poorly defined role in neurotransmission. Previous studies have shown that modifications in the SV2A protein expression could be a direct consequence of disease severity. Furthermore, these SV2A modifications may depend on specific changes in the nerve tissue following the induction of epilepsy and might be present in both excitatory and inhibitory terminals. Thus, we evaluated SV2A protein expression throughout the hippocampi of lithium-pilocarpine rats after status epilepticus (SE) and during early and late epilepsy. In addition, we determined the γ-aminobutyric acid (GABA)ergic or glutamatergic nature associated with SV2A modifications. Wistar rats were treated with lithium-pilocarpine to induce SE and subsequently were shown to present spontaneous recurrent seizures (SRS). Later, we conducted an exhaustive semi-quantitative analysis of SV2A optical density (OD) throughout the hippocampus by immunohistochemistry. Levels of the SV2A protein were substantially increased in layers formed by principal neurons after SE, mainly because of GABAergic activity. No changes were observed in the early stage of epilepsy. In the late stage of epilepsy, there were minor changes in SV2A OD compared with the robust modifications of SE; however, SV2A protein expression generally showed an increment reaching significant differences in two dendritic layers and hilus, without clear modifications of GABAergic or glutamatergic systems. Our results suggest that the SV2A variations may depend on several factors, such as neuronal activity, and might appear in both excitatory and inhibitory systems depending on the epilepsy stage.

Brivaracetam: a novel antiepileptic drug for focal-onset seizures.

Brivaracetam (BRV), the n-propyl analogue of levetiracetam (LEV), is the latest antiepileptic drug (AED) to be licensed in Europe and the USA for the adjunctive treatment of focal-onset seizures with or without secondary generalization in patients aged 16 years or older. Like LEV, BRV binds to synaptic vesicle protein 2A (SV2A), but BRV has more selective binding and a 15- to 30-fold higher binding affinity than LEV. BRV is more effective than LEV in slowing synaptic vesicle mobilization and the two AEDs may act at different binding sites or interact with different conformational states of the SV2A protein. In animal models, BRV provides protection against focal and secondary generalized seizures and has significant anticonvulsant effects in genetic models of epilepsy. The drug undergoes first-order pharmacokinetics with an elimination half-life of 7–8 h. Although BRV is metabolized extensively, the main circulating compound is unchanged BRV. Around 95% of metabolites undergo renal elimination. No dose reduction is required in renal impairment, but it is recommended that the daily dose is reduced by one-third in hepatic dysfunction that may prolong half-life. BRV has a low potential for drug interactions. The efficacy and tolerability of adjunctive BRV in adults with focal-onset seizures have been explored in six randomized, placebo-controlled studies. These showed significant efficacy outcomes for doses of 50–200 mg/day. The most common adverse events reported were headache, somnolence, dizziness, fatigue and nausea. Patients who develop psychiatric symptoms with LEV appear to be at risk of similar side effects with BRV, although preliminary data suggest that these issues are likely to be less frequent and perhaps less severe. As with all AEDs, a low starting dose and slow titration schedule help to minimize side effects and optimize seizure control and thereby quality of life.

Interaction of Approved Drugs with Synaptic Vesicle Protein 2A.

Levetiracetam (LEV) and its recently approved derivative brivaracetam are anti-epileptic drugs with a unique mechanism of action. The synaptic vesicle protein 2A (SV2A) was previously identified as their main target. In the current study, we tested a collection of 500 approved drugs for interaction with the human SV2A protein expressed in Chinese hamster ovary cells. Competition binding studies were performed using cell lysates with high SV2A expression and [3 H]brivaracetam as a radioligand. A hit rate of 3% was obtained, defined as compounds that inhibited radioligand binding by more than 90% at a screening concentration of 20 μM. Subsequent concentration-inhibition curves revealed the antihistaminic prodrug loratadine (Ki = 1.16 μM) and the antimalarial drug quinine (Ki = 2.03 μM) to be the most potent SV2A protein ligands of the investigated drug library. Both compounds were similarly potent as LEV (Ki = 1.74 μM), providing structurally novel scaffolds for SV2A ligands. A pharmacophore model was established, which indicated steric and electronic conformities of brivaracetam with the new SV2A ligands, and preliminary structure-activity relationships were determined. The anti-convulsive effects of the natural product quinine may - at least in part - be explained by interaction with SV2A. Loratadine and quinine represent new lead structures for anti-epileptic drug development.

A Mitochondrial Role of SV2a Protein in Aging and Alzheimer's Disease: Studies with Levetiracetam.

Aberrant neuronal network activity associated with neuronal hyperexcitability seems to be an important cause of cognitive decline in aging and Alzheimer's disease (AD). Out of many antiepileptics, only levetiracetam improved cognitive dysfunction in AD patients and AD animal models by reducing hyperexcitability. As impaired inhibitory interneuronal function, rather than overactive neurons, seems to be the underlying cause, improving impaired neuronal function rather than quieting overactive neurons might be relevant in explaining the lack of activity of the other antiepileptics. Interestingly, improvement of cognitive deficits by levetiracetam caused by small levels of soluble Aβ was accompanied by improvement of synaptic function and plasticity. As the negative effects of Aβ on synaptic plasticity strongly correlate with mitochondrial dysfunction, wehypothesized that the effect of levetiracetam on synaptic activity might be raised by an improved mitochondrial function. Accordingly, we investigated possible effects of levetiracetam on neuronal deficits associated with mitochondrial dysfunction linked to aging and AD. Levetiracetam improved several aspects of mitochondrial dysfunction including alterations of fission and fusion balance in a cell model for aging and early late-onset AD. We demonstrate for the first time, using immunohistochemistry and proteomics, that the synaptic vesicle protein 2A (SV2a), the molecular target of levetiracetam, is expressed in mitochondria. In addition, levetiracetam shows significant effect on the opening of the mitochondrial permeability transition pore. Importantly, the effects of levetiracetam were significantly abolished when SV2a was knockdown using siRNA. In conclusion, interfering with the SV2a protein at the mitochondrial level and thereby improving mitochondrial function might represent an additional therapeutic effect of levetiracetam to improve symptoms of late-onset AD.

Synaptic vesicle protein2A decreases in amygdaloid-kindling pharmcoresistant epileptic rats.

Synaptic vesicle protein 2A (SV2A) involvement has been reported in the animal models of epilepsy and in human intractable epilepsy. The difference between pharmacosensitive epilepsy and pharmacoresistant epilepsy remains poorly understood. The present study aimed to observe the hippocampus SV2A protein expression in amygdale-kindling pharmacoresistant epileptic rats. The pharmacosensitive epileptic rats served as control. Amygdaloid-kindling model of epilepsy was established in 100 healthy adult male Sprague-Dawley rats. The kindled rat model of epilepsy was used to select pharmacoresistance by testing their seizure response to phenytoin and phenobarbital. The selected pharmacoresistant rats were assigned to a pharmacoresistant epileptic group (PRE group). Another 12 pharmacosensitive epileptic rats (PSE group) served as control. Immunohistochemistry, real-time PCR and Western blotting were used to determine SV2A expression in the hippocampus tissue samples from both the PRE and the PSE rats. Immunohistochemistry staining showed that SV2A was mainly accumulated in the cytoplasm of the neurons, as well as along their dendrites throughout all subfields of the hippocampus. Immunoreactive staining level of SV2A-positive cells was 0.483 ± 0.304 in the PRE group and 0.866 ± 0.090 in the PSE group (P < 0.05). Real-time PCR analysis demonstrated that 2(-ΔΔCt) value of SV2A mRNA was 0.30 ± 0.43 in the PRE group and 0.76 ± 0.18 in the PSE group (P < 0.05). Western blotting analysis obtained the similar findings (0.27 ± 0.21 versus 1.12 ± 0.21, P < 0.05). PRE rats displayed a significant decrease of SV2A in the brain. SV2A may be associated with the pathogenesis of intractable epilepsy of the amygdaloid-kindling rats.

Hippocampal low-frequency stimulation increased SV2A expression and inhibited the seizure degree in pharmacoresistant amygdala-kindling epileptic rats

To investigate the effects of hippocampal low-frequency stimulation (Hip-LFS) on the expression of synaptic vesicle protein 2A (SV2A) and on the seizure degree in pharmacoresistant epileptic rats. Eighteen pharmacoresistant epileptic rats were selected from 75 amygdala-kindling rat models of epilepsy by testing their seizure response to phenytoin (PHT) and to phenobarbital (PB). Six pharmacoresistant epileptic rats (PRE group, 6 rats) were used to determine SV2A expression for comparison with the pharmacosensitive epileptic rats (PSE group, 6 rats). The other 12 pharmacoresistant epileptic rats were assigned to a pharmacoresistant control group (PRC group, 6 rats) or to a pharmacoresistant stimulation group (PRS group, 6 rats) and were subjected to the hippocampal stimulation experiment. A stimulation electrode was implanted into the hippocampus for both the PRC group and the PRS group. Hip-LFS was administered twice per day for two weeks. Following 2 weeks of stimulation, seizure duration and frequency were observed, and SV2A mRNA expression and protein content in the hippocampus were measured by real-time PCR and by western blot analysis, respectively. The SV2A mRNA and protein decreased markedly in the PRE group compared with the PSE group. After performing Hip-LFS for two weeks, remarkable increases in SV2A mRNA and protein were observed in the PRS group compared with the PRC group (P<0.05). Simultaneously, the seizure degree of these rats was inhibited. Hip-LFS may have prevented seizures in the pharmacoresistant epileptic rats. The antiepileptic effects of Hip-LFS may be partly achieved by increasing SV2A expression.

Levetiracetam but not valproate inhibits function of CD8+ T lymphocytes

PurposeTo further elucidate possible immune-modulatory effects of valproate (VPA) or levetiracetam (LEV), we investigated their influence on apoptosis and cytotoxic function of CD8+ T lymphocytes in humans. MethodsIn 15 healthy subjects (9 female (60%), 35.7±12.1 years), apoptosis and cytotoxic function of CD8+ T lymphocytes were measured using flow cytometry following in vitro exposure to LEV (5mg/L and 50mg/L) and VPA (10mg/L and 100mg/L). Apoptosis rates were determined after incubation with LEV or VPA for 1h or 24h. Cytotoxic function was assessed following 2h stimulation with mixed virus peptides, using perforin release, CD107a/b expression and proliferation. The presence of synaptic vesicle protein 2A (SV2A) was investigated in human CD8+ T lymphocytes by flow cytometry analysis, Western blot and real time polymerase chain reaction (rtPCR). ResultsHigh concentration of LEV decreased perforin release of CD8+ T lymphocytes (LEV 50mg/L vs. CEF only: 21.4% (interquartile range (IQR) 16.5–35.9%) vs. 16.6% (IQR 12–24.9%), p=0.002). LEV had no influence on apoptosis and proliferation (p>0.05). VPA (100mg/L) slowed apoptosis of CD8+ T lymphocytes after 24h (VPA 100mg/L vs. control: 7.3% (IQR 5.4–9.5%) vs. 11.3% (IQR 8.2–15.1%), p<0.001), but had no effects on perforin release (p>0.05). SV2A protein was detected in CD8+ T lymphocytes. ConclusionLEV decreased degranulation of CD8+ T lymphocytes which may contribute to the increased incidence of upper respiratory tract infections in LEV treated patients. Inhibition of SV2A may be responsible for this effect.

SV2A in Epilepsy: The Plot Thickens

Decreased Expression of Synaptic Vesicle Protein 2A, the Binding Site for Levetiracetam, during Epileptogenesis and Chronic Epilepsy. van Vliet EA, Aronica E, Redeker S, Boer K, Gorter JA. Epilepsia 2009;50(3):422–433. PURPOSE: We previously showed that gene expression of synaptic vesicle protein 2A (SV2A), the binding site for the antiepileptic drug levetiracetam, is reduced during epileptogenesis in the rat. Since absence of SV2A has been associated with increased epileptogenicity, changes in expression of SV2A could have consequences for the progression of epilepsy. Therefore, we investigated hippocampal SV2A protein expression of temporal lobe epilepsy (TLE) patients and in rats during epileptogenesis and in the chronic epileptic phase. METHODS: SV2A immunocytochemistry and Western blot analysis were performed on the hippocampus of autopsy controls, patients that died from status epilepticus (SE), and pharmacoresistant TLE patients. In addition, in epileptic rats, SV2A expression was determined after SE during the acute, latent, and chronic epileptic phase. RESULTS: In control tissue, presynaptic SV2A was expressed in all hippocampal subfields, with strongest expression in mossy fiber terminals. SV2A positive puncta were distributed in a patchy pattern over the somata and dendrites of neurons. SV2A decreased throughout the hippocampus of TLE patients with hippocampal sclerosis (HS), compared to autopsy control, SE, and non-HS tissue. In most rats, SV2A was already decreased in the latent period especially in the inner molecular layer and stratum lucidum. Similarly as in humans, SV2A was also decreased throughout the hippocampus of chronic epileptic rats, specifically in rats with a progressive form of epilepsy. DISCUSSION: These data support previous findings that reduced expression of SV2A could contribute to the increased epileptogenicity. Whether this affects the effectiveness of levetiracetam needs to be further investigated.

Decreased expression of synaptic vesicle protein 2A, the binding site for levetiracetam, during epileptogenesis and chronic epilepsy

We previously showed that gene expression of synaptic vesicle protein 2A (SV2A), the binding site for the antiepileptic drug levetiracetam, is reduced during epileptogenesis in the rat. Since absence of SV2A has been associated with increased epileptogenicity, changes in expression of SV2A could have consequences for the progression of epilepsy. Therefore we investigated hippocampal SV2A protein expression of temporal lobe epilepsy (TLE) patients and in rats during epileptogenesis and in the chronic epileptic phase. SV2A immunocytochemistry and Western blot analysis were performed on the hippocampus of autopsy controls, patients that died from status epilepticus (SE), and pharmacoresistant TLE patients. In addition, in epileptic rats, SV2A expression was determined after SE during the acute, latent, and chronic epileptic phase. In control tissue, presynaptic SV2A was expressed in all hippocampal subfields, with strongest expression in mossy fiber terminals. SV2A positive puncta were distributed in a patchy pattern over the somata and dendrites of neurons. SV2A decreased throughout the hippocampus of TLE patients with hippocampal sclerosis (HS), compared to autopsy control, SE, and non-HS tissue. In most rats, SV2A was already decreased in the latent period especially in the inner molecular layer and stratum lucidum. Similarly as in humans, SV2A was also decreased throughout the hippocampus of chronic epileptic rats, specifically in rats with a progressive form of epilepsy. These data support previous findings that reduced expression of SV2A could contribute to the increased epileptogenicity. Whether this affects the effectiveness of levetiracetam needs to be further investigated.

Binding characteristics of levetiracetam to synaptic vesicle protein 2A (SV2A) in human brain and in CHO cells expressing the human recombinant protein

A specific binding site for the antiepileptic drug levetiracetam (2 S-(oxo-1-pyrrolidinyl)butanamide, Keppra®) in rat brain, referred to as the levetiracetam binding site, was discovered several years ago. More recently, this binding site has been identified as the synaptic vesicle protein 2A (SV2A), a protein present in synaptic vesicles [Lynch, B., Lambeng, N., Nocka, K., Kensel-Hammes, P., Bajjalieh, S.M., Matagne, A., Fuks, B., 2004. The synaptic vesicle protein SV2A is the binding site for the antiepileptic drug levetiracetam. Proc. Natl. Acad. Sci. USA, 101, 9861–9866.]. In this study, we characterized the binding properties of levetiracetam in post-mortem human brain and compared them to human SV2A expressed in Chinese hamster ovary (CHO) cells. The results showed that the binding properties of levetiracetam and [ 3H]ucb 30889, an analogue that was previously characterized as a suitable ligand for levetiracetam binding site/SV2A in rat brain [Gillard, M., Fuks, B., Michel, P., Vertongen, P., Massingham, R. Chatelain, P., 2003. Binding characteristics of [ 3H]ucb 30889 to levetiracetam binding sites in rat brain. Eur. J. Pharmacol. 478, 1–9.], are almost identical in human brain samples (cerebral cortex, hippocampus and cerebellum) and in CHO cell membranes expressing the human SV2A protein. Moreover, the results are also similar to those previously obtained in rat brain. [ 3H]ucb 30889 binding in human brain and to SV2A was saturable and reversible. At 4 °C, its binding kinetics were best fitted assuming a two-phase model in all tissues. The half-times of association for the fast component ranged between 1 to 2 min and represent 30% to 36% of the sites whereas the half-times for the slow component ranged from 20 to 29 min. In dissociation experiments, the half-times were from 2 to 4 min for the fast component (33% to 49% of the sites) and 20 to 41 min for the slow component. Saturation binding curves led to K d values for [ 3H]ucb 30889 of 53 ± 7, 55 ± 9, 70 ± 11 and 75 ± 33 nM in human cerebral cortex, hippocampus, cerebellum and CHO cells expressing SV2A respectively. B max values around 3–4 pmol/mg protein were calculated in all brain regions. Some of the saturation curves displayed curvilinear Scatchard plots indicating the presence of high and low affinity binding sites. When this was the case, K d values from 25 to 30 nM for the high affinity sites (24% to 34% of total sites) and from 200 to 275 nM for the low affinity sites were calculated. This was observed in all brain regions and in CHO cell membranes expressing the SV2A protein. It cannot be explained by putative binding of [ 3H]ucb 30889 to SV2B or C isoforms but may reflect different patterns of SV2A glycosylation or the formation of SV2A oligomers. Competition experiments were performed to determine the affinities for SV2A of a variety of compounds including levetiracetam, some of its analogues and other molecules known to interact with levetiracetam binding sites in rat brain such as bemegride, pentylenetetrazol and chlordiazepoxide. We found an excellent correlation between the affinities of these compounds measured in human brain, rat brain and CHO cells expressing human SV2A. In conclusion, we report for the first time that the binding characteristics of native levetiracetam binding sites/SV2A in human brain and rat brain share very similar properties with human recombinant SV2A expressed in CHO cells.

Translational Research: Human Tissue &amp; Pathology

Abstract 1 Andreas V. Alexopoulos, 1 Cristiane Q. Tilelli, 1 Roger O. Oghlakian, 2 Jorge Gonzalez-Martinez, 2 William E. Bingaman, and 1 Imad M. Najm ( 1 Neurology, Epilepsy Center, Cleveland Clinic Foundation, Cleveland, OH ; and 2 Neurosurgegy, Epilepsy Center, Cleveland Clinic Foundation, Cleveland, OH ) Rationale: The synaptic vesicle protein 2A (SV2A) has been recently identified as the specific binding site for levetiracetam (LEV) in the brain and as a potential target for future antiepileptic drug (AED) therapy. LEV belongs to a new generation of AEDs with a novel mechanism of action seemingly unrelated to traditional AED targets. The objective of our study is to investigate the expression of the SV2A protein in the neocortex of patients with pharmacoresistant epilepsy. We hypothesize that surgically resected epileptic tissue shows a differential expression of the SV2A protein. Methods: Human neocortical tissue specimens from seven patients with histopathologically proven focal cortical dysplasia (FCD) were used for this set of experiments. All patients underwent chronic extraoperative electrocorticographic (ECoG) recordings using subdural grids. “Epileptic areas” exhibiting ictal activity on ECoG (with or without interictal spiking) were identified and separated during surgery from resected “non-epileptic” cortical regions (n = 7). Additional controls consisted of “non-epileptic” tissue acquired from lateral temporal neocortex of patients with hippocampal sclerosis and normal neocortical MRI (n = 3), and human neocortical tissue obtained from autopsy patients without a known history of neurological disease (n = 5). Immunocytochemical staining was performed using polyclonal antibodies against SV2A to study SV2A protein expression in the human tissue specimens. The extent, density and distribution of SV2A protein immunoreactivity were visually analyzed by three independent and blinded observers. Results: Immunocytochemical analysis revealed two main staining patterns: Autopsy controls were characterized by clusters of punctate, “terminal-like” SV2A labeling in the presence of a lightly stained background seen throughout all layers of cortex. In contrast, tissue identified by ECoG as “epileptic” showed intense and diffuse staining of the neuropil with disruption or absence of punctate labeling in all cortical layers. Finally, an intermediate mixed pattern was seen in tissue obtained from “non-epileptic” and lateral temporal neocortex. Conclusions: These distinct SV2A immunoreactivity patterns provide evidence for redistribution of the SV2A protein in the neocortex of patients with FCD and pharmacoresistant epilepsy. Further studies to elucidate the mechanism and functional significance of SV2A redistribution in these patients are currently underway in our laboratory. These findings may have implications for the pathogenesis and treatment of pharmacoresistant epilepsy in patients with focal cortical dysplasia. (Supported by Investigator-initiated study grant to A.V.A. sponsored by UCB-Pharma.)