Neurons In Focal Cortical Dysplasia Research Articles

Increased expression of fibroblast growth factor 13 in cortical lesions of the focal cortical dysplasia

Focal cortical dysplasias (FCDs) are well recognized as important causes of medically intractable epilepsy in both children and adults. To explore the potential role of fibroblast growth factor 13 (FGF13) in intractable epilepsy caused by FCDs, we examined the expression of FGF13 in cortical lesions from 23 patients with FCD type Ia (FCDIa), 24 patients with FCD type IIa (FCDIIa), and 12 patients with FCD type IIb (FCDIIb), and we compared the results with the FGF13 expression levels in control cortex (CTX) brain tissues from 12 nonepileptic normal subjects. 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. 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, our results suggest that the overexpression of FGF13 in FCDs and the cell-specific distribution patterns of FGF13 in misshapen neurons in FCDs could potentially contribute to intractable epilepsy caused by FCDs.

LRP12 silencing during brain development results in cortical dyslamination and seizure sensitization

Correct positioning and differentiation of neurons during brain development is a key precondition for proper function. Focal cortical dysplasias (FCDs) are increasingly recognized as causes of therapy refractory epilepsies. Neuropathological analyses of respective surgical specimens from neurosurgery for seizure control often reveal aberrant cortical architecture and/or aberrantly shaped neurons in FCDs. However, the molecular pathogenesis particularly of FCDs with aberrant lamination (so-called FCD type I) is largely unresolved. Lipoproteins and particularly low-density lipoprotein receptor-related protein 12 (LRP12) are involved in brain development. Here, we have examined a potential role of LRP12 in the pathogenesis of FCDs. In vitro knockdown of LRP12 in primary neurons results in impaired neuronal arborization. In vivo ablation of LRP12 by intraventricularly in utero electroporated shRNAs elicits cortical maldevelopment, i.e. aberrant lamination by malpositioning of upper cortical layer neurons. Subsequent epilepsy phenotyping revealed pentylenetetrazol (PTZ)-induced seizures to be aggravated in cortical LRP12-silenced mice. Our data demonstrates IUE mediated cortical gene silencing as an excellent approach to study the role of distinct molecules for epilepsy associated focal brain lesions and suggests LRP12 and lipoprotein homeostasis as potential molecular target structures for the emergence of epilepsy-associated FCDs.

Increased expression of TRPC5 in cortical lesions of the focal cortical dysplasia.

Focal cortical dysplasias (FCDs) are frequently associated with the medical refractory epilepsy in both children and adults. Transient receptor potential canonical channel 5 (TRPC5), a receptor-operated cation channel, has been well recognized as a regulator in the central nervous system. Here, we examined the expression and cellular distribution of TRPC5 in the specimens from patients with FCDIa (n = 14), FCDIIa (n = 12), and FCDIIb (n = 12) compared with the age-matched control cortex (CTX). TRPC5 mRNA and protein levels were significantly higher in FCDs compared with CTX. Immunohistochemical data showed that TRPC5 was strongly expressed in the misshapen cells, particularly in neuronal microcolumns, dysmorphic neurons, and balloon cells. Moreover, the double-label immunofluorescence analyses demonstrated that TRPC5 localized on NeuN-positive neurons. In addition, its co-localization with glutamate and gamma-aminobutyric acid (GABA) indicated that TRPC5 was distributed on both glutamatergic and GABAergic neurons. Taken together, these results suggested that increased expression of TRPC5 in FCDs and the cell-specific distribution patterns of TRPC5 in the misshapen neurons in FCDs could potentially contribute to the epileptogenesis of FCDs.

Delayed Maturation and Differentiation of Neurons in Focal Cortical Dysplasia With the Transmantle Sign: Analysis of Layer-Specific Marker Expression

Transmantle dysplasia is a rare type of focal cortical dysplasia (FCD) characterized by expansion of the cortex from the deep white matter to the surface and in which there is a FCD IIA or IIB pathologic pattern. To characterize possible mechanisms underlying this regional disorder of radial migrating cells, we studied the expression patterns of neocortical layer-specific markers using immunohistochemistry in surgical specimens from 5 FCD IIA and 4 FCD IIB cases in children. All neuronal cells expressed the mature neuron marker MAP2/2B but not the microglia markers Iba-1 and CD68. Some layer-specific markers showed distinct expression patterns. TBR1-positive, SATB2-positive, and FOXP1-positive cells were diffusely distributed in the cortex and/or the white matter. TBR1-positive and FOXP1-positive cells were generally more numerous in FCD IIB than in FCD IIA and were mostly in the cortical molecular and upper layers. FOXP1-, FOXP2-, and CUTL1-positive cells also expressed the immature neuron marker, Nestin/PROX1, whereas TBR1-, CTIP2-, and SATB2-positive cells only expressed MAP2/2B. These data highlight differences between FCD IIB and FCD IIA with more cells having the immature marker in upper layer markers in the former. By analyzing layer-specific marker expression patterns, we identified apparent neuronal maturation differences between FCD IIA and FCD IIB in cases of transmantle dysplasia.

Abnormal maturation of non-dysmorphic neurons in focal cortical dysplasia: Immunohistochemical considerations

Aim Dysmorphic neurons and balloon cells in focal cortical dysplasia (FCD) reportedly show immaturity and abnormal differentiation with neuronal and glial components. Although normal-looking neurons (NL-neurons) in FCD are major constituent elements, their biological characteristics have never been identified. The aim of this study was to investigate maturation of NL-neurons with the focus on neuronal developmental lineage. Methods Eighteen FCD surgical specimens and controls were examined immunohistochemically using the antibodies for nestin, mammalian achaete-scute complex homolog 1 (Mash1), prospero-related homeobox 1 (Prox1), neuron-specific beta-III tubulin (Tuj1) and microtubule-associated protein 2 (MAP2) of neuronal lineage, glutamic acid decarboxylase (GAD), calretinin (CR) and calbindin (CB) of interneuron markers, and glial fibrillary-acidic protein (GFAP) of glial cell marker. Additionally, we performed fluorescent-double staining with these markers, and semi-quantitative analysis. Results NL-neurons in FCD had both mature and immature components, without interneuron components. NL-neurons in FCD showed abnormal maturation with the combined expression of MAP2 and Mash1/Prox1. Prox1-containing cell distribution in the deep layer was different from that of Mash1-containing cells in the superficial area. The MAP2-containing cell concentration decreased in the order of type I-A, I-B, II-A and II-B, but the Tuj1-containing cell concentration increased. Conclusion These findings may reflect differences in neuronal function and expression timing in developmental stages. From the standpoint of molecular expression, abnormal maturation of NL-neurons may initiate synaptic dysfunction, resulting in intractable seizures of FCD.

Research on distribution and expression of NMDA receptors and parvalbumin-positive neurons in intractable epilepsy-related focal cortical dysplasia

To evaluate the alteration of subunits composition in NMDA receptor and the alterations of the expression and distribution of NMDA receptors and parvalbumin (PV)-positive neurons in focal cortical dysplasia (FCD) cortices. Twenty cases of FCD samples (including all four subtypes of FCD) obtained during epilepsy surgery and 4 controls were analysed by immunohistochemical staining for NR1, NR2A/B and PV. Increased expression of NR1 was detected in the giant neurons and dysmorphic neurons in FCD; while pronounced expression of NR2A/B was detected in immature neurons, giant neurons and dysmorphic neurons of FCD, especially in somata and processes of the immature neurons. Compared with the controls, FCD cortices showed prominent scattered arrangement of PV positive neurons and fibers, dramatically decreased number of PV positive interneurons and PV background staining, especially in foci of FCD II subtype. There are increased expressions of NR1 and NR2A/B subunits in FCD abnormal neurons, as well as scattered and reduced expressions of PV positive neurons and fibers in FCD cortices.

Localization of Breast Cancer Resistance Protein (BCRP) in Microvessel Endothelium of Human Control and Epileptic Brain

Breast cancer resistance protein (BCRP) is a half adenosine triphosphate (ATP)-binding cassette (ABC) transporter expressed on cellular membranes and included in the group of multidrug resistant (MDR)-related proteins. Recently, upregulation of different MDR proteins has been shown in human epilepsy-associated conditions. This study investigated the expression and cellular distribution of BCRP in human control and epileptic brain, including a large number of both neoplastic and nonneoplastic specimens from patients with chronic pharmacoresistant epilepsy. Several epileptogenic pathologies, such as hippocampal sclerosis (HS), focal cortical dysplasia (FCD), dysembryoplastic neuroepithelial tumor, oligodendroglioma astrocytoma, and glioblastoma multiforme were studied by using Western blot and immunocytochemistry. With Western blot, we could demonstrate the presence of BCRP in both normal and epileptic human brain tissue. In contrast to P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP) 2, BCRP expression levels did not change in tissue from patients with HS, compared with control hippocampus. No BCRP immunoreactivity was observed in glial or neuronal cells, including reactive astrocytes and dysplastic neurons in FCD. BCRP expression was, however, increased in tumor brain tissue. Immunocytochemistry demonstrated that BCRP was exclusively located in blood vessels and was highly expressed at the luminal cell surface and in newly formed tumor capillaries. This localization closely resembles that of P-gp. The higher expression observed in astrocytomas by Western blot analysis was related to the higher vascular density within the tumor tissue. These results indicate a constitutive expression of BCRP in human endothelial cells, representing an important barrier against drug access to the brain. In particular, the strong BCRP expression in the microvasculature of epileptogenic brain tumors could critically influence the bioavailability of drugs within the tumor and contribute to pharmacoresistance.

Major vault protein, a marker of drug resistance, is upregulated in refractory epilepsy.

The molecular basis of drug resistance in epilepsy is being explored. Two proteins associated with drug resistance in cancer, P-glycoprotein and multidrug resistance-associated protein 1, are upregulated in human epileptogenic pathologies. Other proteins associated with resistance in cancer include major vault protein (MVP) and breast cancer resistance protein (BCRP). We hypothesized that these proteins would also be upregulated in human epileptogenic pathologies. Hippocampal sclerosis (HS), focal cortical dysplasia (FCD), and dysembryoplastic neuroepithelial tumor (DNT) were studied by using immunohistochemistry for MVP and BCRP. Nonepileptogenic control and histologically normal brain adjacent to epileptogenic tissue were used for comparison. MVP and BCRP were expressed ubiquitously in brain capillary endothelium. Ectopic upregulation of MVP was seen in hilar neurons in HS, dysplastic neurons in FCD, and lesional neurons in DNT. Only in HS cases were rare extralesional neurons immunoreactive. Glial upregulation was not seen. There was no qualitative upregulation of BCRP. These results show that more than one resistance protein may be upregulated in a given epileptogenic pathology and may contribute to drug resistance. Determination of the types, amounts, and distribution of such proteins will be necessary for rational treatment for drug resistance in epilepsy.

Disturbance of Notch-1 and Wnt signalling proteins in neuroglial balloon cells and abnormal large neurons in focal cortical dysplasia in human cortex.

Determination of neuroglial cell fate and neural tube development during embryogenesis is influenced by the Notch/Wnt signalling pathway. We have studied the localisation of several proteins in the Wnt pathway in focal cortical dysplasia (FCD). This disorder, thought to be due to abnormalities of neuronal migration and differentiation, contains regions of morphologically normal neocortex interrupted by areas of neuronal laminar disorganisation, heterotopic white matter neurons, abnormal large neurons and balloon cells of uncertain histogenesis. We found that the subcellular distribution of several proteins involved in the Wnt pathway differed in regions of FCD from normal cortex, and that within the areas of FCD, the pattern varied with cellular phenotype. Thus, in balloon cells, elevated cytoplasmic levels of dishevelled (Dvl-1) protein were accompanied by an absence of Notch-1, increased adenomatous poliposis coli (APC), altered cytoplasmic beta-catenin, and reduced nuclear expression of beta-catenin. A contrasting pattern of expression was found in abnormal large neurons, which demonstrated elevated levels of Notch-1, and glycogen synthase kinase-3beta (GSK-3beta), and normal levels of APC. Our results are consistent with the notion that Wnt/Notch signalling influences neuroglial cell fate, and suggest that a perturbation of Wnt/Notch signalling may contribute to the neuropathology of FCD.