Altered Expression of Astrocyte-Related Receptors and Channels Correlates With Epileptogenesis in Hippocampal Sclerosis.

BACKGROUND: Hippocampal sclerosis (HS) is one of the major causes of intractable epilepsy. Astrogliosis in epileptic brain is a peculiar condition showing epileptogenesis and is thought to be different from the other pathological conditions. The aim of this study is to investigate the altered expression of astrocytic receptors, which contribute to neurotransmission in the synapse, and channels in HS lesions. METHODS: We performed immunohistochemical and immunoblotting analyses of the P2RY1, P2RY2, P2RY4, Kir4.1, Kv4.2, mGluR1, and mGluR5 receptors and channels with the brain samples of 20 HS patients and 4 controls and evaluated the ratio of immunopositive cells and those expression levels. RESULTS: The ratio of each immunopositive cell per glial fibrillary acidic protein-positive astrocytes and the expression levels of all 7 astrocytic receptors and channels in HS lesions were significantly increased. We previously described unique astrogliosis in epileptic lesions similar to what was observed in this study. CONCLUSION: This phenomenon is considered to trigger activation of the related signaling pathways and then contribute to epileptogenesis. Thus, astrocytes in epileptic lesion may show self-hyperexcitability and contribute to epileptogenesis through the endogenous astrocytic receptors and channels. These findings may suggest novel astrocytic receptor-related targets for the pharmacological treatment of epilepsy.

Pathologic Active mTOR Mutation in Brain Malformation with Intractable Epilepsy Leads to Cell-Autonomous Migration Delay.

The activation of phosphatidylinositol 3-kinase-AKTs-mammalian target of rapamycin cell signaling pathway leads to cell overgrowth and abnormal migration and results in various types of cortical malformations, such as hemimegalencephaly (HME), focal cortical dysplasia, and tuberous sclerosis complex. However, the pathomechanism underlying abnormal cell migration remains unknown. With the use of fetal mouse brain, we performed causative gene analysis of the resected brain tissues from a patient with HME and investigated the pathogenesis. We obtained a novel somatic mutation of the MTOR gene, having approximately 11% and 7% mutation frequency in the resected brain tissues. Moreover, we revealed that the MTOR mutation resulted in hyperphosphorylation of its downstream molecules, S6 and 4E-binding protein 1, and delayed cell migration on the radial glial fiber and did not affect other cells. We suspect cell-autonomous migration arrest on the radial glial foot by the active MTOR mutation and offer potential explanations for why this may lead to cortical malformations such as HME.

Expression of astrocyte-related receptors in cortical dysplasia with intractable epilepsy.

Epilepsy is one of the major neurologic diseases, and astrocytes play important roles in epileptogenesis. To investigate possible roles of astrocyte-related receptors in patients with intractable epilepsy associated with focal cortical dysplasia (FCD) and other conditions, we examined resected epileptic foci from 31 patients, including 23 with FCD type I, IIa, or IIb, 5 with tuberous sclerosis complex, and 3 with low-grade astrocytoma. Control samples were from 21 autopsied brains of patients without epilepsy or neurologic deficits and 5 patients with pathologic gliosis without epilepsy. Immunohistochemical and immunoblot analyses with antibodies against purinergic receptor subtypes P2RY1, P2RY2, P2RY4, potassium channels Kv4.2 and Kir4.1, and metabotropic receptor subtypes mGluR1 and mGluR5 were performed. Anti-glial fibrillary acidic protein, anti-NeuN, and anti-CD68 immunostaining was used to identify astrocytes, neurons, and microglia, respectively. Most glial fibrillary acidic protein-immunopositive astrocyte cells in the brain samples from patients with epilepsy were P2RY1-, P2RY2-, P2RY4-, Kv4.2-, Kir4.1-, mGluR1-, and mGluR5-positive, whereas samples from controls and pathologic gliosis showed lower expression levels of these astrocyte-related receptors. Our findings suggest that, although these receptors are necessary for astrocyte transmission, formation of the neuron-glia network, and other physiologic functions, overexpression in the brains of patients with intractable epilepsy may be associated with activation of intracellular and glio-neuronal signaling pathways that contribute to epileptogenesis.

Abnormal maturation and differentiation of neocortical neurons in epileptogenic cortical malformation: unique distribution of layer-specific marker cells of focal cortical dysplasia and hemimegalencephaly.

Focal cortical dysplasia (FCD) and hemimegalencephaly (HME) are major causes of intractable epilepsy in children. The probable pathogenesis of FCD and HMG is the abnormal migration and differentiation of neurons. The aim of the present study was to clarify the abnormal cytoarchitecture, based on neuronal immaturation. Tissue samples were obtained from 16 FCD and seven HME patients, aged between 2 months and 12 years, who had been diagnosed as typical FCD and HME, following surgical treatment for intractable epilepsy. Paraffin-embedded sections were stained with the antibodies of three layer-markers that are usually present only during the fetal period, namely SATB2 (expressed in the upper layer of the normal fetal neocortex), FOXP1 (expressed in the 5th layer), and TBR1 (expressed in the 6th layer). In FCD, SATB2-positive (+) cells located in the middle and deep regions of FCD Ia and Ib, but only in the superficial region of FCD IIa and IIb. FOXP1+ cells diffusely located in the neocortex, especially the upper layer of FCD IIa and IIb. TBR1+ cells mainly located in the middle and deep regions, and also white matter. In FCD IIb, TBR1+ cells were in the superficial region. In HME, SATB2+ and FOXP1+ cells were found diffusely. TBR1+ cells were in the middle and deep regions. On the basis of continued expression of fetal cortical layer-specific markers in FCD and HME brains, the abnormal neocortical formation in both is likely to be the result of disrupted neuronal migration and dysmaturation. The expression pattern is different between FCD and HME.

Neocortical layer formation of human developing brains and lissencephalies: consideration of layer-specific marker expression.

To investigate layer-specific molecule expression in human developing neocortices, we performed immunohistochemistry of the layer-specific markers (TBR1, FOXP1, SATB2, OTX1, CUTL1, and CTIP2), using frontal neocortices of the dorsolateral precentral gyri of 16 normal controls, aged 19 gestational weeks to 1 year old, lissencephalies of 3 Miller-Dieker syndrome (MDS) cases, 2 X-linked lissencephaly with abnormal genitalia (XLAG) cases, and 4 Fukuyama-type congenital muscular dystrophy (FCMD) cases. In the fetal period, we observed SATB2+ cells in layers II-IV, CUTL1+ cells in layers II-V, FOXP1+ cells in layer V, OTX1+ cells in layers II or V, and CTIP2+ and TBR1+ cells in layers V and VI. SATB2+ and CUTL1+ cells appeared until 3 months of age, but the other markers disappeared after birth. Neocortices of MDS and XLAG infants revealed SATB2+, CUTL1+, FOXP1+, and TBR1+ cells diffusely located in the upper layers. In fetal FCMD neocortex, neurons labeled with the layer-specific markers located over the glia limitans. The present study provided new knowledge indicating that the expression pattern of these markers in the developing human neocortex was similar to those in mice. Various lissencephalies revealed abnormal layer formation by random migration.

Acute autonomic sensory and motor neuropathy associated with parvovirus B19 infection.

We report a 9-year-old girl with acute autonomic sensory and motor neuropathy (AASM) associated with human parvovirus B19 (HPV-B19) infection. The patient presented with fever, erythema of the entire body, and abdominal pain with vomiting. The titer of HPV-B19 IgM antibody was significantly elevated. Symptoms such as muscle weakness, severe hyperesthesia, dyshidrosis, and neurogenic bladder associated with autonomic disturbance developed over several days. Intravenous immunoglobulin therapy gave no obvious improvement of her symptoms. Motor and sensory impairment improved slowly without medical treatment, but dysautonomia persisted for a long time. Sural nerve biopsy revealed axonal degeneration of small fibers, involving both myelinated and unmyelinated fibers, which is compatible with the autonomic sensory and motor neuropathy. AASM is very rare in pediatric populations, and there is no report of AASM associated with HPV-B19 infection.

Partial loss of pancreas endocrine and exocrine cells of human ARX-null mutation: consideration of pancreas differentiation.

Aristaless-related homeobox gene (ARX) mutation leads to several neurological disorders including X-linked lissencephaly with abnormal genitalia (XLAG), West syndrome and Partington syndrome, with XLAG being the most severe form. Although some of the brain pathologies of XLAG have already been described, the crucial extra-brain symptoms are severe growth retardation, transient hyperglycemia and intractable diarrhea. Since ARX expresses in the islets of Langerhans during the embryonic stage, these visceral phenotypes may be related to a loss of ARX function, which develops endocrine cells in the pancreas. We investigated the abnormal pancreatic development of XLAG patients with ARX-null mutation. We performed immunohistochemistry of XLAG pancreases, using the antibodies against glucagon, insulin, somatostatin, pancreatic polypeptide, ghrelin, Brn4, Nkx2.2, Mash1, amylase and pancreatic lipase. As the results, the glucagon- and pancreatic polypeptide-producing cells were found to be completely deficient in the islets of Langerhans. We also discovered marked interstitial fibrosis, small exocrine cells with loss of amylase-producing cells and an enlargement of the central lumen of the glandular acini. These pathological findings indicate that ARX contributes not only to endocrine development, but also to exocrine development of the human pancreas, and its deficiency may lead to the severe phenotypes of XLAG patients.

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.

Hemifacial seizures due to ganglioglioma of cerebellum.

We present a male infant with hemifacial seizures refractory to antiepileptic medication. Hemifacial spasms around the left eye were frequent during wakefulness and sleep since birth. He also had mild psychomotor retardation. Magnetic resonance imaging (MRI) revealed a large tumor in the left middle cerebellar peduncle. Ictal single photon emission computed tomography (SPECT) and ictal (18)F-fluorodeoxyglucose [(18)F-FDG] positron emission tomography (PET) revealed hyperperfusion and hyper glucose metabolism at the tumor. Total removal of the tumor resulted in complete disappearance of hemifacial seizures and improved psychomotor development, indicating that the cerebellar tumor caused hemifacial seizures. A histopathological study confirmed that the tumor was a ganglioglioma. This case and the literature on similar cases indicated that this was a new epileptic syndrome originating in the cerebellum. Early diagnosis and early complete removal of the epileptogenic lesion should be recommended for this syndrome.

Discrepancies in cytogenetic results between amniocytes and postnatally obtained blood: trisomy 9 mosaicism.

When amniocentesis reveals a mosaic karyotype and the baby presents with multiple malformations, an analysis of the baby's peripheral blood typically reveals a mosaic karyotype. We present a boy who was prenatally diagnosed by amniocentesis as having trisomy 9 mosaicisim but who had normal G-banding results on postnatal blood karyotyping; the patient also exhibited multiple malformations, including a diaphragmatic hernia, arthrogryposis, undescended testes, and characteristic facies. Because of the discrepancy between the phenotype and karyotype, we repeated the chromosomal studies on multiple occasions. Interphase FISH performed on abdominal wall muscle tissue revealed a mosaic trisomy 9 karyotype: 47,XY, + 9(159)/46,XY (19). Based on these findings, we finally diagnosed the patient as having trisomy 9 mosaicism and counseled the parents that the risk of recurrence was low. We conclude that it is important to be aware of the possibility that the patient can have a normal postnatal blood karyotype and an abnormal phenotype with multiple malformations when trisomy 9 mosaicism is detected prenatally. When the baby's phenotype is abnormal, karyotyping on multiple tissues is useful for confirming clinical impression as well as determining the prognosis and providing accurate genetic counseling.