Hitoshi Takahashi

Prefrontal Abnormality of Schizophrenia Revealed by DNA Microarray: Impact on Glial and Neurotrophic Gene Expression

Abstract: DNA microarrays with isotope labeling from gene‐specific primers enable sensitive detection of rare mRNAs, including neurotrophin and cytokine mRNAs in the brain. Using high‐quality RNA from postmortem brains, gene‐expression profiles covering 1373 genes were assessed in the dorsoprefrontal cortex of schizophrenic patients and compared with those of nonpsychiatric subjects. Statistical analysis of the DNA microarray data confirmed the findings of a previous GeneChip study by Hakak et al. (Proc. Natl. Acad. Sci. USA Vol. 98, pp. 4746‐4751, 2001). The highest frequency of mRNA expression alterations occurred in oligodendrocyte‐ and astrocyte‐related genes in the prefrontal cortex of schizophrenic patients, followed by the category for the genes for growth factors/neurotrophic factors and their receptors. Whether each mRNA signal represents the expression of the individual genes or homologous genes in the category remains to be determined, however. To control for potential medication effects on patients, RNA from cynomolgus monkeys that were treated with haloperidol for 3 months was also subjected to DNA microarray analysis. A few genes overlapped between the gene‐expression profiles of the monkeys and patients. The present profiling study suggests a potential biological link between abnormal neurotrophic signals and impaired glial functions in schizophrenic pathology.

Bilateral periventricular nodular heterotopia due to filamin 1 gene mutation: widespread glomeruloid microvascular anomaly and dysplastic cytoarchitecture in the cerebral cortex

Abstract. Bilateral periventricular nodular heterotopia (BPNH) is a neuronal migration disorder that is characterized by subependymal nodules of gray matter. Recently, a causative gene for BPNH, filamin 1, has been identified, and possible roles of the translated protein in cell migration and blood vessel development have been proposed. We report here the histopathological features of an autopsy case of BPNH with widespread glomeruloid microvascular anomaly and dysplastic cytoarchitecture in the cerebral cortex, in whom we found a novel exon 11 (Val528Met) filamin 1 mutation. Within the periventricular nodules, well-differentiated pyramidal neurons were randomly oriented. A small proportion of neurons were immunolabeled with antibodies raised against calbindin D-28k, parvalbumin, or calretinin. We used a carbocyanine dye (DiI) tracing technique to investigate the extent of fiber projections within and outside the nodules. The labeled fibers formed bundles that extended into the surrounding white matter. Connections between adjacent nodules were evident. Connections between the nodules and the cerebral cortex were also seen, with a small number of labeled fibers reaching the cortex. In the cerebral cortex, small closely packed vessels ran in a parallel fashion throughout all of the layers. Immunohistochemically, the inner rim of individual vessel lumina was labeled by an antibody against factor VIII, and the vessel walls were labeled by antibodies against actin and laminin. Astrocyte processes, labeled with an antibody to glial fibrillary acidic protein, invaded these vascular channels. Ultrastructurally, a network of basal lamina-like materials lined with endothelial cells was evident. The cytoarchitecture of the cerebral cortex was disturbed, in that the columnar neuronal arrangement was distorted around the malformed vessels. This case appears to represent an example of BPNH manifesting widespread developmental anomalies within the blood vessels and the cortical cytoarchitecture in the cerebrum.

Surgical strategy and outcomes for epileptic patients with focal cortical dysplasia or dysembryoplastic neuroepithelial tumor.

Summary: u2002Purpose: The purpose of this study was to clarify and compare the influence of surgical strategy on relief from seizures in patients with focal cortical dysplasia (FCD) and those with dysembryoplastic neuroepithelial tumor (DNT).

A decrease in interleukin-1 receptor antagonist expression in the prefrontal cortex of schizophrenic patients.

Interleukin-1 (IL-1) mediates psychological stress responses by regulating monoamine metabolism and secretion of corticotropin-releasing factor, and is therefore, implicated in various psychiatric diseases. To evaluate the contribution of IL-1 signaling to the brain pathology of schizophrenia, we measured protein and/or mRNA levels for IL-1beta and endogenous IL-1 receptor antagonist (IL-1RA) in the postmortem brain tissues of prefrontal and parietal cortex, putamen, and hypothalamus. Both protein and mRNA levels of IL-1RA were specifically decreased in the prefrontal cortex of schizophrenic patients, whereas IL-1beta levels were not significantly altered in all the regions examined. The IL-1RA decrease was not correlated with the dose of antipsychotics given to patients. There was no influence of this illness on protein levels for IL-1 receptor type 1 in the prefrontal cortex, either. In contrast, IL-1RA serum levels were increased in schizophrenic patients, especially in drug-free patients, as reported previously. These findings suggest that chronic schizophrenia down-regulates IL-1RA production the prefrontal cortex, irrespective of its impact on the periphery. IL-1RA reduction might reflect an immunopathologic trait of the prefrontal region in schizophrenic patients.

Ganglioglioma with a tanycytic ependymoma as the glial component

We studied a cystic ganglioglioma (GG) located in the right frontal lobe of the brain. Interestingly, the fibrillary spindle glial cells were often arranged in a fascicular pattern, and the generally uniform, round-to-oval delicate nuclei appeared to resemble those of ependymoma; and the neoplastic neurons often contained neurofibrillary tangles (NFTs). The glial component was positive for glial fibrillary acidic protein and occasionally contained granular or microvesicular structures positive for epithelial membrane antigen. Ultrastructural investigation revealed that the glial cells were ependymal in nature; intracytoplasmic lumina and intercellular microrosettes lined with cilia and microvilli, as well as long zonulae adherentes, were evident. In addition, chromogranin A-positive granular staining, neurosecretory-granule-like structures, and parallel arrays of microtubules were sometimes associated with the blood vessels. We considered the present case to be an unusual example of GG with an ependymoma, more precisely a tanycytic ependymoma, as the glial component; to our knowledge, the existence of ependymoma as the main glial component of this particular tumor has not been described before. The occurrence of NFTs, which has been reported in several cases of GG, was an additional, unusual feature.

Some glial progenitors in the neonatal subventricular zone migrate through the corpus callosum to the contralateral cerebral hemisphere

The great majority of glial cells of the mammalian forebrain are generated in the perinatal period from progenitors in the subventricular zone (SVZ). We investigated the migration of progenitors from the neonatal (postnatal day 0, P0) rat forebrain SVZ by labeling them in vivo with a green fluorescence protein (GFP) retrovirus and monitoring their movements by time‐lapse video microscopy in P3 slices. We identified a small number of progenitors that migrated tangentially within the corpus callosum (CC) and crossed the midline. These cells retained a relatively uniform morphology: the leading process was extended toward the contralateral side but showed no process branching or turning away from the migratory direction. Net migration requires the elongation of the leading process and nuclear translocation, and the migrating cells in the CC showed both modes. We confirmed the presence of unmyelinated axon bundles within the P3 CC, but failed to detect any radially directed glial processes (vimentin‐ or GLAST‐immunolabeled fibers) spanning through the CC. Confocal images showed a close proximity between neurofilament‐immunolabeled axons and the leading process of the GFP‐expressing progenitors in the CC. The destination of the callosal fibers was examined by applying DiI to the right cingulum; the labeled fibers ran throughout the CC and reached the left cingulate and motor areas. The distribution and final fates of the retrovirus‐labeled cells were examined in P28 brains. A small proportion of the labeled cells were found in the contralateral hemisphere, where, as oligodendrocytes and astrocytes, they colonized predominantly the cortex and the underlying white matter of the cingulate and secondary motor areas. The distribution pattern appears to coincide well with the projection direction of the callosal fibers. Thus, glial progenitors migrate across the CC, presumably in conjunction with unmyelinated axons, to colonize the contralateral hemisphere. J. Comp. Neurol. 458:381–388, 2003.

Neuronal migration disturbance and consequent cytoarchitecture in the cerebral cortex following transplacental administration of methylmercury

Abstract. To understand the effects of methylmercury (MeHg) on neuronal migration in the developing cerebral cortex, we performed double administrations of MeHg and 5-bromo-2-deoxyuridine (BrdU) to pregnant rats on different embryonic days (E11, E13, E16 or E21). Histopathological examination of a proportion of the offspring on postnatal dayxa028 revealed no apparent cytoarchitectural abnormalities in the primary motor and primary somatosensory cortices of the cerebrum. Morphometric analysis revealed no significant differences in total neuron population in either of these areas, and no differences in subpopulations of cells in any of the cortical layers, between any of the MeHg-exposed groups and the control animals. However, BrdU immunohistochemistry revealed an abnormally widespread distribution of the labeled cells throughout cortical layers II–VI of offspring exposed to MeHg on E16 and E21, indicating disruption of the inside-out pattern of neuronal migration. We examined one aspect of cell-fate determination by applying immunohistochemistry with antibodies against calbindin, parvalbumin, calretinin, and γ-aminobutyric acid, but found no differences in the topographic distributions of the antibody-labeled cells in the cortex between the controls and the MeHg-exposed offspring. These results suggest that it is the extrinsic circumstances – rather than the timing of neuron generation – that regulates the expression of these proteins.

Pathologic features of dysplasia and accompanying alterations observed in surgical specimens from patients with intractable epilepsy

Malformations caused by abnormalities of cortical development, or cortical dysplasias, were examined in surgical specimens from 108 patients with medically intractable epilepsy to determine the scope of histopathologic changes. The relevance of the clinical findings was also evaluated. Various types and degrees of dysplastic features were observed in various combinations, including architectural abnormalities, an increased number of neurons in the molecular layer and/or cortical layer II, neuronal clustering, an increased number of satellite oligodendrocytes, abnormal gyration, single and/or aggregates of heterotopic neurons in the white matter, and the appearance of cytologically abnormal cells, such as giant or dysmorphic neurons and balloon cells. In the temporal lobe specimens, microdysgenesis (corresponding to mild malformations caused by abnormalities of cortical development and type IA/B focal cortical dysplasias) was more frequently observed than Taylor-type focal cortical dysplasia (type IIA/B), whereas in the frontal lobe specimens, the frequency of occurrence of both types was even. The ages at seizure onset and surgery of patients with the latter type were significantly lower than those of patients with the former. On the other hand, prominent astrocytosis in the cortex and white matter was evident in all cases, and many corpora amylacea and neurofibrillary tangle-like inclusions were observed in a subset of cases. An ultrastructural investigation revealed dilatation of the postsynaptic dendritic spines and shafts in the cortex and features indicating the occurrence in the white matter of demyelination followed by remyelination. Thus, with regard to the epileptogenic lesions, although dysplastic changes constitute the pathogenetic basis, the overlapping subsequent degenerative processes involving synapses, dendrites, and axons might contribute to the development of epileptogenic processes. Astrocytes might also actively participate in the development of the pathogenesis of epilepsy.

Similarity and variation in gene expression among human cerebral cortical subregions revealed by DNA macroarrays: technical consideration of RNA expression profiling from postmortem samples.

The functional regionality of the human cerebral cortex suggests that a set of genes might be activated in each subregion of the neocortex to support its specific functions. To test this hypothesis, we employed the DNA array technique to compare the mRNA expression profiles of three neocortical subregions of the human brain: prefrontal cortex (Area 46), motor cortex (Area 4) and visual cortex (Area 17). The macroarray analysis on high quality mRNA from postmortem brains revealed that the expression profiles of the different cortical areas are almost similar: only six out of 1088 known genes exhibited significant differences (>2-fold) in their expression. RT-PCR studies with an increased number of samples confirmed that expression of only two genes, annexin II and early growth response protein 1, varied by 2-fold among the regions, whereas expression of the others showed large inter-individual difference. These results suggest that the whole neocortex of humans is more homogeneous than we expected at the level of gross gene expression profiles. In parallel, sensitivity and accuracy of radioisotope-based DNA macroarrays and fluorescence-based DNA microarrays were tested.