Akiyoshi Kakita

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.

Influences of dopaminergic lesion on epidermal growth factor-ErbB signals in Parkinson's disease and its model: neurotrophic implication in nigrostriatal neurons.

Epidermal growth factor (EGF) is a member of a structurally related family containing heparin‐binding EGF‐like growth factor (HB‐EGF) and transforming growth factor alpha (TGFα) that exerts neurotrophic activity on midbrain dopaminergic neurons. To examine neurotrophic abnormality in Parkinsons disease (PD), we measured the protein content of EGF, TGFα, and HB‐EGF in post‐mortem brains of patients with Parkinsons disease and age‐matched control subjects. Protein levels of EGF and tyrosine hydroxylase were decreased in the prefrontal cortex and the striatum of patients. In contrast, HB‐EGF and TGFα levels were not significantly altered in either region. The expression of EGF receptors (ErbB1 and ErbB2, but not ErbB3 or ErbB4) was down‐regulated significantly in the same forebrain regions. The same phenomenon was mimicked in rats by dopaminergic lesions induced by nigral 6‐hydroxydopamine infusion. EGF and ErbB1 levels in the striatum of the PD model were markedly reduced on the lesioned side, compared with the control hemisphere. Subchronic supplement of EGF in the striatum of the PD model locally prevented the dopaminergic neurodegeration as measured by tyrosine hydroxylase immunoreactivity. These findings suggest that the neurotrophic activity of EGF is maintained by afferent signals of midbrain dopaminergic neurons and is impaired in patients with Parkinsons disease.

Perinatal inflammatory cytokine challenge results in distinct neurobehavioral alterations in rats: implication in psychiatric disorders of developmental origin

Maternal stress, viral infection, and obstetric complications, which trigger cytokine signaling, are hypothesized to be involved in schizophrenia and its related disorders. The etiologic contribution of individual cytokines to such psychiatric disorders, however, remains to be evaluated. To estimate the impact of peripheral cytokine challenge on neurobehavioral development, we examined effects of four proinflammatory cytokines on rat neonates and their later behavioral performance. Sublethal doses of interleukin-1 alpha, interleukin-2, interleukin-6, or interferon-gamma were subcutaneously administered to rat pups for 9 days. These animals displayed alterations in physical development, including lower weight gain and/or accelerated eyelid opening. In addition, behavioral abnormalities related to fear/anxiety levels and sensorimotor gating emerged at different developmental stages, depending on the cytokine species administered. During juvenile stages, neonatal interleukin-2 treatment increased exploratory locomotor activity, whereas other cytokine treatments did not. At the post-puberty stage, however, the interleukin-2-induced abnormal motor activity became undetectable, whereas interleukin-1 alpha-treated rats developed abnormalities in startle response, prepulse inhibition (PPI), and social interaction. Subchronic treatment of an anti-psychotic drug, clozapine, ameliorated the impairment of prepulse inhibition without altering startle responses. These animal experiments illustrate that, during early postnatal development, inflammatory cytokine challenge in the periphery can induce future psycho-behavioral and/or cognitive impairments with various latencies, although the pathologic mechanisms underlying these abnormalities remain to be determined.

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.

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.

Frontotemporal dementia with co-occurrence of astrocytic plaques and tufted astrocytes, and severe degeneration of the cerebral white matter: a variant of corticobasal degeneration?

We report two patients who exhibited frontotemporal dementia (FTD) with unusual neuropathological features. The ages of the patients at death were 65 and 67xa0years, the disease durations were 6 and 5xa0years, and the clinical diagnoses were Pick’s disease and corticobasal degeneration (CBD), respectively. At autopsy, both cases exhibited neuropathological findings compatible with those of CBD, including atrophy of the frontal and parietal lobes, neuronal loss and gliosis in the cortical and subcortical regions, and presence of cortical ballooned neurons and astrocytic plaques (APs). In both cases, immunoblotting of insoluble tau exhibited the pattern of selective accumulation of four-repeat tau, a finding that is also compatible with CBD. However, severe degeneration was evident in the frontal and parietal white matter in both cases. Moreover, a striking finding was the widespread presence in the affected cortex of tufted astrocytes (TAs), which are characteristic of progressive supranuclear palsy (PSP). Neither co-occurrence of APs and TAs nor severe degeneration of the cerebral white matter is a feature of either CBD or PSP. No mutations were found in the tau gene in either case. In conclusion, the possibility that these two cases represent a new neuropathological phenotype of non-familial FTD rather than simply a variant of CBD cannot be completely excluded.

Sporadic four-repeat tauopathy with frontotemporal degeneration, parkinsonism and motor neuron disease

We report a sporadic tauopathy of 6-year duration in a 76-year-old woman. Her initial symptoms were asymmetrical parkinsonism and muscle weakness, with apraxia appearing 2xa0years later. The brain showed frontal and temporal cerebral atrophy; severe neuronal loss and gliosis were observed in the precentral cortex (loss of Betz cells was also evident) and premotor area, and in the medial temporal lobe, including the temporal tip, amygdala, and hippocampal CA1-subiculum border zone. The substantia nigra showed moderate neuronal loss and gliosis. In the spinal cord, loss of the anterior horn cells and degeneration of the corticospinal tracts were a characteristic feature. In addition, in the affected regions, the remaining neurons were often found to contain intracytoplasmic inclusions resembling neurofibrillary tangles. Tau immunostaining revealed widespread glial-predominant lesions in the cerebral gray and white matter. In contrast, predominance of neuronal lesions (pretangles/tangles) was a feature in the subcortical gray matter, including the spinal cord. The remaining upper and lower motor neurons were also affected by tau pathology. Accumulated tau in these glial cells and neurons was clearly recognized by a specific antibody against four-repeat (4R) tau. The ultrastructural presence of tau-positive tubular structures was confirmed in the glial cells and neurons (tangles). Immunoblotting of a frozen frontal lobe sample revealed accumulation of 4R-predominant tau isoforms. No mutations were found in the tau gene. These findings indicate that a sporadic 4R tauopathy can cause frontotemporal degeneration, parkinsonism, and motor neuron disease. The present case could represent a new clinicopathological phenotype of non-familial tauopathy.

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.

ErbB1 receptor ligands attenuate the expression of synaptic scaffolding proteins, GRIP1 and SAP97, in developing neocortex

Scaffolding proteins containing postsynaptic density-95/discs large/zone occludens-1 (PDZ) domains interact with synaptic receptors and cytoskeletal components and are therefore implicated in synaptic development and plasticity. Little is known, however, about what regulates the expression of PDZ proteins and how the levels of these proteins influence synaptic development. Here, we show that ligands for epidermal growth factor receptors (ErbB1) decrease a particular set of PDZ proteins and negatively influence synaptic formation or maturation. In short-term neocortical cultures, concentrations of epidermal growth factor and amphiregulin (2-9 pM) decreased the expression of glutamate receptor interacting protein 1 (GRIP1) and synapse-associated protein 97 kDa (SAP97) without affecting postsynaptic density-95 (PSD-95) levels and glial proliferation. In long-term cultures, epidermal growth factor treatment resulted in a decrease in the frequency of pan-PDZ-immunoreactive aggregates on dendritic processes. A similar activity on the same PDZ proteins was observed in the developing neocortex following epidermal growth factor administration to rat neonates. Immunoblotting revealed that administered epidermal growth factor from the periphery activated brain ErbB1 receptors and decreased GRIP1 and SAP97 protein levels in the neocortex. Laser-confocal imaging indicated that epidermal growth factor administration suppressed the formation of pan-PDZ-immunoreactive puncta and dispersed those structures in vivo as well. These findings revealed a novel negative activity of ErbB1 receptor ligands that attenuates the expression of the PDZ proteins and inhibits postsynaptic maturation in developing neocortex.

Pathological Heterogeneity of the Precentral Gyrus in Pick’s Disease: A Study of 16 Autopsy Cases

This report concerns the upper motor neuron involvement in 16 autopsy cases of Pick disease with Pick bodies, including 11 cases reported by us previously. Prominent, circumscribed atrophy of the precentral gyrus, conspicuously in the lower portion, was noted in one case. Loss of Betz cells and astrocytosis of the precentral gyrus layer V were encountered in 15 cases (94%) and eight cases (50%), respectively. Appearance of Pick bodies and ballooned neurons in the precentral gyrus layer V was confirmed in seven cases (44%). Degeneration of the pyramidal tract in the medulla oblongata was noted in all 15 cases in which this structure was examined. Pyramidal signs were observed in four (67%) of the six cases that were neurologically sufficiently examined: hyperreflexia in four cases (67%), spasticity in one case (17%). Babinski sign was not encountered in any of the six cases. In all four cases having pyramidal signs, degeneration of the pyramidal tract was observed. In contrast, two cases having degeneration of the pyramidal tract did not develop pyramidal signs. In Pick’s disease with Pick bodies, obvious involvement of the precentral gyrus and pyramidal tract was not previously noticed. Furthermore, we suggest that pyramidal signs in Pick’s disease with Pick bodies have been underestimated.