Takao Makifuchi

Corticobasal degeneration : etiopathological significance of the cytoskeletal alterations

We have studied brain tissues from three patients with corticobasal degeneration (CBD) histologically, ultrastructurally and immunohistochemically. Ballooned neurons in the cerebral cortex and severe degeneration of the substantia nigra were observed in them all and weakly basophilic neurofibrillary tangles (NFTs) were distributed widely in the basal ganglia and brain stem. Ultrastructural examination demonstrated that the NFTs comprised characteristic 15-nm-wide straight tubules, which showed positive immunohistochemical staining with an antibody against tau, but not ubiquitin. Tau-immunoreactive neuronal cell bodies without NFTs also were found in the cerebral cortex and subcortical nuclei, predominantly in the brain stem, and the greatest number of tau-positive glial inclusions occurred in the cerebral gray and white matter of the pre- and post-central gyri. These inclusions comprised tubular structures with diameters of about 15 nm and were localized in the oligodendroglial cellular cytoplasm and processes. These findings indicate that there is a close cytoskeletal pathological relationship between CBD and progressive supranuclear palsy.

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.

Selective reduction of a PDZ protein, SAP-97, in the prefrontal cortex of patients with chronic schizophrenia

Many postsynaptic density proteins carrying postsynaptic density‐95/discs large/zone occludens‐1 (PDZ) domain(s) interact with glutamate receptors to control receptor dynamics and synaptic plasticity. Here we examined the expression of PDZ proteins, synapse‐associated protein (SAP) 97, postsynaptic density (PSD)‐95, chapsyn‐110, GRIP1 and SAP102, in post‐mortem brains of schizophrenic patients and control subjects, and evaluated their contribution to schizophrenic pathology. Among these PDZ proteins, SAP97 exhibited the most marked change: SAP97 protein levels were decreased to less than half that of the control levels specifically in the prefrontal cortex of schizophrenic patients. In parallel, its binding partner, GluR1, similarly decreased in the same brain region. The correlation between SAP97 and GluR1 levels in control subjects was, however, altered in schizophrenic patients. SAP102 levels were also significantly reduced in the hippocampus of schizophrenic patients, but this reduction was correlated with sample storage time and post‐mortem interval. There were no changes in the levels of the other PDZ proteins in any of the regions examined. In addition, neuroleptic treatment failed to mimic the SAP97 change. These findings suggest that a phenotypic loss of SAP97 is associated with the postsynaptic impairment in prefrontal excitatory circuits of schizophrenic patients.

Aprataxin, the causative protein for EAOH is a nuclear protein with a potential role as a DNA repair protein

Early‐onset ataxia with ocular motor apraxia and hypoalbuminemia (EAOH) is an autosomal recessive neurodegenerative disorder characterized by early‐onset ataxia, ocular motor apraxia, and hypoalbuminemia. Recently, the causative gene for EAOH, APTX, has been identified. Of the two splicing variants of APTX mRNA, the short and the long forms, long‐form APTX mRNA was found to be the major isoform. Aprataxin is mainly located in the nucleus, and, furthermore, the first nuclear localization signal located near the amino terminus of the long‐form aprataxin is essential for its nuclear localization. We found, based on the yeast two‐hybrid and coimmunoprecipitation experiments, that the long‐form but not the short‐form aprataxin interacts with XRCC1 (x‐ray repair cross‐complementing group 1). Interestingly the amino terminus of the long‐form aprataxin is homologous with polynucleotidekinase‐3′‐phosphatase, which has been demonstrated to be involved in base excision repair, a subtype of single‐strand DNA break repair, through interaction with XRCC1, DNA polymerase β, and DNA ligase III. These results strongly support the possibility that aprataxin and XRCC1 constitute a multiprotein complex and are involved in single‐strand DNA break repair, and furthermore, that accumulation of unrepaired damaged DNA underlies the pathophysiological mechanisms of EAOH.

Apoptotic neurons in Alzheimer's disease frequently show intracellular Aβ42 labeling

It is widely accepted that Abeta plays a pivotal role in the pathogenesis of Alzheimers disease (AD) [27]. Attention has been focused mainly on how extracellular Abeta exerts its effects on neuronal cells [7,11,16,32]. However, neuronal degeneration from an accumulation of intracellular Abetax-42 (iAbeta42) occurs in presenilin 1 (PS1) mutant mice without extracellular Abeta deposits [5]. In the present study, intracellular deposits of iAbeta42 are correlated with apoptotic cell death in AD and PS-1 familial AD (PS1 FAD) brains by means of triple staining with antibodies to Abeta, TUNEL, and staining with Hoechst 33342. Neurons simultaneously positive for iAbeta42 and the TUNEL assay were significantly more abundant in AD brains than in controls. The number of apoptotic neurons with intracellular neurofibrillary tangles (iNFTs) was insignificant. Our results indicate that intraneuronal deposition of a neurotoxic form of Abeta seems to be an early event in the neurodegeneration of AD.

Familial amyotrophic lateral sclerosis with a mutation in the Cu/Zn superoxide dismutase gene

Several missense mutations within exons 1, 2, 4 and 5 of the gene for Cu/Zn-binding superoxide dismutase (SOD1) have been discovered to be involved in the development of chromosome 21q-linked familial amyotrophic lateral sclerosis (FALS). We describe here an autopsied patient with FALS, in whom we have recently identified a novel missense mutation in exon 1 of the SOD1 gene. The neuropathological findings were compatible with those described previously in patients with FALS with posterior column involvement. This suggests that mutations of the SOD1 gene may be responsible for this form of FALS.

Amyotrophic lateral sclerosis of Guam: the nature of the neuropathological findings

To elucidate the fundamental differences and similarities of the neuropathological features and etiopathogenesis of the amyotrophic lateral sclerosis (ALS) and parkinsonism-dementia complex (PDC) of Guam, we conducted a topographic, quantitative and histological investigation of tau-containing neurons, neurofibrillary tangles (NFTs), Bunina bodies and ubiquitinated inclusion bodies in 27 non-ALS non-PDC Guamanian subjects, as well as 10 Guam ALS patients, 28 PDC patients, and 5 patients with combined ALS and PDC (ALS-PDC). The topographic distribution of NFTs was basically the same in each disease and also in the non-ALS non-PDC group. There were relatively few, if any, NFTs in non-ALS non-PDC subjects and ALS patients, but there were many, especially in the frontal and temporal cortex, in Guam PDC and ALS-PDC patients. The histological and ultrastructural features of Bunina bodies in Guam ALS and ALS-PDC patients were similar to those reported in classic ALS. The ratio of occurrence of the inclusion in Guam ALS and ALS-PDC patients was similar to that reported so far in classic ALS. Ubiquitinated skein-like inclusion bodies were observed in the spinal anterior horn cells in Guam ALS and ALS-PDC patients. These findings indicate that classic ALS does exist on Guam, that NFTs in Guam ALS patients are merely a background feature widely dispersed in the population, that the mechanism of neuronal degeneration of Guam ALS is basically different from that of PDC, and that Guam ALS occurs initially as classic ALS.

Wobble modification deficiency in mutant tRNAs in patients with mitochondrial diseases

Point mutations in mitochondrial (mt) tRNA genes are associated with a variety of human mitochondrial diseases. We have shown previously that mt tRNALeu(UUR) with a MELAS A3243G mutation and mt tRNALys with a MERRF A8344G mutation derived from HeLa background cybrid cells are deficient in normal taurine‐containing modifications [τm5(s2)U; 5‐taurinomethyl‐(2‐thio)uridine] at the anticodon wobble position in both cases. The wobble modification deficiency results in defective translation. We report here wobble modification deficiencies of mutant mt tRNAs from cybrid cells with different nuclear backgrounds, as well as from patient tissues. These findings demonstrate the generality of the wobble modification deficiency in mutant tRNAs in MELAS and MERRF.

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.

A quantitative study on the expression of synapsin II and N-ethylmaleimide-sensitive fusion protein in schizophrenic patients

The application of DNA array technology to schizophrenic studies enabled us to assess molecular features of this disease. The expression of synapsin II and N-ethylmaleimide-sensitive fusion protein (NSF) mRNAs is reported to decrease in the prefrontal cortex of these patients. We attempted to reproduce this result with two distinct approaches. With high quality samples, mRNA and protein levels for synapsin II and NSF were measured by real-time polymerase chain reaction and by immunoblotting. Both experiments led to the same conclusion: The expression of these presynaptic markers is not altered significantly in the prefrontal cortex of our schizophrenic samples, compared to that in control subjects. These observations suggest that the neurochemical impairments of synapses reported in schizophrenia are not evident for all presynaptic markers and needs to be re-evaluated at molecular levels.