Clinical and genetic studies of families with the tau N279K mutation (FTDP-17).

The tau N279K mutation was identified in four separately ascertained families in the United States, Japan, and France and in another recently discovered affected individual in Japan. The authors analyzed genealogical and clinical records and DNA samples. Average age at onset was 43 years; survival time was 7 years. All families exhibited similar clinical features, with parkinsonism, dementia, and supranuclear palsy uniformly seen. A founder effect indicated by a shared disease haplotype was seen only in two Japanese families. The N279K mutation can develop independently in different parts of the world.

Caspase activities and tumor necrosis factor receptor R1 (p55) level are elevated in the substantia nigra from parkinsonian brain.

The activities of caspase-1 and caspase-3 were measured by use of fluoropeptides as substrates for the first time in the brain (substantia nigra, caudate nucleus, putamen, cerebellum, and frontal cortex) from control and parkinsonian patients. The activities of caspases in the brain were significantly higher in the substantia nigra from parkinsonian patients than those in the brain from control patients (p < 0.01). However, the activities of caspases in the caudate nucleus, putamen, cerebellum, and frontal cortex showed no significant difference between parkinsonian and control patients. The tumor necrosis factor (TNF) receptor R1 (TNF-R1, p55) level was also elevated in the substantia nigra of the parkinsonian brain in comparison with that of controls (p < 0.05). Since both caspases and TNF-R1 may play important roles in apoptotic cell death through TNF-alpha-induced signaling pathway, our present data suggest the presence of a proapoptotic environment in the substantia nigra of parkinsonian brain, probably inducing vulnerability of neurons and glias towards a variety of noxious factors.

A single nucleotide polymorphism of dopamine transporter gene is associated with Parkinson's disease.

We identified two polymorphisms out of all coding regions of the dopamine transporter gene. One existed in exon 9 (1215A/G) and another in exon 15 (1898T/C). The 1215G was significantly less frequent among patients with Parkinson's disease than the controls. Although the polymorphism caused no amino acid substitution, we concluded that it was associated with decreasing the susceptibility to Parkinson's disease through mechanisms other than the protein function of dopamine transporter.

A mutation in the microtubule-associated protein tau in pallido-nigro-luysian degeneration.

We detected a missense mutation in exon 10 of tau that causes a substitution at codon 279 (N279K) in a Japanese patient with a familial background of parkinsonism and dementia originally described as pallido-nigro-luysian degeneration. This mutation is the same as one seen in a Caucasian family with pallido-ponto-nigral degeneration. The similarities between these two families suggest a common genetic mechanism that may account for the peculiar distribution of neuroglial degeneration with tauopathy.

Brain-derived growth factor and nerve growth factor concentrations are decreased in the substantia nigra in Parkinson's disease.

Using highly sensitive sandwich enzyme-linked immunosorbent assays (ELISA), we measured for the first time the concentrations of brain-derived growth factor (BDNF) in the brain (substantia nigra, caudate nucleus, putamen, cerebellum, and frontal cortex) from control and parkinsonian patients. BDNF in the human brain (the order of ng/mg protein) was significantly lower specifically in the nigrostriatal dopamine (DA) regions from parkinsonian patients than in those from control patients. The concentration of nerve growth factor (NGF) was also significantly decreased in the substantia nigra of parkinsonian patients in comparison with that in the controls. Since BDNF and NGF may play important roles in survival and differentiation of neuronal cells, the present data indicate that the lack of neurotrophins, especially BDNF, may be involved in the pathogenesis of PD during progress of neurodegeneration of the nigrostriatal DA neurons.

Spinocerebellar ataxia type 6 in relation to CAG repeat length.

UNLABELLED: The purpose of the present study was to assess the relationship between clinical characteristics of spinocerebellar ataxia type 6 (SCA6) and CAG repeat length. MATERIALS AND METHODS: We examined clinical symptoms of 54 patients with SCA6. CAG repeat length was compared among subgroups divided by clinical manifestations. RESULTS: The major symptom was progressive cerebellar ataxia. Truncal or limb ataxia, dysarthria, and nystagmus were observed in more than 80% of the patients. In analysis of CAG repeat length in patients with different types of nystagmus, CAG repeat length was the longest when both upbeat and downbeat nystagmus existed (P < 0.01). In addition, CAG repeat length was longer when the initial symptom was ataxic gait and was shorter when the initial symptom was dysarthria or ocular symptom (P < 0.05). CONCLUSION: Clinical features of SCA6 might be influenced by the length of abnormal CAG repeat.

A novel missense mutant inactivates GTP cyclohydrolase I in dopa-responsive dystonia.

Dopa-responsive dystonia (DRD) due to mutant GTP cyclohydrolase I (GCH) shows the considerable heterogeneity of clinical phenotypic expression. To explain the clinical diversity, we studied a Japanese family with a novel mutant GCH (GCH-G90V), where an affected heterozygote had a higher mutant/normal mRNA ratio than an unaffected heterozygote. Coexpression experiments using the mutant with wild-type GCH showed that GCH-G90V inactivated the normal enzyme in a dose-dependent manner, suggesting that the dominant negative effect of a mutant GCH on the normal enzyme might be one of the molecular mechanisms for the clinical heterogeneity of DRD.

Transgenic mice harboring a full-length human mutant DRPLA gene exhibit age-dependent intergenerational and somatic instabilities of CAG repeats comparable with those in DRPLA patients.

Dentatorubral-pallidoluysian atrophy (DRPLA) is one among an increasing number of hereditary neurodegenerative diseases determined as being caused by unstable expansion of CAG repeats coding for polyglutamine stretches. To investigate the molecular mechanisms underlying CAG repeat instability, we established three transgenic lines each harboring a single copy of a full-length human mutant DRPLA gene carrying a CAG repeat expansion. These transgenic mice exhibited an age-dependent increase (+0.31 per year) in male transmission and an age-dependent contraction (-1.21 per year) in female transmission. Similar tendencies in intergenerational instabilities were also observed in human DRPLA parent-offspring pairs. The intergenerational instabilities of the CAG repeats may be interpreted as being derived from the instability occurring during continuous cell division of spermatogonia in the male, and that occurring during the period of meiotic arrest in the female. The transgenic mice also exhibited an age-dependent increase in the degree of somatic mosaicism which occurred in a cell lineage-dependent manner, with the size range of CAG repeats being smaller in the cerebellum than in other tissues including the cerebrum, consistent with observations in autopsied tissues of DRPLA patients. Thus, the transgenic mice described in this study exhibited age-dependent intergenerational as well as somatic instabilities of expanded CAG repeats comparable with those observed in human DRPLA patients, and are therefore expected to serve as good models for investigating the molecular mechanisms of instabilities of CAG repeats.

Triggering of neuronal cell death by accumulation of activated SEK1 on nuclear polyglutamine aggregations in PML bodies.

BACKGROUND: A novel class of inherited human neurodegenerations is now known to be caused by expanded CAG repeats encoding polyglutamines. Polyglutamine-containing protein fragments have been shown to accumulate as aggregates in the nucleus and in the cytoplasm, and to induce cell death when expressed in cultured cells, leading to the proposal that polyglutamine aggregation is an important step in the pathogenesis. Supporting this, nuclear inclusions containing expanded polyglutamines have been identified in neurones from the brains of patients and in neurones from transgenic mouse models of this class of neural disorders. RESULTS: We analysed the consequences of polyglutamine expression in PC12 neuronal cells. Activated SEK1 accumulated with nuclear but not cytoplasmic polyglutamine aggregations, which consequently triggers cell death. Cell death induced by polyglutamine expression was inhibited by a dominant-negative SEK1 (DN-SEK1), but not by DN-SEK1 tagged with a nuclear export signal. Steady state SEK1 expression itself was enhanced two to three-fold. Nuclearly aggregated polyglutamines, which were identified in PML bodies, co-localized with not only activated SEK1 but also activated c-Jun. We also observed that nuclear inclusion-positive neurones from brains with Huntington's disease expressed SEK1. CONCLUSIONS: This study provides molecular links between the neurodegeneration observed in polyglutamine diseases, cell death signalling kinase cascades and nuclear subdomains related to cell death. We propose that the nuclear PML bodies containing polyglutamine aggregates activate the SEK1-JNK kinase cascade, resulting in the transduction of a death signal.

No association between apolipoprotein E alleles and olivopontocerebellar atrophy.

Apolipoprotein E (apo E) epsilon4 is a risk factor for sporadic and late-onset familial Alzheimer's disease, but it is not well known whether the apo E is associated with spinocerebellar degeneration. We studied the frequency of apo E allele in 59 olivopontocerebellar atrophy (OPCA) patients, including 13 pathologically confirmed cases. The distribution of the apo E allele frequency did not differ between OPCA patients and controls. Apo E allele does not influence the development of OPCA.

Asymmetrical changes in the fodrin alpha subunit in the superior temporal cortices in schizophrenia.

BACKGROUND: We examined possible abnormalities in neural structural proteins that may underlie morphometric changes reported in the left superior temporal cortices (Brodmann's area 22) of schizophrenics. METHODS: Particulate proteins of the superior temporal cortices taken at autopsy from 11 schizophrenic and 9 control brains were fractionated by gel electrophoresis. Target proteins, identified by reading their amino acid sequences, were immunoquantified using the specific antibody. RESULTS: Amino acid sequences of the 150-kDa proteins on sodium dodecyl sulfate/polyacrylamide gel electrophoresis, which were significantly increased on the left side of schizophrenic superior temporal cortices, revealed that they were proteolytic fragments of the alpha subunit of fodrin, a major cytoskeletal protein underlying the plasma membrane. Immunoquantification using the specific antibodies against alpha and beta subunits of fodrin indicated that there exist concomitant decreases in the full-length 240-kDa form and increases in the 150-kDa form of alpha-fodrin with no changes of the 235-kDa form of beta-fodrin in the left superior temporal cortices of the schizophrenic brains. CONCLUSIONS: The findings may be a possible molecular basis for linking morphometric changes to neurochemical pathophysiology in schizophrenia.

Molecular features of the CAG repeats of spinocerebellar ataxia 6 (SCA6).

Spinocerebellar ataxia 6 (SCA6) is an autosomal dominant spinocerebellar degeneration caused by the expansion of the polymorphic CAG repeat in the human alpha1A voltage-dependent calcium channel subunit gene (CACNL1A4 gene). We have analyzed 60 SCA6 individuals from 39 independent SCA6 Japanese families and found that the CAG repeat length is inversely correlated with the age of onset (n = 58, r = -0.51, P < 0.0001). SCA6 chromosomes contained 21-30 repeat units, whereas normal chromosomes displayed 6-17 repeats. There was no overlap between the normal and affected CAG repeat number. The anticipation of the disease was observed clinically in all eight parent-child pairs that we examined; the mean age of onset was significantly lower (P = 0.0042) in children than in parents. However, a parent-child analysis showed the increase in the expansion of CAG repeats only in one pair and no diminution in any affected cases. This result suggests that factors other than CAG repeats may produce the clinical anticipation. A homozygotic case could not demonstrate an unequivocal gene dosage effect on the age of onset.

A unique origin and multistep process for the generation of expanded DRPLA triplet repeats.

Dentatorubral and pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder associated with the expansion of a CAG repeat at chromosome band 12p13. Epidemiological studies have demonstrated an increased prevalence of DRPLA in Japan, although several DRPLA kindreds of non-Japanese ancestry have been identified. To define the molecular basis for this geographic variation in prevalence, we have analyzed haplotypes around the repeat in several different ethnic groups. Two intragenic biallelic polymorphisms distinguished three haplotypes, each of which formed a predominant haplotype found in the three major racial populations. All the expanded repeats of Japanese and Caucasian patients studied were associated with a particular haplotype, which otherwise was associated with longer repeats commonly found in Asians. Our results support a multi-step model for repeat expansion, and suggest that expanded DRPLA repeats may have evolved from an ancient chromosomal haplotype of Asian origin. We also propose that a combination of a highly polymorphic microsatellite marker with relatively stable biallelic markers in a range of PCR amplification is a powerful tool for studies on human genome diversity, which may reveal the ancient human migration and the formation of ethnic groups.

Somatic mosaicism of CAG repeat in dentatorubral-pallidoluysian atrophy (DRPLA).

An unstable expansion of CAG repeat in the coding region of the DRPLA gene on chromosome 12p is the mutation specific for hereditary dentatorubral-pallidoluysian atrophy (DRPLA). We studied the CAG expansion in brain and other tissues from six unrelated DRPLA patients. The CAG repeat lengths showed distinct differences between tissues. The sizes of the CAG expansion in various regions of the brain except the cerebellum were generally larger by several repeats than in other peripheral tissues. Brain samples showed greater variation of the expansion compared with other tissues, but neither the size of the CAG expansion nor the degree of CAG repeat variation parallels the detailed findings of neuropathological involvement. We conclude that somatic instabilities of the CAG repeat cause tissue variability of the CAG repeat size in DRPLA but other region or cell type-specific factors would be involved to explain the selectivity of cell damage in DRPLA.

DNA analysis in hereditary dentatorubral-pallidoluysian atrophy: correlation between CAG repeat length and phenotypic variation and the molecular basis of anticipation.

Hereditary dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disease with variable clinical phenotypes. Progressive ataxia, choreoathetosis, and dementia are the main clinical features of adult-onset cases, whereas the main feature in juvenile-onset DRPLA is progressive myoclonus epilepsy. Earlier onset is apparent in successive generations (anticipation). The molecular abnormality underlying DRPLA is an expanded, unstable CAG trinucleotide repeat on chromosome 12p. We analyzed 71 DNA samples obtained from 12 Japanese DRPLA pedigrees that included 38 affected individuals. Normal alleles had 7 to 23 repeats, DRPLA alleles 53 to 88 repeats. DRPLA alleles also were detected in five asymptomatic family members. Patients with juvenile onset had significantly larger repeats than did those with adult onset, and there was a significant negative correlation between CAG repeat length and age at onset. In 80% of the paternal transmissions, there was an increase of more than five repeats, whereas all the maternal transmissions showed either a decrease or an increase of fewer than five repeats. There was a significant correlation between father-child differences in repeat length and differences in age at onset. The analysis of CAG repeat length is a reliable diagnostic test for DRPLA and is of value for the presymptomatic detection of individuals at risk. The expansion of CAG repeats is important in phenotypic variation and anticipation. In addition, the sex of the transmitting parent has a significant effect on the molecular mechanism of anticipation.

Anticipation in hereditary dentatorubral-pallidoluysian atrophy.

Anticipation refers to the progressively earlier onset and increase in disease severity in successive generations. We studied four families with hereditary dentatorubral-pallidoluysian atrophy (DRPLA), a neurodegenerative disease, and anticipation was present in the mode of inheritance. In subsequent generations DRPLA shows an earlier onset and more severe as well as additional symptoms. Older onset patients suffer from cerebellar ataxia with or without dementia, whereas younger onset patients present as progressive myoclonus epilepsy syndrome, which consists of mental retardation, dementia, and cerebellar ataxia as well as epilepsy and myoclonus. Anticipation with paternal transmission was significantly greater than with maternal transmission.

Increase in [3H]cAMP binding sites and decrease in Gi alpha and Go alpha immunoreactivities in left temporal cortices from patients with schizophrenia.

To search for possible alterations in second messenger systems in the temporal cortex (Brodmann's area 22) of patients with schizophrenia, we measured the binding activities of [3H]adenosine 3',5'-cyclic monophosphate ([3H]cAMP) and [3H]4 beta-phorbol 12,13-dibutyrate ([3H]PDBu) which can label the regulatory subunit of cAMP-dependent protein kinase (protein kinase A) and the regulatory domain of Ca2+/phospholipid-dependent protein kinase (protein kinase C), respectively. We also immunoquantified the variable subunits of guanine nucleotide binding proteins (G-proteins), using specific polyclonal antisera against Gs alpha, Gi alpha and Go alpha. Brains were obtained at autopsy on 10 patients with schizophrenia and 10 age-matched control subjects. Representative Scatchard plots for specific [3H]cAMP bindings to the soluble fraction consisted of a single component with high affinity (Kd = 2.36 nM, Bmax = 737 fmol/mg protein). Among the tested adenyl and guanyl nucleotides, or neuroleptics, cAMP alone potently inhibited the binding (Ki = 4.95 nM). The binding sites for [3H]cAMP were discretely localized, and were in the order of: cerebral cortex = hypothalamus = amygdala > hippocampus = neostriatum = thalamus = nucleus accumbens > globus pallidus = cerebellum. Specific [3H]cAMP bindings to the soluble fractions were about 30% greater in the left temporal cortices of schizophrenic patients, as compared to findings in the right side of the patients and the left side of the control subjects, no control brain showed this asymmetry. The specific [3H]PDBu binding in schizophrenic and control groups did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Pallidonigroluysian degeneration with iron deposition: a study of three autopsy cases.

In the basal ganglia of three autopsy cases of pallidonigroluysian degeneration, we found marked iron deposition, a finding which has not been mentioned previously in the literature. Besides severe astrogliosis and neuronal loss in the pallidum, Luysian body and nigra, granular deposits of brown pigments were found in the neuropil, microglias, oligodendrocytes and astrocytes in three such the nuclei and the striatum. These brown pigments proved histochemically to be iron. Our histochemical semiquantitative study showed a significantly stronger reaction for iron in the degenerated nuclei in these three cases than in control cases comprising non-degenerative and the other degenerative diseases. Quantitative study with inductively coupled emission spectrometry also demonstrated a markedly higher iron content in the globus pallidus and the striatum in comparison with the control cases. The possibility is discussed that iron deposition plays a role in generating the lesions of pallidonigroluysian degeneration.

The loss of beta II-protein kinase C in the striatum from patients with Huntington's disease.

We have examined the levels of protein kinase C (PKC) in autopsied brains of patients with Huntington's disease (HD), using [3H]4-beta-phorbol-12,13-dibutyrate ([3H] PDBu) and antisera against the PKC subspecies. In the caudate nucleus and putamen from patients with HD, the specific binding for [3H]PDBu was significantly decreased by 74 and 68%, respectively, as compared to findings in controls. The beta II-PKC immunoreactivities were significantly reduced by 65%, whereas the alpha-PKC immunoreactivities increased by 146%, in the putamen. There were no differences in the beta I- or gamma-PKC immunoreactivities in the putamen between HD and controls. These results suggest the differential localization of four PKC subspecies in human striatum and the involvement of four subspecies in different aspects of HD pathophysiology.