Attenuated nuclear shrinkage in neurones with nuclear inclusions of SCA1 brains.

BACKGROUND: Spinocerebellar ataxia type 1 (SCA1) is one of the autosomal dominant neurodegenerative disorders commonly linked to pathological expansion of the CAG repeat of the relevant gene. Nuclear inclusions and neurodegeneration are both triggered by this pathological expansion of the CAG/polyglutamine repeat on ataxin-1, but it remains to be determined whether or not nuclear inclusion formation is associated with accelerated neurodegeneration. OBJECTIVE: To examine the influence of nuclear inclusions on nuclear size and deformity in human brains from patients suffering from SCA1. MATERIAL: Pontine sections of brains obtained at necropsy from seven patients with SCA1 and five controls. METHODS: The size and deformity of each neuronal nucleus was quantified. Nuclei with and without inclusions were examined separately to assess the possible influence of nuclear inclusions on neurodegeneration. RESULTS: Nuclear shrinkage and deformity were more marked in SCA1 brains than in controls. This shrinkage was attenuated in neurones containing nuclear inclusions. CONCLUSIONS: The existence of nuclear inclusions in SCA1 is presumably linked to a mechanism that attenuates rather than accelerates nuclear shrinkage. This in vivo finding may provide a clue to constructing a rational therapeutic strategy for combating neurodegeneration associated with nuclear inclusions.

A linkage disequilibrium at the candidate gene locus for 16q-linked autosomal dominant cerebellar ataxia type III in Japan.

We previously mapped the gene responsible for autosomal dominant cerebellar ataxia (ADCA) type III to a 10.9-cM interval between D16S3089 and D16S515 on chromosome 16q. This region, however, was identical to the candidate locus of spinocerebellar ataxia type 4 (SCA4). In this study, we extended our research to refine the gene locus of the disease by applying linkage disequilibrium with 20 microsatellite DNA markers. With 9 markers flanked by D16S3031 and D16S3107, we found that the affected individuals in six families had a common haplotype on their disease chromosomes. Furthermore, linkage disequilibrium was demonstrated with 5 informative markers: D16S3019 (P = 0.013), D16S3067 (P = 0.008), D16S3141 (P = 0.011), D16S496 (P = 0.032), and D16S3107 (P = 0.000). These results indicate that the disease could have originated from a common ancestor harboring a mutation within a less than 3-cM region between D16S3043 and D16S3095. The founder alleles were also observed in other patients with ADCA type III unrelated to the six families.

A gene on SCA4 locus causes dominantly inherited pure cerebellar ataxia.

BACKGROUND: Several different genes or their loci have been identified for autosomal dominant cerebellar ataxia (ADCA). However, other types of ataxia remain unassigned. OBJECTIVE: To identify a new locus for ADCA. METHODS: Six Japanese families with ADCA with pure cerebellar syndrome (ADCA type III) were examined. These families had been molecularly excluded for spinocerebellar ataxia (SCA) types 1 through 3, 5 through 8, and 10. Clinical examination was undertaken, and a genome-wide linkage search was performed on 250 microsatellite DNA markers. RESULTS: Strong evidence for linkage was found with markers on human chromosome 16q, and haplotype and multipoint analyses further refined the gene locus in a 10.9-cM interval between D16S3089 and D16S515. Linkage disequilibrium was further found with the marker D16S3107 within the interval. The locus was exactly the candidate interval of SCA4, a rare form of ADCA clinically characterized by ataxia with sensory neuropathy and pyramidal tract signs. This would suggest that SCA4 and our ADCA type III are likely to be allelic disorders with different clinical features. CONCLUSION: The current study provides evidence that a gene on the SCA4 locus causes a pure cerebellar syndrome.

Dual enhancement of double immunofluorescent signals by CARD: participation of ubiquitin during formation of neurofibrillary tangles.

Amplification with catalyzed reporter deposition (CARD) greatly enhances peroxidase signals, which has been utilized to amplify immunohistochemical labelings including fluorochromes. Here we describe a strategy to amplify each of two immunofluorescent signals without crosstalk on double-stained histological sections from human autopsied brains with Alzheimer's disease (AD). One of the two primary antibodies (anti-Abeta or anti-PHF-tau) was probed by a species-specific secondary antibody conjugated with horseradish peroxidase (HRP), which was visualized by FITC-labeled tyramide. After inactivation of HRP, the other primary antibody was probed by another species-specific secondary antibody conjugated with HRP. Amplification with biotinylated tyramide was followed by streptavidin-conjugated Cy-5, which specifically labeled the latter epitope. It was found that Abeta and PHF-tau were localized to senile plaques and neurofibrillary tangles (NFTs), respectively, which verified lack of crosstalk on the double-stained section. Localization of ubiquitin and PHF-tau was looked for at higher magnification in NFT-bearing neurons. Although these two epitopes were colocalized in some neurons, ubiquitin was not always present in PHF-tau positive NFTs. Discrepancy between PFH-tau and ubiquitin, verified inter- and intracellularly, may represent different stages of NFT formation. This is the first report of successful CARD amplification of two different fluorescent signals on double-labeling immunohistochemistry, which is now proved to be powerful in detecting epitopes in relation to AD-related lesions. Improved intensity over tenfold of the two fluorescent signals without crosstalk will expand the application of the multilabeling method with fluorochromes.

[Diffusion images on brain MRI in Creutzfeldt-Jakob disease].

We report a 72-year-old man with Creutzfeldt-Jakob disease. He showed a progressive dementia, myoclonus, and other neurological symptoms. DNA analysis showed a normal variation of prion gene (codon 129, Met/Met: codon 219, Glu/Glu). He had periodic synchronous discharge on electroencephalogram and brain atrophy on CT scan and MRI. Diffusion images on his brain MRI revealed a marked increase in signal intensity in the caudate nuclei, putamen, and cerebral cortices. These changes may represent spongy changes of the brain and seem to be a feature of brain MRI in Creutzfeldt-Jakob disease.

Regional differences in genetic subgroup frequency in hereditary cerebellar ataxia, and a morphometrical study of brain MR images in SCA1, MJD and SCA6.

Molecular genetic assessments of 69 individuals in 44 families with hereditary cerebellar ataxia (HCA) were made to determine the relative frequencies of subtypes of HCA in Yamagata, Japan. Fifteen families (34%) had SCA1, none had SCA2, nine (20%) had MJD, five (11%) had SCA6 and nine (20%) had DRPLA. These findings differ markedly from those in other regions of Japan and the rest of the world. A morphometrical study of the brain MR images also was made on 38 individuals with SCA1 (n = 14), MJD (n = 8) or SCA6 (n = 16). In SCA1, the ventral pons was atrophic in proportion to the amount of cerebellar atrophy. In MJD, both the pons and the cerebellum were atrophic, cerebellar atrophy being less pronounced than that in SCA1 and SCA6. While both the major and minor axes of the ventral pons were proportionally decreased in SCA1, the minor axis was more decreased than the major axis in MJD. In SCA6, a mild reduction in the ratio of the ventral pontine area to the posterior fossa area (Pv/PF) was observed as well as obvious cerebellar atrophy. These findings indicate that in MR images SCA1, MJD and SCA6 show different atrophic features of the cerebellum and brainstem.

Abducens nerve enhancement in acute ophthalmoparesis.

Acute ophthalmoparesis (AO) is a monophasic disease characterized by acute onset of paresis of the extraocular muscles without ataxia or areflexia. Here we report a case of AO with gadolinium enhancement in the cisternal portion of the abducens nerves using contrast-enhanced three-dimensional magnetic resonance imaging.

Novel deletion and insertion mutations cause splicing defects, leading to severe reduction in mRNA levels of the A subunit in severe factor XIII deficiency.

In order to explore molecular mechanisms for factor XIII deficiency, a patient (Nagoya I) was examined at the DNA and RNA levels. Nucleotide sequence analysis of the patient's DNA amplified by PCR revealed that he had a 20 bp deletion at the boundary of exon I/intron A, and an insertion of T in the invariant GT dinucleotide at the splicing donor site of exon IV/intron D. The presence of these heterozygous mutations was confirmed by restriction digestion of the amplified fragments of the proband and his parents. RT-PCR analysis demonstrated that only one kind of mRNA without exon IV was detected in Nagoya I, although its level was greatly reduced to less than 5% of normal. The other detective allele of the A subunit gene containing the 20 bp deletion was not detected. Thus, both mutations impaired normal processing of mRNA for the A subunit, resulting in his severe factor XIII deficiency.

Localization of the gustatory pathway in the human midbrain.

The localization of the secondary gustatory pathway in the human brainstem still remains uncertain. Here we report two patients with small vascular lesions in the unilateral midbrain tegmentum who presented with taste disturbance on the ipsilateral side of the tongue. In both cases, the dorsomedial mesencephalic tegmental region lateral to the oculomotor nucleus, including the central tegmental tract and the ventral part of the periaqueductal gray, was involved commonly in the lesions. The secondary gustatory pathway arising from the nucleus of the solitary tract appears to run rostrally, without crossing, to the ipsilateral thalamic nucleus through the dorsomedial part of the tegmental region at the rostral level of the midbrain.