Katsuji Yoshioka

The 717Val→Ile substitution in amyloid precursor protein is associated with familial Alzheimer's disease regardless of ethnic groups

Alzheimers disease (AD) is a devastating neurological disorder and the leading cause of dementia among aged individuals. The human amyloid beta protein, which is a cleavage product of amyloid precursor protein (APP), is a major component of the amyloid deposited in the brain of patients with AD. By using PCR direct sequencing of exon 17 (encoding part of the beta protein) of the APP gene, we have found that a Japanese AD patient harbours a C to T substitution, responsible for a valine to isoleucine change at position 717, heterogeneously. The mutation is exactly the same as that found in a Caucasian AD family by Goate et al. (1). Furthermore, the mutation was shown to co-segregate with AD in his family. These results suggest that the Val----Ile change in the APP causes AD, regardless of ethnic background.

Haplotype analysis of familial amyloidotic polyneuropathy

SummaryFamilial amyloidotic polyneuropathy (FAP) is an autosomal dominant genetic disease characterized by systemic accumulation of amyloid fibrils. A major component of FAP anyloid has been identified as variant transthyretin (TTR, also called prealbumin). In particular, a variant with the substitution 30Val→Met has been commonly found in FAP of various ethnic groups. To understand the origin and spread of the Val→Met mutation, we analyzed DNA polymorphisms associated with the TTR gene in six Japanese FAP families and several Portuguese FAP patients. Three distinct haplotypes associated with the Val→Met mutation were identified in Japanese FAP families, one of which was also found in Portuguese patients. On the other hand, it was found that the Val→Met mutation can be explained by a C-T transition at the CpG dinucleotide sequence of a mutation hot spot. Thus, our findings indicate that the Val→Met mutation has probably recurred in the human population, to generate FAP families of independent origin.

Assignment of the prealbumin (PALB) gene (familial amyloidotic polyneuropathy) to human chromosome region 18q11.2–q12.1

SummaryThe assignment of the human prealbumin (PALB) gene to chromosome region 18q11–q12.1 has been achieved using a human genomic probe in the study of human-mouse somatic cell hybrids and by in situ hybridization. Because familial amyloidotic polyneuropathy was reported previously to be due to a mutation in prealbumin, it can be inferred that the gene for this disorder also maps to 18q11.2–q12.1.

Generation of transgenic mice producing a human transthyretin variant: a possible mouse model for familial amyloidotic polyneuropathy.

Type I familial amyloidotic polyneuropathy (FAP) results from the systemic deposition of a plasma transthyretin (TTR) variant with a Val----Met change at position 30. In an attempt to establish a model of this disease, we generated transgenic mice producing the variant TTR. A DNA fragment containing the mouse metallothionein-I promoter fused to the structural gene coding for the human TTR variant was microinjected into fertilized mouse eggs. Among 72 mice that developed from these eggs, ten carried the fusion gene and three of these showed significant concentrations of the variant TTR in their serum. These mice may be useful in elucidating the pathogenesis of FAP and in establishing a therapy for this intractable disorder.

Postnatal development of mRNA specific for a metabotropic glutamate receptor in the rat brain

We examined the ontogenesis of a subtype of metabotropic glutamate receptors, termed mGluR1, which is linked to phosphoinositide metabolism, in various regions of rat brain during neonatal development. Northern blot analyses of mGluR1 mRNA indicated that mRNA increased monotonously or remained at plateau levels during the first 5 weeks after birth. In situ hybridization analyses supported this conclusion. The result is in contrast with the reported development of the activity in excitatory amino acid-stimulated phosphoinositide turnover during the same period. The latter increases during the first few weeks and then decreases sharply.

Molecular analysis of a variant type of familial amyloidotic polyneuropathy showing cerebellar ataxia and pyramidal tract signs.

A Japanese family with atypical type I familial amyloidotic polyneuropathy (FAP) in Iiyama, Japan was studied. Most of the family members have dysfunctions in the central nervous system, in addition to typical symptoms of type I FAP. The transthyretin (TTR, also called prealbumin) gene of the atypical FAP(FAP-IY) was analyzed with recombinant DNA techniques and a RIA method. FAP-IY was found to have the mutation responsible for the methionine-for-valine substitution at position 30 of TTR, as in the case of typical type I FAP. However, analysis of DNA polymorphisms in the TTR locus showed that FAP-IY has a genetic background differing from that of the typical type I FAP. These observations lead to the consideration that a genetic factor(s) involved in the dysfunction of the central nervous system may locate in a chromosome region in close proximity to the TTR gene.

Genetic and clinical studies of japanese patients with familial amyloid polyneuropathy

We examined the DNA analysis of familial amyloid polyneuropathy (FAP) patients and their families from Nagano and Hiroshima prefectures in Japan using recombinant DNA techniques and compared the results with the clinical features. This study indicated that the valine-methionine change prealbumin gene was closely related to the clinical features of type 1 FAP. The DNA analysis was valuable for the definite diagnosis of type 1 FAP even in sporadic and asymptomatic cases. FAP patients from Iiyama city and Ogawa village area in the Nagano prefecture had the same mutation despite differences in clinical features. The onset of the sporadic FAP cases was later than that of the FAP patients who had family histories.

Genetic analysis of familial amyloidotic polyneuropathy, an autosomal dominant disease

Familial amyloidotic polyneuropathy (FAP) is an autosomal dominant genetic disease, and the major component of the amyloid fibrils from FAP patients was shown to be variants of transthyretin (TTR) with single amino acid substitutions. The nucleotide sequence analysis of the TTR cDNA and its corresponding gene enabled us to detect the base substitutions responsible for the variant TTR by conventional Southern blotting or polymerase chain reaction (PCR) method and allowed us to screen a number of FAP families in Japan. Among seven TTR variants related to FAP, all the FAP patients tested in Japan had the particular 30Val----Met mutation. Haplotype analysis revealed that the Val----Met mutation has recurred frequently in the population to generate the FAP families of independent origins. Although the primary cause of FAP has become clear, extensive screening of FAP families revealed that there existed late onset cases and also patients with atypical symptoms in FAP families with the Val----Met mutation, suggesting that the expression of FAP is a complex process and affected by some (unknown) factors other than TTR.

Toward Establishment of an Animal Model for Familial Amyloidotic Polyneuropathy: Generation and Characterization of Transgenic Mice

Type I familial amyloidotic polyneuropathy (FAP) results from the systemic accumulation of a plasma transthyretin (TTR) variant with a Val to Met change at position 30. As an approach to clarify the pathological process of this disease, we attempted to produce an animal model by introducing the mutated TTR gene into the mouse germ line. A total of ten transgenic mice carrying the mouse metallothionein-I-human variant TTR fusion gene was generated. To characterize these mice, the integrated fusion gene and its products were analyzed by various methods. The data demonstrate that the introduced genes are actually expressed and the variant TTR is secreted into the serum. These mice should be useful in elucidating the biochemical and biophysical nature of the variant form of TTR and eventually the disease process of type I FAP.

HAPLOTYPE ANALISIS OF FAMILIAL AMYLOIDOTIC POLYNEUROPATHY: AN EVIDENCE FOR MULTIPLE ORIGINS OF THE Val+Met MUTATION

The variant of transthyretin (TTR, also called prealbumin) has been identified as a major component of amyloid fibrils of familial amyloidotic polyneuropathy (FAP). In particular, the variant with30 Val→Met substitution has been commonly found in FAP of various ethnic groups. To understand the origin and spread of the Val→Met mutation, we have analyzed DNA polymorphisms associated with the TTR gene in six Japanese FAP families and several Portuguese FAP patients. Three distinct haplotypes associated with the Val→Met mutation were identified in Japanese FAP families, one of which was also found in Portuguese patients. Nucleotide sequence analysis revealed that the Val→Met mutation is caused by a C-T transition at a CpG dinucleotide sequence of mutation hotspot on the anti-sense strand of TTR gene DNA. These results suggest that the Val→Met mutation has frequently recurred in human population to generate FAP families in various ethnic groups.