Biomedical subjects

Keikichi Takahashi

Publications and source records attributed to Keikichi Takahashi.

8 recordsLinked to original sources

PubMed2006

Notch3 ectodomain is a major component of granular osmiophilic material (GOM) in CADASIL.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is an inherited systemic vascular disorder characterized by recurrent subcortical ischemic strokes leading to vascular dementia. The gold standard to confirm the diagnosis is to identify a mutation in the underlying gene NOTCH3, encoding a transmembrane receptor protein. Granular osmiophilic material (GOM) deposition around vascular smooth muscle cells is a specific diagnostic feature of CADASIL and electron microscopic examination of a skin biopsy is another useful method for its diagnosis. Although accumulation of Notch3 ectodomain on the surface of vascular smooth muscle cells has been reported, the composition of GOM has not been elucidated. To elucidate the relationship between Notch3 protein and GOM, we performed postembedding immunogold electron microscopy using cryofixed and freeze substituted skin taken from two CADASIL patients. Our results demonstrate that GOM around vascular smooth muscle cells was specifically labeled with antibodies against the extracellular portion of Notch3 but not with antibodies recognizing the intracellular Notch3 domain. In non-CADASIL skin sections, no antibody binding was detected around the small dermal arteries. From these results, the major component of GOM in CADASIL patients is the ectodomain of the Notch3 gene product. Our results shed light on the relationship between Notch3 gene mutations and morphological deposition of GOM around the vascular smooth muscle cells.

Adult↗

PubMed2006

CADASIL-causing mutations do not alter Notch3 receptor processing and activation.

CADASIL is associated with mutations in the Notch3 gene but the causal mechanisms of the disorder remain unclear. We studied effects of widely established mutations on Notch3 receptor processing and ligand-mediated activation in stable lines of HEK293 and SH-SY5Y cells expressing either human wild-type or mutant Notch3 receptor. None of the four mutations (R90C, R133C, C185R and R449C) affected quantities of the full-length, amino-terminal or carboxyl-terminal fragments and did not impair intracellular trafficking in both cell types. The Jagged 1, Jagged 2 and Delta ligand-mediated S2 site cleavage and signal transduction were also observed to be similar in both wild-type and mutants, which exhibited similar rates of degradation of full-length, amino-terminal and carboxyl-terminal fragments. Our results suggest that the arteriopathy in CADASIL is caused by other mechanisms not necessarily involving Notch3 processing and activation.

Blotting, Western↗

PubMed2005

Functional redundancy of the Notch gene family during mouse embryogenesis: analysis of Notch gene expression in Notch3-deficient mice.

The Notch3 gene, a member of the Notch gene family, is expressed in a wide variety of tissues during development. We generated and analyzed Notch3-deficient mice to assess the in vivo role of the Notch3 gene. Consistent with previous observation of Krebs et al. [Characterization of Notch3-deficient mice: normal embryonic development and absence of genetic interactions with a Notch1 mutation, Genesis 37 (3) (2003) 139-143], the Notch3-/- mice were viable, fertile, and developed normally despite abundant expression of Notch3 in various embryonic tissues. We examined the details of Notch1, 2, and 4 expressions in the Notch3-/- embryos compared with those in wild-type embryos. As a result, we found that a deficiency in Notch3 did not affect the expression of Notch1, 2, and 4, and that either Notch1 or Notch2, or sometimes both, was always expressed in all Notch3-expressing tissues examined. These results support the idea that other Notch genes functionally compensate for Notch3 during embryonic development. We also surveyed the adult tissues of Notch3-/- mice and found significantly fewer thymocytes in 10-week-old mice. Therefore, the thymus might be a target tissue affected by Notch3 deficiency.

Animals↗

PubMed2005

[A case of early stage CADASIL showing only dizziness and vertigo with a novel mutation of Notch 3 gene].

We report a 39-year-old woman who presented with only dizziness and vertigo for 2 months. Neurological examination revealed no abnormalities except for hypereflexia on the left side extremities. Neurootological examination revealed no abnormalities. MRI of the brain demonstrated patchy hyperintensity areas on FLAIR images in the periventricular white matter and external capsule. Her grandmother had cerebral infarction and her father is suffering from multi-infarct dementia. Her second older sister who similarly had dizziness and vertigo demonstrated similar MRI findings characterized by patchy hyperintensity areas in the white matter and external capsule even though she had no risk factors for atherosclerosis. Her third older sister also had dizziness and vertigo and had patchy hyperintensity areas in the white matter in her brain MRI even though she had no risk factors for atherosclerosis. Based on this family history, we suspected that she had cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Mutational analysis of Notch3 gene disclosed a novel missense mutation substituting arginine for cysteine at codon 206 (C206R) in exon 4 of the Notch3 gene, confirming the diagnosis of CADASIL. Interestingly, similar dizziness and vertigo were present not only in the patient, but also in the other two sisters who had the same gene mutation as the patient. This report supports the idea that the external capsule lesion is one of the signs suggestive of CADASIL as a diagnosis.

Brain↗

PubMed2004

Development of a safe oral Abeta vaccine using recombinant adeno-associated virus vector for Alzheimer's disease.

A new oral vaccine for Alzheimer's disease was developed using recombinant adeno-associated virus vector carrying Abeta cDNA (AAV/Abeta). Oral administration of the vaccine without adjuvant induced the expression and secretion of Abeta1-43 or Abeta1-21 in the epithelial cell layer of the intestine in amyloid precursor protein transgenic mice. Serum antibody levels were elevated for more than six months, while T cell proliferative responses to Abeta was not detected. Brain Abeta burden was significantly decreased compared to the control without inflammatory changes. This oral AAV/Abeta vaccine seems to be promising for prevention and treatment of Alzheimer's disease.

Administration, Oral↗

PubMed2003

Genetic, clinical and pathological studies of CADASIL in Japan: a partial contribution of Notch3 mutations and implications of smooth muscle cell degeneration for the pathogenesis.

We have examined Notch3 mutations in patients with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) whose samples were submitted to us in Japan. The subjects were composed of 21 Japanese, 1 Iranian, 1 Korean and 1 Canadian families. Mutations in the Notch3 gene were found in 7 of 24 families examined. These were R133C in two unrelated Japanese families, and R213K, C174F and R169C in each Japanese family. In addition, we have found R90C in an Iranian family and C174R in a Korean family. Thus, contribution of Notch3 gene mutations is less than one fourth of Japanese CADASIL families, suggesting the existence of other causative genes in CADASIL. It is also of interest to know that Notch3 mutant CADASIL exists in other Asian countries. We next examined the localization of Notch3 protein in the tissue by immunohistochemistry. It was restricted to the wall of arterioles in the brain and other organs. In the brain, there was no difference in the staining pattern among arterioles in the cortex, white matter and meninges. The staining was negative in the venule and capillaries as well as in neurons and glial cells. From the staining pattern, it was recognized to be expressed in the vascular smooth muscle cells in the adult tissue. In an autopsy case with R213K mutation, we could see numerous cerebral infarcts and arteriole wall degeneration with deposits of granular osmiophilic material (GOM). However, it is interesting to note that occlusion of arterioles was rarely observed and the GOM was negative for Notch3 staining. These findings suggest that hemodynamic abnormalities due to smooth muscle cell degeneration may be important in the pathogenesis of CADASIL.

Age of Onset↗

PubMed2002

Microtubule associated protein (tau) gene variability in patients with frontotemporal dementia.

Frontotemporal dementia represents up to 10% of all dementias and is, next to Alzheimer's disease and Lewy body disease, the third most common cause of degenerative dementia. The term "frontotemporal dementia" covers a range of conditions, including Pick's disease, frontal lobe degeneration and dementia associated with motor neurone disease. Neuropathologically FTD is characterised by atrophy of the frontal and temporal lobes of the cerebral cortex, often with additional subcortical changes. Both familial and more frequently sporadic forms of FTD can be recognised. Recently, mutations in the microtubule-associated protein (tau) gene have been found in families with frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). The identification of mutations in the tau gene indicates that the protein plays a central role in the process of neurodegeneration. Epidemiology of frontotemporal dementias in Poland remains still unknown. A prevalence of tau mutations among Polish patients has not been established yet. Here, we report results of a mutational analysis of the tau gene among Polish FTD patients. No pathogenic mutation was found in the analysed sample. The study confirmed that the frequency of tau mutations is very low and depends strongly on the clinical criteria used to select patients. Mutations in the tau gene account only for a small number of FTD cases with a clear autosomal dominant pattern of disease inheritance. Therefore there should exist additionalgenetic and non-genetic factors contributing to the pathogenesis of both familial (linked and non-linked to chromosome 17) and sporadic forms of FTD.

Aged↗

PubMed2002

A novel mutation at position +11 in the intron following exon 10 of the tau gene in FTDP-17.

Mutations in the microtubule-associated tau gene are responsible for frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). A reduced ability of the mutated microtubule-associated tau protein to interact with microtubules causes microtubule destabilization leading to deleterious effects on axonal transport and the formation of tau filaments. Here, we describe a new mutation of the tau gene, a T --> C transition at position +11 of the intron following exon 10 (T --> C 3'E10 +11) in the family showing frontotemporal dementia with very early age of onset (the first decade of proband's life). The T -->C 3'E10 +11 mutation caused a large increase in the proportion of transcripts containing exon 10 detected by exon-trapping analysis. Our study confirmed that the T --> C 3'E10 +11 mutation, as the other 5' splice site mutations of tau exon 10, modifies alternative splicing of exon 10.

Animals↗