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Biomedical subjects

J Sasaki

Publications and source records attributed to J Sasaki.

At least 19 recordsLinked to original sources
PubMed2001

Novel mutations in ABCA1 gene in Japanese patients with Tangier disease and familial high density lipoprotein deficiency with coronary heart disease.

Mutations in the ATP-binding cassette transporter 1 (ABCA1) gene have been recently identified as the molecular defect in Tangier disease (TD) and familial high density lipoprotein deficiency (FHA). We here report novel mutations in the ABCA1 gene in two sisters from a Japanese family with TD who have been described previously (S. Ohtaki, H. Nakagawa, N. Kida, H. Nakamura, K. Tsuda, S. Yokoyama, T. Yamamura, S. Tajima, A. Yamamoto, Atherosclerosis 49 (1983)) and a family with FHA. Both probands of TD and FHA developed coronary heart disease. Sequence analysis of the ABCA1 gene from the patients with TD revealed a homozygous G to A transition at nucleotide 3805 of the cDNA resulting in the substitution of Asp 1229 with Asn in exon 27, and a C to T at nucleotide 6181 resulting in the substitution of Arg 2021 with Trp in exon 47. Sequence analysis of the ABCA1 gene from the FHA patient revealed a homozygous 4 bp CGCC deletion from nucleotide 3787 to 3790 resulting in premature termination by frameshift at codon 1224. These mutations were confirmed by restriction digestion analysis, and were not found in 141 control subjects. Our findings indicate that mutations in the ABCA1 gene are associated with TD as well as FHA.

ATP Binding Cassette Transporter 1↗
PubMed2001

Apolipoprotein E genotype, serum lipids, and colorectal adenomas in Japanese men.

We examined the relation of serum lipids and apolipoprotein E genotype to colorectal adenomas among 205 cases and 220 controls with normal colonoscopy in Japanese men. With adjustment for body mass index, cigarette smoking, alcohol use, and other covaiates, odds ratios of proximal and distal adenomas associated with the presence of an allele varepsilon4 were 0.59 (95% confidence interval 0.23-1.45) and 0.99 (0.50-1.98), respectively. While serum total and LDL cholesterol were unrelated to both proximal and distal adenomas, serum triglycerides were positively related to distal adenomas. The findings suggest that altered lipid metabolism may be differentially associated with tumorigenesis in the proximal and distal colorectum.

Adenoma↗
PubMed2001

Structural organization, complete genomic sequences and mutational analyses of the Fukuyama-type congenital muscular dystrophy gene, fukutin.

Fukuyama-type congenital muscular dystrophy (FCMD) is an autosomal recessive severe muscular dystrophy in combination with cerebral cortical dysplasia. Previously, we identified the gene responsible for FCMD, termed fukutin, through positional cloning. In this study, we have sequenced 131892 bp of genomic DNA in the region of the fukutin gene on chromosome 9q31 and obtained its complete genomic structure. The fukutin genomic sequence spans approximately 100 kb and is organized into 10 exons (41-6067 bp) and nine introns (1841-21460 bp). Using these sequence data, we have identified three novel fukutin mutations in FCMD patients. We have also located a putative TATA box in the flanking 5' region and identified numerous alternatively spliced fukutin mRNA transcripts. Analysis of expressed sequence tag clusters within the region revealed two novel genes upstream of the fukutin gene. These data provide fundamental information to support detailed genetic and functional analyses of the fukutin gene.

Alternative Splicing↗
PubMed2001

A novel WD40 repeat protein, WDC146, highly expressed during spermatogenesis in a stage-specific manner.

We have cloned a novel cDNA encoding a protein with eight WD repeat motifs and a domain similar to collagen. As the predicted size of the protein was 146 kDa, the gene was named WDC146. Here, we characterized the genomic structure, gene products, and the expression profiles. The human WDC146 gene had 22 exons spanning over 105 kb, and these exons were distributed in three islands intervened by two long introns of around 40 kb. A minimum promoter region was identified within a 0.5 kb 5'-upstream region of exon 1. WDC146 mRNA was most highly expressed in human testis on Northern blot analysis. In mouse tissues, the highest expression was also observed in testis. By in situ hybridization on rat tissues, WDC146 mRNA was detected preferentially in the pachytene stage of spermatocytes in testis, and weakly in white pulp/ marginal band of spleen and in cortex of thymus. WDC146 protein was found to be localized in nucleus. These data implied that WDC146 protein may play important roles in the mechanisms of cytodifferentiation and/or DNA recombination.

Amino Acid Sequence↗
PubMed2001

Recombinant proapoA-I(Lys107del) shows impaired lipid binding associated with reduced binding to plasma high density lipoprotein.

In the present study apoA-I (Lys 107del), a naturally occurring human apoA-I variant with a deletion of Lys 107, was expressed in E. coli to examine the effect of this mutation on lipid binding, cholesterol efflux and lecithin:cholesterol acyltranferase (LCAT) activation. Dimyristoyl phosphatidylcholine (DMPC) binding studies revealed slow interaction of proapoA-I(Lys107del) with DMPC relative to normal proapoA-I. After preincubation with human plasma lipoprotein (d<1.225 g/ml) for 1 h at 37 degrees C, 125I-labeled normal proapoA-I chromatographed as a single peak with the high density lipoprotein (HDL) fraction, whereas 125I-labeled proapoA-I(Lys107del) chromatographed with both HDL and free proapoA-I (26% of the radioactivity). Circular dichroism measurements showed that the alpha-helical content of lipid-bound proapoA-I (Lys107del) was reduced to 64 versus 73% of normal proapoA-I. Non-denaturing gradient gel electrophoresis of reconstituted HDL assembled with either proapoA-I(Lys107del) or normal proapoA-I showed that the mutation led to the formation of a second population of smaller rHDL particles. DMPC/proapoA-I(Lys107del) and normal DMPC/proapoA-I complexes exhibited a similar capacity to promote cholesterol efflux from fibroblasts. ProapoA-I (Lys107del) also activated LCAT similar to wild type proapoA-I and human plasma apoA-I. We conclude that deletion of Lys 107 substantially alters the lipid binding properties of the protein, which correlated with reduced binding to plasma HDL in vitro, but did not affect the capacity of the mutant/lipid complex to promote cholesterol efflux or activate LCAT.

Apolipoprotein A-I↗
PubMed2001

Construction of an infectious cDNA clone of Aichi virus (a new member of the family Picornaviridae) and mutational analysis of a stem-loop structure at the 5' end of the genome.

Aichi virus is the type species of a new genus, Kobuvirus, of the family Picornaviridae. In this study, we constructed a full-length cDNA clone of Aichi virus whose in vitro transcripts were infectious to Vero cells. During construction of the infectious cDNA clone, a novel sequence of 32 nucleotides was identified at the 5' end of the genome. Computer-assisted prediction of the secondary structure of the 5' end of the genome, including the novel sequence, suggested the formation of a stable stem-loop structure consisting of 42 nucleotides. The function of this stem-loop in virus replication was investigated using various site-directed mutants derived from the infectious cDNA clone. Our data indicated that correct folding of the stem-loop at the 5' end of the positive strand, but not at the 3' end of the negative strand, is critical for viral RNA replication. The primary sequence in the lower part of the stem was also suggested to be crucial for RNA replication. In contrast, nucleotide changes in the loop segment did not so severely reduce the efficiency of virus replication. A double mutant, in which both nucleotide stretches of the middle part of the stem were replaced by their complementary nucleotides, had efficient RNA replication and translation abilities but was unable to produce viruses. These results indicate that the stem-loop at the 5' end of the Aichi virus genome is an element involved in both viral RNA replication and production of infectious virus particles.

Amino Acid Sequence↗
PubMed2001

Methylprednisolone accelerates the resolution of glomerulonephritis by sensitizing mesangial cells to apoptosis.

Glucocorticoid has long been used to treat patients with glomerulonephritis because it ameliorates mesangial cell proliferation and proteinuria, in part by suppressing nuclear factor-kappa B (NF-kappaB) activation, which regulates the transcription of various pro-inflammatory genes. Recent evidence shows that NF-kappaB activation increases the resistance to TNF-alpha-induced apoptosis in mesangial cells. We examined glomerular cell proliferation and apoptosis along with NF-kappaB activation in the Thy-1.1 nephritis model. We also evaluated TNF-alpha-induced apoptosis in cultured mesangial cells. Methylprednisolone treatment ameliorated mesangial hypercellularity in Thy-1.1 nephritis by decreasing proliferating cells and increasing apoptosis in the glomeruli. These effects were associated with suppressed NF-kappaB activation. This in vitro study revealed that treatment with methylprednisolone and TNF-alpha induced cultured mesangial cell apoptosis. These results suggest that methylprednisolone may accelerate the resolution phase of Thy-1.1 nephritis in part by sensitizing mesangial cells to apoptosis.

Animals↗
PubMed2001

[A case of remnant gastric cancer responding to neoadjuvant TS-1 therapy].

We report the case a 77-year-old male with remnant gastric cancer successfully treated with TS-1 as neoadjuvant chemotherapy. His treatment was daily oral administration of 100 mg TS-1 for 28 days. This therapy was safely carried out on an outpatient basis. The histological diagnosis of the resected stomach revealed complete disappearance of cancer cells in the stomach and the regional lymph nodes. This case suggests that TS-1 may have a potent therapeutic effect in neoadjuvant chemotherapy for recurrent gastric cancer.

Administration, Oral↗
PubMed2000

Neuronal expression of the fukutin gene.

Fukuyama-type congenital muscular dystrophy (FCMD), a relatively common autosomal recessive disorder in Japan, is characterized by severe congenital muscular dystrophy in combination with cortical dysgenesis (polymicrogyria). The gene responsible for FCMD encodes a novel protein, fukutin, which is likely to be an extracellular protein. Pathological study of brain tissue from FCMD fetuses revealed frequent breaks in the glia limitans and basement membrane complex. Disruption of the basal lamina in FCMD muscle was also seen. Thus, structural alteration of the basal lamina appears to play a key role in the pathophysiology of FCMD. To investigate the role of fukutin in brain anomalies, we examined fukutin mRNA expression in the human brain. Northern blot and RT-PCR analysis revealed that the fukutin gene is expressed at similar levels in fetal and adult brain, whereas its expression is much reduced in FCMD brains. Tissue in situ hybridization analysis revealed fukutin mRNA expression in the migrating neurons, including Cajar-Retzius cells and adult cortical neurons, as well as in hippocampal pyramidal cells and cerebellar Purkinje cells. However, we observed no expression in the glia limitans, the subpial astrocytes (which contribute to basement membrane formation) or other glial cells. In the FCMD brain, neurons in regions with no dysplasia showed fair expression, whereas transcripts were nearly undetectable in the overmigrated dysplastic region. These observations suggest that fukutin function may influence neuronal migration itself rather than formation of the basement membrane. Furthermore, differences in mRNA levels among neurons in early developmental stages may partially differentiate normal and abnormal regions.

Adult↗
PubMed2000

Virus-mediated transduction of apolipoprotein E (ApoE)-sendai develops lipoprotein glomerulopathy in ApoE-deficient mice.

Lipoprotein glomerulopathy (LPG) is a unique renal disease characterized by thrombus-like substances in markedly dilated glomerular capillaries, dysbetalipoproteinemia, and elevated plasma concentrations of apoE. Recent studies identified several apoE mutations in patients with LPG, including apoE2(R145P) Sendai (apoE-Sendai). Virus-mediated transduction of apoE-Sendai in apoE-deficient hypercholesterolemic mice resulted in insufficient correction of hypercholesterolemia and a marked and temporal induction of plasma triglyceride levels. In vitro binding studies showed that apoE-Sendai has a reduced affinity for the low density lipoprotein receptor, suggesting that dysbetalipoproteinemia in LPG is caused by the apoE mutation. Furthermore, histological examination revealed marked intraglomerular depositions of apoE-containing lipoproteins in mice injected with apoE-Sendai virus. These LPG-like depositions were detected 6 days after virus injection and were sustained for at least 60 days. Our results demonstrated that apoE-Sendai is an etiological cause of LPG.

Adenoviridae↗
PubMed2000

Proton transport by sensory rhodopsins and its modulation by transducer-binding.

The study of light-induced proton transfers in the archaeal sensory rhodopsins (SR), phototaxis receptors in Halobacterium salinarum, has contributed important insights into their mechanism of signaling to their cognate transducer subunits in the signaling complex. Essential features of the bacteriorhodopsin (BR) pumping mechanism have been conserved in the evolution of the sensors, which carry out light-driven electrogenic proton transport when their transducers are removed. The interaction of SRI with its transducer blocks proton-conducting channels in the receptor thereby inhibiting its proton pumping, indicating that the pump machinery, rather than the transport activity itself, is functionally important for signaling. Analysis of SRII mutants has shown that the salt bridge between the protonated Schiff base and its counterion Asp73 constrains the receptor in its inactive conformation. Similarly, in BR, the corresponding salt bridge between the protonated Schiff base and Asp85 contributes to constraining the protein in a conformation in which its cytoplasmic channel is closed. Transducer chimera studies further indicate that the receptor conformational changes are transmitted from the sensors to their cognate transducers through transmembrane helix-helix interaction. These and other results reviewed here support a signaling mechanism in which tilting of helices on the cytoplasmic side (primarily outward tilting of helix F), similar to that which occurs in BR in its open cytoplasmic channel conformation, causes structural alterations in the transducer transmembrane helices.

Archaeal Proteins↗