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Biomedical subjects

N Shimozawa

Publications and source records attributed to N Shimozawa.

At least 37 records · Page 2Linked to original sources
PubMed2000

PEX3 is the causal gene responsible for peroxisome membrane assembly-defective Zellweger syndrome of complementation group G.

Peroxisome biogenesis disorders (PBDs) such as Zellweger syndrome (ZS) and neonatal adrenoleukodystrophy are autosomal recessive diseases caused by defects in peroxisome assembly, for which 13 genotypes have been identified. Expression of the human peroxin Pex3p cDNA encoding a 373-amino-acid peroxisomal membrane protein morphologically and biochemically restored peroxisome biogenesis, including peroxisomal membrane assembly, in fibroblasts from PBDG-02, a patient with complementation group G (CG-G) ZS. Patient PBDG-02 carried a homozygous, inactivating mutation-a 97-bp deletion of nucleotide residues at positions 942-1038-resulting in a 32-amino-acid truncation and in a frameshift inducing both a 3-amino-acid substitution and a termination codon. Genomic PCR analysis revealed mutation of T-->G at eight bases upstream of the splicing site at the boundary of intron 10 and exon 11 of PEX3 gene, giving rise to a deletion of all of exon 11. When assessed by expression in a pex3 mutant of Chinese hamster ovary cells and the patient's fibroblasts, PBDG-02-derived PEX3 cDNA was found to be defective in peroxisome-restoring activity. These results provide evidence that PEX3 is a novel, pathogenic gene responsible for CG-G PBDs.

Amino Acid Sequence↗
PubMed2000

Identification of PEX3 as the gene mutated in a Zellweger syndrome patient lacking peroxisomal remnant structures.

Peroxisome biogenesis disorders, of which 13 complementation groups have been identified, are subdivided with regard to two major dysfunctions: peroxisomal matrix protein import and peroxisomal membrane synthesis. Detectable remnant membrane structures are evident only in the former. Molecular defects have been defined in 10 PEX genes, including eight related to protein import and two to membrane synthesis. We now have evidence that the human complete cDNA encoding Pex3p, a peroxisomal membrane protein (PMP) factor for the proper localization of PMPs, rescues the import of both PMP and the matrix protein in fibroblasts from a Zellweger syndrome patient of complementation group G. This patient was homozygous for a 1 base insertion in the codon for V182, which resulted in a change of codon (182-183) and introduced a termination codon (184), which inactivated PMP and matrix protein import by Pex3p. A PEX3-defective CHO mutant clone, ZPG208, was of the same complementation group as group G.

ATP-Binding Cassette Transporters↗
PubMed2000

Rapid isolation and characterization of CHO mutants deficient in peroxisome biogenesis using the peroxisomal forms of fluorescent proteins.

We isolated and characterized CHO mutants deficient in peroxisome assembly using green fluorescent protein (GFP) and blue fluorescent protein (BFP) as the fluorescent probes to study the molecular mechanism of peroxisome biogenesis. We used stable transformants of CHO cells expressing GFP appending peroxisome targeting signal-1 (PTS1) and/or peroxisome targeting signal-2 (PTS2) as the parent strains for rapid isolation of the mutants. We have obtained six peroxisome-deficient mutants by visual screening of the mislocalizations of the peroxisomal GFPs. Mutual cell fusion experiments indicated that the six mutants isolated were divided into four complementation groups. Several of the mutants obtained possessed defective genes: the PEX2 gene was defective in SK24 and PT54; the PEX5 gene in SK32 and the PEX7 gene in PT13 and PT32. BE41, which belonged to the fourth complementation group, was not determined. When peroxisomal forms of BFP were transiently expressed in mutant cells, the peroxisomal BFPs appending both PTS1 and PTS2 appeared to bypass either the PTS1 or PTS2 pathway for localization in SK32. This observation suggested that other important machinery, in addition to the PTS1 or PTS2 pathway, could be involved in peroxisome biogenesis. Thus, our approach using peroxisomal fluorescent proteins could facilitate the isolation and analysis of peroxisome-deficient CHO mutants and benefit studies on the identification and role of the genes responsible for peroxisome biogenesis.

Animals↗
PubMed2000

Molecular mechanism of detectable catalase-containing particles, peroxisomes, in fibroblasts from a PEX2-defective patient.

Patients with peroxisome biogenesis disorders (PBD) can be identified by detection of peroxisomes in their fibroblasts, by means of immunocytochemical staining using an anti-catalase antibody. We report here data on three PBD patients with newly identified mutations (del550C and del642G) in the PEX2 gene which encodes a 35-kDa peroxisomal membrane protein containing two membrane-spanning and a C-terminal cysteine-rich region. Some of the fibroblasts from the patient with the del642G mutation contained numerous catalase-containing particles, whereas no fibroblasts containing such particles were found in the patient with the del550C mutation. We confirmed that the del642G mutation caused a partial defect in peroxisome synthesis and import by expression of the mutated PEX2 into PEX2-defective CHO mutant cells. We propose that the two putative membrane-spanning segments in Pex2p are important domains for peroxisome assembly and import and that a defect in one of these domains severely affects PBD patients. Furthermore, a defect in the C-terminal portion of Pex2p exposed to the cytosol containing a RING finger motif caused the mild phenotype, residual enzyme activities, and mosaic detectable peroxisomes in fibroblasts from the patient.

Amino Acid Sequence↗
PubMed2000

Four resections for hepatic metastasis from gastric cancer: histochemical analysis of cell proliferation, apoptosis, and angiogenesis.

In a patient with gastric cancer (GC) associated with one synchronous and three metachronous hepatic metastases (HM), who underwent four hepatectomies, we carried out histochemical investigations regarding cell proliferation, apoptosis, and angiogenesis in the GC and HM. Tissue samples were taken from the primary GC and four HM. Ki-67 immunostaining was performed to evaluate cell proliferation and determine the labeling index (Ki-67 LI; ie, the percentage of cancer cells with nuclei stained for Ki-67). Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) was performed to evaluate apoptosis and determine the apoptotic index (ie, the percentage of TUNEL-positive cells), and immunostaining for factor VIII-related antigen was performed to evaluate angiogenesis and measure microvessel density (MVD). The Ki-67 LI was 43.2% in the primary GC and 39.9% in the synchronous HM, and the LI increased with the number of resections of metachronous HM. The apoptotic index was 3.36% in the primary GC, and 5.30% in the synchronous HM, and the index decreased after further resections of the metachronous HM. The MVD was 35 in the primary GC, and 22 in the synchronous HM, and it increased with the number of resections of metachronous HM. The primary GC in this patient may have strongly influenced the growth of HM through effects on cell proliferation, apoptosis, and angiogenesis.

Adenocarcinoma↗
PubMed2000

Restoration of biochemical function of the peroxisome in the temperature-sensitive mild forms of peroxisome biogenesis disorder in humans.

We have found that peroxisome assembly is temperature-sensitive (ts) in mild forms of peroxisome biogenesis disorders (PBDs), that is all infantile Refsum disease (IRD) patients and a few neonatal adrenoleukodystrophy patients of several complementation groups. The number of peroxisomes increased daily in incubation at 30 degrees C in the ts cells. Oxidation of very long-chain fatty acids, processing of acyl-CoA oxidase and dihydroxyacetonephosphate acyltransferase activity also improved after 8 days incubation at 30 degrees C in the IRD fibroblasts. These biochemical functions of the peroxisome did not change at 30 degrees C in Zellweger fibroblasts. Number of peroxisomes gradually decreased after 4 days when the temperature shifted from 30 to 37 degrees C in the ts cells. These results indicate that the biochemical functions of peroxisome are also restored by incubation at 30 degrees C in the mild and ts phenotype of PBDs, and the results will aid to predict the severity and the prognosis of affected children.

Animals↗
PubMed2000

Congenital myotonic dystrophy: report of paternal transmission.

A female neonate born to a healthy mother was hospitalized because of enlargement of the lateral ventricles, muscle weakness, irregular respiration, and poor sucking. Characteristic facial appearance such as high forehead and carp mouth were noted. The father had mild manifestations of adult type myotonic dystrophy, including muscle weakness of the extremities, percussion myotonia and atrophy of the facial muscles. PCR analysis and southern blot analysis revealed that CTG repeats in the myotonic dystrophy gene of the infant and the father were about 1000 and 400, respectively. This is a rare case showing paternally transmitted congenital myotonic dystrophy and seems to be the first report describing a neonate.

Brain↗
PubMed2000

Survival and recurrence after hepatic resection of 386 consecutive patients with hepatocellular carcinoma.

BACKGROUND: Although hepatic resection is one of the most effective treatments for hepatocellular carcinoma (HCC), the longterm results of hepatic resection of this malignancy are far from satisfactory. The potential benefits of hepatectomy for patients with HCC have not been fully delineated. This study aimed to identify surgical outcomes of 386 consecutive patients with HCC undergoing hepatic resection. STUDY DESIGN: The retrospective study looked at records of 293 men and 93 women. The mean age was 63.2 years. Preoperative transarterial chemoembolizaton and portal vein embolization were performed in 138 patients (35.8%) and 8 patients (2.1%), respectively. Sixty-two patients (16.1 %) had major hepatectomy and the other 324 (83.9%) had minor hepatectomy. Thirty-seven of 386 patients (9.6%) had a noncurative operation. RESULTS: The 30-day (operative) mortality rate was 4.1%, and there were 11 additional late deaths (2.9%). Two hundred fourteen of 327 patients (65.4%) had recurrence after curative resection. Unfavorable factors for survival and recurrence were resection between 1983 and 1990, Child class B or C, cirrhosis, a high value of indocyanine green retention-15, a large amount of intraoperative blood loss, stage IV disease, positive surgical margin, vascular invasion, and postoperative complications. Preoperative transarterial chemoembolization increased the recurrence rate and showed no contribution to prognosis. Currently, 106 patients (27.5%) are alive: 7 (1.8%) after more than 10 years and 43 (11.1%) after more than 5 years. Mean and median overall survivals after operation were 38 months and 29 months, respectively. The 5-year and 10-year overall or disease-free survival rates after hepatic resection were 34.4% and 10.5% or 23.3% and 7.8%, respectively. CONCLUSIONS: The longterm survival rate after operation remains unsatisfactory mainly because of the high recurrence rate. Preoperative transarterial chemoembolization should be avoided because of a high risk of postoperative recurrence. Treatment strategies for recurrent HCC may play an important role in achieving better prognosis after operation, especially in patients with more than Child class B, cirrhosis, high values of indocyanine green retention-15, massive intraoperative blood loss, stage IV disease, positive surgical margin, vascular invasion, and postoperative complications.

Adult↗
PubMed2000

Bone marrow transplantation for the treatment of X-linked adrenoleukodystrophy.

The effects of bone marrow transplantation (BMT) in X-linked childhood adrenoleukodystrophy (ALD) are described in four Japanese patients. Two older patients, 10-year-old boys with IQ 60 and difficulty in school, had favourable results. IQ levels and MRI findings were generally maintained after BMT. One patient showed improvement of gait disturbance. They have both attended ordinary schools after BMT, although a learning disorder persists. On the other hand, two other younger patients with a rapid course and indeterminate IQ at BMT showed deterioration of neurological functions. Indication for BMT seems to be a maintained IQ level, preferably higher than 80, since it seems to be difficult to normalize IQ level after BMT. Younger patients have higher risk of developing a rapidly progressive form of the disease. Identification of presymptomatic boys, and serial and careful follow-up by neuropsychological and neuroradiological studies, are essential prerequisites to successful BMT in X-ALD.

Adrenoleukodystrophy↗
PubMed2000

Temperature-sensitive mutation of PEX6 in peroxisome biogenesis disorders in complementation group C (CG-C): comparative study of PEX6 and PEX1.

Peroxisome biogenesis disorders (PBD), including Zellweger syndrome, neonatal adrenoleukodystrophy, and infantile Refsum disease, are a group of genetically heterogeneous autosomal-recessive diseases caused by mutations in PEX genes that encode peroxins, proteins required for peroxisome biogenesis. Zellweger syndrome patients present the most severe phenotype, whereas neonatal adrenoleukodystrophy patients are intermediate and infantile Refsum disease patients have the mildest features. PEX6 is a causative gene for PBD of complementation group C (CG-C) and encodes the peroxin Pex6p, one of the ATPases associated with diverse cellular activities and a member of the same family of proteins as Pex1p, a causative protein for PBD of CG-E (CG1). Here, we identified the temperature sensitivity of peroxisomes in the fibroblasts of a patient with neonatal adrenoleukodystrophy in CG-C. Peroxisomes were morphologically and biochemically formed at 30 degrees C but not at 37 degrees C. This patient was homozygous for a missense mutation, T-->C at nucleotide 170 resulting in a change from leucine to proline at amino acid 57 (L57P) in Pex6p. CG-C cell mutants (ZP92) in the Chinese hamster ovary transfected with L57P in HsPEX6 revealed the same temperature-sensitive phenotype. However, PEX1-deficient Chinese hamster ovary cell mutants (ZP101) transfected with L111P in PEX1, the counterpart to L57P in PEX6, showed no temperature sensitivity. In addition, ZP92 transfected with G708D in PEX6, the counterpart to the temperature-sensitive mutation G843D in PEX1, revealed no temperature-sensitive phenotype. These results indicate that L57P in Pex6p is a temperature-sensitive mutation causing the milder phenotype in a patient with PBD in CG-C. They also indicate that the amino acid residues responsible for temperature sensitivity do not seem to be conserved between Pex6p and Pex1p.

ATPases Associated with Diverse Cellular Activitie↗
PubMed2000

Temperature sensitivity in peroxisome assembly processes characterizes milder forms of peroxisome biogenesis disorders.

Peroxisome biogenesis disorders (PBDs) contain various clinical phenotypes; Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), decreasing in the clinical severity in this order. We found that all IRD cell lines and some NALD lines belonging to several different complementation groups are temperature-sensitive in peroxisome assembly; that is, they lacked catalase-positive peroxisomes at 37 degrees C, but do gain the peroxisomes at 30 degrees C. We identified heterozygous mutations E55K/R119Stop in the PEX2 gene of an IRD patient of complementation group F. The E55K mutation was the direct cause of the temperature-sensitivity because similar phenotypes could be transferred to PEX2-defective CHO cells by transfecting the mutant gene. Thus, temperature-sensitive peroxisome assembly is representative of milder forms of PBDs.

Humans↗
PubMed2000

Very-long-chain fatty acid metabolism in adrenoleukodystrophy protein-deficient mice.

X-linked adrenoleukodystrophy (X-ALD) is characterized by progressive mental and motor deterioration, with demyelination of the central and peripheral nervous system. Its principal biochemical abnormality is the accumulation of very-long-chain fatty acids (VLCFAs) in tissues and body fluids, caused by the impairment of peroxisomal beta-oxidation. The authors have generated a line of mice deficient in ALD protein (ALDP) by gene targeting. ALDP-deficient mice appeared normal clinically, at least up to 12 mo. Western blot analysis showed absence of ALDP in the brain, spinal cord, lung, and kidney. The amounts of C26:0 increased by 240% in the spinal cord. VLCFA beta-oxidation in cultured hepatocytes was reduced to 50% of normal. The authors investigated the roles of ALDP in VLCFA beta-oxidation using the ALDP-deficient mice. Very-long-chain acyl-CoA synthetase (VLACS) is functionally deficient in ALD cells. The impairment of VLCFA beta-oxidation in the ALDP-deficient fibroblasts was not corrected by over-expression of VLACS only, but was done by co-expression of VLACS and ALDP, suggesting that VLACS requires ALDP to function. VLACS was detected in the peroxisomal and microsomal fractions of the liver from both types of mice. Peroxisomal VLACS was clearly decreased in the ALDP-deficient mouse. Thus, ALDP is involved in the peroxisomal localization of VLACS.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed1999

Functional heterogeneity of C-terminal peroxisome targeting signal 1 in PEX5-defective patients.

To investigate mechanisms related to functions of the peroxisome targeting signal (PTS) 1 receptor, Pex5p, we analyzed peroxisome matrix protein import in fibroblasts from three patients with peroxisome biogenesis disorders, all with different mutations in the PEX5 gene. The patients 2-01 (Zellweger syndrome) and 2-05 (neonatal adrenoleukodystrophy) have the reported mutations, R390X and N489K, and patient 2-03 (infantile Refsum disease) has a newly identified mutation, S563W. Fibroblasts from 2-03 (S563W) were detected in both PTS1 and PTS2 imports despite the PEX5 defect, findings in contrast with fibroblasts from 2-05 (N489K) severely defective in PTS1 import and those from 2-01 (R390X) severely defective in both PTS1 and PTS2. The PTS1 receptor in 2-03 is functional for only the C-terminal -SKL sequence (acyl-CoA oxidase) and had little or no function for C-terminal -AKL (D-bifunctional protein and sterol carrier protein 2) and -KANL (catalase) sequences, respectively. After transfection of these mutated PEX5 cDNA into the PEX5-defective CHO mutant, transformants of ZP102 revealed that each mutation was responsible for each dysfunction of the PTS1 import. It seems apparent that -AKL and -KANL are poorer variants of PTS1 and are likely to be more susceptible to effects of mutation of its receptor, Pex5p.

17-Hydroxysteroid Dehydrogenases↗
PubMed1999

Newly identified Chinese hamster ovary cell mutants defective in peroxisome assembly represent complementation group A of human peroxisome biogenesis disorders and one novel group in mammals.

We isolated peroxisome biogenesis-defective mutants from rat PEX2-transformed Chinese hamster ovary (CHO) cells, using the 9-(1'-pyrene)nonanol/ultraviolet method. A total of 18 mutant cell clones showing cytosolic localization of catalase were isolated. By complementation group (CG) analysis by means of PEX cDNA transfection and cell fusion, cell mutants, ZP124 and ZP126, were found to belong to two novel CGs of CHO mutants. Mutants, ZP135 and ZP167, were also classified to the same CG as ZP124. Further cell fusion analysis using 12 CGs fibroblasts from patients with peroxisome deficiency disorders such as Zellweger syndrome revealed that ZP124 belonged to human CG-A, the same group as CG-VIII in the United States. ZP126 could not be classified to any of human and CHO CGs. These mutants also showed typical peroxisome assembly-defective phenotypes such as severe loss of catalase latency and impaired biogenesis of peroxisomal enzymes. Collectively, ZP124 represents CG-A, and ZP126 is in a newly identified CG distinct from the 14 mammalian CGs previously characterized.

Animals↗