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Biomedical subjects

Keiichi Ozono

Publications and source records attributed to Keiichi Ozono.

At least 37 records · Page 2Linked to original sources
PubMed2005

Roberts syndrome is caused by mutations in ESCO2, a human homolog of yeast ECO1 that is essential for the establishment of sister chromatid cohesion.

Roberts syndrome is an autosomal recessive disorder characterized by craniofacial anomalies, tetraphocomelia and loss of cohesion at heterochromatic regions of centromeres and the Y chromosome. We identified mutations in a new human gene, ESCO2, associated with Roberts syndrome in 15 kindreds. The ESCO2 protein product is a member of a conserved protein family that is required for the establishment of sister chromatid cohesion during S phase and has putative acetyltransferase activity.

Acetyltransferases↗
PubMed2005

Anti-inflammatory therapy by ibudilast, a phosphodiesterase inhibitor, in demyelination of twitcher, a genetic demyelination model.

BACKGROUND: Twitcher mouse (twi/twi) is an authentic murine model of Krabbe's disease. Accumulation of psychosine, resulting in apoptosis of oligodendrocytes and subsequent demyelination, is a cardinal event to the pathogenesis of this disease. Moreover, recruitment of inflammatory cells plays a significant role in the pathological process in the twi/twi central and peripheral nervous systems. In this study, we investigated the 1) the relationship between tumor necrosis factor-alpha (TNFalpha), pro-inflammatory cytokine, and the progression of this disease and 2) effect of the anti-inflammatory therapy by ibudilast, a phosphodiesterase inhibitor. METHODS: We quantified the expression level of TNFalpha and TNF-receptor mRNA in twi/twi using semi-quantitative RT-PCR. The relationship between TNFalpha expression, apoptosis of oligodendrocytes and demyelination was studied with immunohistochemistry and TUNEL method. We then treated twi/twi with a daily intraperitoneal injection of ibudilast (10 mg/kg), which suppress TNFalpha production in the brain. RESULTS: We found that TNFalpha-immunoreactive microglia/macrophages appeared in the twi/twi brain and that the mRNA levels of TNFalpha and TNF-receptor 1 was increased with the progression of demyelination. The distribution profile of TNFalpha-immunoreactive microglia/macrophages overlapped that of TUNEL-positive oligodendrocytes in the twi/twi brain. When twi/twi was treated with ibudilast from PND30, the number of oligodendrocytes undergoing apoptosis was markedly reduced and demyelination was milder. Obvious improvement of clinical symptom was noted in two of five. The failure of constant clinical improvement by ibudilast may result from hepatotoxicity and/or the inhibition of proliferation of NG2-positive oligodendrocyte precursors. CONCLUSION: We conclude that anti-inflammatory therapy by a phosphodiesterase inhibitor can be considered as a novel alternative therapy for Krabbe's disease.

Journal Article↗
PubMed2005

Successful stenting for renal artery stenosis in a patient with Alagille syndrome.

A 12-year-old girl with Alagille syndrome manifested severe hypertension caused by renal artery stenosis in a solitary functioning kidney. Percutaneous transluminal angioplasty (PTA) and stenting was performed, but the hypertension persisted. On the next day, acute renal failure occurred with the administration of angiotensin-converting enzyme inhibitor, and migration of the stent was confirmed by angiography. Thus, a second stent was placed with success. Since then, the hypertension has been controlled with anti-hypertensive medication, and the renal function has recovered to normal range.

Alagille Syndrome↗
PubMed2005

Common mutations F310L and T1559del in the tissue-nonspecific alkaline phosphatase gene are related to distinct phenotypes in Japanese patients with hypophosphatasia.

UNLABELLED: A total of 22 Japanese patients with hypophosphatasia were included in a study analysing the relationship between mutations in the tissue-nonspecific alkaline phosphatase (TNSALP) gene and the severity of the phenotype in Japanese patients with hypophosphatasia. The enzymatic activity of some of the identified mutant TNSALP proteins was also examined using corresponding expression vectors. Eighteen mutations, including 6 novel ones, were identified in the patients. Among them, the common mutations were F310L and T1559del. Of note, five patients with F310L mutation in one of the alleles exhibited a relatively mild phenotype without respiratory complications despite its perinatal onset. In contrast, the T1559del mutation is associated with perinatal lethal and infantile forms when not found in patients with the F310L mutation. The genotype-phenotype relationship was, to some extent, consistent with the enzymatic activity of the mutant ALP proteins; mutations K207E and G409C found in a surviving case of infantile hypophosphatasia, as well as F310L, retained some residual activities, whereas T1559del caused a complete loss of activity. CONCLUSION: In Japanese patients, the common mutations F310L and T1559del are associated with the relatively mild and lethal forms of hypophosphatasia, respectively. Our results may enhance the importance of genotyping patients with hypophosphatasia to predict their prognosis.

Alkaline Phosphatase↗
PubMed2005

The role of fibroblast growth factor 23 for hypophosphatemia and abnormal regulation of vitamin D metabolism in patients with McCune-Albright syndrome.

McCune-Albright syndrome (MAS) is sometimes complicated by hypophosphatemia and abnormally low levels of 1,25(OH)(2)D in the presence of hypophosphatemia. Recently, fibroblast growth factor 23 (FGF-23) was reported as a phosphaturic and a causal factor of abnormal vitamin D metabolism. This abnormal phosphate and vitamin D metabolism is well known to be found in oncogenic and X-linked hypophosphatemia. We furthermore reported increased circulating plasma FGF-23 levels in patients with oncogenic and X-linked hypophosphatemia. To determine whether FGF-23 may be involved in the pathogenesis of MAS, we measured plasma FGF-23 levels in six MAS patients. As a control for hypophosphatemia, we also investigated the plasma FGF-23 levels in two patients with hereditary hypophosphatemic rickets with hypercalciuria (HHRH). We also investigated the correlation of plasma FGF-23 levels with serum phosphate and 1,25(OH)(2)D levels after short-term pamidronate therapy in three MAS patients. Plasma FGF-23 levels were significantly increased in patients with MAS compared to normal controls, whereas they were not increased in HHRH patients. Serum phosphate levels of the MAS patients were significantly lower than those observed in normal controls. Plasma FGF-23 levels showed significant negative correlation with serum phosphate concentrations. In three MAS patients, pamidronate therapy decreased plasma FGF-23 levels, which showed significant negative correlation with serum 1,25(OH)(2)D concentrations. These data suggested that FGF-23 is a possible causal factor for hypophosphatemia and abnormal vitamin D metabolism in MAS.

Adolescent↗
PubMed2005

Epilepsy in Wolf-Hirschhorn syndrome (4p-).

PURPOSE: We investigated the evolution of epilepsy, seizure types, and effective drugs in Wolf-Hirschhorn syndrome, which is a malformation syndrome often with refractory seizures and status epilepticus. METHODS: We reviewed 11 cases of Wolf-Hirschhorn syndrome (age range, 2-25 years; SD, 7.2 years) and who were treated in Osaka University or Osaka Medical Center of Research Institute for Maternal and Child Health. RESULTS: In all patients, febrile or afebrile convulsions had developed. Epileptic seizures included alternative hemiconvulsions, generalized tonic-clonic seizures, focal clonic seizures, tonic seizures, and epileptic spasms. Seizures were often induced by a high fever or a hot bath. Status epilepticus occurred in all patients, including one patient who died at the first status epilepticus. In some cases, intratracheal intubation was needed because of respiratory insufficiency. The effective antiepileptic drugs for long-term use were sodium bromide (four of four), followed by clorazepate (CLP; one of two), and nitrazepam (NZP; two of four). Sodium bromide was particularly effective for preventing status epilepticus. The mean age of last status epilepticus in patients receiving sodium bromide (1 year 8 months) was significantly younger than that in those not treated with sodium bromide (3 year 4 months). CONCLUSIONS: We identified that, in most patients of Wolf-Hirschhorn syndrome, the frequency of both seizures and status epilepticus decreased gradually after age 5 years. However, during infancy, status epilepticus sometimes resulted in permanent disability or even death. We propose that sodium bromide should be used as the initial treatment for the prevention of the development of status epilepticus associated with Wolf-Hirschhorn syndrome.

Abnormalities, Multiple↗
PubMed2005

Tacrolimus-related encephalopathy following allogeneic stem cell transplantation in children.

Tacrolimus is a potent immunosuppressive drug widely used to prevent and treat graft-versus-host disease (GVHD) in stem cell transplantation (SCT). Among 49 patients receiving tacrolimus who underwent SCT from January 2000 to July 2003, 10 patients (20%) developed encephalopathy. The commonly observed symptoms were convulsions and drowsiness, and most patients complained of signal symptoms such as headache, nausea, and cortical blindness before onset. The most common abnormality on neuroimages was high-intensity lesions in white matter on magnetic resonance imaging T2-weighted or fluid-attenuated inversion recovery images. At onset, all patients were receiving treatment for acute GVHD (grade II/III) or extensive chronic GVHD and demonstrated an abrupt increase in blood pressure from baseline levels. The serum tacrolimus concentration was generally within acceptable levels at onset. Symptoms gradually improved in all patients when the blood pressure was lowered with antihypertensive medication, regardless of continued tacrolimus administration following a short-term suspension. The pathogenesis of tacrolimus-related encephalopathy is multifactorial, although refractory GVHD and a sudden increase in blood pressure seem to be major predisposing factors. Because the withdrawal of tacrolimus or switching to less potent anti-GVHD agents usually worsens the GVHD, the administration of tacrolimus should be managed by closely monitoring serum levels and controlling blood pressure.

Antihypertensive Agents↗
PubMed2005

[Management of hypoparathyroidism].

The aim of therapy in all hypoparathyroid states is to restore serum calcium to levels sufficient enough to alleviate symptoms of acute hypocalcemia and to prevent the complications of chronic hypocalcemia and hypercalcemia. The main pharmacologic agents available are calcium and vitamin D preparations. In this review, we comment on the usage and management of these agents. Furthermore, prospective therapeutics are discussed.

Calcium↗
PubMed2004

Skeletal defects in ringelschwanz mutant mice reveal that Lrp6 is required for proper somitogenesis and osteogenesis.

Here, we present evidence that Lrp6, a coreceptor for Wnt ligands, is required for the normal formation of somites and bones. By positional cloning, we demonstrate that a novel spontaneous mutation ringelschwanz (rs) in the mouse is caused by a point mutation in Lrp6, leading to an amino acid substitution of tryptophan for the evolutionarily conserved residue arginine at codon 886 (R886W). We show that rs is a hypomorphic Lrp6 allele by a genetic complementation test with Lrp6-null mice, and that the mutated protein cannot efficiently transduce signals through the Wnt/beta-catenin pathway. Homozygous rs mice, many of which are remarkably viable, exhibit a combination of multiple Wnt-deficient phenotypes, including dysmorphologies of the axial skeleton, digits and the neural tube. The establishment of the anteroposterior somite compartments, the epithelialization of nascent somites, and the formation of segment borders are disturbed in rs mutants, leading to a characteristic form of vertebral malformations, similar to dysmorphologies in individuals suffering from spondylocostal dysostosis. Marker expression study suggests that Lrp6 is required for the crosstalk between the Wnt and notch-delta signaling pathways during somitogenesis. Furthermore, the Lrp6 dysfunction in rs leads to delayed ossification at birth and to a low bone mass phenotype in adults. Together, we propose that Lrp6 is one of the key genetic components for the pathogenesis of vertebral segmentation defects and of osteoporosis in humans.

Aging↗
PubMed2004

Involvement of phosphoinositide 3-kinase signaling pathway in chondrocytic differentiation of ATDC5 cells: application of a gene-trap mutagenesis.

Gene-trap mutagenesis is based on the notion that the random insertion of a trapping vector may disturb the function of inserted genes. Here, we applied this method to murine mesenchymal ATDC5 cells, which differentiate into mature chondrocytes in the presence of insulin. As the trap vector we used pPT1-geo, which lacks its own promoter and enhancer, but contains a lacZ-neo fusion gene as a reporter and selection marker driven by the promoter of the trapped gene. After pPT1-geo was introduced into ATDC5 cells by electroporation, the neomycin-resistant clones were screened for beta-galactosidase activity. The selected clones were cultured in differentiation medium to evaluate the chondrogenic phenotype. The clones no. 6-30 and 6-175, which exhibited impaired and accelerated mineralization, respectively, were subjected to further analysis. In clone no. 6-30 in which the gene coding for the p85alpha subunit of phosphoinositide 3-kinase (PI3K) was trapped, the expression of marker genes of early chondrocytes including collagen type II, aggrecan, and PTH/PTHrP receptor was delayed. The insulin-induced stimulation of growth was reduced in clone no. 6-30 compared with the parental ATDC5 cells. Moreover, treatment of parental ATDC5 cells with a specific inhibitor of PI3K, LY294002, phenocopied clone no. 6-30, suggesting the involvement of PI3K signaling in the chondrogenic differentiation of ATDC5 cells. Clone no. 6-175 with accelerated mineralization was revealed to have a gene homologous to human KIAA0312 trapped, whose function remains unclear. Taken together, the gene-trap in ATDC5 cells might be useful to identify the molecules involved in chondrogenic differentiation.

Animals↗
PubMed2004

Analysis of recombinant human saposin A expressed by Pichia pastoris.

Saposins (SAPs) are small glycoproteins required for activation of sphingolipid hydrolysis by lysosomal enzymes. Four SAPs, SAP-A, -B, -C, and -D, are proteolytically cleaved from a single gene product termed prosaposin. The mature coding sequence of human SAP-A tagged with 6-histidine was expressed in Pichia pastoris and the recombinant protein was purified from the culture supernatant by simple purification steps with an immobilized metal ion affinity column, a Concanavalin A column, and reversed-phase HPLC. Secreted SAP-A contained both glycosylated and nonglycosylated forms. Both forms of SAP-A activated galactocerebroside and 4-methylumbelliferyl beta-d-glucoside hydrolysis by galactocerebrosidase and glucocerebrosidase. SAP-A expressed in P. pastoris should be useful for further structural and functional analysis of this protein.

Amino Acid Sequence↗
PubMed2004

LRRC8 involved in B cell development belongs to a novel family of leucine-rich repeat proteins.

In a previous study, we isolated a novel gene, LRRC8 (leucine-rich repeat-containing 8), in a girl with congenital agammaglobulinemia. We have now identified four unknown LRRC8-like genes, named TA-LRRP, AD158, LRRC5, and FLJ23420. Their predicted structures are very similar to each other, and highly conserved between humans and the mouse. All five genes encode proteins consisting of 16 extracellular leucine-rich repeats (LRRs), all of which have four transmembrane regions except for FLJ23420. These genes belong to a novel family, designated the LRRC8 family, within the superfamily of LRR proteins. TA-LRRP, AD158, and LRRC5 might be implicated in proliferation and activation of lymphocytes and monocytes.

Amino Acid Sequence↗
PubMed2004

Examination of megalin in renal tubular epithelium from patients with Dent disease.

Dent disease is characteristic for the urinary loss of low-molecular-weight proteins and calcium, leading to renal calcification and, in some patients, chronic renal failure. This disorder is caused by loss-of-function mutations in the renal chloride channel gene, CLCN5. The animal model of this disease has demonstrated the possible role of disturbed megalin expression, which is a member of the low-density lipoprotein receptor family and is associated with renal reabsorption of a variety of proteins, in Dent disease. We examined the expression of megalin in the renal tubular epithelium of two unrelated patients with Dent disease. One patient, whose CLCN5 gene was completely deleted, showed significantly decreased staining of megalin compared with controls, while there was no change in another patient with partial deletion of the gene. These results demonstrated that mutation of CLCN5 in some patients with Dent disease may impair the expression of megalin, resulting in abnormal calcium metabolism, manifested as hypercalciuria and nephrocalcinosis.

Calcium Metabolism Disorders↗
PubMed2004

Role of TAFII-17, a VDR binding protein, in the increased osteoclast formation in Paget's Disease.

UNLABELLED: In contrast to normal OCL precursors, pagetic OCL precursors express MVNP and form OCL at physiologic concentrations of 1,25(OH)2D3, as do normal OCL precursors transfected with the MVNP gene. Using a GST-VDR chimeric protein, we identified TAFII-17 as VDR binding protein expressed by pagetic OCL precursors and MVNP transduced normal OCL precursors. TAF(II)-17 was in part responsible for the increased 1,25(OH)2D3 responsivity of pagetic OCL precursors. INTRODUCTION: Pagetic osteoclasts (OCLs) and their precursors express measles virus nucleocapsid protein (MVNP) and form large numbers of OCLs at low concentrations of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. Similarly, normal OCL precursors transfected with MVNP also form OCLs at low concentrations of 1,25(OH)2D3. These results suggest that expression of MVNP in OCL precursors enhances vitamin D receptor (VDR)-mediated gene transcription. MATERIALS AND METHODS: To determine the mechanism for the increased OCL formation capacity of pagetic OCL precursors in response to 1,25(OH)2D3, lysates from pagetic and MVNP-transduced normal OCL precursors were incubated with a GST-VDR chimeric protein. RESULTS: A 17-kDa peptide that bound VDR was detected in MVNP-transduced cells and pagetic OCL precursors treated with 1,25(OH)2D3. This peptide was identified as TAFII-17, a component of the TFIID transcription complex. Expression of increased levels of TAFII-17 in cells allowed TAFII-17 to bind to VDR at low concentrations of 1,25(OH)2D3. An antisense oligonucelotide (AS-ODN) to TAFII-17 significantly decreased OCL formation in response to 1,25(OH)2D3 in pagetic but not normal marrow cultures by approximately 40%. Transfection of TAFII-17 or MVNP into NIH3T3 cells increased VDR transcriptional activity as measured by DR-3 reporter assays. CONCLUSION: These data show that expression of the MVNP gene in OCL precursors results in increased levels of TAFII-17. TAFII-17 can bind VDR at low concentrations of 1,25(OH)2D3. These results suggest that MVNP expression in Paget's OCL precursors increases expression of a component(s) of the VDR transcription complex that can increase OCL formation.

Bone Marrow Cells↗
PubMed2004

C-3 epimerization of vitamin D3 metabolites and further metabolism of C-3 epimers: 25-hydroxyvitamin D3 is metabolized to 3-epi-25-hydroxyvitamin D3 and subsequently metabolized through C-1alpha or C-24 hydroxylation.

Recently, it was revealed that 1alpha,25-dihydroxyvitamin D3 (1alpha,25(OH)2D3) and 24R,25-dihydroxyvitamin D3 (24,25(OH)2D3) were metabolized to their respective epimers of the hydroxyl group at C-3 of the A-ring. We now report the isolation and structural assignment of 3-epi-25-hydroxyvitamin D3 (3-epi-25(OH)D3 as a major metabolite of 25-hydroxyvitamin D3 (25(OH)D3) and the further metabolism of C-3 epimers of vitamin D3 metabolites. When 25(OH)D3 was incubated with various cultured cells including osteosarcoma, colon adenocarcinoma, and hepatoblastoma cell lines, 3-epi-25(OH)D3 and 24,25 (OH)2D3 were commonly observed as a major and minor metabolite of 25(OH)D3, respectively. 25(OH)D3 was at least as sensitive to C-3 epimerization as 1alpha, 25(OH)2D3 which has been reported as a substrate for the C-3 epimerization reaction. Unlike these cultured cells, LLC-PK1 cells, a porcine kidney cell line, preferentially produced 24,25(OH)2D3 rather than 3-epi-25(OH)D3. We also confirmed the existence of 3-epi-25(OH)D3 in the serum of rats intravenously given pharmacological doses of 25(OH)D3. The cultured cells metabolized 3-epi-25OHD3 and 3-epi-1alpha,25(OH)2D3 to 3-epi-24,25(OH)2D3 and 3-epi-1alpha,24,25(OH)3D3, respectively. In addition, we demonstrated that 3-epi-25(OH)D3 was metabolized to 3-epi-1alpha,25(OH)2D3 by CYP27B1 and to 3-epi-24,25(OH)2D3 by CYP24 using recombinant Escherichia coli cell systems. 3-Epi-25(OH)D3, 3-epi-1alpha,25(OH)2D3, and 3-epi-24,25(OH)2D3 were biologically less active than 25(OH)D3, 1alpha,25(OH)2D3, and 24,25(OH)2D3, but 3-epi-1alpha,25(OH)2D3 showed to some extent transcriptional activity toward target genes and anti-proliferative/differentiation-inducing activity against human myeloid leukemia cells (HL-60). These results indicate that C-3 epimerization may be a common metabolic pathway for the major metabolites of vitamin D3.

24,25-Dihydroxyvitamin D 3↗