Biomedical subjects

Yoichi Matsubara

Publications and source records attributed to Yoichi Matsubara.

41 records · Page 3Linked to original sources

PubMed2002

Heterozygous GLDC and GCSH gene mutations in transient neonatal hyperglycinemia.

Transient neonatal hyperglycinemia is clinically or biochemically indistinguishable from nonketotic hyperglycinemia at onset. In the case of transient neonatal hyperglycinemia, the elevated plasma and cerebrospinal fluid glycine levels are normalized within 2 to 8 weeks. To elucidate the pathogenesis of transient neonatal hyperglycinemia, we studied three patients by screening mutations in the genes that encode three components of the glycine cleavage system. Heterozygous mutations were identified in all of the three patients, suggesting that transient neonatal hyperglycinemia develops in some heterozygous carriers for nonketotic hyperglycinemia.

Amino Acid Oxidoreductases↗

PubMed2002

Identification of GFAP gene mutation in hereditary adult-onset Alexander's disease.

Alexander's disease, a leukodystrophy characterized by Rosenthal fibers (RFs) in the brain, is categorized into three subtypes: infantile, juvenile, and adult. Although most are sporadic, occasional familial Alexander's disease cases have been reported for each subtype. Hereditary adult-onset Alexander's disease shows progressive spastic paresis, bulbar or pseudobulbar palsy, palatal myoclonus symptomatologically, and prominent atrophy of the medulla oblongata and upper spinal cord on magnetic resonance imaging. Recent identification of GFAP gene mutations in the sporadic infantile- and juvenile-onset Alexander's disease prompted us to examine the GFAP gene in two Japanese hereditary adult-onset Alexander's disease brothers with autopsy in one case. Both had spastic paresis without palatal myoclonus, and magnetic resonance imaging showed marked atrophy of the medulla oblongata and cervicothoracic cord. The autopsy showed severely involved shrunken pyramids, but scarce Rosenthal fibers (RFs). Moderate numbers of Rosenthal fibers (RFs) were observed in the stratum subcallosum and hippocampal fimbria. In both cases, we found a novel missense mutation of a G-to-T transition at nucleotide 841 in the GFAP gene that results in the substitution of arginine for leucine at amino acid residue 276 (R276L). This is the first report of identification of the causative mutation of the GFAP gene for neuropathologically proven hereditary adult-onset Alexander's disease, suggesting a common molecular mechanism underlies the three Alexander's disease subtypes.

Alexander Disease↗

PubMed2002

Lack of evidence for a significant association between nonsyndromic cleft lip with or without cleft palate and the retinoic acid receptor alpha gene in the Japanese population.

Nonsyndromic cleft lip with or without cleft palate (NSCLP) is one of the most common craniofacial malformations. Both genetic and environmental factors are thought to be involved in the pathogenesis. The retinoic acid receptor alpha ( RARA) is one of the candidate genes for the pathogenesis of NSCLP. An association between a PstI restriction fragment length polymorphism or D17S579 microsatellite marker polymorphism of the RARA gene and NSCLP was previously suggested, but no nucleotide change that may influence the gene expression or the protein sequence has been reported to date. To investigate the possible association between the RARA gene and NSCLP in Japanese patients, we performed a transmission disequilibrium test (TDT) using three microsatellite markers at the RARA locus in 48 parent-offspring trios. The allele-wise TDT did not show evidence of an association between the RARA gene and NSCLP. We also screened nucleotide changes in eight patients with family histories using exon-by-exon direct sequencing. We found a novel nucleotide change (1161C>T) that is located in exon 1 of the RARA gene in one patient whose father also had the disease. Because the 1161C>T was inherited from the patient's healthy mother, the mutation was not considered to be responsible for NSCLP. We then screened all probands for the nucleotide changes in the promoter region of the RARA gene using denaturing high-performance liquid chromatography. A novel nucleotide length polymorphism of a thymidine tract was identified in three patients. No association between this polymorphism and NSCLP was observed. Our findings suggest that the RARA gene variations do not contribute to the development of NSCLP in the Japanese population.

Alleles↗

PubMedDate not supplied

Wild-type phenylalanine hydroxylase activity is enhanced by tetrahydrobiopterin supplementation in vivo: an implication for therapeutic basis of tetrahydrobiopterin-responsive phenylalanine hydroxylase deficiency.

We previously proposed a novel disease entity, tetrahydrobiopterin (BH4)-responsive phenylalanine hydroxylase (PAH) deficiency, in which administration of BH4 reduced elevated levels of serum phenylalanine [J. Pediatr. 135 (1999) 375-378]. Subsequent reports indicate that the prevalence of BH4-responsive PAH deficiency is much higher than initially anticipated. Although growing attention surrounds treatment with BH4, little is known about the mechanism of BH4 responsiveness. An early report indicates that BH4 concentration in rat liver was 5 microM where Km for BH4 of rat PAH was estimated to be 25 microM in an oxidation experiment using a liver slice, suggesting relative insufficiency of BH4 in liver in vivo. In the present study, we developed a breath test for mice using [1-13C]phenylalanine in order to examine the BH4 responsiveness of normal PAH in vivo. The reliability of the test was verified using BTBR mice and its mutant strain lacking PAH activity, Pahenu2. BH4 supplementation significantly enhanced 13CO2 production in C57BL/6 mice when phenylalanine was pre-loaded. Furthermore, BH4 apparently activated PAH in just 5 min. These observations suggest that submaximal PAH activity occurs at the physiological concentrations of BH4 in vivo, and that PAH activity can be rapidly enhanced by supplementation with BH4. Thus, we propose a possible hypothesis that the responsiveness to BH4 in patients with PAH deficiency is due to the fact that suboptimal physiological concentrations of BH4 are normally present in hepatocytes and the enhancement of the residual activity may be associated with a wide range of mutations.

Animals↗

PubMedDate not supplied

Atypical variants of nonketotic hyperglycinemia.

Clinical symptoms in atypical nonketotic hyperglycinemia (NKH) are heterogeneous, in sharp contrast to uniform severe neurological symptoms in the classical NKH. A review of the literature of atypical NKH cases reveals three forms: neonatal, infantile, and late onset. The presentation in the neonatal form is similar to the classical one but the subsequent outcome is significantly better. Mental retardation and behavioral abnormalities are prevalent in both infantile and late onset forms although the phenotype in late onset atypical NKH is more heterogeneous. Patients with the atypical NKH tend to have a lower CSF/plasma glycine ratio when compared with the classical form, but overlap occurs. Hyperglycinemia in the neonatal and infantile atypical NKH, similar to the classical form, is caused by a deficient glycine cleavage system, whereas the cause of hyperglycinemia in late onset atypical NKH is unknown. A mutation of the T-protein AMT gene and several mutations of P-protein GLDC gene have been identified in homozygous or compound heterozygous state. Some of the GLDC mutations are associated with residual glycine decarboxylase activity when expressed in COS7 cells and early therapeutic intervention may be crucial to improve the outcome in patients harboring such mutations. Identification of more mutations causing atypical NKH and information about the mutations' effect on enzyme activity may help to predict patients with a milder phenotype as well as those who may respond to early therapeutic intervention.

Glycine↗