Takuji Imamura

Molecular characterization of galactokinase deficiency in Japanese patients

AbstractGalactokinase (GALK) deficiency is an autosomal recessive disorder, which causes cataract formation in children not maintained on a lactose-free diet. We characterized the human GALK gene by screening a Japanese genomic DNA phage library, and found that several nucleotides in the 5′-untranslated region and introns 1, 2, and 5 in our GALK genomic analysis differed from published data. A 20-bp tandem repeat was found in three places in intron 5, which were considered insertion sequences. We identified five novel mutations in seven unrelated Japanese patients with GALK deficiency. There were three missense mutations and two deletions. All three missense mutations (R256W, T344M, and G349S) occurred at CpG dinucleotides, and the T344M and G349S mutations occurred in the conserved region. The three missense mutations led to a drastic reduction in GALK activity when individual mutant cDNAs were expressed in a mammalian cell system. These findings indicated that these missense mutations caused GALK deficiency. The two deletions, of 410delG and 509–510delGT, occurred at the nucleotide repeats GGGGGG and GTGTGT, respectively, and resulted in in-frame nonsense codons at amino acids 163 and 201. These mutations arose by slipped strand mispairing. All five mutations occurred at hot spots in the CpG dinucleotide for missense mutations and in short direct repeats for deletions. These five mutations in Japanese have not yet been identified in Caucasians. We speculate that the origin of GALK mutations in Japanese is different from that in Caucasians.

Molecular characterization of 6-pyruvoyl-tetrahydropterin synthase deficiency in Japanese patients.

AbstractWe identified three mutations in four Japanese patients with central type 6-pyruvoyl-tetrahydropterin synthase (PTPS) deficiency. One missense mutation was a C-to-T transition, resulting in the substitution of Pro by Ser at codon 87 (P87S) in exon 5. Another missense mutation was a G-to-A transition, resulting in the substitution of Asp by Asn at codon 96 (D96N) in exon 5. A splicing mutation was found by skipping of exon 4 on PTPS mRNA analysis, and a G-to-A transition at the third base of codon 81 (E81E) and at the terminal base in exon 4 were detected on genomic PTPS DNA analysis. The E81E mutation affected the splice donor site of exon 4 and caused the splicing error. In COS cell expression analysis, the P87S and D96N mutant constructs revealed, respectively, 52% and 10% of wild-type activity. Patients with P87S/P87S (52%/52% in-vitro PTPS activity) exhibited 0.11 and 0 μU/g hemoglobin [Hb] in erythrocyte PTPS activity (wild-type control: 11-29 μU/gHb) erythrocyte PTPS activity, and the patient with P87S/D96N mutations (52%/10%) had 0.97 μU/gHb in PTPS erythrocyte activity. The PTPS erythrocyte activity did not coincide with the in-vitro PTPS activity based on patient genotype.

Experimental Research on a New Treatment for Maternal Phenylketonuria(PKU)

More girls with phenylketonuria (PKU) enter childbearing ages, and most such women are mentally normal, having been born since newborn screening was initiated in the 1970s and treated from early infancy with a low phenylalanine (Phe) diet. Women with PKU not treated prior to conception can have a pregnancy that results in serious fetal damage1. Maternal PKU as a cause of mental retardation and birth defects is a new phenomenon. There will be an increased need for specific therapies in maternal PKU. Low Phe diet is essential for the treatment of maternal PKU. It should be started before pregnancy and it is necessary to maintain their plasma Phe levels around 5 mg/dl throughout their pregnancy2. However they are usually controlled around 10 mg/dl because of the difficulty of the diet therapy. We made an animal model of maternal PKU by the intravenous injection of Phe to pregnant guinea-pigs, and examined plasma, liver and brain Phe levels in their fetuses after an intravenous administration of 6R-5,6,7,8-tetrahydrobiopterin (R-BH4) to the mothers.

Prenatal diagnosis of 6-pyruvoyl tetrahydropterin synthase deficiency in seven subjects

H. SHINTAKU 1, K. J. HSIAO 2, T. T. LIu 2, T. IMAMURA 1, Y. HASE 3, R. G. CHEN 4, G. ISSHIKI 1 and T. OURA 5 1Department of Pediatrics, Osaka City University Medical School, 1-5-7 Asahimachi, Abeno-ku, Osaka 545 Japan; 2Institutes of Genetics and Biochemistry, National Yong Ming Medical College, and Department of Medical Research, Veterans General Hospital, Taipei 11216, Republic of China; 3First Division of Pediatrics, Childrens Medical Center of Osaka City, Osaka 537, Japan; 4Department of Pediatrics, Shanghai Institute for Pediatric Research, Shanghai, China; 5Osaka Municipal Rehabilitation Center for the Disabled, Osaka 547, Japan

Neopterin in Subacute Sclerosing Panencephalitis

Subacute sclerosing panencephalitis (SSPE) has a very poor prognosis. In recent years, the introduction of various treatments including inosiplex and interferon has somewhat improved the survival rate1,2. However, there are large variations in the response of patients. It is difficult to forecast the response and prognosis on the basis of clinical symptoms alone, but sequential recordings by computed tomography (CT) and magnetic resonance imaging (MRI) can be used to identify the lesions and severity of the disease, providing information that may be correlated with changes in the neurological symptoms3. A number of laboratory tests have been used to define the clinical stage of patients with SSPE. Here, we report that sequential monitoring of neopterin, ferritin, and creatine kinase (CK) in the cerebrospinal fluid (CSF) of two patients with SSPE was useful as an index of the progress of the disease.

Clinical features of women with Turner syndrome experiencing transition period in Japan

Turner syndrome results from the entire or partial loss of the second X chromosome, and is associated with a number of medical problems. Affected women require long-term medical follow-up. This study investigated the status of medical follow-up focusing on the transition for young adult women with Turner syndrome (TS). The clinical profiles of 63 women with TS over the age of 16 were retrospectively examined. Thirty-three women are continuously followed by pediatric endocrinologists at our pediatric division. Twenty women were transferred to gynecologists as primary care physicians. Eight young adult women dropped out of the regular health check-up from our pediatric division even though 7 women were undergoing estrogen replacement therapy. We further reviewed the complications and management of the 33 women who were continuously followed at our pediatric division. A high incidence of obesity and liver dysfunction were observed in this age group (23.5±8.7). Nineteen out of 33 women consulted a cardiologist in the adult care division for cardiovascular complications. In the analysis of 20 women who were transferred to gynecologists, mainly two gynecologists accepted the transfer and have become accustomed to clinical care for TS. Seven women who were followed by the gynecologist in our facility were adequately managed for lifelong complications. Since there is no clear framework for transition in Japan, coordination with other specialists, especially gynecologists, is essential for the successful management of adult women with TS. Patient education and provision of information are required for establishing self-advocacy, which will prevent drop-out.

Poor response to substitution therapy with cortisone acetate in patients with congenital adrenal hyperplasia.

Although cortisone acetate is approved worldwide as corticosteroid substitution therapy in congenital adrenal hyperplasia (21-hydroxylase deficiency), its effectiveness is uncertain since its biologic activity depends on activation by 11β-hydroxysteroid dehydrogenase (11β-HSD). We sought to compare the effect of cortisone acetate with that of hydrocortisone. In 10 patients with congenital adrenal hyperplasia, cortisone acetate was replaced with hydrocortisone in substitution therapy. During this change, blood concentrations of 17-hydroxy-progesterone, adrenocorticotropin (ACTH), and requirements for each drug were monitored. Concentrations of 17-hydroxyprogesterone decreased (mean 10.1 vs. 48.6 ng/ml), as did those of ACTH. Cortisone acetate dose requirements averaged 33.9 mg/m2, while hydrocortisone dose requirements averaged only 20.3 mg/m2. In one of the patients resistant to cortisone acetate therapy, DNA sequences in the coding regions and promoter of the 11β-HSD gene were analyzed, detecting no genetic abnormalities. Cortisone acetate is inferior to hydrocortisone as substitution therapy in patients with congenital adrenal hyperplasia.

Experimental Research on a Fetal Treatment for Tetrahydrobiopterin Deficiency

Tetrahydrobiopterin (BH4) synthase deficiency has a high incidence of low birth weight,1 and some of them had a mild mental retardation in spite of their early treatment2. In this study we performed an intravenous loading of 2,4-diamino-6-hydroxypyrimidine (DAHP) with a small amount of BHU, and successfully made a model of fetal BH4 deficiency. We investigated the possibility of the fetal therapy of BH4 deficiency in this model by measurements of phenylalanine(Phe), tyrosine(Tyr), BH4, dopamine and catecholamines.

Oral administration of liposomally entrapped tetrahydrobiopterin.

Tetrahydrobiopterin (BH4) has been used for the therapy of BH4-deficient patients. However, BH4 is poorly absorbed from the intestine. The plasma level of biopterin that was reached after oral administration of BH4 to a BH4-deficient patient was reported to be 1–2% of the levels reached after either intravenous or subcutaneous administration1. This poor absorption from the intestine needs a large amount of BH4 for the oral therapy, leading to high costs.