Hideki Iwata

Morquio disease: Isolation, characterization and expression of full-length cDNA for human N-acetylgalactosamine-6-sulfate sulfatase

We cloned and sequenced a full-length cDNA of human placental N-acetylgalactosamine-6-sulfate sulfatase, the enzyme deficient in Morquio disease. The 2339-nucleotide sequence contained 1566 nucleotides which encoded a polypeptide of 522 amino acid residues. The deduced amino acid sequence was composed of a 26-amino acid N-terminal signal peptide and a mature polypeptide of 496 amino acid residues including two potential asparagine-linked glycosylation sites. Expression of the cDNA in transfected deficient fibroblasts resulted in higher production of this sulfatase activity than in untransfected deficient fibroblasts. The cDNA clone was hybridized to only a 2.3-kilobase species of RNA in human fibroblasts. The amino acid sequence of N-acetylgalactosamine-6-sulfate sulfatase showed a high degree of homology with those of other sulfatases such as human arylsulfatases A, B or C, glucosamine-6-sulfatase, iduronate-2-sulfatase and sea urchin arylsulfatase.

A novel mtDNA C11777A mutation in Leigh syndrome.

A novel mitochondrial DNA point mutation, a C-to-A mutation at nucleotide position (np) 11,777, was identified in two unrelated patients out of 100 with Leigh syndrome. This mutation converted a highly evolutionary conserved arginine to a serine at codon 340 in ND4 gene. This codon was also converted by a G-to-A mutation at np 11,778, the most common mutation associated with Lebers hereditary optic neuropathy (LHON), but the amino acid replacement was different (R340S vs. R340H). Cybrid study revealed that the percentage of heteroplasmy was correlated with complex I function and that the novel mutation caused a much more deleterious effect than the np 11,778 LHON mutation in complex I activity.

Intravenous Immunoglobulins Suppress Immunoglobulin Productions by Suppressing Ca2+ ‐Dependent Signal Transduction Through Fc γ Receptors in B Lymphocytes

A high dose intravenous immunoglobulin (IVIG) therapy is used in the treatment of a wide range of autoimmune disorders. However, the mechanisms of the action of IVIGs remain poorly understood. To analyse the mechanisms of effects of IVIGs on immunoglobulin (Ig) production of B cells, the effects of IVIGs on B lymphoblastoid cell lines transformed by Epstein‐Barr virus (LCLs) were investigated. The productions of IgG or IgM of LCLs were dose‐dependently suppressed by polyethylene glycol (PEG)‐treated IVIG or pH 4‐treated 1VIG though the productions were not or only slightly suppressed by pepsin‐treated IVIG. The suppression by IVIGs was blocked by anti‐human IgG Fc or anti‐Fc γ RII. C μ gene expression and μ s C terminal gene expression of LCLs were suppressed by PEG‐treated IVIG, whereas neither C μ gene expression nor μ s C terminal gene expression of LCLs were suppressed by pepsin‐treated IVIG. Although the increase in intracellular calcium concentration in LCLs was not suppressed by pepsin‐treated IVIG, the increase was suppressed by PEG‐treated IVIG. This suppressing effect of PEG‐treated IVIG on intracellular calcium concentration of LCLs was blocked by anti‐human IgG Fc or anti‐ Fc γ RII. Our results suggest that IVIGs suppressed the Ca2+ ‐dependent signal transduction through Fc γ R on B‐cell membrane, consequently, the transcription of C γ mRNA, especially secreted γ mRNA was suppressed in the B cells.

Mucopolysaccharidosis IVA: polymorphic haplotypes and informative RFLPs in the Japanese population

Seven different restriction fragment length polymorphisms (RFLPs) at the N-acetylgalactosamine-6-sulfate sulfatase (GALNS) locus were analyzed using Southern blotting and polymerase chain reaction based techniques to search for the frequency of each RFLP produced by StyI, SphI, HaeIII, StuI, HapII, XhoI, and BamHI restriction endonucleases, respectively, in 36 mutant alleles, including two sibling cases and 100 normal alleles. Calculation of heterozygosity indexes showed that these RFLPs were polymorphic, ranging from 0.31 to 0.69 in mucopolysaccharidosis IVA (MPS IVA) patients compared with 0.21 to 0.65 in normal individuals. There was some significant difference in several RFLPs and in the combination with four kinds of RFLPs (SphI, StuI, HapII, XhoI polymorphisms). The normal alleles were composed of 13 different RFLPs haplotypes; the most common among the Japanese population carrying normal alleles was haplotype 8 (bDEF1) (31.3%), the others being dispersed. The same haplotype 8 was the most frequent in the mutant alleles (44.4%), with seven further haplotypes. These findings revealed the striking variety of polymorphic haplotypes in the MPS IVA gene. By using these five kinds of RFLPs, we examined the theoretical informativity of haplotype analysis in heterozygote detection in nine unrelated MPS IVA families and ten unrelated normal families. All the members of the MPS IVA families studied were diagnosed as a patient, carrier, or noncarrier. We propose that prenatal diagnosis or family analysis in cases in which mutations have not been characterized is now feasible.

A severely brain-damaged case of 3-hydroxyisobutyric aciduria

We report a male case of 3-hydroxyisobutyric aciduria (3HiB-uria) with severe brain damage. He had mild asphyxia at birth. He needed tube feeding for a month. He showed mild dysmorphic features, including low set ears, a long philtrum and micrognathia. At 4 months of age he had acute encephalopathy. Thereafter, severe brain damage remained and mechanical ventilation care was needed all day. After he had been admitted to our hospital at 3 years of age, repeated organic acid analysis of urine confirmed the diagnosis of 3HiB-uria. This patient had been previously diagnosed as having cerebral palsy and sequelae of acute encephalopathy.

Apneustic breathing in children with brainstem damage due to hypoxic–ischemic encephalopathy

To confirm the presence of apneusis in patients with hypoxic–ischemic encephalopathy and to clarify which factors influence their respiratory patterns, polygraphic studies were performed on two patients. Apneusis was clinically suspected in both patients who had severe brainstem damage. In one subject, inputs of vagal afferents from the gastrointestinal tract and the urinary bladder often resulted in extreme tachypnea instead of apneusis. Lung inflation facilitated expiration during inspiratory arrest. Expiration preceded a periodic inhibition of rigospastic discharge in the right biceps muscle. In the other subject, prolonged inspiratory pauses with cyanosis occurred with or without preceding epileptic seizure. Both phenytoin dose reduction and treatment with tandospirone, a serotonin‐1A agonist, were effective in improving the respiratory distress in this subject.

Mucopolysaccharidosis IVA: a comparative study of polymorphic DNA haplotypes in the Caucasian and Japanese populations

SummaryMucopolysaccharidosis IVA (MPS IVA) is an autosomal recessive disorder caused by deficiency of the lysosomal enzymeN-acetylgalactosamine-6-sulphate sulphatase (GALNS). The genetic heterogeneity at the GALNS locus was studied in 62 mutant alleles and 376 normal alleles in the Caucasian population and also in 40 mutant and 100 normal alleles in the Japanese population. For this study, six different restriction fragment length polymorphisms (RFLPs) at the GALNS locus were analysed to search for the frequency of each RFLP produced byStyI,SphI,RsaI,HaeIII,StuI andHapII restriction endonucleases. We detected a total of 27 haplotypes in the Caucasian and Japanese population. Of these 27 haplotypes, 18 haplotypes were present in the Caucasian population and the most common of these was haplotype 1 (ABHcde) in both mutant and normal alleles. In contrast, in the Japanese population we found 20 of the 27 haplotypes and the most common in mutant and normal alleles was haplotype 2 (abhcDE). Within these two populations a parent in the MPS IVA family has an average probability of greater than 77% (in the Caucasian population 77.27% and in the Japanese population 78.26%) of being heterozygous, and hence informative for linkage, at one or more GALNS RFLP sites. Our results delineate the molecular heterogeneity of MPS IVA haplotypes, as well as their significant interpopulation variation, and make prenatal diagnosis and carrier detection possible in the majority of families with one affected child.

Siblings of Schwartz-Jampel syndrome with abnormal muscle computed tomographic findings.

Schwartz-Jampel syndrome (SJS) is a disorder characterized by myotonia, joint contractures, skeletal abnormalities, facial dysmorphism and growth retardation. We present two boys of ages 4 and 8 years with SJS. Their clinical, electromyographic and histopathological findings were similar to those described, except for computed tomography (CT) images that revealed diffuse high attenuation in sternocleidomastoid muscles and low attenuation in the paraspinal, quadriceps, sartorius, soleus and gastrocnemius muscles. This is the first report describing abnormal muscle CT findings associated with SJS. Additional studies of muscle CT might help to improve understanding of the pathogenesis of SJS.

Practice of Pentobarbital Therapy in Convulsive Status Epilepticus in Children with Epilepsy

Purpose: We studied the detailed practical procedures and management of the complications of pentobarbital (PTB) therapy for convulsive status epilepticus (C‐SE) in children with epilepsy.