Atsuko Noguchi

SLC7A7 genomic structure and novel variants in three Japanese lysinuric protein intolerance families

Lysinuric protein intolerance (LPI) is a rare inherited disease caused by defective transport of the dibasic amino acids at the basolateral membranes of epithelial cells in the renal tubules and small intestine. The metabolic defect leads to brain dysfunction caused by hyperammonemia with a functional impairment of the urea cycle. Recently, mutations in the human SLC7A7 cDNA coding for y+LAT‐1, which express dibasic amino acid transport activity, were reported to be responsible for LPI. In the present study, we examined the genomic structure of SLC7A7 by DNA sequencing of PCR products, and determined that the gene had 11 exons and 10 introns spanning about 18 kb of genomic DNA. We also identified an alternative RNA splicing at the 5′ untranslated region of the SLC7A7 mRNA in human peripheral blood leukocytes, cultured lymphoblasts, and fibroblasts. As a result of mutational analysis of SLC7A7 in three Japanese LPI families, we found a nonsense mutation (R410X), a splicing mutation(911+1G>A) in intron 4, and four silent polymorphisms (201C/T, 445A/G, 784C/T, 946T/C). Identification of the genomic structure of SLC7A7 may provide a molecular basis for a genetic survey for LPI. Hum Mutat 15:367–372, 2000.

Spread and predominance in Japan of novel G1P[8] double-reassortant rotavirus strains possessing a DS-1-like genotype constellation typical of G2P[4] strains

Rotavirus is a major cause of severe gastroenteritis in children <5 years of age worldwide, and two, live attenuated rotavirus vaccines are globally available. As rotavirus vaccines are introduced into national immunization programs, there is an increasing need to monitor circulating wild-type strains. However, few studies have systematically examined their full genotype constellation. This study was therefore undertaken to characterize the whole genotype constellation of circulating rotavirus strains in three widely-separated locations in Japan during the 2012 rotavirus season when rotavirus vaccines became available in the country for the first time. Of 107 rotavirus-positive specimens, 50 (46.7%) strains collected from all three locations possessed an unusual G1-P[8]-I2-R2-C2-M2-A2-N2-T2-E2-H2 constellation in which a typical G2P[4] strain appeared to have acquired its two surface protein genes from the most common G1P[8] strain. These G1P[8] double-reassortant strains were shown to possess the 11 genome segments virtually indistinguishable from each other in their nucleotide sequences and phylogenetic lineages except for two strains that underwent further intra-genotype reassortment. Successful spread to and predominance in broad locations across Japan of novel rotavirus strains possessing a genotype constellation that was previously thought not to be preferred suggests unexpected genomic flexibility of the genotype constellation.

A Cluster of Lysinuric Protein Intolerance (LPI) Patients in a Northern Part of Iwate, Japan due to a Founder Effect

Lysinuric protein intolerance is an autosomal recessive disease characterized by defective transport of the dibasic aminoacids. Mutational analysis of LPI patients in the northern part of Japan revealed that six were homozygous for the R410X mutation and two others were compound heterozygotes of R410X and other unknown mutations. In the population epidemiology study in a local cluster in the northern part of Iwate, ten heterozygotes were found in 1190 newborn babies leading to an estimated LPI incidence of 1/57,000. Polymorphism analysis revealed two major alleles, A and B, in intron 8. While the population frequency of allele A was 0.9 and that of allele B was 0.1 in the northern part of Japan the R410X mutations were exclusively on allele B in 31 chromosomes suggesting a founder effect. Genetic analysis in patients revealed strong linkage disequilibrium with D14S283 and TCRA indicating that the R410X mutation occurred before at least 130 generations ago (about 2600 years). The R410X mutation was shown to be useful as a molecular marker for screening LPI patients in the northern part of Japan. Hum Mutat 16:270–271, 2000.

Infantile Pain Episodes Associated with Novel Nav1.9 Mutations in Familial Episodic Pain Syndrome in Japanese Families.

Painful peripheral neuropathy has been correlated with various voltage-gated sodium channel mutations in sensory neurons. Recently Nav1.9, a voltage-gated sodium channel subtype, has been established as a genetic influence for certain peripheral pain syndromes. In this study, we performed a genetic study in six unrelated multigenerational Japanese families with episodic pain syndrome. Affected participants (n = 23) were characterized by infantile recurrent pain episodes with spontaneous mitigation around adolescence. This unique phenotype was inherited in an autosomal-dominant mode. Linkage analysis was performed for two families with 12 affected and nine unaffected members, and a single locus was identified on 3p22 (LOD score 4.32). Exome analysis (n = 14) was performed for affected and unaffected members in these two families and an additional family. Two missense variants were identified: R222H and R222S in SCN11A. Next, we generated a knock-in mouse model harboring one of the mutations (R222S). Behavioral tests (Hargreaves test and cold plate test) using R222S and wild-type C57BL/6 (WT) mice, young (8–9 weeks old; n = 10–12 for each group) and mature (36–38 weeks old; n = 5–6 for each group), showed that R222S mice were significantly (p < 0.05) more hypersensitive to hot and cold stimuli than WT mice. Electrophysiological studies using dorsal root ganglion neurons from 8–9-week-old mice showed no significant difference in resting membrane potential, but input impedance and firing frequency of evoked action potentials were significantly increased in R222S mice compared with WT mice. However, there was no significant difference among Nav1.9 (WT, R222S, and R222H)-overexpressing ND7/23 cell lines. These results suggest that our novel mutation is a gain-of-function mutation that causes infantile familial episodic pain. The mouse model developed here will be useful for drug screening for familial episodic pain syndrome associated with SCN11A mutations.

A case report of pediatric fulminant hepatitis treated with plasma diafiltration.

Abstract:  Plasma diafiltration (PDF) is blood purification therapy in which simple plasma exchange is performed with a membrane plasma separator while dialysate flows outside the hollow fibers. A 14‐year‐old boy with fulminant hepatitis underwent two sessions of PDF and one session of hemodiafiltration. We infused filtered replacement fluid for artificial kidneys at a dialysate flow rate of 600 mL/h and a replacement flow rate of 450 mL/h. We infused fresh frozen plasma (1200 mL) and 25% albumin solution (50 mL) intravenously over 8 h. Each PDF session lasted 8 h. The patients total bilirubin, interleukin‐18, and cystatin C levels decreased with treatment, and he recovered from hepatic failure. PDF may be an extremely useful blood purification therapy for pediatric fulminant hepatitis in terms of both medical economics and cytokine removal.

Fatigue and quality of life in citrin deficiency during adaptation and compensation stage

Citrin-deficient children and adolescents between adult-onset type II citrullinemia and neonatal intrahepatic cholestasis by citrin deficiency do not have clear clinical features except for unusual diet of high-fat, high-protein, and low-carbohydrate food. The aims of the present study are to characterize fatigue and quality of life (QOL) in citrin-deficient patients during adaptation and compensation stage, and to define the relationship between fatigue and QOL. The study subjects were 55 citrin-deficient patients aged 1-22years (29 males) and 54 guardians. Fatigue was evaluated by self-reports and proxy-reports of the PedsQL Multidimensional Fatigue Scale. QOL was evaluated by the PedsQL Generic Core Scales. Both scale scores were significantly lower in child self-reports (p<0.01 and p<0.05, respectively) and parent proxy-reports (p<0.01 and p<0.01, respectively) than those of healthy children. Citrin-deficient patients with scores of 50 percentile or less of healthy children constituted 67.5% of the sample for the Fatigue Scale and 68.4% for the Generic Core Scales. The PedsQL Fatigue Scale correlated with the Generic Core Scales for both the patients (r=0.56) and parents reports (r=0.71). Assessments by the patients and their parents showed moderate agreement. Parents assessed the condition of children more favorably than their children. The study identified severe fatigue and impaired QOL in citrin-deficient patients during the silent period, and that such children perceive worse fatigue and poorer QOL than those estimated by their parents. The results stress the need for active involvement of parents and medical staff in the management of citrin-deficient patients during the silent period.

Novel mutation in the TMPRSS6 gene with iron-refractory iron deficiency anemia

Iron‐refractory iron deficiency anemia (IRIDA) is a rare autosomal recessive disease characterized by congenital hypochromic microcytic anemia, low transferrin saturation, low serum iron, normal–high serum ferritin, and increased hepcidin. This disease is caused by loss‐of‐function mutations in TMPRSS6 that lead to high hepcidin and result in severe anemia. We report our experience with an 11‐year‐old Japanese girl with hypochromic microcytic anemia, low serum iron, and high serum ferritin, with anemia that was refractory to the oral iron that was prescribed frequently from early childhood. Presence of high hepcidin suggested a diagnosis of IRIDA, which was eventually confirmed by identification of a novel homozygous mutation, p.Pro354Leu, in the TMPRSS6 gene. This case suggests that serum hepcidin should be routinely measured for differential diagnosis when patients with IDA are unresponsive to oral iron or have unusual clinical features.

The useful preliminary diagnosis of Niemann-Pick disease type C by filipin test in blood smear.

Niemann-Pick disease type C (NP-C) is an autosomal recessive lysosomal lipid storage disorder characterized with accumulation of cholesterol in endosomes and lysosomes. The diagnosis of NP-C is difficult due to its heterogeneous group of diseases. Biochemical diagnosis of NP-C is conducted by cholesterol staining with cultured skin fibroblasts and confirmed by the analysis of genetic mutations of NPC1 or NPC2 gene. Here, we report an easier biochemical diagnostic method with blood smear by filipin staining.

Chylothorax in a polysplenia infant with cor triatriatum, pulmonary stenosis and sick sinus syndrome

SummaryAn infant with chylothorax and polysplenia is described. Her chylothorax was refractory and related to right-sided heart failure derived from pulmonary stenosis, cor triatriatum, and sick sinus syndrome. In addition to Brock operation and cardiac pacing, thoracic duct ligation was performed, but it resulted in an only transient amelioration of the chylothorax. Eventually, the chylothorax resolved when total cardiac repair was performed for cor triatriatum. We propose that, in a patient with chylothorax and right-sided heart failure caused by compound cardiac malformations, as in this patient early surgical treatment for the underlying disease of right-sided heart failure should be considered.

Clinical and genetic features of Japanese patients with lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is a rare autosomal recessive disorder affecting the transport of cationic amino acid caused by mutations in solute carrier family 7 amino acid transporter light chain, y+L system, member 7 (SLC7A7). This disorder occurs worldwide, especially in Finland and Japan, where founder effect mutations have been reported. Detailed features of the clinical symptoms and mutation types in Japanese LPI, however, remain unclear to date.