Yasuhiro Naiki

Congenitally defective aldosterone biosynthesis in humans: The involvement of point mutations of the P-450C18 gene (CYP11B2) in CMO II deficient patients

The gene for steroid 18-hydroxylase (P-450C18) has been recently assigned to encode corticosterone methyl oxidases Type I and Type II which were previously postulated to catalyze the final two steps in the biosynthesis of aldosterone in humans. Molecular genetic analysis of the P-450C18 gene is three patients from three different families affected with CMO II deficiency has indicated that a point mutation of CGG----TGG (181Arg----Trp) in exon 3 and one of GTG----GCG (386Val----Ala) in exon 7 occur exclusively in the gene of the patients. Analysis of PCR products by restriction enzymes (HapII and HphI) has indicated that the patients are homozygous and the unaffected parent is heterozygous for both mutations, in accordance with the established concept that CMO II deficiency is inherited in an autosomal recessive manner. These data clearly provide the molecular genetic basis for the characteristic biochemical phenotype of CMO II clinical variants.

A novel mutation (c.951C>T) in an exonic splicing enhancer results in exon 10 skipping in the human mitochondrial acetoacetyl-CoA thiolase gene.

Mitochondrial acetoacetyl-CoA thiolase (T2) deficiency is an inherited disorder affecting isoleucine catabolism and ketone body metabolism. A Japanese female developed a severe ketoacidotic attack at the age of 7 months. Urinary organic acid analysis showed elevated excretion of 2-methyl-3-hydroxybutyrate but not tiglylglycine. She was diagnosed as having T2 deficiency by enzyme assay using fibroblasts. Mutation analysis revealed a compound heterozygote of c.556G>T(D186Y) and c.951C>T(D317D). Since c.951C>T does not cause amino acid change, we performed cDNA analysis and found that exon 10 skipping had occurred in the c.951C>T allele. A computer search using an ESE finder showed that an exonic splicing enhancer sequence, SF2/ASF, was located in CTGA(951)CGC. We hypothesized that the exonic splicing enhancer is necessary for accurate splicing since the first nucleotide of exon 10 is C, which weakens the splice acceptor site of intron 9. We made a mini gene construct including exon 9-truncated intron 9-exon 10-truncated intron 10-exon 11 for a splicing experiment. We also made three mutant constructs which alter the SF2/ASF site (947C>T, 951C>T, 952G>A). An min-gene splicing experiment clearly showed that exon 10 skipping was induced in all three mutant constructs. Moreover, additional substitution of G for C at the first nucleotide of exon 10 resulted in normal splicing in these three mutants. These results confirmed that c.951C>T diminished the effect of the exonic splicing enhancer and caused exon 10 skipping.

Living donor liver transplantation for glycogen storage disease type Ib

Glycogen storage disease type 1b (GSD‐1b) is due to an autosomal recessive inborn error of carbohydrate metabolism caused by defects in glucose‐6‐phosphatase translocase. Patients with GSD‐1b have severe hypoglycemia with several clinical manifestations of hepatomegaly, obesity, a doll‐like face, and neutropenia. Liver transplantation has been indicated for severe glucose intolerance. This study retrospectively reviewed 4 children with a diagnosis of GSD‐1b who underwent living‐donor liver transplantation (LDLT). Between November 2005 and June 2008, 96 children underwent LDLT with overall patient and graft survival of 92.3%. Of these, 4 (4.2%) were indicated for GSD‐1b. All patients are doing well with an excellent quality of life because of the stabilization of glucose intolerance, decreased hospital admission, and normalized neutrophil count. LDLT appears to be a feasible option and is associated with a better quality of life for patients with GSD‐1b. Long‐term observation may be necessary to collect sufficient data to confirm the efficacy of this treatment modality. Liver Transpl 15:1867–1871, 2009.

Living‐donor liver transplantation for propionic acidemia

Kasahara M, Sakamoto S, Kanazawa H, Karaki C, Kakiuchi T, Shigeta T, Fukuda A, Kosaki R, Nakazawa A, Ishige M, Nagao M, Shigematsu Y, Yorifuji T, Naiki Y, Horikawa R. Living‐donor liver transplantation for propionic acidemia.

Rare pseudoautosomal copy-number variations involving SHOX and/or its flanking regions in individuals with and without short stature

Pseudoautosomal region 1 (PAR1) contains SHOX, in addition to seven highly conserved non-coding DNA elements (CNEs) with cis-regulatory activity. Microdeletions involving SHOX exons 1–6a and/or the CNEs result in idiopathic short stature (ISS) and Leri–Weill dyschondrosteosis (LWD). Here, we report six rare copy-number variations (CNVs) in PAR1 identified through copy-number analyzes of 245 ISS/LWD patients and 15 unaffected individuals. The six CNVs consisted of three microduplications encompassing SHOX and some of the CNEs, two microduplications in the SHOX 3′-region affecting one or four of the downstream CNEs, and a microdeletion involving SHOX exon 6b and its neighboring CNE. The amplified DNA fragments of two SHOX-containing duplications were detected at chromosomal regions adjacent to the original positions. The breakpoints of a SHOX-containing duplication resided within Alu repeats. A microduplication encompassing four downstream CNEs was identified in an unaffected father–daughter pair, whereas the other five CNVs were detected in ISS patients. These results suggest that microduplications involving SHOX cause ISS by disrupting the cis-regulatory machinery of this gene and that at least some of microduplications in PAR1 arise from Alu-mediated non-allelic homologous recombination. The pathogenicity of other rare PAR1-linked CNVs, such as CNE-containing microduplications and exon 6b-flanking microdeletions, merits further investigation.

Living-donor liver transplantation for carbamoyl phosphate synthetase 1 deficiency.

Kasahara M, Sakamoto S, Shigeta T, Fukuda A, Kosaki R, Nakazawa A, Uemoto S, Noda M, Naiki Y, Horikawa R. Living‐donor liver transplantation for carbamoyl phosphate synthetase 1 deficiency.
Pediatr Transplantation 2010: 14:1036–1040.

Temple syndrome: comprehensive molecular and clinical findings in 32 Japanese patients

PurposeTemple syndrome (TS14) is a rare imprinting disorder caused by aberrations at the 14q32.2 imprinted region. Here, we report comprehensive molecular and clinical findings in 32 Japanese patients with TS14.MethodsWe performed molecular studies for TS14 in 356 patients with variable phenotypes, and clinical studies in all TS14 patients, including 13 previously reported.ResultsWe identified 19 new patients with TS14, and the total of 32 patients was made up of 23 patients with maternal uniparental disomy (UPD(14)mat), six patients with epimutations, and three patients with microdeletions. Clinical studies revealed both Prader-Willi syndrome (PWS)-like marked hypotonia and Silver-Russell syndrome (SRS)-like phenotype in 50% of patients, PWS-like hypotonia alone in 20% of patients, SRS-like phenotype alone in 20% of patients, and nonsyndromic growth failure in the remaining 10% of patients in infancy, and gonadotropin-dependent precocious puberty in 76% of patients who were pubescent or older.ConclusionThese results suggest that TS14 is not only a genetically diagnosed entity but also a clinically recognizable disorder. Genetic testing for TS14 should be considered in patients with growth failure plus both PWS-like hypotonia and SRS-like phenotypes in infancy, and/or precocious puberty, as well as a familial history of Kagami-Ogata syndrome due to maternal microdeletion at 14q32.2.

Systematic molecular analyses of SHOX in Japanese patients with idiopathic short stature and Leri-Weill dyschondrosteosis

The etiology of idiopathic short stature (ISS) and Leri–Weill dyschondrosteosis (LWD) in European patients is known to include SHOX mutations and copy-number variations (CNVs) involving SHOX and/or the highly evolutionarily conserved non-coding DNA elements (CNEs) flanking the gene. However, the frequency and types of SHOX abnormalities in non-European patients and the clinical importance of mutations in the CNEs remains to be clarified. Here, we performed systematic molecular analyses of SHOX for 328 Japanese patients with ISS or LWD. SHOX abnormalities accounted for 3.8% of ISS and 50% of LWD cases. CNVs around SHOX were identified in 16 cases, although the ~47 kb deletion frequently reported in European patients was absent in our cases. Probably damaging mutations and benign/silent substitutions were detected in four cases, respectively. Although CNE-linked substitutions were detected in 15 cases, most of them affected poorly conserved nucleotides and were shared by unaffected individuals. These results suggest that the frequency and mutation spectrum of SHOX abnormalities are comparable between Asian and European patients, with the exception of a European-specific downstream deletion. Furthermore, this study highlights the clinical importance and genetic heterogeneity of the SHOX-flanking CNVs, and indicates a limited clinical significance of point mutations in the CNEs.

Loss-of-Function SOX10 Mutation in a Patient with Kallmann Syndrome, Hearing Loss, and Iris Hypopigmentation

Background: Kallmann syndrome (KS) is a clinically and genetically heterogeneous disorder consisting of hypogonadotropic hypogonadism and anosmia. KS is occasionally associated with deafness. Recently, mutations in SOX10, a well-known causative gene of Waardenburg syndrome (WS) characterized by deafness, skin/hair/iris hypopigmentation, Hirschsprung disease, and neurological defects, have been identified in a few patients with KS and deafness. However, the current understanding of the clinical consequences of SOX10 mutations remains fragmentary. Case Report: A Japanese male patient presented with sensory deafness, blue irises, and anosmia, but no hair/skin hypopigmentation, Hirschsprung disease, or neurological abnormalities. He showed no pubertal sex development at 15.1 years of age. Blood examinations revealed low levels of FSH and testosterone. Results: Molecular analysis detected a de novo p.Leu145Pro mutation in SOX10, which has previously been reported in a patient with WS and Hirschsprung disease. The mutation was predicted to be probably damaging. The mutant protein barely exerted in vitro transactivating activity. Conclusions: These results highlight the significance of SOX10 haploinsufficiency as a genetic cause of KS with deafness. Importantly, our data imply that the same SOX10 mutations can underlie both typical WS and KS with deafness without skin/hair hypopigmentation, Hirschsprung disease, or neurological defects.

Proposal of New Auxological Standards for Japanese Girls with Turner Syndrome

We recently published new reference growth charts for Japanese girls with Turner syndrome (TS) based on the cross-sectional data of 1,447 subjects beyond the secular trend of growth in Japan. This study was undertaken for their validation and, if necessary, modification before general application. For validation, 24 subjects who had data both at younger (≤5 yr) and older ages (≥13 yr) were used. We analyzed the concordance/discordance of their height standard deviation score (SDS) defined by the charts between the two age periods. For modification, the LMS method was used with 5,772 longitudinal measurements obtained both from the previously analyzed subjects and 118 newly recruited subjects who had been followed up at the National Center for Child Health and Development or Toranomon Hospital. Significant and critical discordance (mean difference, 1.95 SDS; 95% confidence interval (CI), 1.53–2.36; p<0.0001) was detected in height SDS. This prompted us to perform the modifications. A similar analysis using the modified charts revealed no significant discordance (mean difference, 0.27 SDS; 95%CI: –0.17 – 0.71; p=0.22). They seem more adequate for clinical applications for girls with TS born after 1970. New auxological standards for Japanese girls with TS were proposed.