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Aim: To determine the prevalence of SLC25A13 mutations in the Thai population., Methods: A total of 1537 subjects representing the Thai population were screened for a novel pathologic allele p.Met1? (c.2T > C) and six previously known common SLC25A13 mutations: [I] (c.851_854delGTAT), [II] (g.IVS11 + 1G > A), [III] (c.1638_1660dup), [IV] (p.S225X), [V] (IVS13 + 1G > A), and [XIX] (g.IVS16ins3kb) using a newly developed TaqMan and established HybProbe assay, respectively. Sanger sequencing was employed for specimens showing an aberrant peak to confirm the targeted mutation as well as the unknown aberrant peaks detected. Frequencies of the mutations identified were compared in each region. Carrier frequency and disease prevalence of citrin deficiency caused by SCL25A13 mutations were estimated., Results: p.Met1? was identified in the heterozygous state in 85 individuals, giving a carrier frequency of 1/18, which suggests possible selective advantage of this variant. The question of p.Met1? homozygote lethality remains unanswered which may serve as an explanation as to why this homozygote has yet to be identified in patients/controls even with high allele frequency. The p.Met1? mutation has rarely been studied in populations other than Thai and Chinese; therefore, may have been overlooked. Development of the TaqMan assay in the present study would allow a simple, rapid, and cost-effective method for mass screening. Heterozygous mutations: [XIX] and [I] were identified in 17 individuals, giving a carrier rate of 1/90 and a calculated homozygote rate of 1/33000. Two novel variants, g.IVS11 + 17C > G and c.1311C > T, of unknown clinical significance were identified at low frequency., Conclusion: This study highlighted the current underestimation of citrin deficiency and suggests the possible selective advantage of the p.Met1? allele.

Aim: To investigate the differences in the mutation spectra of the SLC25A13 gene mutations from specific regions of China., Methods: Genetic analyses of SLC25A13 mutations were performed in 535 patients with neonatal intrahepatic cholestasis from our center over eight years. Unrelated infants with at least one mutant allele were enrolled to calculate the proportion of SLC25A13 mutations in different regions of China. The boundary between northern and southern China was drawn at the historical border of the Yangtze River., Results: A total of 63 unrelated patients (about 11% of cases with intrahepatic cholestasis) from 16 provinces or municipalities in China had mutations in the SLC25A13 gene, of these 16 (25%) were homozygotes, 28 (44%) were compound heterozygotes and 19 (30%) were heterozygotes. In addition to four well described common mutations (c.851_854del, c.1638_1660dup23, c.615+5G>A and c.1750+72_1751-4dup17insNM_138459.3:2667 also known as IVS16ins3kb), 13 other mutation types were identified, including three novel mutations: c.985_986insT, c.287T>C and c.1349A>G. According to the geographical division criteria, 60 mutant alleles were identified in patients from the southern areas of China, 43 alleles were identified in patients from the border, and 4 alleles were identified in patients from the northern areas of China. The proportion of four common mutations was higher in south region (56/60, 93%) than that in the border region (34/43, 79%, χ(2) = 4.621, P = 0.032) and the northern region (2/4, 50%, χ(2) = 8.288, P = 0.041)., Conclusion: The SLC25A13 mutation spectra among the three regions of China were different, providing a basis for the improvement of diagnostic strategies and interpretation of genetic diagnosis.

Objectives: Citrullinemia type I is a rare metabolic disorder and the distribution of mutations in the ASS1 gene varies among ethnic groups. We aimed to determine the molecular characteristics of citrullinemia type I in Korean patients., Design and Methods: Biochemical and clinical findings were investigated and mutations in the ASS1 gene were identified using direct sequencing method in five patients with high citrulline levels. We also reviewed previous genotypes reported for Korean patients with citrullinemia type I., Results: We identified five mutations in 10 mutant alleles from the five patients. The most common mutation was the Gly324Ser mutation, which was present in 40% of the mutant alleles, followed by the c.421-2A>G mutation (30% of the mutant alleles). The other mutations (c.1128-6_1188dup67, Arg127Gln, and Arg279Gln) were identified in one mutant allele each. A comprehensive review of previous Korean reports revealed that Gly324Ser, c.421-2A>G, and c.1128-6_1188dup67 mutations accounted for 80.8% of the total mutations reported to date. In terms of genotype-phenotype correlations, a patient homozygous for the c.421-2A>G mutation had fatal clinical manifestations and two patients who were compound heterozygous for the Gly324Ser and c.1128-6_1188dup67 mutations presented with a mild clinical course., Conclusion: We provided important information about the mutational spectrum of ASS1 gene in Korean patients with citrullinemia type I and demonstrated a difference in common mutations in the ASS1 gene according to ethnic and geographic backgrounds., (Copyright © 2012 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.)

Citrin deficiency, aetiologically linked to mutations of SLC25A13 gene, has two clinical phenotypes, namely adult-onset type II citrullinaemia (CTLN2) and neonatal/infantile intrahepatic cholestasis, caused by citrin deficiency (NICCD). Malaysian patients with NICCD, especially of Malay and East Malaysian indigenous descent, have never been reported in the literature. We present the clinical features, biochemical findings and results of molecular analysis in 11 Malaysian children with NICCD. In this case series, all patients manifested prolonged cholestatic jaundice and elevated citrulline levels. The other more variable features included failure to thrive, bleeding diathesis, hypoproteinaemia, abnormal liver enzymes, prolonged coagulation profile, hyperammonaemia, hypergalactosaemia, multiple aminoacidaemia, elevated α-feto protein and urinary orotic acid as well as liver biopsies showing hepatitis and steatosis. DNA analysis of SLC25A13 revealed combinations of 851del4(Ex9), IVS16ins3kb and 1638ins23. Most of our patients recovered completely by the age of 22 months. However, one patient had ongoing symptoms at the time of reporting and one had died of liver failure. Since a small percentage of children with NICCD will develop CTLN2 and the mechanisms leading to this is yet to be defined, ongoing health surveillance into adulthood is essential.