Overview of Citrin Deficiency:SLC25A13 Mutations and the Frequency / 实用儿科临床杂志

Citrin deficiency, autosomal recessive disorder, caused by mutation of SLC25A13 gene on chromosome 7q21.3 has two major phenotypes : neonatal intrahepatic chnlestatic hepatitis(N1CCD) and adult-onset type Ⅱ citrullinemia(CTLN2).So far, we have identified 52 SLC25A13 mutations and diagnosed the patients not only in Japan(166 CTLN2 and 238 NICCD) but also in other countries.We have detected 76 Chinese, 13 Korean and 15 Vietnamese patients with the same mutations as Japanese, and 13 patients(from Israel, UK, USA or Czech)with mutations different from those found in Japanese,indicating a wide distribution of citrin deficiency.DNA diagnoses of 13 known SLG25A13 mutations revealed that the carrier frequency was high in East Asian populations:Chinese(73/4 600=1/63) ,Japanese(21/1372=1/65) and Korean(25/2 690=1/108), suggesting that near by 100 000 East Asians are liomozygotes.It is important to find out patients with citrin deficiency,to treat them,and to prevent onset of severe CTLN2.

Identification and diagnosis of three novel mutations in SLC25A13 gene of neonatal intrahepatic cholestasis caused by citrin deficiency / 中华儿科杂志

<p><b>OBJECTIVE</b>Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD, OMIM #605814) is a novel autosomal recessive disease caused by mutations in the gene SLC25A13 that encodes for citrin, a liver-type aspartate/glutamate carrier located in the mitochondrial inner membrane. SLC25A13 was cloned in 1999 by Kobayashi et al at Kagoshima University in Japan, and until now, most of the NICCD patients reported in the world were Japanese. Most of the Chinese NICCD patients diagnosed by genetic analysis had the same SLC25A13 mutations as Japanese, however, in some cases, known mutations were not detected. This research aimed to identify novel SLC25A13 mutations in Chinese NICCD patients and to explore the experimental conditions for their genetic diagnosis.</p><p><b>METHODS</b>Genomic DNA was extracted from blood samples of 3 NICCD patients from Taiwan (P757), Guangdong (P1194) and Hebei province (P1443) of China, respectively, and all the 18 exons and their flanking sequences of SLC25A13 gene were sequenced. Furthermore, the identified novel mutations were diagnosed by amplification with PCR, digestion with corresponding restriction endonuclease, and agarose gel electrophoresis.</p><p><b>RESULTS</b>Three novel mutations identified in SLC25A13 gene of the 3 NICCD patients were an abnormal splicing IVS7-2A > G (P757), a missense A541D (c.1622C > A, P1194) and a nonsense R319X (c.955C > T, P1443). The PCR-restriction fragment length polymorphism (RFLP) procedures for their genetic diagnosis were also established, with specific fragments on electrophoresis after digestion of the PCR products with three different restriction endonucleases Msp I, Hpy188I and Taq I, respectively.</p><p><b>CONCLUSIONS</b>So far as we know, the three novel mutations in SLC25A13 gene of Chinese NICCD patients were first identified, suggesting that SLC25A13 mutation distributed in Chinese population is somewhat different from that in Japanese. Moreover, the PCR-RFLP diagnostic procedures established in this research provide valuable tools not only for the genetic diagnosis of NICCD but also for further molecular epidemiologic investigations in Chinese population.</p>

SLC25A13 gene mutation analysis in a pedigree of neonatal intrahepatic cholestasis caused by citrin deficiency / 中华儿科杂志

<p><b>OBJECTIVE</b>Neonatal intrahepatic cholestasis caused by citrin deficiency (NICCD, MIM#605814) is an inherited metabolic disease resulting from mutations of the gene SLC25A13, which encodes citrin, a liver-type mitochondrial aspartate-glutamate carrier. Mutation analysis is necessary for definitive diagnosis of NICCD patients. So far (March, 2007), 36 kinds of mutation, including 7 nonsense, 10 missense, 11 abnormal splicing, 4 insertion and 4 deletion, have been identified by Kobayashi's group, who cloned the gene in Kagoshima, Japan. To date, most of the NICCD patients reported in the world are Japanese. This study aimed to explore the gene diagnosis procedure of two known SLC25A13 mutations in a pedigree with an NICCD patient from China.</p><p><b>METHODS</b>DNA was extracted from dried blood spots collected with filter papers from the proband and other 9 members in a NICCD pedigree from China, and then PCR amplification and agarose gel electrophoresis were performed, revealing two mutations preliminarily, which were further proved by Genescan, a procedure established in our laboratory already. Furthermore, the positions and characteristics of the mutations were finally confirmed by DNA sequencing.</p><p><b>RESULTS</b>The proband is a compound heterozygote of two mutations, 851-854del in exon 9 and 1638-1660dup in exon 16 of SLC25A13 gene. His mother and brother carry the former mutation, which predicts a frameshift and introduction of a stop codon at position 286, while his father, one aunt and her son carry the latter, resulting in a frameshift at codon 554, and introducing a stop codon at position 570.</p><p><b>CONCLUSION</b>A deletion mutation 851-854del in exon 9 and an insertion mutation 1638-1660dup in exon 16 of SLC25A13 gene were identified in the pedigree, providing reliable evidences for both diagnostic confirmation of the patient and the genetic counseling from other members in the pedigree.</p>