Identification of 16 novel mutations in the argininosuccinate synthetase gene and genotype-phenotype correlation in 38 classical citrullinemia patients.
Classical citrullinemia (CTLN1), a rare autosomal recessive disorder, is caused by mutations of the argininosuccinate synthetase (ASS) gene, localized on chromosome 9q34.1. ASS functions as a rate-limiting enzyme in the urea cycle. Previously, we identified 32 mutations in the ASS gene of CTLN1 patients mainly in Japan and the United States, and to date 34 different mutations have been described in 50 families worldwide. In the present study, we report ASS mutations detected in 35 additional CTLN1 families from 11 countries. By analyzing the entire coding sequence and the intron-exon boundaries of the ASS gene using RT-PCR and/or genomic DNA-PCR, we have identified 16 novel mutations (two different 1-bp deletions, a 67-bp insertion, and 13 missense) and have detected 12 known mutations. Altogether, 50 different mutations (seven deletion, three splice site, one duplication, two nonsense, and 37 missense) in 85 CTLN1 families were identified. On the basis of primary sequence comparisons with the crystal structure of E. coli ASS protein, it may be concluded that any of the 37 missense mutations found at 30 different positions led to structural and functional impairments of the human ASS protein. It has been found that three mutations are particularly frequent: IVS6-2A>G in 23 families (Japan: 20 and Korea: three), G390R in 18 families (Turkey: six, U.S.: five, Spain: three, Israel: one, Austria: one, Canada: one, and Bolivia: one), and R304W in 10 families (Japan: nine and Turkey: one). Most mutations of the ASS gene are "private" and are distributed throughout the gene, except for exons 5 and 12-14. It seems that the clinical course of the patients with truncated mutations or the G390R mutation is early-onset/severe. The phenotype of the patients with certain missense mutations (G362V or W179R) is more late-onset/mild. Eight patients with R86H, A118T, R265H, or K310R mutations were adult/late-onset and four of them showed severe symptoms during pregnancy or postpartum. However, it is still difficult to prove the genotype-phenotype correlation, because many patients were compound heterozygotes (with two different mutations), lived in different environments at the time of diagnosis, and/or had several treatment regimes or various knowledge of the disease.
Gao
Hong-Zhi
HZ
Department of Biochemistry, Faculty of Medicine, Kagoshima University, Kagoshima, Japan.
Kobayashi
Keiko
K
Tabata
Ayako
A
Tsuge
Hideaki
H
Iijima
Mikio
M
Yasuda
Tomotsugu
T
Kalkanoglu
H Serap
HS
Dursun
Ali
A
Tokatli
Aysegul
A
Coskun
Turgay
T
Trefz
Friedrich K
FK
Skladal
Daniela
D
Mandel
Hanna
H
Seidel
Joerg
J
Kodama
Soichi
S
Shirane
Seiko
S
Ichida
Takafumi
T
Makino
Shigeru
S
Yoshino
Makoto
M
Kang
Jong-Hon
JH
Mizuguchi
Masashi
M
Barshop
Bruce A
BA
Fuchinoue
Shohei
S
Seneca
Sara
S
Zeesman
Susan
S
Knerr
Ina
I
Rodés
Margarita
M
Wasant
Pornswan
P
Yoshida
Ichiro
I
De Meirleir
Linda
L
Abdul Jalil
Md
M
Begum
Laila
L
Horiuchi
Masahisa
M
Katunuma
Nobuhiko
N
Nakagawa
Shiro
S
Saheki
Takeyori
T
D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D001124:Argininosuccinate Synthase / Q000235:genetics* / Q000502:physiology; D002675:Child, Preschool; D002874:Chromosome Mapping; D020159:Citrullinemia / Q000235:genetics* / Q000473:pathology; D018389:Codon, Nonsense / Q000235:genetics; D004252:DNA Mutational Analysis; D005260:Female; D005787:Gene Frequency / Q000235:genetics; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense / Q000235:genetics / Q000502:physiology; D010641:Phenotype
D018389:Codon, Nonsense; D001124:Argininosuccinate Synthase