Am. J. Hum. Genet. 51:1406-1412, 1992
Three Novel Mutations in the Liver-Type Arginase Gene in Three Unrelated Japanese Patients with Argininemia Takako Uchino, * Yougo Haraguchi, * Juan M. Aparicio, * Naoki Mizutani, Masamune Higashikawa,§ Haruko Naitoh,II Masataka Morit and Ichiro Matsuda* 'Department of Pediatrics and TInstitute for Medical Genetics, Kumamoto University School of Medicine, Kumamoto, Japan; $Department of Pediatrics, University of Nagoya School of Medicine, Nagoya, Japan; §National Suzuka Hospital, Suzuka, Japan; and IlDepartment of Neurology, National Children's Hospital, Tokyo
Summary Argininemia is caused by a hereditary deficiency of liver-type arginase (E.C.3.5.3.1) and is characterized by psychomotor retardation and spastic tetraplegia. We examined findings in three Japanese patients with argininemia, by using the PCR, cloning, and sequencing procedures. We found three different mutationsG-to-A-365 in exon 4, G-to-C-703 in exon 7, and C-del-842 in exon 8-thereby leading to mutant arginase proteins of W122X, G235R, and L282FS, respectively. Patient 1 was a compound heterozygote, inheriting the allele with G-to-A-365 from his mother and the allele with G-to-C-703 from his father. Patients 2 and 3 were homozygotes of the allele with G-to-C-703 and of the allele with C-del-842, respectively. Expression tests of these mutant arginases in Escherichia coli indicated that the mutant arginase of W122X did not remain a stable product. The other two mutant arginases-G235R and L282FS-were detected by immunoblot analyses. There was no evidence of activity of the three mutant arginases expressed in E. coli. We tentatively conclude that argininemia is heterogeneous, at the molecular level.
Introduction
Argininemia (McKusick 20780) is caused by a deficiency in liver-type arginase (E.C.3.5.3.1) activity and is autosomal recessive. In Japan, six patients with argininemia have been identified. The clinical manifestations of argininemia are mental retardation, spastic tetraplegia, hyperactivity of deep-tendon reflexes, seizures, and failure to grow (Brusilow and Horwich 1989). All these features are generally progressive. Hyperargininemia is thought to be more closely linked to neurological damage than is hyperammonemia (Brusilow and Horwich 1989). In 1987, we isolated the complete cDNA of human liver-type arginase (Haraguchi et al. 1987). Human liver-type arginase consists of 322 amino acid residues, and the estimated molecular mass is 34,732.
The arginase gene has 11.5 kb, including eight exons (Takiguchi et al. 1988), and the arginase gene is on the chromosome 6q23 (Sparkes et al. 1986). Direct analysis of the arginase gene should aid in elucidating the molecular pathology of arginase deficiency. We report here our findings in three unrelated Japanese patients with argininemia. We detected three mutations - a nonsense mutation in exon 4, a missense mutation in exon 7, and a frameshift mutation in exon 8. These mutations are different from those previously reported in the arginase gene (Haraguchi et al. 1990). Arginase deficiency is apparently genetically heterogeneous. Patients and Methods Patients
Received June 4, 1992. Address for correspondence and reprints: Dr. Ichiro Matsuda, Department of Pediatrics, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto, 860 Japan. C 1992 by The American Society of Human Genetics. All rights reserved. 0002-9297/ 92/5106-0024$02.00
1406
Clinical manifestations in the three patients are summarized in table 1 (Mizutani et al. 1983; Shibui et al. 1986; Kubo et al. 1987). Patient 1 was the product of a nonconsanguineous marriage. All patients had classical clinical features of arginase deficiency, i.e.,
1407
Novel Mutations in Arginase Table I Clinical Manifestations
Sex ................................
Age (years) in 1991 ................................ Consanguinity ................................ Age at onset of neurological symptoms ........ Mental retardation ................................
Patient ta
Patient 2b
Patient 3c
Male 7
Male 31
Male 13
+
+
Three Novel Mutations in the Liver-Type Arginase Gene in Three Unrelated Japanese Patients with Argininemia Takako Uchino, * Yougo Haraguchi, * Juan M. Aparicio, * Naoki Mizutani, Masamune Higashikawa,§ Haruko Naitoh,II Masataka Morit and Ichiro Matsuda* 'Department of Pediatrics and TInstitute for Medical Genetics, Kumamoto University School of Medicine, Kumamoto, Japan; $Department of Pediatrics, University of Nagoya School of Medicine, Nagoya, Japan; §National Suzuka Hospital, Suzuka, Japan; and IlDepartment of Neurology, National Children's Hospital, Tokyo
Summary Argininemia is caused by a hereditary deficiency of liver-type arginase (E.C.3.5.3.1) and is characterized by psychomotor retardation and spastic tetraplegia. We examined findings in three Japanese patients with argininemia, by using the PCR, cloning, and sequencing procedures. We found three different mutationsG-to-A-365 in exon 4, G-to-C-703 in exon 7, and C-del-842 in exon 8-thereby leading to mutant arginase proteins of W122X, G235R, and L282FS, respectively. Patient 1 was a compound heterozygote, inheriting the allele with G-to-A-365 from his mother and the allele with G-to-C-703 from his father. Patients 2 and 3 were homozygotes of the allele with G-to-C-703 and of the allele with C-del-842, respectively. Expression tests of these mutant arginases in Escherichia coli indicated that the mutant arginase of W122X did not remain a stable product. The other two mutant arginases-G235R and L282FS-were detected by immunoblot analyses. There was no evidence of activity of the three mutant arginases expressed in E. coli. We tentatively conclude that argininemia is heterogeneous, at the molecular level.
Introduction
Argininemia (McKusick 20780) is caused by a deficiency in liver-type arginase (E.C.3.5.3.1) activity and is autosomal recessive. In Japan, six patients with argininemia have been identified. The clinical manifestations of argininemia are mental retardation, spastic tetraplegia, hyperactivity of deep-tendon reflexes, seizures, and failure to grow (Brusilow and Horwich 1989). All these features are generally progressive. Hyperargininemia is thought to be more closely linked to neurological damage than is hyperammonemia (Brusilow and Horwich 1989). In 1987, we isolated the complete cDNA of human liver-type arginase (Haraguchi et al. 1987). Human liver-type arginase consists of 322 amino acid residues, and the estimated molecular mass is 34,732.
The arginase gene has 11.5 kb, including eight exons (Takiguchi et al. 1988), and the arginase gene is on the chromosome 6q23 (Sparkes et al. 1986). Direct analysis of the arginase gene should aid in elucidating the molecular pathology of arginase deficiency. We report here our findings in three unrelated Japanese patients with argininemia. We detected three mutations - a nonsense mutation in exon 4, a missense mutation in exon 7, and a frameshift mutation in exon 8. These mutations are different from those previously reported in the arginase gene (Haraguchi et al. 1990). Arginase deficiency is apparently genetically heterogeneous. Patients and Methods Patients
Received June 4, 1992. Address for correspondence and reprints: Dr. Ichiro Matsuda, Department of Pediatrics, Kumamoto University School of Medicine, 1-1-1 Honjo, Kumamoto, 860 Japan. C 1992 by The American Society of Human Genetics. All rights reserved. 0002-9297/ 92/5106-0024$02.00
1406
Clinical manifestations in the three patients are summarized in table 1 (Mizutani et al. 1983; Shibui et al. 1986; Kubo et al. 1987). Patient 1 was the product of a nonconsanguineous marriage. All patients had classical clinical features of arginase deficiency, i.e.,
1407
Novel Mutations in Arginase Table I Clinical Manifestations
Sex ................................
Age (years) in 1991 ................................ Consanguinity ................................ Age at onset of neurological symptoms ........ Mental retardation ................................
Patient ta
Patient 2b
Patient 3c
Male 7
Male 31
Male 13
+
+
