Haplotype analysis suggests that the two predominant mutations in Japanese patients with holocarboxylase synthetase deficiency are founder mutations

J Hum Genet (2000) 45:358–362 © Jpn Soc Hum Genet and Springer-Verlag 2000 ORIGINAL ARTICLE Xue Yang · Yoko Aoki · Xue Li · Osamu Sakamoto Masahiro Hiratsuka · Kenneth Michael Gibson Shigeo Kure · Kuniaki Narisawa · Yoichi Matsubara Yoichi Suzuki Haplotype analysis suggests that the two predominant mutations in Japanese patients with holocarboxylase synthetase deficiency are founder mutations Received: August 31, 2000 / Accepted: September 28, 2000 Abstract Holocarboxylase synthetase (HCS) deficiency is a rare autosomal recessive disorder of biotin metabolism. Including three new Japanese patients we diagnosed in this study, ten Japanese families have, so far, been accumulated. In these families, the mutations 237Leu . Pro (seven alleles) and 1067delG (five alleles) were predominant; 508Arg . Trp and 550Val . Met mutations were identified in three families in the heterozygous form and in one patient in the homozygous form, respectively. To determine the origin of these mutations, we identified new polymorphic microsatellite markers in the HCS gene and analyzed the haplotypes of the patients. All the 237Leu . Pro and the 1067delG alleles were associated with haplotype 2-2. This finding is consistent with the notion that these mutations are founder mutations in the Japanese population. Three Japanese 508Arg . Trp alleles were associated with several haplotypes, including 2-3 and 1-4. The haplotype of a Taiwanese patient homozygous for the 508Arg . Trp mutation was 2-3/2-3. The haplotype of one Japanese patient homozygous for the 550Val . Met mutation was 1-4/1-4, whereas that of a Jewish patient with the same homozygous mutation was 2-3/2-3. Both mutations were associated with at least two haplotypes and were found in several ethnic groups. The changes 508Arg . Trp and 550Val . Met occurred at CpG dinucleotide. The data suggest that these two mutations represent a mutational hot-spot. X. Yang · Y. Aoki · X. Li · O. Sakamoto · M. Hiratsuka · S. Kure · Y. Matsubara · Y. Suzuki (*) Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan Tel. 181-22-717-8140; Fax 181-22-717-8142 e-mail: K.M. Gibson Department of Molecular and Medical Genetics, Oregon Health Sciences University, Portland, OR, USA K. Narisawa Faculty of Science and Welfare, Tohoku Bunka Gakuen University, Sendai, Japan Key words Holocarboxylase synthetase · Multiple carboxylase deficiency · Biotin · Mutation · Microsatellite markers· Haplotype Introduction Holocarboxylase synthetase (HCS: EC 6.3.1.10) is an enzyme that catalyzes biotin incorporation into various carboxylases. Four carboxylases that require biotin as a coenzyme have been identified in mammalian cells: acetylCoA carboxylase (EC 6.4.1.2), a rate-limiting enzyme in fatty acid synthesis; pyruvate carboxylase (EC 6.4.1.1), a key enzyme in gluconeogenesis; propionyl-CoA carboxylase (EC 6.4.1.3), and 3-methylcrotonyl-CoA carboxylase (EC 6.4.1.4), which is involved in amino acid catabolism. Because the biotinylation of these carboxylases is essential for their enzymatic activities, a defect in HCS decreases the activity of several carboxylases, affecting various metabolic processes in cells. HCS deficiency (McKusick 253270) is therefore also referred to as biotin-responsive multiple carboxylase deficiency (MCD). Patients with HCS deficiency have acute episodes of metabolic acidosis and characteristic organic aciduria during the neonatal to early infantile period. Symptoms include tachypnea, feeding difficulties, seizures, and severe dermatitis. Patients may recover from metabolic acidosis within a few days after they start biotin therapy (Wolf 1995). We isolated human HCS cDNA and have analyzed mutations among Japanese and other ethnic groups of patients with an HCS deficiency (Suzuki et al. 1994; Aoki et al. 1995; Aoki et al. 1999). The mutations 237Leu . Pro (nucleotide change 997T . C) and 1067delG predominated only among the Japanese patients. The 508Arg . Trp (1809C . T) mutation has been found in two unrelated Japanese patients (Sakamoto et al. 1998), as well as in non-Japanese patients (Dupuis et al. 1996). The 550Val . Met (1935G . A) mutation has also been found in many ethnic groups (Dupuis et al. 1996; Aoki et al. 1997; Zammarchi et al. 1998). To determine the origin of these mutations in B. Jochimsen et al.: Stetteria hydrogenophila families with an HCS deficiency, we analyzed the haplotypes of normal and mutant HCS alleles. Patients and methods Patients The offspring of non-consanguineous Japanese parents, patient 1 developed severe ketoacidosis on the second day of life and died at the age of 5 days. Organic aciduria typical of MCD was present. HCS activity was assayed as described previously (Suzuki et al. 1996). The enzymatic activity in the patient’s liver autopsy sample was 5.0% of the control value. Patient 2 is a girl born to unrelated Japanese parents. This patient developed an upper respiratory infection at the age of 8 months that was followed by metabolic acidosis and a skin infection. Because urinary organic acid was indicative of MCD, biotin was administered. Her physical and mental development proceeded normally when she received 40 mg/day of biotin. The HCS activity in lymphoblasts was 14.1% of the control value. 359 Patient 3 was also a Japanese girl, the offspring of a nonconsanguineous marriage. She developed severe ketoacidosis on the first postpartum day and died 5 days later. A child of the same parents (is girl) born before her had also died at the age of 4 days. An HCS deficiency was demonstrated by assaying the enzyme activity in fibroblasts from the patient (5.5% of the control value). The other patients analyzed in this study have been described elsewhere (for references see Table 1). This study was approved by the Ethics Committee of Tohoku University School of Medicine. Mutation in HCS-deficient patients Genomic DNA from fibroblasts, lymphoblasts, or an autopsy sample was prepared, using a SepaGene Kit (Sanko Junyaku, Tokyo, Japan). DNA was extracted from dried blood spots obtained from the parents, the grandparents, and control individuals, as described (Ogasawara et al. 1994). The 997T . C (237Leu . Pro) and the 1067delG mutations were screened, using polymerase chain reactionrestriction fragment length polymorphism (PCR-RFLP), as described (Aoki et al. 1995). The 508Arg . Trp (1809C . Table 1. Mutations and haplotypes of patients with holocarboxylase synthetase (HCS) deficiency Family 1 (Japanese) 2 (Japanese) 3 (Japanese) 4 (Japanese) 5 (Japanese) 6 (Japanese) 7 (Japanese) 8 (Japanese) 9 (Japanese) 10 (Japanese) 11 (Taiwanese) 12 (Jewish) a Individual HCS mutation CAAA repeat ATTC repeat Father Mother Patient Father Mother Patient Father Mother Patient Father Mother Patient Father Mother Patient Sister 1 Sister 2 Father Mother Patient Father Mother Patient 1 Patient 2 Father Mother Patient Patient 1067delG 237Leu (...truncated)