N-Acetyltransferase Polymorphism Among Northern Sudanese

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N-Acetyltransferase Polymorphism Among Northern Sudanese said al-yahyaee, 1 uzma gaffar, 2 maryam m. al-ameri, 3 mansoor qureshi, 2 fahad zadjali, 1 baderldin h. ali, 1 and riad bayoumi 1 Abstract Interindividual and interethnic differences in allele frequencies of N-acetyltransferase (NAT2) single nucleotide polymorphisms (SNPs) are responsible for phenotypic variability of adverse drug reactions and susceptibility to cancer. We genotyped the seven NAT2 common SNPs in 127 randomly selected unrelated northern Sudanese subjects using allele-specific and RFLP polymerase chain reaction (PCR) based methods. Molecular genotyping was enough to designate alleles for 41 individuals unambiguously, whereas 63 individuals’ alleles were inferred from haplotypes previously described. In the remaining 23 individuals, however, the phase of the SNPs could not be decided because of multiple SNP heterozygotes. Using computational methods in the HAP and Phase programs, we confirmed the inferred alleles of the 62 individuals and predicted the remaining 23 ambiguous alleles. Twelve NAT2 alleles were identified. Four alleles coded for rapid acetylators (18%), and eight alleles coded for slow acetylators (82%). Two genotypes coded for rapid acetylation (3.9%), 10 for intermediate acetylation (27.6%), and 13 for slow acetylation (68.5%). The G191A African SNP and the G857A predominantly Asian SNP were each detected at a low frequency of 3.1%. The combination of molecular and computational analysis was useful in resolving ambiguous genotypes of NAT2 in multiple SNP heterozygotes. Among the northern Sudanese the SNPs associated with slow acetylation are more prevalent than in Caucasians and Asians. This and other African studies are suggestive of an African origin for NAT2-associated polymorphism.

The arylamine N-acetyltransferase (NAT2; EC 2.3.1.5) is a phase II xenobiotic metabolizing enzyme responsible for hepatic acetylation of arylamine and hydrazine drugs and various xenobiotics (Boukouvala and Fakis 2005). There are rapid, intermediate, and slow acetylator phenotypes. NAT2 polymorphism greatly affects the frequency and prevalence of the slow acetylator alleles in different ethnic groups (Evan 1992; Lin et al. 1993, 1994; Agúndez et al. 1996; Sim et al. 2003). For example, only 10–15% of Japanese are slow acetylators (Hiratsuka et al. 2002), 1 Departments of Biochemistry and Pharmacology, College of Medicine and Health Sciences, Sultan Qaboos University, Al Khod, P.O. Box 35, Muscat 123, Sultanate of Oman. 2 Department of Biochemistry, Faculty of Medicine and Health Sciences, United Arab Emirates University, Al-Ain, United Arab Emirates. 3 Al-Ain Hospital, Ministry of Health, Al-Ain, United Arab Emirates.

Human Biology, August 2007, v. 79, no. 4, pp. 445–452. Copyright © 2007 Wayne State University Press, Detroit, Michigan 48201-1309 KEY WORDS: N-ACETYLTRANSFERASE (NAT2), AFRICA, SUDANESE, BIOINFORMATICS TOOLS, ALLELE HAPLOTYPE, DRUG-METABOLIZING ENZYMES, DRUG TOXICITY, CANCER.

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whereas in some African populations the frequency approaches 70% (Homeida et al. 1986; Ali and Bashir 1991; Loktionov et al. 2002). NAT2 polymorphism is transmitted in an autosomal recessive fashion (Dupret and Rodrigues-Lima 2005). There are seven common single nucleotide polymorphisms (SNPs) in the coding region of the NAT2 gene. Four single base-pair substitutions at positions 191, 341, 590, and 857 result in amino acid substitutions that lead to a decrease in acetylation capacity. SNPs at positions 282 and 481 are silent SNPs, and the SNP at position 803 is a nonsynonymous substitution that does not change the phenotype. According to the consensus NAT2 gene nomenclature (Vatsis et al. 1995; Hein et al. 2000a, 2000b), a combination of sets of SNPs constitute distinct haplotypes that are considered alleles of the haplotype system. These haplotypes predict the acetylation status, which was found to be closely associated with individual differences in drug efficacy and side effects as well as susceptibility to some types of cancer (Boukouvala and Fakis 2005). Because of its medical interest, NAT2 polymorphism has been extensively studied and has been found to exhibit wide variations among European, Asian, and some African populations (Chowbay et al. 2005; Boukouvala and Fakis 2005; Patin et al. 2006a). In this study we have genotyped the seven common NAT2 SNPs in 127 northern Sudanese of Arab-African admixture who were previously reported to have more HLA alleles than other African populations (Ward et al. 1989). Thus this ArabAfrican admixture was expected to show further interpopulation variations among Africans.

Subjects and Methods Subjects. One hundred twenty-seven unrelated northern Sudanese attending Al-Ain Hospital, United Arab Emirates, were randomly sampled. Their ages ranged from 12 to 60 years. Blood was collected in EDTA-coated containers, and DNA was extracted from leukocytes using the phenol-chloroform method. Polymerase Chain Reaction. Amplification of genomic DNA was carried out using the polymerase chain reaction (PCR) with the pair of primers Nat-Hu 14 and Nat-Hu 16, as described previously by Hickman and Sim (1991) and Woolhouse et al. (1997). The 1002-bp PCR product was subsequently used in all experiments for the detection of the seven common NAT2 SNPs. NAT2 Genotyping. The nomenclature used for NAT2 genotyping follows those adopted by Hein et al. (2000a, 2000b). Six of the common SNPs—G191A, C282T, C481T, G590A, A803G, and G857A—were detected using restriction fragment length polymorphism (RFLP). The 1002-bp PCR product was digested with MspI, FokI, KpnI, TaqI, DdeI, and BamHI, respectively. Conditions for digestion and detection of DNA fragments have been described previously (Hickman and Sim 1991; Doll et al. 1995; Woolhouse et al. 1997; Bayoumi et al. 1997). The T341C nucleotide substitution was genotyped using allele-specific PCR (Doll et

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al. 1995). Briefly, the initial NAT2 PCR product was amplified using the senseoligonucleotides 341WT and 341MUT for specific amplification of wild-type and mutant alleles, in conjunction with Nat-Hu 16 as an antisense oligonucleotide. Amplification conditions were denaturation at 94°C for 1 min, annealing at 60.5°C for 30 s, and extension at 72°C for 1 min. PCR was carried out for 30 cycles. A 681-bp fragment was generated. Computational Analysis. Because multiple SNPs are found in some genotypes, it was important to determine the phase of these SNPs, that is, whether the SNPs are located in one or the other of the homologous pairs of chromosomes. Because the seven common NAT2 SNPs appear to be in strong linkage disequilibrium, it is possible to resolve almost all genotype ambiguities using computational haplotype analysis (Stephens and Donnelly 2003; Halperin and Eskin 2004). We performed computational analysis using a Bayesian model algorithm implemented in the Phase program (version 2.1) (Stephens et al. 2001). Phase is based on a Markov chain Monte Carlo method with a recombination model based on the decay of linkage disequilibrium with distance. Many studies, some of which were performed on the NAT2 data sets, have compared the different haplotyping algorithms and have come to the conclusion that the Phase algorithm performs better and has a lower error rate (Stephens and Donnelly 2003; Adkins 2004; Niu 2004; Sabbagh and Darlu 2005). Genotype data for the seven SNPs from the 127 unrelated individuals were used in the computational analysis. The relative distances between the SNPs were entered into the Phase program, and other parameters were set at default values. The default parameters yielded the best low rate, with a maximum phase probability of 1.00 and a minimum of 0.98. The phylogenetic tree of the NAT2 SNPs was constructed using an imperfect phylogeny approach implemented in the haplotype resolution program (HAP, version 3.0) (Halperin and Eskin 2004; also available at http://research.calit2.net/ hap/). Parameters used in the HAP program were set at default. Hardy-Weinberg equilibrium was tested for each SNP using the HAP program, and haplotype diversity was estimated using the formula   k  n 2 Hˆ = pi , 1− n−1 i−1

(1)

where n is the sample size in number of chromosomes, k is the number of different alleles, and pi is the frequency of the ith allele (Nei 1987).

Results NAT2 SNPs. The frequency of the tested point SNPs is shown in Table 1. The three commonest SNPs detected were A803G (55.1%), T341C (47.2%), and

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Table 1. Frequency of the Tested SNP Alleles and Resulting Haplotype Alleles of NAT2 Among 127 Northern Sudanese SNP Allele

Haplotype Allele

SNP

Identification

Frequency (95% CI)

P Value a

Allele

Frequency

G191A C282T T341C

rs1801279 rs1041983 rs1801280

0.031 (0.01–0.052) 0.334 (0.276–0.392) 0.472 (0.411–0.533)

0.714 0.793 0.632

0.0866 0.0039 0.4527

C481T G590A A803G G857A

rs1799929 rs1799930 rs1208 rs1799931

0.457 (0.396–0.518) 0.287 (0.231–0.343) 0.551 (0.49–0.612) 0.031 (0.01–0.052)

0.595 0.832 0.882 0.011 b

NAT2*4 (wild type) NAT2*5A (341C + 481T) NAT2*5B (341C + 481T + 803G) NAT2*5C (341C + 803G) NAT2*6A (282T + 590A) NAT2*6B (590A) NAT2*7B (282T + 857A) NAT2*12A (803G) NAT2*12B (282T + 803G) NAT2*13 (282T) NAT2*14A (191A) NAT2*14B (191A + 282T)

0.0157 0.2834 0.0039 0.0314 0.0787 0.0039 0.0078 0.0236 0.0078

a. P value for Hardy-Weinberg equilibrium test. b. Not following Hardy-Weinberg equilibrium at 1 degree of freedom.

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3.86452pt PgVar C481T (45.7%). The G191A African SNP and the G857A predominantly Asian SNP were each detected at a low frequency of 3.1%. With the exception of the G857A predominantly Asian SNP, all detected SNPs were in Hardy-Weinberg equilibrium. NAT2 Alleles. Twelve different allelic variants were identified (Table 1). NAT2*5B (341C + 481T + 803G) and NAT2*6A (282T + 590A) occurred at high frequencies of 45.3% and 28.3%, respectively. The wild-type allele, NAT2*4, occurred at a relatively low frequency of 8.7%. Some rare alleles occurring at a frequency less than 1% were observed: NAT2*5A, *6B, *12B, *13, and *14B. Four alleles coded for rapid acetylation (*4, *12A, *12B, and *13), giving an overall allele frequency of 18%. The remaining eight alleles coded for slow acetylation, giving an overall allele frequency of 82%. Phylogeny analysis predicted that both the G191A African SNP and the G857A predominantly Asian SNP constitute the most recent alleles (Figure 1). The northern Sudanese subjects had very high estimates of haplotype diversity at 0.98. NAT2 Genotypes. It was possible to successfully genotype 41 individuals using restriction enzyme digestion of biallelic PCR products. In 63 individuals alleles could be inferred from haplotypes previously described (Hein et al. 2000a, 2000b). In 24 individuals it was not possible to resolve phase ambiguities. For example, nine individuals had a combination of 341C, 481T, and 803G SNPs, which potentially results in three alternative genotypes: NAT2*4/*5B, NAT2*5A/*12A, or NAT2*5D/*12C. Computational analysis predicted that NAT2*4/*5B would be

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Figure 1.

Predicted (using the HAP program) phylogenetic tree of NAT2 alleles among 127 northern Sudanese.

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1.682pt PgVar the most likely allele at 99% accuracy. Twenty-five genotypes were found among the northern Sudanese, predicting an overall phenotype of 8%, 40%, and 52% for rapid, intermediate, and slow acetylators, respectively (Table 2).

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Discussion The seven common SNPs of NAT2 found in northern Sudanese gave in combination twelve different haplotype alleles. When the frequency and composition of NAT2 alleles were compared with world populations, several observations were noted. First, the overall allele frequencies of NAT2 in northern Sudanese were similar to their closest neighbor, the Somalis (Patin et al. 2006a), but were different from other populations (Boukouvala and Fakis 2005; Patin et al. 2006a). Second, the northern Sudanese had some of the lowest allele frequencies of the wildtype allele NAT2*4, similar to some other African populations (Patin et al. 2006a, 2006b). Third, the northern Sudanese had NAT2*5B as the most common allele, similar to what has been reported for most Caucasians and Arabs (Boukouvala and Fakis 2005; Patin et al. 2006a). Fourth, in the northern Sudanese the combination of the seven common SNPs resulted in twelve haplotype alleles, which are by far more than that detected in other populations except the Ateke population (Patin et al. 2006a). Furthermore, higher haplotype diversity was obtained among northern Sudanese compared with other African, Caucasian, and Asian populations (Sabbagh and Darlu 2005; Patin et al. 2006a). It is possible that the Arab-African-Hamitic admixture of northern Sudanese explains this greater diversity in NAT2 alleles, as was previously suggested for

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Table 2. Genotypes of NAT2 Haplotypes Among 127 Northern Sudanese Genotype Definitive genotypes NAT2*4/*12A NAT2*5B/*5B NAT2*6A/*6A NAT2*7B/*7B NAT2*12A/*12A Inferred genotypes NAT2*4/*5C NAT2*5A/*6A NAT2*5B/*5C NAT2*5B/*6A NAT2*5B/*6B NAT2*5B/*7B NAT2*5B/*12A NAT2*5B/*12B NAT2*5B/*14A NAT2*5B/*14B NAT2*5C/*14A NAT2*6A/*7B NAT2*6A/*13 NAT2*6A/*14B NAT2*12A/*14A Computationally predicted genotypes a NAT2*4/*5B NAT2*4/*6A NAT2*4/*7B NAT2*5B/*13 NAT2*6A/*12A

Predicted Phenotype

Frequency

Rapid Slow Slow Slow Rapid

0.0157 0.1968 0.0787 0.0078 0.0236

Intermediate Slow Slow Slow Slow Slow Intermediate Intermediate Slow Slow Slow Slow Intermediate Slow Intermediate

0.0078 0.0078 0.0157 0.2834 0.0078 0.0157 0.0629 0.0078 0.0314 0.0078 0.0078 0.0157 0.0078 0.0078 0.0078

Intermediate Intermediate Intermediate Intermediate Intermediate

0.0708 0.0629 0.0157 0.0078 0.0236

a. Predicted by Phase and HAP programs.

HLA alleles in the same population (Ward et al. 1989). This is further supported by the observation that the northern Sudanese have in addition to the Africanspecific SNP, the Asian-specific SNP. The Asian-specific SNP, which is found in other Arab populations (Woolhouse et al. 1997; Tanira et al. 2003), might have originated in the Middle East and might have been introduced into the Asian populations during the human demic diffusion (Quintana-Murci et al. 2001). It is interesting to note that the phylogeny analysis predicted that both the African- and Asian-specific SNPs would be found in the most recently acquired alleles among the northern Sudanese (see Figure 1). The Asian-specific SNP might have been introduced recently because it is the only SNP that is not in Hardy-Weinberg equilibrium (see Table 1). The diverse haplotype alleles among the northern Sudanese resulted in 25 genotypes, of which the predicted slow acetylator phenotype was the most prevalent. This is consistent with findings in other Middle Eastern, European, and Central and East African populations (Patin et al. 2006a). In our study the T341C

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SNP had the highest contribution to the slow acetylator phenotype, particularly NAT2*5B. This SNP was recently found to have the highest growth rate among all NAT2 mutations and might have favored a positive selective advantage for the slow acetylators in Eurasians (Patin et al. 2006a). NAT2 acetylation polymorphism plays an important role in the activation and/or deactivation of a large and diverse number of aromatic amines and clinically used hydrazine drugs. This genetic variation in acetylation has been shown to be responsible for drug-induced toxicity and is associated with disease and cancer susceptibility (Boukouvala and Fakis 2005). Thus it is important to consider the impact of NAT2 polymorphism in cancer risk. The construction of haplotype phases (genotypes) in the northern Sudanese subjects had 19% ambiguous genotypes resulting from multiple SNP heterozygotes. Recently, Sabbagh and Darlu (2005) recommended computational analysis using the Phase program to infer haplotype phases in the NAT2 gene to resolve ambiguities. Using this method, we resolved the ambiguity to a near 98% accuracy. This method was also recently used to construct NAT2 allele haplotypes in other African populations (Patin et al. 2006b). The combination of molecular and computational analysis has proven to be a robust, cheap, and fast approach to resolving ambiguous genotypes. This approach will facilitate the phenotypic designation of NAT2, which will lead to better monitoring of risks associated with cancer and adverse drug reactions. In conclusion, molecular genotyping combined with computational analysis was successfully applied to resolve NAT2 haplotype alleles in northern Sudanese subjects with multiple heterozygote SNPs. The northern Sudanese subjects had both the African- and Asian-specific SNPs, which resulted in more diverse NAT2 alleles compared to other populations. Among the 25 genotypes detected, the predicted slow acetylator phenotype was the most prevalent in the Sudanese subjects, consistent with other African populations and Caucasians. Received 10 November 2006; revision received 22 March 2007.

Literature Cited Adkins, R. M. 2004. Comparison of the accuracy of methods of computational haplotype inference using a large empirical dataset. BMC Genet. 5(22). Agúndez, J. A. G., M. Olivera, C. Martinez et al. 1996. Identification and prevalence study of 17 allelic variants of the human NAT2 gene in a white population. Pharmacogenetics 6(5):423–428. Ali, B. H., and A. A. Bashir. 1991. Polymorphic acetylation of sulpha-dimidine in healthy Northern Sudanese. Ann. Saudi Med. 11:483–484. Bayoumi, R. A. L., M. M. Qureshi, M. M. Al-Amri et al. 1997. The N-acetyltransferase G191A SNP among Sudanese and Somalis. Pharmacogenetics 7(5):397–399. Boukouvala, S., and G. Fakis. 2005. Arylamine N-acetyltransferases: What we learn from genes and genomes. Drug Metab. Rev. 37(3):511–564. Chowbay, B., S. Zhou, and E. J. Lee. 2005. An interethnic comparison of polymorphisms of the genes encoding drug-metabolizing enzymes and drug transporters: Experience in Singapore. Drug Metab. Rev. 37(2):327–378.

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Doll, M. A., A. J. Fretland, A. C. Deitz et al. 1995. Determination of human NAT2 acetylator genotype by restriction fragment-length polymorphism and allele-specific amplification. Anal. Biochem. 231(2):413–420. Dupret, J. M., and F. Rodrigues-Lima. 2005. Structure and regulation of the drug metabolizing enzymes arylamine N-acetyltransferases. Curr. Med. Chem. 12(3):311–318. Evan, D. A. P. 1992. N-acetyltransferase. In Pharmacogenetics of Drug Metabolism, W. Kalow, ed. New York: Pergamon Press, 95–178. Halperin, E., and E. Eskin. 2004. Haplotype reconstruction from genotype data using imperfect phylogeny. Bioinformatics 20(12):1842–1849. Hein, D. W., M. A. Doll, A. J. Fretland et al. 2000a. Molecular genetics and epidemiology of the NAT1 and NAT2 acetylation polymorphisms. Cancer Epidemiol. Biomark. Prev. 9(1):29–42. Hein, D. W., D. M. Grant, and E. Sim. 2000b. Update on consensus arylamine N-acetyltransferase gene nomenclature. Pharmacogenetics 10(4):291–292. Hickman, D., and E. Sim. 1991. N-acetyltransferase polymorphism: Comparison of phenotype and genotype in humans. Biochem. Pharmacol. 42(5):1007–1014. Hiratsuka, M., Y. Kishinkawa, Y. Takekuma et al. 2002. Genotyping of the N-acetyltransferase 2 polymorphism in the prediction of adverse drug reaction to isoniazid in Japanese patients. Drug Metab. Pharmacokin. 17(4):357–362. Homeida, M., O. I. Abboud, O. El-Dawi et al. 1986. The acetylator phenotypes of Sudanese subjects. Arab J. Med. 5:30–31. Lin, H. J., C.-Y. Han, B. K. Lin et al. 1993. Slow acetylator mutations in the human polymorphic Nacetyltransferase gene in 786 Asians, blacks, Hispanics, and whites: Application to metabolic epidemiology. Am. J. Hum. Genet. 52(4):827–834. Lin, H. J., C.-Y. Han, B. K. Lin et al. 1994. Ethnic distribution of slow acetylator SNPs in the polymorphic N-acetyltransferase (NAT2) gene. Pharmacogenetics 4(3):125–134. Loktionov, A., W. Moore, S. P. Spencer et al. 2002. Differences in N-acetylation genotypes between Caucasians and black South Africans. Cancer Detect. Prevent. 26(1):15–22. Nei, M. 1987. Molecular Evolutionary Genetics. New York: Columbia University Press. Niu, T. 2004. Algorithms for inferring haplotypes. Genet. Epidemiol. 27:334–347. Patin, E., L. B. Barreiro, P. C. Sabeti et al. 2006a. Deciphering the ancient and complex evolutionary history of human arylamine N-acetyltransferase genes. Am. J. Hum. Genet. 78(3):423–436. Patin, E., C. Harmant, K. K. Kidd et al. 2006b. Sub-Saharan African coding sequence variation and haplotype diversity at the NAT2 gene. Hum. Mutat. 27(7):720–730. Quintana-Murci, L., C. Krausz, T. Zerjal et al. 2001. Y-chromosome lineages trace diffusion of people and languages in southwestern Asia. Am. J. Hum. Genet. 68(2):537–542. Sabbagh, A., and P. Darlu. 2005. Inferring haplotypes at the NAT2 locus: The computational approach. BMC Genet. 6(30). Sim, E., K. Pinter, A. Mustaq et al. 2003. Arylamine N-acetyltransferases: A pharmacogenic approach to drug metabolism and endogenous function. Biochem. Soc. Trans. 31(pt. 3):615–619. Stephens, M., and P. Donnelly. 2003. A comparison of Bayesian methods for haplotype reconstruction from population genotype data. Am. J. Hum. Genet. 73(5):1162–1169. Stephens, M., N. J. Smith, and P. Donnelly. 2001. A new statistical method for haplotype reconstruction from population data. Am. J. Hum. Genet. 68(4):978–989. Tanira, M. O. M., M. Simsek, K. Al-Balushi et al. 2003. Distribution of arylamine N-acetyltransferase 2 (NAT2) genotypes among Omanis. Sultan Qaboos Univ. Med. J. 5(1–2):9–14. Vatsis, K. P., W. W. Weber, D. A. Bell et al. 1995. Nomenclature for N-acetyltransferases. Pharmacogenetics 5(1):1–17. Ward, F. E., J. B. Jensen, N. H. Abdul Hadi et al. 1989. HLA genotypes and variant alleles in Sudanese families of Arab-Negroid tribal origin. Hum. Immunol. 24(4):239–251. Woolhouse, N. M., M. M. Qureshi, S. M. A. Bastaki et al. 1997. Polymorphic N-acetyltransferase (NAT2) genotyping of Emiratis. Pharmacogenetics 7(1):73–82.

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