Polymorphisms of uridine-diphosphoglucuronosyltransferase 1A7 gene in Taiwan Chinese

Abstract

Aim: Single nucleotide polymorphisms (SNPs) of uridine-diphosphoglucuro-nosyltransferase 1A7 (UGT1A7) gene are associated with the development of orolaryngeal cancer, hepatocellular carcinoma, and colorectal cancer. We performed this research to establish the techniques for determining UGT1A7 gene and basic data of this gene for Taiwan Chinese.

Methods: We collected blood samples from 112 healthy adults and 505 subjects carrying different genotypes of UGT1A1, and determined the promoter area and the entire sequence of UGT1A7 exon 1 by polymerase chain reaction. We designed appropriate primers and restriction enzymes to detect variant UGT1A7 genotypes found in the study subjects.

Results: Six SNPs at nucleotides 33, 387, 391, 392, 622, and 756 within the coding region of UGT1A7 exon 1 were found. The incidence of UGT1A7 *1/*2 (N129R131W208/K129K131W208) was predominant (35.7%) while that of UGT1A7 *3/*3 (K129K131R208/K129K131R208) was the least (2.7%). The allele frequency of UGT1A7*3, which exists in a considerable proportion of Caucasians (0.361) and Japanese (0.255), was identified only to be 0.152 in our study subjects. A novel variation at nucleotide -57 in the upstream was found, which was associated with SNPs at nucleotides 33, 387, 391, 392, and 622 in one of the variant haplotypes. The nucleotide changes at positions 387, 391, 392 and 756 were in linkage in another variant haplotype. The allele frequency of UGT1A7*3 was 0.018, 0.158, 0.242, 0.433, and 0.920 in subjects carrying wild, A(TA) (6)TAA/A(TA)(7)TAA, A(TA)(7)TAA/A(TA)(7)TAA, 211G/211A, and 211A/211A variants of UGT1A1 gene, respectively. By using natural or mutagenesis primers, we successfully detected the variations at nucleotides -57, 33, 387, and 622 with the restriction enzymes HpyCH4 IV, Taq I, Afl II, and Rsa I, respectively.

Conclusion: The results indicate that the allele frequencies of UGT1A7 gene in Taiwan Chinese are different from those in Caucasians and Japanese. Carriage of the nucleotide 211- variant UGT1A gene is highly associated with UGT1A7*3. The restriction-enzyme-digestion method for the determination of nucleotides -57 (or 33, or 622) and 387 can rapidly identify genotypes of UGT1A7 in an individual.

Figure 1

Representative electropherograms of (A) homozygous N¹²⁹ R¹³¹ (nucleotides 387-392: TGACCG), (B) heterozygous K¹²⁹ K¹³¹ (nucleotides 387-392: T/GGACC/AG/A), (C) homozygous K¹²⁹ K¹³¹ (nucleotides 387- 392: GGACAA), (D) homozygous W²⁰⁸ (nucleotide 622: T), (E) heterozygous W²⁰⁸/R²⁰⁸ (nucleotide 622: T/C), (F) - 57 T, and (G) - 57 T/G. Sequences were read reversely and nucleotides were translated into complements for (A), (B), and (C). The arrows indicate the sites of single nucleotide polymorphism.

Figure 2

Results of restriction fragments at nucleotides (A) 387, (B) 622, and (C) -57, digested by Afl II, Rsa I, and HpyCH4 IV, respectively. The bands of 19, 54, and 57 bp were too small to be seen (bp = base pair, M: DNA size marker, N: wild type, V: variant).