Correlation of mutational analysis to clinical features in Taiwanese patients with Gilbert's syndrome

Bilirubin metabolism and UDP-glucuronosyltransferase 1A1 variants in Asians: Pathogenic implications and therapeutic response

In the Asian general population, at least six single-nucleotide variants (SNVs) in the UDP-glucuronosyltransferase (UGT) 1A1 gene have been identified: -3279T>G, -53A(TA)₆ TAA>A(TA)₇ TAA, 211G>A, 686C>A, 1091C>T, and 1456T>G. Each of these six SNVs was observed in at least four ethnic groups of the 12 Asian populations studied. In East Asian populations, the descending frequency of these six SNVs was as follows: -3279G>[-53A(TA)₇ TAA, 211A]>(686A, 1091T)>1456G. Because of the presence of linkage disequilibrium and the expulsion phenomenon, when the SNVs -3279G, -53A(TA)₇ TAA, 211A, and 686A were simultaneously involved, 15 instead of the estimated 81 genotypes were observed. Those carrying 686AA or 1456GG developed Gilbert's syndrome or Crigler-Najjar syndrome type 2. Both -53A(TA)₇ TAA/A(TA)₇ TAA and 211AA are the main causes of Gilbert's syndrome in East Asian populations. In East Asian populations, the 211AA genotype is the main cause of neonatal hyperbilirubinemia, whereas -53A(TA)₇ TAA/A(TA)₇ TAA exerts a protective effect on hyperbilirubinemia development in neonates fed with breast milk. Both 211A and -53A(TA)₇ TAA are significantly associated with adverse drug reactions induced by irinotecan (one of the most widely used anticancer agents) in Asians. However, at least three common SNVs (-3279G, -53A(TA)₇ TAA, and 211A) should be comprehensively analyzed. This study investigated the clinical significance of these six SNVs and demonstrated that examining UGT1A1 variants in Asian populations is considerably challenging.

Analysis of the UGT1A1 Genotype in Hyperbilirubinemia Patients: Differences in Allele Frequency and Distribution

Objective

The spectrum of UDP-glucuronyl transferase A1 (UGT1A1) variants in hereditary unconjugated hyperbilirubinemia varies markedly between different ethnic populations. This study evaluated the UGT1A1 genotypes in hyperbilirubinemia patients from southeastern China.

Methods

We enrolled 60 patients from southeastern China (44 men and 16 women; age range: 3-76 years) with unconjugated hyperbilirubinemia and performed genetic analysis of the UGT1A1 gene by direct sequencing.

Results

For patients with Gilbert syndrome, 85% (47/55) harbored pathogenic variants of UGT1A1⁎60. Both UGT1A1⁎28 and UGT1A1⁎81 were detected in the promoter region of UGT1A1. Additionally, 83% (20/24) of patients with Gilbert syndrome heterozygous for UGT1A1⁎60 had an association with heterozygous variation of UGT1A1⁎28 or UGT1A1⁎81, while 91% (21/23) of Gilbert syndrome patients homozygous for UGT1A1⁎60 had biallelic variations of UGT1A1⁎28 and UGT1A1⁎81. We detected 213 UGT1A1 allelic variants, including six novel variations, with the most frequent allele being the UGT1A1⁎60, followed by UGT1A1⁎28 and UGT1A1⁎6. All of the patients showed multiple sites of variants in UGT1A1; however, variation number was not associated with bilirubin levels (P>0.05).

Conclusions

The spectrum of UGT1A1 variants in southeastern Chinese patients was distinct from other ethnic populations. Our findings broaden the knowledge concerning traits associated with UGT1A1 variants and help profile genotype-phenotype correlations in hyperbilirubinemia patients.

Effect of UDP-glucuronosyltransferase 1A1 activity on risk for developing Gilbert's syndrome

Variations at the six nucleotides -3279 (T > G), -53 (A[TA]₆ TAA > A[TA]₇ TAA), 211 (G > A), 686 (C > A), 1091 (C > T), and 1456 (T > G) in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene were determined in 178 Taiwanese patients with Gilbert's syndrome and in 200 healthy adults. Every subject was classified as a genotype depending on variation status of the six nucleotides in the UGT1A1 gene. The UGT1A1 activity for each genotype was calculated and then those genotypes were divided into 10 subgroups (Q1~Q10) according to their UGT1A1 activities, by using 10% as an interval. There were 24 genotypes observed, with UGT1A1 activity ranged 9%~100% of normal. There were two and six subjects with Gilbert's syndrome and none of healthy controls carrying genotypes in the Q1 and Q2 subgroups, respectively. The odds of developing Gilbert's syndrome were significantly higher for subjects carrying genotypes in the Q3, Q4, and Q5 subgroups than for those with genotype in the Q10 subgroup (odds ratios: 240.22, 59.80, and 14.67, respectively, P < .001 for each). Among the 178 patients of Gilbert's syndrome, serum bilirubin value was inversely correlated with UGT1A1 activity (r = -.306, P < .001). The sensitivity was 72.0% and the specificity was 90.5% by using UGT1A1 activity ≦40% of normal as the cut-off point to distinguish between healthy subjects and patients of Gilbert's syndrome. Our results demonstrate that UGT1A1 activity is certainly a determinate for serum bilirubin value and UGT1A1 activity ≦40% of normal is a proper risk factor for the development of Gilbert's syndrome.

Restriction fragment length polymorphism effectively identifies exon 1 mutation of UGT1A1 gene in patients with Gilbert's Syndrome

BACKGROUND & AIMS

Gilbert's syndrome causes pharmacological variation in drug glucuronidation and unexpected toxicity from therapeutic agents. The two common genotypes of Gilbert's syndrome are a dinucleotide polymorphism (TA)7 in TATA-Box as well as the 211G>A mutation in the coding exon 1, particularly in Asians, of human UGT1A1 gene. In this study, we aimed to establish an effective method to detect the 211G>A mutation.

METHODS

The coding exon 1 sequence of human UGT1A1 gene was analysed by Vector NTI software. The 211G>A mutation in the coding exon 1 of UGT1A1 gene was determined by restriction fragment length polymorphism (RFLP) method. Serum total bilirubin level was measured as well.

RESULTS

A newly identified BsmBI site was located in the coding exon 1 of UGT1A1 gene. The 211G>A mutation in the coding exon 1 of UGT1A1 gene was determined by DNA RFLP. Furthermore, we reported our present work on genetic analysis of mutations of UGT1A1 gene, and the correlation of UGT1A1 mutations with serum total bilirubin levels in Taiwanese population. The results showed that 15 subjects carried 211G>A mutation in 23 subjects related with Gilbert's syndrome. The homozygous 211G>A mutant as well as simultaneously heterozygous mutants both in TATA-Box and 211G>A significantly increased the risk of Gilbert's syndrome similar to subjects carrying homozygous TATA-Box mutant.

CONCLUSIONS

BsmBI RFLP is an effective method to detect 211G>A mutation in the coding exon 1 of UGT1A1 gene. The common 211G>A mutation is one of the causes of Gilbert's syndrome in Taiwanese population.

Spectrum of UGT1A1 Variations in Chinese Patients with Crigler-Najjar Syndrome Type II

Crigler–Najjar Syndrome type II (CNS-II) is an autosomal recessive hereditary condition of unconjugated hyperbilirubinemia without hemolysis, with bilirubin levels ranging from 102.6 μmol/L to 342 μmol/L. CNS-II is caused by a deficiency of UDP-glucuronyl transferase (UGT), which is encoded by the UDP-glucuronyl transferase 1A1 gene (UGT1A1). In East Asian populations, the compound homozygous UGT1A1 G71R and Y486D variants are frequently observed in cases with bilirubin levels exceeding 200 μmol/L. In this study, we investigated the spectrum of UGT1A1 variations in Chinese CNS-II patients. We sequenced the enhancer, promoter, and coding regions of UGT1A1 in 11 unrelated Chinese CNS-II patients and 80 healthy controls. Nine of these patients carried variations that are here reported for the first time in CNS-II patients, although they have been previously reported for other types of hereditary unconjugated hyperbilirubinemia. These individual variations have less influence on UGT activity than do the compound homozygous variation (combination of homozygous G71R variant and Y486D variant). Therefore, we propose that the spectrum of UGT1A1 variations in CNS-II differs according to the bilirubin levels.

Partitioning Reference Intervals by Use of Genetic Information

BACKGROUND

Reference intervals that incorporate genetic information could reduce the misidentification of unusual test results caused by non–disease-associated genetic variation and increase the detection of results indicating underlying pathology. Subdividing reference groups by genetic effects, however, may lead to increased uncertainty around reference interval endpoints (because of the smaller subgroup sample sizes), thus offsetting any benefits.

METHODS

We evaluated CLSI guidelines to develop a method appropriate for partitioning reference intervals on the basis of genetic variants with dominant or recessive effects. This method uses information available before reference samples are recruited, thus allowing a preliminary decision regarding partitioning to be made before sampling. We used this method to evaluate the example of Gilbert syndrome.

RESULTS

The decision point for partitioning occurs when the percentage of total variance attributable to a dominant or recessive genetic polymorphism exceeds 4%. Similarly, partitioning decision curves are presented based on difference in means between 2 subgroups, sample SD, and subgroup or allele frequency. Laboratory-specific partitioned reference intervals for Gilbert syndrome appear to be statistically warranted for white and African-American populations, but not for Asian populations.

CONCLUSIONS

We present a simple method to evaluate whether partitioning based on dominant or recessive genetic effects is statistically justified. Important limitations remain that, in many situations, will preclude integration of genetic, laboratory, and clinical information. As society moves toward personalized medicine, additional research is needed on how to evaluate patient normality while accounting for additive genetic, multigenic, and other multifactorial effects.

Uridine 5'-diphospho-glucuronosyltransferase genetic polymorphisms and response to cancer chemotherapy

Pharmacogenetics aims to elucidate how genetic variation affects the efficacy and side effects of drugs, with the ultimate goal of personalizing medicine. Clinical studies of the genetic variation in the uridine 5'-diphosphoglucuronosyltransferase gene have demonstrated how reduced-function allele variants can predict the risk of severe toxicity and help identify cancer patients who could benefit from reduced-dose schedules or alternative chemotherapy. Candidate polymorphisms have also been identified in vitro, although the functional consequences of these variants still need to be tested in the clinical setting. Future approaches in uridine 5'-diphosphoglucuronosyltransferase pharmacogenetics include genetic testing prior to drug treatment, genotype-directed dose-escalation studies, study of genetic variation at the haplotype level and genome-wide studies.

An overview of the recent progress in irinotecan pharmacogenetics

Recent developments in a number of molecular profiling technologies, including genomic/genetic testing, proteomic profiling and metabolomic analysis have allowed the development of 'personalized medicine'. Irinotecan is one of the models for personalized medicine based on pharmacogenetics, and a number of clinical studies have revealed significant associations between UGT1A1*28 and irinotecan toxicity. Based on this cumulative evidence, the US FDA and pharmaceutical companies revised the irinotecan label in June 2005. However, a recommended strategy for irinotecan-dose adjustments based on individual genetic factors has not yet been fully established. This article provides an overview of recent progress in irinotecan pharmacogenetics and discusses the clinical significance of the UGT1A1 genotype/haplotype with regard to severe irinotecan toxicity.

Uridine diphosphate glucuronosyl transferase 1A1 promoter polymorphism is associated with choledocholithiasis in Taiwanese patients

BACKGROUND AND AIMS

The gene product of the uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1) is crucial to bilirubin metabolism. Mutations in this gene subsequently result in disease presented with unconjugated hyperbilirubinemia. A previous study showed that a TA-repeat polymorphism in the promoter region of this gene might play a role in the metabolism of bilirubin. Whether this polymorphism might predispose choledocholithiasis is unclear.

METHODS

We recruited 32 patients who were diagnosed with pigment choledocholithiasis (common bile duct stones) by endoscopic retrograde cholangiopancreatography (ERCP) morphology and 107 population controls. The TA-repeat in the UGT1A1 promoter was genotyped.

RESULTS

We found that among the 32 patients, 15 (46.9%) were wild type (A[TA](6)TAA homozygous); 15 (46.9%) were a heterozygous variation (A[TA[(6)TAA/A[TA](7)TAA) and 2 (6.2%) were a homozygous variation (A[TA](7)TAA). Among the controls, 81 (75.7%) were wild type, 23 (21.5%) were a heterozygous variation and 3 (2.8%) were a homozygous variation. The genotype distribution was significantly different between patients and controls.

CONCLUSIONS

The results suggest that the UGT1A1 promoter TA-repeat polymorphism is associated with choledocholithiasis in Taiwanese patients.

Variations in the UDP-glucuronosyltransferase 1A1 gene for the development of unconjugated hyperbilirubinemia in Taiwanese

INTRODUCTION

Results of several studies have indicated that the variation of c.-3279T>G in the UDP-glucuronosyltransferase (UGT)1A1 gene could be a further factor for the development of hyperbilirubinemia. However, this variant has not been reported in the Taiwanese population.

MATERIALS & METHODS

PCR-restriction fragment length polymorphism was utilized to determine variants at nucleotides -3279 (*60), -53 (*28) and 211 (*6) in the UGT1A1 gene for 178 Taiwanese hyperbilirubinemic patients and 200 controls.

RESULTS

A total of ten and nine diplotypes were observed in the hyperbilirubinemic patients and controls, respectively. Subjects possessing diplotypes of compound haplotypes (*60/*28, *60/*6, *1/*60 plus *1/*28 plus *1/*6); *60/*60; *60/*60 plus 1/*28 and *6/*6 were significantly related to hyperbilirubinemia development, with an odds ratio of 7.83-188.00 (p = 0.012 approximately <0.001). A subgroup possessing diplotypes of *60/*60 plus *28/*28 were only found in hyperbilirubinemic patients, not in the controls. Bilirubin concentration amongst these patients carrying a diplotype of *60/*60 plus *28/*28 (mean [SD]: 39.2 [10.77] micromol/l) was significantly higher than that in the diplotype subgroups of *60/*60 plus *1/*28 (30.4 [4.10] micromol/l) and *6/*6 (30.3 [3.08] micromol/l) (p = 0.046 and 0.034, respectively).

CONCLUSIONS

The c.-3279T>G variant is a further factor for the development of hyperbilirubinemia. Our results also demonstrate that possessing the *60/*60 plus *28/*28 diplotype in the UGT1A1 gene is a determinant of relatively higher bilirubin values amongst hyperbilirubinemic patients.

Cord blood bilirubin level in relation to bilirubin UDP-glucuronosyltransferase gene missense allele in Chinese neonates

AIM

To investigate bilirubin UDP-glucuronosyltransferase (UGT1A1) gene allele in healthy Chinese neonates, their cord bilirubin level and the subsequent hyperbilirubinemia to determine relationships among them.

METHODS

Cord blood of 48 neonates was obtained to determine the exon 1 of UGT1A1 gene, total serum bilirubin, albumin, glutamic-pyruvic transaminase (GPT), glutamic-oxalacetic transaminase (GOT) and haemoglobin (Hb) concentration. Neonatal jaundice was assessed by measurement of transcutaneous bilirubin (TCB) and serum bilirubin. Neonates were divided into two groups according to mutant or normal allele to compare the variables.

RESULTS

Nineteen infants had the nucleotide 211 G-->A allele, 3 had the heterozygous variation (686C-->A, 845 A-->T, 231G-->A). In the 211 A allele group, cord bilirubin was significantly higher than in the 211 G allele group (p = 0.034), but there were no differences in albumin (p = 0.678), GPT (p = 0.460), GOT (p = 0.440) and Hb (p = 0.886). The TCB (at 48, 96 h), the frequency of the hyperbilirubinemia and prolonged jaundice were also significantly higher in the 211 A allele group.

CONCLUSIONS

The UGT1A1 gene codon G71R allele is a risk factor for neonatal hyperbilirubinemia in the Chinese population. Its effect on bilirubin metabolism may present early on, as well as late in foetal life.

Combined UGT1A1 and UGT1A7 variant alleles are associated with increased risk of Gilbert’s syndrome in Taiwanese adults

Gilbert's syndrome (GS) is caused by a reduction in the activity of hepatic bilirubin UDP-glucuronosyltransferase (UGT). This reduction is associated with UGT1A1*28 and UGT1A1*6 polymorphisms. Recent research also showed that carriage of UGT1A1*6 allele were significantly related with UGT1A7*3. Polymerase chain reaction-restriction fragment length polymorphism were utilized to determine UGT1A7 and UGT1A1 genes for 207 patients with GS and 207 gender/age-matched healthy controls. For the 207 healthy controls, linkage disequilibrium was observed between -57UGT1A7 and 622UGT1A7 loci (D' = 1.00 and r(2) = 1.00), -57UGT1A7 and 211UGT1A1 loci (D' = 0.72 and r(2) = 0.36), respectively. A dose-response effect for number of at-risk allele of UGT1A1 and risk for GS was noted (odds ratio (OR) = 8.19 for heterozygous UGT1A1*28 genotype; OR = 124.96 for homozygous UGT1A1*28 genotype; and p for trend <0.05). Patients with combined genotypes carrying UGT1A7 variant alleles and UGT1A1 variant alleles (including UGT1A1*28 and UGT1A1*6) are associated with increased risk of GS (OR = 13.96 for patients with combined genotype carrying at least one variant allele of UGT1A1 and UGT1A7). In conclusion, the -57UGT1A7 (T>G) is highly associated with UGT1A7*3 and moderately associated with 211UGT1A1 (G>A). Certain UGT1A1/UGT1A7 combined genotypes are risk factors of GS.

Crigler-Najjar syndrome type 2

Crigler-Najjar syndrome is a rare disorder of bilirubin metabolism with two distinct forms: type 1 and type 2. We report three patients with Crigler-Najjar syndrome type 2 (CN-2). All patients had serum bilirubin values higher than 171 micromol/L and deep yellow skin color. The results of other liver function tests, glucose-6-phosphate dehydrogenase activity and hematology tests were normal, and immunologic tests for hepatitis A, B and C were negative, although one patient had slightly elevated alanine aminotransferase level (45 IU/L). Polymerase chain reaction and sequence analysis of the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene revealed a novel homozygous T>A mutation at nucleotide 479 in exon 1 (Val160Glu) of patient 1, a novel homozygous A>G mutation at nucleotide 610 in exon 1 (Met204Val) of patient 2, and a homozygous T>G variation at nucleotide 1456 in exon 5 (Tyr486Asp) plus a heterozygous G>A variation at nucleotide 211 in exon 1 (Gly71Arg/normal) of patient 3. Two of these mutations were novel and variations identified within the coding region of the UGT1A1 gene were considered the cause of CN-2 in all three patients.

Frequencies of A(TA)7TAA, G71R, and G493R mutations of the UGT1A1 gene in the Malaysian population

BACKGROUND

Gilbert syndrome is caused by defects in the uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) gene. These mutations differ among different populations and many of them have been found to be genetic risk factors for the development of neonatal jaundice.

OBJECTIVES

The objective was to determine the frequencies of the following mutations in the UGT1A1 gene: A(TA)7TAA (the most common cause of Gilbert syndrome in Caucasians), G71R (more common in the Japanese and Taiwanese population), and G493R (described in a homozygous Malay woman with Crigler-Najjar syndrome type 2) in a group of Malaysian babies with hyperbilirubinemia and a group of normal controls.

METHODS

The GeneScan fragment analysis was used to detect the A(TA)7TAA variant. Mutation screening of both G71R and G493R was performed using denaturing high performance liquid chromatography.

RESULTS

Fourteen out of fifty-five neonates with hyperbilirubinemia (25%) carried the A(TA)7TAA mutation (10 heterozygous, 4 homozygous). Seven out of fifty controls (14%) carried this mutation (6 heterozygous, 1 homozygous). The allelic frequencies for hyperbilirubinemia and control patients were 16 and 8%, respectively (p=0.20). Heterozygosity for the G71R mutation was almost equal among both groups (5.5% for hyperbilirubinemia patients and 6.0% for controls; p=0.61). One subject (1.8%) in the hyperbilirubinemia group and none of the controls were heterozygous for the G493R mutation (p=0.476).

CONCLUSIONS

The A(TA)7TAA seems more common than the G71R and G493R mutations in the Malaysian population.

Genetic factors related to unconjugated hyperbilirubinemia amongst adults

Some variations in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene are involved in the development of unconjugated hyperbilirubinemia. We hypothesize that other genetic factors may also be associated with this disease. A total of 227 adults with normal routine haematology and liver function (apart from bilirubin testing for which they revealed bilirubin > or = 25.7 micromol/l and unconjugated bilirubin/total bilirubin > or = 80%), and 235 sex- and age-matched controls, were recruited. All subjects were analysed for UGT1A1, glucose-6-phosphate dehydrogenase (G6PD) and organic anion transporter polypeptide 2 (OATP2) genotypes using polymerase chain reaction-restriction fragment length polymorphism. The results indicated that G6PD deficiency, variant UGT1A1 gene and variant OATP2 gene were risk factors for hyperbilirubinemia. The odds ratios (OR) (with 95% confidence interval) were 220.83 (34.68-1406.30), 73.61 (17.01-318.63), 45.15 (11.19-182.22), 15.46 (4.35-54.99) and 6.51 (1.83-23.09), respectively, for individuals featuring the common UGT1A1/OATP2 haplotypes homozygous/heterozygous, compound heterozygous/heterozygous, compound heterozygous/wild-type, heterozygous/heterozygous and heterozygous/wild-type variations amongst subjects with normal G6PD activity. Amongst the subjects with G6PD deficiency, the OR was 159.00 (24.57-1028.94) for individuals carrying variations in both UGT1A1 and OATP2 genes. The UGT1A1/OATP2 haplotypes homozygous/wild-type, homozygous/compound heterozygous and homozygous/homozygous for G6PD normal and variant/wild-type for G6PD deficient individuals were only observed in the case group, and not in the control group. Amongst hyperbilirubinemic adults, bilirubin values tended to parallel variation status of their haplotypes. Adults featuring certain haplotypes in UGT1A1, OATP2 and G6PD genes face a high risk of developing unconjugated hyperbilirubinemia.

Molecular genetics of unconjugated hyperbilirubinemia in Taiwanese

In bilirubin metabolism, increased destruction of erythrocytes, defect in the function of organic anion transporter polypeptide 2 (OATP2) or UDP-glucuronosyltransferase 1A1 (UGT1A1) may result in unconjugated hyperbilirubinemia. Although glucose-6-phosphate dehydrogenase (G6PD) deficiency is known to be associated with the development of neonatal hyperbilirubinemia, it was observed that in neonates severe hyperbilirubinemia caused by G6PD deficiency, without associated polymorphisms in the UGT1A1 or the OATP2 gene, was preventable. Variations at the nucleotide (nt) 388 of OATP2 gene and nt-211 of UGT1A1 gene, were found to be a risk factor for severe hyperbilirubinemia amongst Taiwanese neonates, respectively. G6PD deficiency, variations at nts 388 and 521 of OATP2 gene, and variations at nt-211 and in the promoter area of UGT1A1 gene were reported to be the risk factors for the occurrence of mild hyperbilirubinemia amongst Taiwanese adults. The status of the haplotypes of G6PD, OATP2, and UGT1A1 genes affected the odds ratio and the bilirubin levels in the hyperbilirubinemic subjects. Moreover, carriage of the variant-211 UGT1A1 allele, as well as UGT1A7*3 allele, was demonstrated to represent a risk factor for the development of, and a determinant for, metastases associated with Taiwanese colorectal-cancer patients. Further investigation is warranted to evaluate this phenomenon.

Polymorphisms of uridine-diphosphoglucuronosyltransferase 1A7 gene in Taiwan Chinese

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)₆TAA/A(TA)₇TAA, A(TA)₇TAA/A(TA)₇TAA, 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.

Coinheritance of variant UDP-glucuronosyl transferase 1A1 gene and glucose-6-phosphate dehydrogenase deficiency in adults with hyperbilirubinemia

A total of 115 male adults with unconjugated hyperbilirubinemia were divided into six subgroups according to their glucose-6-phosphate dehydrogenase (G6PD) status (normal and deficient) and UDP-glucuronosyl transferase 1 (UGT1) A1 genotypes (heterozygous variation, compound heterozygous variation and homozygous variation). The mean (SD) value of serum bilirubin in the subjects with G6PD deficiency and homozygous variation in UGT1A1 gene was 51.3 (17.8) micromol/l, which was significantly higher compared to that in the other five subgroups. Among the 115 study subjects, five patients had bilirubin values greater than 51.3 micromol/l. All five of these subjects had a homozygous variant UGT1A1 genotype and four of them were G6PD deficient. Our data suggest that pronounced hyperbilirubinemia in G6PD-deficient male adults is attributable to the coinheritance of homozygous variation in the UGT1A1 gene.