UGT1A1(TA)n promoter polymorphism—A new case of a (TA)8 allele in Caucasians

The Mutation Hotspots at UGT1A Locus May Be Associated with Gilbert's Syndrome Affecting the Taiwanese Population

Gilbert's syndrome is mainly diagnosed through genetic analysis and is primarily detected through a mutation in the promoter region of the UGT1A1 gene. However, most of the research has been conducted on Caucasian populations. In this study, we studied the Han population in Taiwan to investigate the possibility of other mutations that could cause Gilbert's syndrome. This study comprised a test group of 45 Taiwanese individuals with Gilbert's syndrome and 180 healthy Taiwanese individuals as a control group. We extracted DNA from the blood samples and then used Axiom Genome-Wide TWB 2.0 array plates for genotyping. Out of 302,771 single nucleotide polymorphisms (SNPs) from 225 subjects, we detected 57 SNPs with the most significant shift in allele frequency; 27 SNPs among them were located in the UGT1A region. Most of the detected SNPs highly correlated with each other and are located near the first exon of UGT1A1, UGT1A3, UGT1A6, and UGT1A7. We used these SNPs as an input for the machine learning algorithms and developed prediction models. Our study reveals a good association between the 27 SNPs detected and Gilbert's syndrome. Hence, this study provides a reference for diagnosing Gilbert's syndrome in the Taiwanese population in the future.

Influence of UGT1A1 promoter polymorphism, α-thalassemia and βs haplotype in bilirubin levels and cholelithiasis in a large sickle cell anemia cohort

Hyperbilirubinemia in patients with sickle cell anemia (SCA) as a result of enhanced erythrocyte destruction, lead to cholelithiasis development in a subset of patients. Evidence suggests that hyperbilirubinemia may be related to genetic variations, such as the UGT1A1 gene promoter polymorphism, which causes Gilbert syndrome (GS). Here, we aimed to determine the frequencies of UGT1A1 promoter alleles, alpha thalassemia, and β^S haplotypes and analyze their association with cholelithiasis and bilirubin levels. The UGT1A1 alleles, -3.7 kb alpha thalassemia deletion and β^S haplotypes were determined using DNA sequencing and PCR-based assays in 913 patients with SCA. The mean of total and unconjugated bilirubin and the frequency of cholelithiasis in GS patients were higher when compared to those without this condition, regardless of age (P < 0.05). Cumulative analysis demonstrated an early age-at-onset for cholelithiasis in GS genotypes (P < 0.05). Low fetal hemoglobin (HbF) levels and normal alpha thalassemia genotype were related to cholelithiasis development (P > 0.05). However, not cholelithiasis but total and unconjugated bilirubin levels were associated with β^S haplotype. These findings confirm in a large cohort that the UGT1A1 polymorphism influences cholelithiasis and hyperbilirubinemia in SCA. HbF and alpha thalassemia also appear as modulators for cholelithiasis risk.

UGT1A1 (TA)n Promoter Genotype: Diagnostic and Population Pharmacogenetic Marker in Serbia

The UGT1A1 enzyme is involved in the metabolism of bilirubin and numerous medications. Unconjugated hyperbilirubinemia, commonly presented as Gilbert syndrome (GS), is a result of decreased activity of the UGT1A1 enzyme, variable number of TA repeats in the promoter of the UGT1A1 gene affects enzyme activity. Seven and eight TA repeats cause a decrease of UGT1A1 activity and risk GS alleles, while six TA repeats contribute to normal UGT1A1 activity and non-risk GS allele. Also, the UGT1A1 (TA)_n promoter genotype is recognized as a clinically relevant pharmacogenetic marker. The aim of this study was to assess diagnostic value of UGT1A1 (TA)_n promoter genotyping in pediatric GS patients. Correlation of the UGT1A1 (TA)_n genotypes and level of unconjugated bilirubin at diagnosis and after hypocaloric and phenobarbitone tests in these patients was analyzed. Another aim of the study was to assess pharmacogenetic potential of UGT1A1 (TA)_n variants in Serbia. Fifty-one pediatric GS patients and 100 healthy individuals were genotyped using different methodologies, polymerase chain reaction (PCR) followed by acrylamide electrophoresis, fragment length analysis and/or DNA sequencing. Concordance of the UGT1A1 (TA)_n promoter risk GS genotypes with GS was found in 80.0% of patients. Therefore, UGT1A1 (TA)_n promoter genotyping is not a reliable genetic test for GS, but it is useful for differential diagnosis of diseases associated with hyperbilirubinemia. Level of bilirubin in pediatric GS patients at diagnosis was UGT1A1 (TA)_n promoter genotype-dependent. We found that the frequency of pharmacogenetic relevant UGT1A1 (TA)_n promoter genotypes was 63.0%, pointing out that UGT1A1 (TA)_n promoter genotyping could be recommended for preemptive pharmacogenetic testing in Serbia.

Genetic susceptibility to Gilbert's syndrome in a valencian population; efficacy of the fasting test

OBJECTIVE

To describe the populational distribution of the UGT1A1*28 variant (genetic variant code rs8175347) located in the promotor of the UGT gene and correlate its genotypes with the results of the fasting test, as well as its relationship with the biochemical disorder of Gilbert's syndrome (GS) in a Valencian population.

PATIENTS AND METHODS

We studied the prevalence of the genotypes (TA)_6/6 (TA)_6/7 and (TA)_7/7 of the deleterious variant rs8175347 in 144 patients with hyperbilirubinemia, 38 of whom had previously undergone the fasting test to diagnose GS, and in 150 control patients. By analysing the genomic region of the TATA box of the UGT1A1 gene promotor using Sanger sequencing, we established the correlation between the rs8175347 genotypes and the fasting test results and with the patients' biochemical disorders.

RESULTS

The rate of heterozygosity of allele (TA)₇ in the control population was 32% and increased to 87.59% among the patients with suspected GS. The rate of genotype TA_7/7 was 81.94% among the patients with hyperbilirubinemia, compared with 11.33% in the control patients. The fasting test showed a 15.79% rate of false negatives and a 5.26% rate of false positives.

CONCLUSIONS

The high frequency of allele (TA)₇ among the Valencian control population, almost double the 5% reported for European control patients, confirms the high rate of GS reported in the Spanish population, without observing significant differences between the geographical ends of the country. The efficacy and reliability of the fasting test for the diagnosis of GS is questionable.

Influence of UGT1A1 gene methylation level in colorectal cancer cells on the sensitivity of the chemotherapy drug CPT-11

OBJECTIVE

To study the influence of the methylation level of UGT1A1 gene related to CPT-11 metabolic enzymes in colorectal cancer cells on the sensitivity of chemotherapy drugs.

METHODS

Test the changes in sensitivity of seven colorectal cancer cell strains that have been/not been subject to DAC treatment to CPT-11, analyze its correlation with CES2, UGT1A1 and GUSB mRNA expression according to IC50; screen the effective interference sequence of UGT1A1 siRNA, test the changes in cytotoxicity of CPT-11 after UGT1A1 siRNA is transfected, select RK0 cells and make them transfected with the chemosynthetic UGT1A1 siRNA after their UGT1A1 expression is restored with or without demethylation treatment.

RESULTS

The sensitivity of different colorectal cancer cell strains to CPT-11 showed difference (P<0.05), UGT1A1 expression in colorectal cell lines had a negative correlation with the IC50 (r=0.790648, P<0.05), the interference efficiency of the screened UGT1A1 siRNA was up to 78%. The IC50 value of siRNA decreased by nearly one time after transfected with HT-29 (P<0.01); which of methylated RK0 cells of UGT1A1 gene increased instead after the demethylation treatment. However, the IC50 value of the demethylation treatment group increased compared with the non-demethylation treatment group after UGT1A1 siRNA was transfected.

CONCLUSIONS

The cytotoxicity of CPT-11 to colorectal cancer cells has a negative correlation with UGT1A1 expression, and positive correlation with CES2 and GUSB. The specific silencing UGT1A1 gene of siRNA could significantly increase the sensitivity of CPT-11 to the chemotherapy of colorectal cancer cells. UGT1A1 methylation was an important factor affecting the chemosensitivity of CPT-11.

Severe neonatal hyperbilirubinemia and UGT1A1 promoter polymorphism

OBJECTIVE

To assess whether UGT1A1 promoter polymorphisms associated with Gilbert Syndrome (GS) occur with a greater frequency in neonates with severe hyperbilirubinemia.

STUDY DESIGN

In a case-control study performed at a single hospital center in Italy, 70 case subjects with severe hyperbilirubinemia (defined as bilirubin level ≥20 mg/dL or 340 μmol/L) and 70 controls (bilirubin level <12 mg/dL or 210 μmol/L) were enrolled. Both case and control subjects were full term newborns. Polymerase chain reaction analysis on blood spot was performed to determine the frequency of UGTA1A1 promoter polymorphisms in cases and controls.

RESULTS

No statistical difference in the prevalence of UGTA1A1 gene variants was found between cases and controls (P = 1). Thirteen infants homozygous for (TA)7 polymorphism associated with GS were in the case group (18.6%) and 14 in the control group (20.0%). A heterozygous group was also equally distributed between cases (44.3%) and controls (42.9%). No (TA)8 repeat was found in the 2 groups.

CONCLUSIONS

In our study population, GS polymorphism alone does not appear to play a major role in severe neonatal hyperbilirubinemia in neonates without signs of hemolysis.

Body fat percentage is a major determinant of total bilirubin independently of UGT1A1*28 polymorphism in young obese

Objectives

Bilirubin has potential antioxidant and anti-inflammatory properties. The UGT1A1*28 polymorphism (TA repeats in the promoter region) is a major determinant of bilirubin levels and recent evidence suggests that raised adiposity may also be a contributing factor. We aimed to study the interaction between UGT1A1 polymorphism, hematological and anthropometric variables with total bilirubin levels in young individuals.

Methods

350 obese (mean age of 11.6 years; 52% females) and 79 controls (mean age of 10.5 years; 59% females) were included. Total bilirubin and C-reactive protein (CRP) plasma levels, hemogram, anthropometric data and UGT1A1 polymorphism were determined. In a subgroup of 74 obese and 40 controls body composition was analyzed by dual-energy X-ray absorptiometry.

Results

The UGT1A1 genotype frequencies were 49.9%, 42.7% and 7.5% for 6/6, 6/7 and 7/7 genotypes, respectively. Patients with 7/7 genotype presented the highest total bilirubin levels, followed by 6/7 and 6/6 genotypes. Compared to controls, obese patients presented higher erythrocyte count, hematocrit, hemoglobin and CRP levels, but no differences in bilirubin or in UGT1A1 genotype distribution. Body fat percentage was inversely correlated with bilirubin in obese patients but not in controls. This inverse association was observed either in 6/7 or 6/6 genotype obese patients. UGT1A1 polymorphism and body fat percentage were the main factors affecting bilirubin levels within obese patients (linear regression analysis).

Conclusion

In obese children and adolescents, body fat composition and UGT1A1 polymorphism are independent determinants of total bilirubin levels. Obese individuals with 6/6 UGT1A1 genotype and higher body fat mass may benefit from a closer clinical follow-up.

UGT1A1 gene variants and clinical risk factors modulate hyperbilirubinemia risk in newborns

OBJECTIVE

To study the contribution of UGT1A1 gene variants and clinical risk factors in modulating hyperbilirubinemia risk in newborns.

STUDY DESIGN

Seven UGT1A1 gene variants and clinical risk factors were studied in 113 hyperbilirubinemia cases and 218 control newborns. Hyperbilirubinemia was defined as the total serum bilirubin levels >95th percentile of the American Academy of Pediatrics nomogram. The study population included term (37 to 41 weeks) newborns below 2 weeks of age.

RESULT

UGT1A1 gene variants, namely, c.211G>A, g.-3279T>G, TATA box polymorphism and CAT insertion were identified as independent molecular risk factors for neonatal hyperbilirubinemia, whereas c.686C>A, c.1091C>T and c.1456T>G were not detected in study cohort. Among clinical risk factors, excessive weight loss, sepsis and ABO incompatibility emerged as independent risk factors. Co-expression of UGT1A1 variants and clinical risk factors further accentuated the risk of neonatal hyperbilirubinemia.

CONCLUSION

Multiple risk factors, whether genetic or clinical, are instrumental in modulating hyperbilirubinemia risk in newborns. Disordered bilirubin conjugation through interactions of UG1TA1 gene variants contributes to the clinical phenotype of neonatal hyperbilirubinemia.

Heme oxygenase-1 gene variants and hyperbilirubinemia risk in North Indian newborns

Heme oxygenase-1 (HO-1) is a rate-limiting enzyme in bilirubin metabolism, and its genetic variant may modulate hyperbilirubinemia risk in neonates. The aim of the present study was to assess the association between heme oxygenase-1 gene variants and hyperbilirubinemia risk in Indian newborns. In a prospective case-control study, we analyzed (GT)n repeats and g.-413A>T variant of HO-1 gene and UGT1A1 gene variants in 100 case newborns with total serum bilirubin (TSB) levels exceeding 95th percentile and 100 control newborns with TSB levels below 75th percentile on the hour-specific bilirubin nomogram of the American Academy of Pediatrics. Study population consisted of term (37-41 weeks) and late preterm (34-36 weeks) newborns during the first 2 weeks of age. In our analysis, the (GT)n allele was highly polymorphic, ranging in number from 15 to 40. The incidence of short (GT)n allele (≤ 20) was significantly higher in neonates with hyperbilirubinemia than in controls. Although g.-413A>T variant was widely prevalent in the study population, no difference was noted in its prevalence between cases and controls. Short (GT)n repeats of HO-1 gene, c.211G>A variant of UGT1A1 gene, and excessive weight loss were independent risk factors for neonatal hyperbilirubinemia. In the presence of two or more risk factors, the odds of developing neonatal hyperbilirubinemia were high. Shorter (GT)n genotype in the promoter region of HO-1 gene is significantly associated with hyperbilirubinemia risk in Indian newborns. This genotype may interact with other genetic and clinical risk factors to further potentiate hyperbilirubinemia risk in newborns.

The effect of UGT1A1 promoter polymorphism in the development of hyperbilirubinemia and cholelithiasis in hemoglobinopathy patients

Present study was aimed to explore the effect of (TA)n UGT1A1 gene promoter polymorphism on bilirubin metabolism, bilirubinaemia, predisposition to cholelithiasis and subsequent cholecystectomy, in Sickle-Cell Anemia (SCA) and beta-Thalasemia major (bTH) in Kuwaiti subjects compared to other population. This polymorphism was analyzed and correlated to total bilirubin and cholelithiasis in 270 age, gender, ethnically matched subjects (92 bTH, 116 SCA and 62 Controls) using PCR, dHPLC, fragment analysis and direct sequencing. Four genotypes of UGT1A1 were detected in this study (TA6/6, TA6/7, TA6/8 and TA7/7). (TA)6/8 was found only in four individuals; hence it was not included in the analysis. There was a statistically significant association of genotypes with serum total bilirubin levels in both bTH and SCA groups (p<0.001). Subjects with (TA)7/7 had the highest total serum bilirubin level (178.7 ± 3.5 µmole/l). A significant association was observed between allele (TA)7 and cholelithiasis development (p = 0.0001). The 40%, 67.5% and 100% of SCA with (TA)6/6, (TA)6/7 and (TA)7/7 respectively developed cholelithiasis and were subsequently cholecystectomized. Our results confirm UGT1A1 (TA)7 allele as one of the factors accounting for the hyperbilirubinemia and cholelithiasis observed in SCA and bTH.

Early complication in Sickle Cell Anemia children due to A(TA)<formula>_n</formula> TAA polymorphism at the promoter of UGT1A1 gene

AIM: To determine the implication of the polymorphism namely A(TA)nTAA of UGT1A1 in lithogenesis for the first time in Tunisia among sickle cell anemia (SCA) children patients. MATERIAL AND METHODS: Our study was performed in 2010 and it involved 76 subjects chosen as control group characterized with normal hemoglobin status and presence of cholelithiasis and 102 SCA pediatric patients among whom 52 have cholelithiasis. We analyzed the polymorphism A(TA)_{n} TAA at the UGT1A1 promoter and the relationships between the various A(TA)_{n} TAA genotypes and alleles and bilirubin levels and occurrence of cholelithiasis. RESULTS AND DISCUSSION: The repartition of genotypes found according to serum bilirubin level shows a significant association between genotypes carried variant (TA)_{7} and hyperbilirubinemia (p< 0.05). We demonstrated the association of two genotypes with gallstones formation among SCA children patients: (TA)_{7}/(TA)_{7} and (TA)_{7}/(TA)_{8} with p=8.1 × 10^{ - 8} and p=0.01 respectively. (TA)_{7} and (TA)_{8} allele variants act as a risk factor for early gallstones formation in SCA patients with p=5.8 × 10^{ -9} and p=0.01 respectively. As for the control group only the genotype (TA)_{7}/(TA)_{7} presented a risk factor for gallstones formation. CONCLUSION: The novelty of this report is that it is the first time that a similar study was made on the Tunisian children sickle cell population and that the results show a clear association of (TA)_{7} variant in early gallstones formation in Tunisian SCA children. Interestingly our findings highlighted the association of (TA)_{8} variant as well, which was not found in previous studies.

Coexistence of Gilbert syndrome with hereditary haemolytic anaemias

Background

Gilbert syndrome is an inherited disease characterised by mild unconjugated hyperbilirubinaemia caused by mutations in UGT1A1 gene which lead to decreased activity of UDP-glucuronosyltransferase 1A1. The most frequent genetic defect is a homozygous TA dinucleotide insertion in the regulatory TATA box in the UGT1A1 gene promoter.

Methods and results

182 Polish healthy individuals and 256 patients with different types of hereditary haemolytic anaemias were examined for the A(TA)nTAA motif. PCR was performed using sense primer labelled by 6-Fam and capillary electrophoresis was carried out in an ABI 3730 DNA analyser. The frequency of the (TA)7/(TA)7 genotype in the control group was estimated at 18.13%, (TA)6/(TA)7 at 45.05% and (TA)6/(TA)6 at 36.26%. There was a statistically significant difference in the (TA)6/(TA)6 genotype distribution between healthy individuals and patients with glucose-6-phosphate dehydrogenase deficiency (p=0.041). Additionally, uncommon genotypes, (TA)5/(TA)6, (TA)5/(TA)7 and (TA)7/(TA)8 of the promoter polymorphism, were discovered.

Conclusion

Genotyping of the UGT1A1 gene showed distinct distribution of the common A(TA)nTAA polymorphism relative to other European populations. Because of a greater risk of hyperbilirubinaemia due to hereditary haemolytic anaemia, the diagnosis of Gilbert syndrome in this group of patients is very important.

Inter and intra-ethnic differences in the distribution of the molecular variants of TPMT, UGT1A1 and MDR1 genes in the South Indian population

Molecular variants of polymorphic drug metabolizing enzymes and drug transporters are attributed to differences in individual's therapeutic response and drug toxicity in different populations. We sought to determine the genotype and allele frequencies of polymorphisms for major phase II drug-metabolizing enzymes (TPMT, UGT1A1) and drug transporter (MDR1) in South Indians. Allelic variants of TPMT (*2,*3A,*3B,*3C & *8), UGT1A1 (TA)6>7 and MDR1 (2677G>T/A & 3435C>T) were evaluated in 450-608 healthy South Indian subjects. Genomic DNA was extracted by phenol-chloroform method and genotype was determined by PCR-RFLP, qRT-PCR, allele specific PCR, direct sequencing and SNaPshot techniques. The frequency distributions of TPMT, UGT1A1 and MDR1 gene polymorphisms were compared between the individual 4 South Indian populations viz., Tamilian, Kannadiga, Andhrite and Keralite. The combined frequency distribution of the South Indian populations together, was also compared with that of other major populations. The allele frequencies of TPMT*3C, UGT1A1 (TA)7, MDR1 2677T, 2677A and 3435T were 1.2, 39.8, 60.3, 3.7, and 61.6% respectively. The other variant alleles such as TPMT*2, *3A, *3B and *8 were not identified in the South Indian population. Sub-population analysis showed that the distribution of UGT1A1 (TA)6>7 and MDR1 allelic variants differed between the four ethnic groups. However, the frequencies of TPMT*3C allele were similar in the four South Indian populations. The distribution of TPMT, UGT1A1 and MDR1 gene polymorphisms of the South Indian population was significantly different from other populations.

Evaluation of UGT1A1 and SULT1A1 polymorphisms with lipid levels in women with different hormonal status

BACKGROUND

Estrogens influence many physiological processes including cardiovascular health. Polymorphisms in phase I and II estrogen metabolism enzymes are associated with lipid levels in women.

METHODS

A cross-sectional study was carried out with 269 postmenopausal women, 116 who received oral hormonal therapy (HT) (39-75 years) with estrogens or estrogens plus progestagen, 153 that did not receive any HT (38-85 years), and 155 premenopausal women (18-52 years). Polymorphisms in UGT1A1 (rs5839491) and SULT1A1 (rs1042028) were analysed by PCR-based methods. Adjusted lipid levels means were compared among genotypes by one-way analysis of variance, with corrections for multiple testing.

RESULTS

The UGT1A1*28 polymorphism was associated with total cholesterol (T-chol) (p = 0.030; corrected p = 0.060) and low-density lipoprotein cholesterol (LDL-C) levels (p = 0.011, corrected p = 0.022) in premenopausal women. The premenopausal and postmenopausal women, both carriers of SULT1A1*2/*2, had lower levels of T-chol and LDL-C means than carriers of the SULT1A1*1/*1 (p = 0.004, corrected p = 0.008 and 0.009, corrected p = 0.018, respectively).

CONCLUSION

The data showed the presence of an association between the UGT1A1*28/*28 and SULT1A1*2/*2 and T-chol and LDL-C levels in women with different hormonal status. No previous studies investigated the association of the polymorphisms examined in this study with lipoprotein levels in women separately by hormonal status.

Effects of UGT1A1*28 polymorphism on raloxifene pharmacokinetics and pharmacodynamics

AIMS

Raloxifene concentrations were reported to correlate approximately with serum bilirubin levels. Bilirubin is a typical UGT1A1 substrate. Based on these facts, we postulated a hypothesis that UGT1A1 is the key enzyme for metabolic clearance of raloxifene and that the common UGT1A1*28 polymorphism significantly contributes to the large pharmacokinetic variability of raloxifene.

METHODS

Serum samples from postmenopausal osteoporotic patients treated with raloxifene were assayed for the concentrations of raloxifene and its glucuronides by liquid chromatography-mass spectrometry-mass spectrometry. The same samples were also genotyped for the presence of UGT1A1*28 polymorphism by the single-strand conformation polymorphism method. The pharmacodynamic effect was evaluated by measuring the change in bone mineral density (BMD) in femoral neck, hip and lumbar spine after 12 months' raloxifene therapy.

RESULTS

Patients homozygous for the *28 allele showed significantly, twofold higher raloxifene glucuronide concentrations compared with the hetero- and homozygotes for the wild-type allele: 558 +/- 115 nmol l(-1) compared with 295 +/- 43 nmol l(-1), respectively (P = 0.012). This indicates a higher raloxifene exposure in the *28/*28 group. Consequently, a significantly greater increase in hip BMD was observed in subjects homozygous for the *28 allele compared with the group carrying at least one copy of the wild-type allele: 4.4 +/- 2.4% compared with 0.3 +/- 1.4% (P = 0.035).

CONCLUSIONS

In this study it is shown that a relatively common UGT1A1*28 polymorphism may considerably influence raloxifene pharmacokinetics and pharmacodynamics. Underlying mechanisms and clinical implications of our findings are also discussed.

Gilbert syndrome as a predisposing factor for cholelithiasis risk in the Greek adult population

We investigated the hypothesis that coinheritance of the common A(TA)(n)TAA promoter mutation at the UGT1A1 locus associated with Gilbert syndrome is a risk factor for gallstone formation in a homogeneous adult population, by conducting a case-control study that included 198 adult patients with cholelithiasis and 152 healthy controls both of Greek origin. Three genotypes were found: 7/7 (17.8% in controls and 23.3% in patients), 6/7 (33.5% in controls and 46.5% in patients), and normal homozygous 6/6 (48.7% in controls and 30.3% in patients). The Gilbert UGT1A1 genotypes 6/7 and 7/7 show significant association (odds ratio 2.225, 95% confidence interval 1.373-3.605, p=0.001, and odds ratio 2.101, 95% confidence interval 1.171-3.770, p=0.013, respectively) with cholelithiasis risk. This association supports the theory that genetic factors are responsible for a fraction of symptomatic gallstone disease; however, further studies are required in different ethnic groups to fully elucidate the involvement of Gilbert syndrome in gallstone disease.

UGT1A1 gene polymorphisms in North Indian neonates presenting with unconjugated hyperbilirubinemia

Genetic factors are implicated in pathogenesis of neonatal hyperbilirubinemia. In this nested case-control study, we determined 1) frequency of thymine-adenine (TA)n promoter polymorphism and Gly71Arg mutation in uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene in neonates > or =35-wk gestation presenting with bilirubin levels > or =18 mg/dL and controls, 2) interaction among (TA)n promoter polymorphism, glucose-6-phosphate dehydrogenase (G6PD) gene mutations, and peak bilirubin. The number of TA repeats was assessed by PCR-single-strand conformation polymorphism (SSCP) analysis and Gly71Arg mutation by PCR-RFLP. Fifty samples of both mutations were verified with DNA sequencing. One hundred twenty-seven neonates were enrolled (77 hyperbilirubinemics, 50 controls). The incidence of (TA)n polymorphism was higher in babies with hyperbilirubinemia [89.6% vs. 50%, OR 8.63 (95% CI, 3.2-24.1)]. Gly71Arg mutation was not found either in hyperbilirubinemics or controls. A novel polymorphism (Ala72Pro) at codon position 72 of exon 1 was detected in all 50 samples (21 hyperbilirubinemics, 29 controls), which were sequenced. Presence of variant (TA)n promoter (adjusted OR, 10.6; 95% CI, 3.3-34.2), G6PD deficiency (adjusted OR, 20.6; 95% CI, 3.6-117.3), and history of jaundice in sibling requiring phototherapy (adjusted OR, 12.6; 95% CI, 1.1-141.6) were independent risk factors for bilirubin levels > or =18 mg/dL.

UGT1A1 gene polymorphism as a potential factor inducing iron overload in the pathogenesis of type 1 hereditary hemochromatosis

Aim Hereditary hemochromatosis is a common genetic disorder characterized by iron overload and subsequent organ damage. It is caused in most cases by HFE gene mutations which penetrance can be affected by many factors. The aim of this study was to establish the role of UGT1A1 gene polymorphism and serum bilirubin concentration in the pathogenesis of hereditary hemochromatosis. Methods Biochemical, histopathological and genetic data indicating iron excess and serum total bilirubin concentration were determined in 32 patients with the type 1 hereditary hemochromatosis. Fluorescent molecular probes assays were used for genotyping of UGT1A1*28 and UGT1A1*60 mutations in these individuals. Results High incidence and a significant correlation of UGT1A1 gene mutations with increased serum bilirubin level and lower grades of liver tissue inflammatory activity were observed in study participants. UGT1A1*28 and UGT1A1*60 mutations were strongly linked together. Two of the subjects presented very rare genotypes of UGT1A1 gene: (TA)(5/7) and c.-64G>C heterozygotes. Conclusions UGT1A1 gene polymorphism and as its consequence of high serum bilirubin level may promote iron accumulation in hemochromatosis patients by reducing the activity of inflammation. We proposed a possible mechanism of this interaction.

Gilbert syndrome

Az ismert familiáris, nem konjugált hyperbilirubinaemiák közé tartozó Gilbert-szindróma az átlagpopuláció 7–10%-át érintő benignus kórkép. Tünetei rendszerint aspecifikusak, egyedül az esetlegesen előforduló sárgaság, továbbá az enyhén emelkedett nem konjugált bilirubin szintje utal a rendellenességre. Más laborértékek és a májbiopszia általában nem mutat eltérést a normálistól. A betegség hátterében a legtöbb esetben az UDP-glükuronil-transzferáz gén részleges működészavara áll. A gén azt az enzimet kódolja, amely a bilirubin glükuronsavval való konjugációját segíti. Noha a Gilbert-szindróma diagnosztizálása korábban hagyományos laboratóriumi módszerekkel és családi anamnézis felvételével történt, napjainkban lehetőség van az UDP-glükuronil-transzferáz gén genetikai variánsainak meghatározására. A gén promoterrégiójában, homozigóta formában lévő (TA)-inszerció – (TA)7/(TA)7– a betegek 80–100%-ában jelen van, és az aktív UDP-glükuronil-transzferáz mennyiségének csökkenéséhez vezet. A kódolórégióban található missense mutációk szerepe még nem teljesen tisztázott, de a (TA)7promotervariánssal való együttes előfordulásuk magyarázatul szolgálhat az emelkedett bilirubinszintre és a sárgaságra, valamint a Gilbert-szindróma családi halmozódására.

Coexpression of gene polymorphisms involved in bilirubin production and metabolism

OBJECTIVE

The potential for genetically determined conditions to modulate the risk for developing neonatal hyperbilirubinemia is increasingly being recognized. The aims of this investigation were to (1) develop genotyping assays for an expanded panel of mutations and polymorphisms across 3 genes that are involved in bilirubin production and metabolism (glucose-6-phosphate dehydrogenase [G6PD], uridine diphosphate glucuronosyl transferase 1A1 [UGT1A1], and organic anion transporter polypeptide 1B1 [OATP1B1]) and (2) determine their allele frequencies in 450 anonymous DNA samples of US residents with ancestry from all of the major regions of the world.

METHODS

Genotyping assays were developed on the basis of allele-specific hybridization and melting peak analysis of the probe set and the match or mismatch template. Allele frequencies and the complexity of coinheritance of multiple genetic variants across G6PD, UGT1A1, and OATP1B1 genes in DNA samples from the DNA Polymorphism Discovery Resource of the National Human Genome Research Institute were determined by using this expanded panel.

RESULTS

Genetic polymorphisms of the UGT1A1 promoter, specifically the T-3279G phenobarbital responsive enhancer module and the (thymidine-adenine)(7) dinucleotide repeat TATAA box variants, were common. Similarly, OATP1B1 coding sequence gene variants were frequently observed. Moreover, in more than three quarters of the samples, >or=2 variants were detected, reflecting a high degree of polymorphism coexpression across these genes, including those who carried the African A(-) G6PD mutation.

CONCLUSIONS

We conclude that this expanded panel of mutations and polymorphisms can serve as an effective instrument to study the genetic architecture of hyperbilirubinemia and speculate an important role for genetic polymorphism coinheritance in determining hyperbilirubinemia risk in newborns.

Rare TA repeats in promoter TATA box of the UDP glucuronosyltranferase (UGT1A1) gene in Croatian subjects

BACKGROUND

Gilbert's syndrome is a chronic or recurrent mild unconjugated hyperbilirubinemia caused by decreased activity of UDP glucuronosyltranferase (UGT1A1). The most common cause of Gilbert's syndrome in Caucasians is homozygous variant of the A(TA)7TAA promoter polymorphism. Alleles with five or eight TA repeats have also been described, but they are very rare in Caucasian populations.

METHODS

Over a 6-year period (2001-2006), 1109 subjects with suspected Gilbert's syndrome were included in this study. Genotyping of (TA)6 and (TA)7 alleles was performed using high-resolution electrophoretic separation of amplified PCR products on Spreadex EL300 gels. In seven subjects, aberrant electrophoretic patterns were observed and additionally sequenced on an ABI Prism 310 Genetic Analyzer.

RESULTS

Genotype distributions for 1102 subjects with (TA)6 or (TA)7 alleles were as follows: 54.10%, 26.33% and 18.94% for the (TA)7/(TA)7, (TA)6/(TA)7 and (TA)6/(TA)6, respectively. Sequencing of seven samples that could not be identified as one of these alleles identified four subjects with the (TA)5/(TA)7, two with the (TA)7/(TA)8 and one with the (TA)6/(TA)8 genotype.

CONCLUSION

Genotyping of TA repeats in the promoter region of the UGT1A1 gene revealed the presence of rare alleles with five or eight TA repeats, with a very high frequency of the (TA)7 allele in subjects suspected of having Gilbert's syndrome.

Bilirubin in clinical practice: a review

Bilirubin is an endogenous compound that can be toxic under certain conditions but, on the other hand, mild unconjugated hyperbilirubinaemia might protect against cardiovascular diseases and tumour development. Serum bilirubin levels are often enhanced under a variety of clinical conditions. These are discussed and the mechanisms are outlined.

Comparison of three methods for genotyping the UGT1A1 (TA)n repeat polymorphism

OBJECTIVES

The UGT1A1 promoter contains a (TA)n repeat polymorphism. The 7 repeat allele is associated with decreased enzyme activity and patients homozygous for this allele treated with irinotecan may experience life-threatening toxicity. Here, we have compared three methods [DNA sequencing, fragment analysis, and the Invader assay (Third Wave Technologies)] for genotyping this polymorphism.

RESULTS

All of the DNA samples (n=119) had concordant genotype calls between the sequencing and size-based methods. The Invader method was also concordant if the genotypes were 6/6, 6/7, or 7/7. Both the size-based method and the Invader method had straightforward data analysis, while interpretation of the sequencing results was occasionally more challenging. The Invader method required more concentrated DNA for analysis, was more expensive, and had a limited genotyping spectrum.

CONCLUSION

All three methods were valuable for genotyping the UGT1A1 (TA)n repeat, with the sequencing and size-based assays having the fewest drawbacks.