Gilbert and Crigler Najjar syndromes: an update of the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene mutation database

Mechanisms and emerging strategies for irinotecan-induced diarrhea

Irinotecan (also known as CPT-11) is a topoisomerase I inhibitor first approved for clinical use as an anticancer agent in 1996. Over the past more than two decades, it has been widely used for combination regimens to treat various malignancies, especially in gastrointestinal and lung cancers. However, severe dose-limiting toxicities, especially gastrointestinal toxicity such as late-onset diarrhea, were frequently observed in irinotecan-based therapy, thus largely limiting the clinical application of this agent. Current knowledge regarding the pathogenesis of irinotecan-induced diarrhea is characterized by the complicated metabolism of irinotecan to its active metabolite SN-38 and inactive metabolite SN-38G. A series of enzymes and transporters were involved in these metabolic processes, including UGT1A1 and CYP3A4. Genetic polymorphisms of these metabolizing enzymes were significantly associated with the occurrence of irinotecan-induced diarrhea. Recent discoveries and progress made on the detailed mechanisms enable the identification of potential biomarkers for predicting diarrhea and as such guiding the proper patient selection with a better range of tolerant dosages. In this review, we introduce the metabolic process of irinotecan and describe the pathogenic mechanisms underlying irinotecan-induced diarrhea. Based on the mechanisms, we further outline the potential biomarkers for predicting the severity of diarrhea. Finally, based on the current experimental evidence in preclinical and clinical studies, we discuss and prospect the current and emerging strategies for the prevention of irinotecan-induced diarrhea.

Association of UGT1A1 gene variants, expression levels, and enzyme concentrations with 2,3,7,8-TCDD exposure in individuals exposed to Agent Orange/Dioxin

Among the congener of dioxin, 2,3,7,8-TCDD is the most toxic, having a serious long-term impact on the environment and human health. UDP-glucuronosyltransferase 1A1 (UGT1A1) plays a crucial role in the detoxification and excretion of endogenous and exogenous lipophilic compounds, primarily in the liver and gastrointestinal tract. This study aimed to investigate the association of UGT1A1 gene polymorphisms, expression levels, and enzyme concentration with Agent Orange/Dioxin exposure. The study included 100 individuals exposed to Agent Orange/Dioxin nearby Da Nang and Bien Hoa airports in Vietnam and 100 healthy controls. UGT1A1 SNP rs10929303, rs1042640 and rs8330 were determined by Sanger sequencing, mRNA expression was quantified by RT-qPCR and plasma UGT1A1 concentrations were measured by ELISA. The results showed that UGT1A1 polymorphisms at SNPs rs10929303, rs1042640 and rs8330 were associated with Agent Orange/Dioxin exposure (OR = 0.55, P = 0.018; OR = 0.55, P = 0.018 and OR = 0.57, P = 0.026, respectively). UGT1A1 mRNA expression levels and enzyme concentration were significantly elevated in individuals exposed to Agent Orange/Dioxin compared to controls (P < 0.0001). Benchmark dose (BMD) analyses showed that chronic exposure to 2,3,7,8-TCDD contamination affects the UGT1A1 mRNA and protein levels. Furthermore, UGT1A1 polymorphisms affected gene expression and enzyme concentrations in individuals exposed to Agent Orange/Dioxin. In conclusion, UGT1A1 gene polymorphisms, UGT1A gene expression levels and UGT1A1 enzyme concentrations were associated with Agent Orange/Dioxin exposure. The metabolism of 2,3,7,8-TCDD may influence UGT1A gene expression and enzyme concentrations.

Neuroprotective Roles of the Biliverdin Reductase-A/Bilirubin Axis in the Brain

Biliverdin reductase-A (BVRA) is a multi-functional enzyme with a multitude of important roles in physiologic redox homeostasis. Classically, BVRA is well known for converting the heme metabolite biliverdin to bilirubin, which is a potent antioxidant in both the periphery and the brain. However, BVRA additionally participates in many neuroprotective signaling cascades in the brain that preserve cognition. Here, we review the neuroprotective roles of BVRA and bilirubin in the brain, which together constitute a BVRA/bilirubin axis that influences healthy aging and cognitive function.

Case report: Crigler-Najjar syndrome type 1 in Croatia-more than a one in a million: a case series

Crigler-Najjar syndrome (CNS) is an exceedingly rare autosomal recessive disease with an estimated incidence of 1 in a million live births. CNS type 1 (CNS1) is the most severe form, characterized by severe unconjugated hyperbilirubinemia since birth due to the absence of hepatic uridine 5'-diphosphate glucuronyltransferase (UGT1A1) activity. Daily phototherapy (PT) and liver transplant (LT) are the mainstays of therapy. Here, we present a higher-than-expected incidence of CNS1 in Croatia (6,1 in a million). In the last 31 years, we treated eight CNS1 patients from five families with no reported consanguinity. Four patients are descendants of an isolated enclave in Kosovo with a small gene pool and a high potential for inbreeding. Severe unconjugated hyperbilirubinemia was verified in a neonatal period and PT was initiated. Four patients underwent LT from living-related donors. One of them had unsuccessful hepatocyte transplantation earlier. LT was successful in three patients, and one patient died due to primary graft dysfunction. Four patients are currently treated with 9-12 h daily PT with inconsistent disease control, and gradually increasing bilirubin. One patient developed kernicterus before LT, while others have normal psychomotor development and no neurologic impairment. Genetic testing of the UGT1A1 gene in six patients from three families revealed three different homozygous mutations (c.722_723 delAG, c.717_718 delAG, and c.1021 C >T), all previously described in other populations. There is a possibility of the founder effect as an explanation for the higher incidence of CNS1 in at least a subgroup of Croatians.

Free Bilirubin Induces Neuro-Inflammation in an Induced Pluripotent Stem Cell-Derived Cortical Organoid Model of Crigler-Najjar Syndrome

Bilirubin-induced neurological damage (BIND), which might progress to kernicterus, occurs as a consequence of defects in the bilirubin conjugation machinery, thus enabling albumin-unbound free bilirubin (BF) to cross the blood-brain barrier and accumulate within. A defect in the UGT1A1 enzyme-encoding gene, which is directly responsible for bilirubin conjugation, can cause Crigler-Najjar syndrome (CNS) and Gilbert's syndrome. We used human-induced pluripotent stem cell (hiPSC)-derived 3D brain organoids to model BIND in vitro and unveil the molecular basis of the detrimental effects of BF in the developing human brain. Healthy and patient-derived iPSCs were differentiated into day-20 brain organoids, and then stimulated with 200 nM BF. Analyses at 24 and 72 h post-treatment point to BF-induced neuro-inflammation in both cell lines. Transcriptome, associated KEGG, and Gene Ontology analyses unveiled the activation of distinct inflammatory pathways, such as cytokine-cytokine receptor interaction, MAPK signaling, and NFκB activation. Furthermore, the mRNA expression and secretome analysis confirmed an upregulation of pro-inflammatory cytokines such as IL-6 and IL-8 upon BF stimulation. This novel study has provided insights into how a human iPSC-derived 3D brain organoid model can serve as a prospective platform for studying the etiology of BIND kernicterus.

A Rare Case of Primary Sjogren's Syndrome Coexisting With Gilbert Syndrome

Gilbert syndrome (GS) is an autosomal recessive inherited bilirubin metabolism disorder characterized by chronic unconjugated hyperbilirubinemia in the absence of hemolysis and liver disease. Primary Sjogren's syndrome (pSS), mainly occurring in women, is a common connective tissue disease (CTD) wherein bilirubin levels are generally reduced. We report a rare case of pSS coexisting with GS. A 35-year-old female patient presented to our hospital with pSS and chronic unconjugated hyperbilirubinemia, for which low-dose methylprednisolone was ineffective. The patient's liver function test results were normal, serological tests for hepatitis virus were negative, and abdominal ultrasound did not indicate abnormal liver morphology. Bone mineral density determination showed that the Z scores of the left femoral neck and lumbar spine were -1.9 and -2.6, respectively, with T scores of -2.1 and -2.8, respectively. Full-exon sequencing revealed a homozygous TA insertion in the TATA box (A(TA)7TAA) and a heterozygous base substitution from C to A at nucleotide position 686 in exon 1 (c.686C>A) in the uridine glucuronosyltransferase 1A1 (UGT1A1) gene. Therefore, the patient was diagnosed with pSS, GS, and osteoporosis. The dose of methylprednisolone was then reduced and gradually stopped, and treatment for osteoporosis was strengthened. To our knowledge, this is the first report of pSS with GS. It is important to clarify the cause of hyperbilirubinemia in patients with CTD, including pSS, which affects the formulation of correct treatment plans.

Mild Crigler-Najjar Syndrome with Progressive Liver Disease-A Multicenter Retrospective Cohort Study

Crigler-Najjar Syndrome (CNS) with residual activity of UDP-glucuronosyltransferase 1A1 (UGT1A1) and no need for daily phototherapy is called mild Crigler-Najjar Syndrome. Most of these patients need medical treatment for enzyme induction (phenobarbital) to lower blood levels of unconjugated bilirubin (UCB). Apart from this, no long-term problems have been described so far. The phenotype of patients with the homozygous pathogenic variant c.115C>G p.(His39Asp) in UGT1A1 is described as variable. Clinical observations of our patients led to the assumption that patients with variant c.115C>G have a mild CNS phenotype while having a high risk of developing progressive liver disease. For mild CNS disease, progressive liver disease has not been described so far. Therefore, we conducted a retrospective multicenter analysis of 14 patients with this particular variant, aiming for better characterization of this variant. We could confirm that patients with variant c.115C>G have a high risk of progressive liver disease (seven of fourteen), which increases with age despite having a very mild CNS phenotype. Earlier predictors and causes for an unfavorable disease course are not detectable, but close follow-up could identify patients with progressive liver disease at the beginning. In conclusion, these patients need close and specialized follow-up. Our study questions whether fibrosis in the CNS is really driven by high amounts of UCB or phototherapy.

Petukhov P, Kurilova OV, Ilinsky VV, Trakhtman PE, Dadali EL, Samokhodskaya LM, Kamalov AA, Kost OA. Blood ACE Phenotyping for Personalized Medicine: Revelation of Patients with Conformationally Altered ACE

Background: The angiotensin-converting enzyme (ACE) metabolizes a number of important peptides participating in blood pressure regulation and vascular remodeling. Elevated blood ACE is a marker for granulomatous diseases and elevated ACE expression in tissues is associated with increased risk of cardiovascular diseases. Objective and Methodology: We applied a novel approach -ACE phenotyping-to find a reason for conformationally impaired ACE in the blood of one particular donor. Similar conformationally altered ACEs were detected previously in 2-4% of the healthy population and in up to 20% of patients with uremia, and were characterized by significant increase in the rate of angiotensin I hydrolysis. Principal findings: This donor has (1) significantly increased level of endogenous ACE inhibitor in plasma with MW less than 1000; (2) increased activity toward angiotensin I; (3) M71V mutation in ABCG2 (membrane transporter for more than 200 compounds, including bilirubin). We hypothesize that this patient may also have the decreased level of free bilirubin in plasma, which normally binds to the N domain of ACE. Analysis of the local conformation of ACE in plasma of patients with Gilbert and Crigler-Najjar syndromes allowed us to speculate that binding of mAbs 1G12 and 6A12 to plasma ACE could be a natural sensor for estimation of free bilirubin level in plasma. Totally, 235 human plasma/sera samples were screened for conformational changes in soluble ACE. Conclusions/Significance: ACE phenotyping of plasma samples allows us to identify individuals with conformationally altered ACE. This type of screening has clinical significance because this conformationally altered ACE could not only result in the enhancement of the level of angiotensin II but could also serve as an indicator of free bilirubin levels.

UGT1A1 variants in Chinese Uighur and Han newborns and its correlation with neonatal hyperbilirubinemia

To explore the correlation between UGT1A1 variant and neonatal hyperbilirubinemia in Chinese Uighur and Han populations. We conducted this study in Urumqi, China. Umbilical cord blood specimens and clinical information of term infants born in the studied center were collected. Variation status of UGT1A1 was determined by direct sequencing or capillary electrophoresis analysis. 102 Uighur and 99 Han normal term neonates, together with 19 hospitalized term newborns (10 Uighur and 9 Han) due to significant hyperbilirubinemia were enrolled into the final analysis. The incidence of neonates with high-risk transcutaneous bilirubin level (TCB) were much higher in Han newborns than in Uighur newborns(P = 0.01). Also, there was statistically significant difference in (TA) 7 promoter mutation of UGT1A1 between Han and Uighur group(χ2 = 4.675, P = 0.03). Furthermore, exon mutation (c.211 and /or c.1091) in UGT1A1 gene was significantly associated with increased TCB level (ORadj = 1.41, 95%CI: 0.25-2.51, P = 0.002) and higher risk of hyperbilirubinemia in both Han and Uighur infants after adjusted for covariates (ORadj = 2.21, 95%CI: 1.09-4.49, P = 0.03). In conclusion, UGT1A1 promoter polymorphism seem to be an important genetic modulator of plasma bilirubin level and neonatal hyperbilirubinemia risk within ethnic groups. Genetic assessment of UGT1A1 coding variants may be useful for clinical diagnosis of neonatal jaundice.

Bilirubin-Induced Neurological Damage: Current and Emerging iPSC-Derived Brain Organoid Models

Bilirubin-induced neurological damage (BIND) has been a subject of studies for decades, yet the molecular mechanisms at the core of this damage remain largely unknown. Throughout the years, many in vivo chronic bilirubin encephalopathy models, such as the Gunn rat and transgenic mice, have further elucidated the molecular basis of bilirubin neurotoxicity as well as the correlations between high levels of unconjugated bilirubin (UCB) and brain damage. Regardless of being invaluable, these models cannot accurately recapitulate the human brain and liver system; therefore, establishing a physiologically recapitulating in vitro model has become a prerequisite to unveil the breadth of complexities that accompany the detrimental effects of UCB on the liver and developing human brain. Stem-cell-derived 3D brain organoid models offer a promising platform as they bear more resemblance to the human brain system compared to existing models. This review provides an explicit picture of the current state of the art, advancements, and challenges faced by the various models as well as the possibilities of using stem-cell-derived 3D organoids as an efficient tool to be included in research, drug screening, and therapeutic strategies for future clinical applications.

Messenger RNA as a personalized therapy: The moment of truth for rare metabolic diseases

Inborn errors of metabolism (IEM) encompass a group of monogenic diseases affecting both pediatric and adult populations and currently lack effective treatments. Some IEM such as familial hypercholesterolemia or X-linked protoporphyria are caused by gain of function mutations, while others are characterized by an impaired protein function, causing a metabolic pathway blockage. Pathophysiology classification includes intoxication, storage and energy-related metabolic disorders. Factors specific to each disease trigger acute metabolic decompensations. IEM require prompt and effective care, since therapeutic delay has been associated with the development of fatal events including severe metabolic acidosis, hyperammonemia, cerebral edema, and death. Rapid expression of therapeutic proteins can be achieved hours after the administration of messenger RNAs (mRNA), representing an etiological solution for acute decompensations. mRNA-based therapy relies on modified RNAs with enhanced stability and translatability into therapeutic proteins. The proteins produced in the ribosomes can be targeted to specific intracellular compartments, the cell membrane, or be secreted. Non-immunogenic lipid nanoparticle formulations have been optimized to prevent RNA degradation and to allow safe repetitive administrations depending on the disease physiopathology and clinical status of the patients, thus, mRNA could be also an effective chronic treatment for IEM. Given that the liver plays a key role in most of metabolic pathways or can be used as bioreactor for excretable proteins, this review focuses on the preclinical and clinical evidence that supports the implementation of mRNA technology as a promising personalized strategy for liver metabolic disorders such as acute intermittent porphyria, ornithine transcarbamylase deficiency or glycogen storage disease.

Perioperative Management of Patient with Esophageal Carcinoma and Crigler-Najjar Syndrome Type 2: A Case Report

Background

Crigler-Najjar syndrome type 2 (CNS-II) is a rare genetic disease that is associated with a lack of uridine diphosphate-glucuronosyltransferase. Esophageal carcinoma is the sixth most common cause of cancer-related death worldwide, for which surgery is the most effective treatment. Reports on patients with both conditions requiring surgery are limited and The impact of hyperbilirubinemia caused by CNS-II on the perioperative period is unknown. Previous studies have found that patients with Crigler-Najjar syndrome have an increased risk of gallstones and related complications, which also poses corresponding challenges to the treatment. Herein, we present a patient with CNS-II who underwent successful thoracoscopic surgery for esophageal carcinoma.

Case summary

A 65-year-old male presented to our hospital with a choking sensation after eating. A physical examination showed yellowing of the sclera and skin. The patient manifested persistent jaundice since birth and had visited many hospitals, but the cause remained undiagnosed. We performed genetic testing, which confirmed CNS-II. Gastroscopy indicated esophageal carcinoma. A multidisciplinary team discussion was carried out to determine the appropriate treatment and perioperative management for this patient. The results show that surgical resection was the most appropriate approach. Finally, the patient underwent thoracoscopic surgery for esophageal carcinoma without complications.

Conclusion

Esophageal carcinoma in patients with Crigler-Najjar syndrome is a rare case, and perioperative management is key in the treatment process. It is necessary to pay close attention to the changes of the disease to prevent complications.

Genetic testing of UGT1A1 in the diagnosis of Gilbert syndrome: The discovery of seven novel variants in the Chinese population

BACKGROUND

Genetic testing of UGT1A1 was used to facilitate the diagnosis of Gilbert syndrome, and analyze the distribution features of pathogenic variants in the Chinese population.

METHODS

DNA was extracted from whole blood samples of patients with unconjugated hyperbilirubinemia, and sequencing of the UGT1A1 gene was performed after PCR amplification. After alignment with reference sequences, the known pathogenic variants were identified, the variant spectrum was analyzed, and the pathogenicity of novel variants was predicted using online mutation prediction tools.

RESULTS

A total of 117 patients were confirmed with Gilbert syndrome by UGT1A1 genetic diagnosis, where the most common pathogenic variants included promoter A(TA)₇ TAA insertion and p.Gly71Arg missense variant. Following novel variants were also identified: p.Ala61Gly, p.Tyr67Phe, p.Leu166Alafs*16, p.Arg240Lys, p.Ser306Phe, p.Arg341Gln, and p.Glu424* variants.

CONCLUSIONS

Genetic testing of UGT1A1 in clinical practices could facilitate confirming Gilbert syndrome and performing differential diagnosis. The pathogenic variant spectrum in the Chinese population was similar to other Asian populations. The novel pathogenic variants identified in this study require further investigation.

Effect of the genetic mutant G71R in uridine diphosphate-glucuronosyltransferase 1A1 on the conjugation of bilirubin

We aimed to investigate the effect of the genetic mutant G71R (c. 211G > A) in uridine diphosphate (UDP)-glucuronosyltransferase 1A1 (UGT1A1) on the glucuronidation of unconjugated bilirubin. The UGT1A1 wild-type and mutant G71R gene sequences were inserted into the lentiviral vector GV358 plasmid and then transfected into COS-7 cells. Real-time polymerase chain reaction and western blot analyses were used to determine mRNA and protein expression levels of UGT1A1, respectively. High-performance liquid chromatography was used to quantitate the levels of conjugated bilirubin. The results showed no significant difference in the mRNA and protein expression levels between the UGT1A1 wild-type and G71R homozygous and heterozygous mutants. The level of conjugated bilirubin reached a maximum in wild-type UGT1A1-transfected COS-7 cells. However, relative to the UGT1A1 wild-type, conjugated bilirubin concentrations were 71 and 22% with G71R heterozygous- and G71R homozygous-transfected COS-7 cells, respectively. In conclusion, we successfully established in vitro cell models of the UGT1A1 wild-type and the G71R homozygous and heterozygous mutants using a lentiviral vector. Furthermore, the catalytic activity for unconjugated bilirubin was lower in the mutant G71R than the UGT1A1 wild-type enzyme, and a weaker effect was observed in the homozygote.

Dependence of blood biochemical parameters on various genotypes of the UGT1A1 gene associated with gilbert's syndrome

Diagnosis of Gilbert's syndrome is based on the detection of homozygous carriage of an additional TA-repeat in the promoter of the UGT1A1 gene, leading to a decrease in the activity of the UGT enzyme. No large studies have been done in the Russian Federation on the prevalence of carriage of Gilbert's syndrome, as well as the biochemical and molecular profile of such patients. The aim of the study is to evaluate biochemical and molecular genetic parameters in patients with Gilbert's syndrome in Russia. The study included 124 healthy volunteers (group 1) and 5650 patients with suspected Gilbert's syndrome (group 2). The number of TA-repeats of the promoter region of the UGT1A1 gene was determined by the method of fragment analysis for all participants. The following biochemical parameters were analyzed for 299 patients from group 2: the level of bilirubin and its fractions, AST, ALT, cholesterol and LDL. In group 1 the prevalence of genotype (TA)6/(TA)6 was 39,52%, (TA)6/(TA)7 - 53,23%, (TA)7/(TA)7 - 7,26%, no rare forms were found. In group 2 the prevalence of genotype (TA)6/(TA)6 was 6,04%, (TA)6/(TA)7 - 20,05%, (TA)7/(TA)7 - 73,7%, rare alleles - 0,2%. Rare alleles included (TA)5/(TA)6, (TA)5/(TA)7, (TA)6/(TA)8 and (TA)7/(TA)8, as well as a new genotype not described in the literature previously - (TA)7/(TA)9. When assessing the level of total bilirubin and its fractions, a difference was revealed between the genotype of Gilbert's syndrome (TA)7/(TA)7 and the reference genotype (TA)6/(TA)6, and between genotypes (TA)7/(TA)7 and (TA)6/(TA)7. A significant increase in total bilirubin was demonstrated in carriers of a larger number of TA-repeats. There was no significant difference in the concentration of ALT, AST, cholesterol or LDL between different genotypes.The number of TA-repeats of the UGT1A1 gene affects the increase of total bilirubin and its indirect fraction, including the cases of rare allelic variants (TA≤5, TA≥8), but not the activity of ALT and AST and the lipid profile.

Study single nucleotide polymorphism in Promoter region of UGT1A1 Gene in Iraqi Patients with Gilbert's syndrome

This study aimed to detect genetic variants of the UGT1A1 gene in patients with Gilbert's syndrome. To detect this, primers were designed; PCR and direct sequencing were done for the promoter area of the gene as a diagnostic tool for the detection of any polymorphism. Variation and polymorphism were detected within the promoter mutants of the UDP glycosyltransferase _UGT1A1 gene that causes hyperbilirubinemia in a group of Iraqi patients compared with a group of the normal healthy individual as controls. The patients with hyperbilirubinemia in this study were 30 in which the total bilirubin level was more than 12 mg/dl serum; they included 25 males and 5 females, while the control group consisted of 20 healthy individuals. This study was carried out from September 2019 till April 2021. The result displayed high occurrence of Gilbert syndrome within male patients than in females, and regarding the analyses of mutation of bilirubin UDP glycosyltransferase _UGT1A1 gene, it is clear that the genotypic distribution of variation among the hyperbilirubinemia patients included all 30 patients, while SNP was detected in 18 patients out of 30 which indicate that the UGT1A1 gene mutation was a likely risk factor for the development of hyperbilirubinemia related Gilbert syndrome in Iraq. The homozygous and heterozygous polymorphisms A/G inside the promoter region of the UGT1A1 gene were effectively identified by sequencing. Our finding suggests that TA repeats and allele of UGT1A1 polymorphism A/G are associated with Gilbert's syndrome and act as genetic markers of this disease in Iraqi patients. To analyze data and sequence variation in gene, generous software was used after amplifying the gene. All processes include DNA extraction, PCR amplification, sequencing, and assembly.

UGT1A1 mutation association with increased bilirubin levels and severity of unconjugated hyperbilirubinemia in ABO incompatible newborns of China

BACKGROUND

Neonatal hyperbilirubinemia causing jaundice is common in East Asian population. Uridine diphosphate glucuronosyltransferase isoenzyme (UGT1A1) glucuronidates bilirubin and converts the toxic form of bilirubin to its nontoxic form.

METHOD

A retrospective study was conducted to review clinical information of ABO hemolysis neonates (ABO HDN) admitted to the Department of Neonatology, referred for neonatal hyperbilirubinemia, in a large general hospital of southern China from 2011 to 2017. Variation status of UGT1A1 was determined by direct sequencing or genotype assays.

RESULT

Sixty-nine ABO HDNs were included into the final analysis. UGT1A1 c.211 G > A mutation (UGT1A1*6, p.Arg71Gly, rs4148323) was significantly associated with the increased bilirubin level in ABO HDNs, after adjusted by age, sex and feeding method (P = 0.019 for TBIL, P = 0.02 for IBIL). Moreover, heterozygous and/or homozygous UGT1A1 mutations in the coding sequence region were significantly associated with the increased risk of developing hazardous hyperbilirubinemia (as defined by TSB > 427 umol/L) as compared those with a normal UGT1A1 genotype (OR_adj = 9.16, 95%CI 1.99-42.08, P = 0.002) in the study cohort.

CONCLUSION

UGT1A1 variant in coding region is actively involved in the pathogenesis of ABO hemolysis related neonatal hyperbilirubinemia. Genetic assessment of UGT1A1 may be useful for clinical diagnosis of neonatal unconjugated hyperbilirubinemia.

Novel mutations in Uridyl-diphosphate-glucuronosyl-transferase 1A1 (UGT1A1) gene in Tunisian patients with unconjugated hyperbilirubinemia

INTRODUCTION

Unconjugated hyperbilirubinemia (UCB) is a feature of Gilbert's syndrome (GS) and Crigler-Najjar's syndrome (CNS), which are two hereditary defects in bilirubin metabolism. Both syndromes are linked to mutations in the UGT1A1 gene, which cause either the decrease or the absence of the UGT1A1 enzymatic activity. Here, we investigated the molecular basis of the UGT1A1 gene in Tunisian patients presenting with unconjugated hyperbilirubinemia.

METHODS

Twenty-four patients with UCB were investigated. The screening protocol for hemoglobinopathies, enzymopathies, and membrane defects was executed in all patients. Afterward, the molecular analysis of the entire UGT1A1 gene was performed by DNA Sanger sequencing. Several bioinformatic tools were used to explore the effects of novel mutations.

RESULTS

Fifteen different UGT1A1 variations were identified, among which four are described here for the first time. In exon 5, the c.1412C > G; p.(Ala471Gly) and c.1589C > T; p.(Ser530Phe) mutations were detected in patients presenting with CNS type I and GS, respectively. In the 3'UTR region of UGT1A1, the c.*90C > T mutation was detected in 3 patients with CNS type I. In the same region, the c.*388C > T defect was found in a GS patient. A deleterious and damaging effect on the UGT1A1 protein were predicted for both exonic mutations. Furthermore, novel microRNAs were identified as targetting the mutated sequences for the 3'UTR mutations.

CONCLUSION

Our study provides novel data on UCB among Tunisians. Furthermore, we report four novel mutations associated with both GS and CNS. The identification of these mutations increases the spectrum of the UGT1A1 mutations and contributes to an understanding of the molecular abnormalities associated with unconjugated hyperbilirubinemia.

Gilbert syndrome with systemic lupus erythematosus presenting with persistent unconjugated hyperbilirubinemia: A case report

Gilbert syndrome (GS) is a hereditary unconjugated hyperbilirubinemia that results from mutations in the bilirubin uridine diphosphate-glucuronosyltransferase (UGT1A1) gene. To the best of our knowledge, there are currently no reports that focus on patients with systemic lupus erythematosus (SLE) coexisting with GS. The present study aimed to evaluate the clinical characteristics and genotype of UGT1A1 in a Chinese patient with SLE and GS. Complete medical records and laboratory data were reviewed for a patient with SLE referred to Ruijin Hospital (Shanghai, China) for treatment between March 2016 and January 2020. Genetic analysis of the UGT1A1 gene was performed by PCR amplification and Sanger sequencing. The serum total bilirubin and unconjugated bilirubin concentrations on admission were 96.2 and 86.8 µmol/l, respectively. The homozygous mutation c.1456T>G (p.Y486D) in exon 5 was detected in this patient. The patient had a good response to phenobarbital orally at a dose of 30 mg/day and a decrease in serum bilirubin was observed. Elevated unconjugated hyperbilirubinemia in SLE needs to be differentiated from other diseases, such as GS, which can be diagnosed by UGT1A1 genetic sequencing.

Isolated Elevated Bilirubin

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Establishment of the experimental procedure for prediction of conjugation capacity in mutant UGT1A1

UDP-glucuronosyltransferase 1A1 (UGT1A1) is an enzyme that is found in the endoplasmic reticulum membrane and can reportedly have a large number of amino acid substitutions that result in the reduction of glucuronidation capacity. For example, adverse drug reactions when patients receive CPT-11 (irinotecan) such as in cancer chemotherapy are caused by amino acid substitutions in UGT1A1. We previously found that the extent of the docking when the hydroxyl residue of bilirubin was oriented toward UDP-glucuronic acid correlated with in vitro conjugation capacity. In this study, we analyzed the conformation of mutant UGT1A1s by means of structural optimization with water and lipid bilayers instead of the optimization in vacuo that we used in our previous study. We then derived a mathematical model that can predict the conjugation capacities of mutant UGT1A1s by using results of substrate docking in silico and results of in vitro analysis of glucuronidation of acetaminophen and 17β-estradiol by UGT1A1s. This experimental procedure showed that the in silico conjugation capacities of other mutant UGT1A1s with bilirubin or SN-38 were similar to reported in vitro conjugation capacities. Our results suggest that this experimental procedure described herein can correctly predict the conjugation capacities of mutant UGT1A1s and any substrate.

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.

Coupling AAV-mediated promoterless gene targeting to SaCas9 nuclease to efficiently correct liver metabolic diseases

Non-integrative AAV-mediated gene therapy in the liver is effective in adult patients, but faces limitations in pediatric settings due to episomal DNA loss during hepatocyte proliferation. Gene targeting is a promising approach by permanently modifying the genome. We previously rescued neonatal lethality in Crigler-Najjar mice by inserting a promoterless human uridine glucuronosyl transferase A1 (UGT1A1) cDNA in exon 14 of the albumin gene, without the use of nucleases. To increase recombination rate and therapeutic efficacy, here we used CRISPR/SaCas9. Neonatal mice were transduced with two AAVs: one expressing the SaCas9 and sgRNA, and one containing a promoterless cDNA flanked by albumin homology regions. Targeting efficiency increased ~26-fold with an eGFP reporter cDNA, reaching up to 24% of eGFP-positive hepatocytes. Next, we fully corrected the diseased phenotype of Crigler-Najjar mice by targeting the hUGT1A1 cDNA. Treated mice had normal plasma bilirubin up to 10 months after administration, hUGT1A1 protein levels were ~6-fold higher than in WT liver, with a 90-fold increase in recombination rate. Liver histology, inflammatory markers, and plasma albumin were normal in treated mice, with no off-targets in predicted sites. Thus, the improved efficacy and reassuring safety profile support the potential application of the proposed approach to other liver diseases.

UGT1A1 genotypes and unconjugated hyperbilirubinemia phenotypes in post-neonatal Chinese children: A retrospective analysis and quantitative correlation

To retrospectively analyze and quantitatively correlate UGT1A1 (bilirubin UDP- glucuronosyltransferase gene) genotypes and unconjugated hyperbilirubinemia (UCH) phenotypes among Chinese children.We retrospectively reviewed UCH patients, quantitatively analyzed genotype-phenotype correlation by comparing with healthy controls. Pfam database, SWISS-model, and Pymol were used for UGT1A1 protein domain analysis and protein modeling for assessing the effect of novel missense variants on protein structure.Seventy four cases, including 21 prolonged unconjugated hyperbilirubinemia (PUCH), 30 Gilbert syndrome (GS), 22 Crigler-Najjar syndrome type II (CNS-II), and 1 Crigler-Najjar syndrome type I (CNS-I) phenotypes were analyzed. Total of 21 variants, including 7 novel variants (c.764T>A/p.L255Q, c.1112C>T/p.T371I, c.1028C>A/p.S343X, c.1047delG/p.I350YfsX16, c.996 + 5G>C/g.6923G>C, c.287G>A/p.G96E, and c.1142G>A/p.S381N) were found. In the multiple regression model, heterozygous A(TA)7TAA, G71R/P364L, and Y486D/other mutations were significantly associated with increased risk of GS, PUCH, and CNS-II, respectively. Total allele number is significantly associated with GS and CNS-II, with each increase in total allele number, the odds ratio (OR) of having GS and CNS-II increased by 1.46 and 4.47 fold, respectively. Having only functional polymorphisms in UGT1A1 gene is associated with increased risk of PUCH, and GS with OR values of 5.67 (95% CI: 1.52-21.13), and 3.88 (95% CI: 1.02-14.78), respectively. Having only mutation is associated with significantly increased risk of having GS phenotype (OR: 34.00, 95% CI: 4.65-248.37), but not CNS-II. Polymorphism plus mutation had the strongest association with CNS-II with OR value of 64.80 (95% CI: 7.68-546.41), followed by GS (OR: 4.53, 95% CI: 1.08-19.08).We detected 7 novel variants, and quantitatively calculated risks of having specific phenotypes using genetic data. Among Chinese children, G71R and P364L is independently associated with PUCH, A(TA)7TAA is associated with GS, and Y486D or other disease-causing mutations were associated with CNS-II. Multiple alleles were associated with more severe phenotypes. Combined variant of G71R+Y486D is a common occurrence among Chinese children with UCH.

Case report: multiple UGT1A1 gene variants in a patient with Crigler-Najjar syndrome

BACKGROUND

Inherited unconjugated hyperbilirubinemia is caused by variants in the gene UGT1A1 leading to Gilbert's syndrome and Crigler-Najjar syndrome types I and II. These syndromes are differentiated on the basis of UGT1A1 residual enzymatic activity and its affected bilirubin levels and responsiveness to phenobarbital treatment.

CASE PRESENTATION

In this report, we present a boy with Crigler-Najjar syndrome type II with high unconjugated bilirubin levels that decreased after phenobarbital treatment but increased in adolescence. Four different UGT1A1 gene variants have been identified for this patient, of which one is novel (g.11895_11898del) most likely confirming diagnose molecularly.

CONCLUSIONS

The presented case highlights the challenges encountered with the interpretation of molecular data upon identification of multiple variants in one gene that are causing different degree reducing effect on enzyme activity leading to several clinical conditions.

Liver Cirrhosis in a Patient with Crigler Najjar Syndrome

INTRODUCTION

Crigler Najjar (CN) disease is a genetic disorder which results in increased unconjugated bilirubin level. Liver parenchyma was previously considered structurally normal. Recent reports describe significant fibrosis in the liver parenchyma of patients with CN syndrome.

CASE REPORT

We present a patient with persistent unconjugated hyperbilirubinemia, clinically diagnosed as CN-2, with a UGT1 A1 p. H39D (c.115C > G) (His → Asp) mutation. She required hepatic transplantation at the age of 17.5 years for biliary cirrhosis. Explanted liver histopathology revealed regenerative cirrhotic nodules with dilated bile ducts filled with bile plugs.

CONCLUSION

CN can develop significant hepatic fibrosis/cirrhosis requiring liver transplantation.

Promoterless gene targeting without nucleases rescues lethality of a Crigler-Najjar syndrome mouse model

Crigler‐Najjar syndrome type I (CNSI) is a rare monogenic disease characterized by severe neonatal unconjugated hyperbilirubinemia with a lifelong risk of neurological damage and death. Liver transplantation is the only curative option, which has several limitations and risks. We applied an in vivo gene targeting approach based on the insertion, without the use of nucleases, of a promoterless therapeutic cDNA into the albumin locus of a mouse model reproducing all major features of CNSI. Neonatal transduction with the donor vector resulted in the complete rescue from neonatal lethality, with a therapeutic reduction in plasma bilirubin lasting for at least 12 months, the latest time point analyzed. Mutant mice, which expressed about 5–6% of WT Ugt1a1 levels, showed normal liver histology and motor‐coordination abilities, suggesting no functional liver or brain abnormalities. These results proved that the promoterless gene therapy is applicable for CNSI, providing therapeutic levels of an intracellular ER membrane‐bound enzyme responsible for a lethal liver metabolic disease.

Uridine 5'-diphospho-glucronosyltrasferase: Its role in pharmacogenomics and human disease

Biotransformation is an enzyme-catalyzed process in which the body converts endogenous compounds, xenobiotics and toxic substances into harmless or easily excreted metabolites. The biotransformation reactions are classified as phase I and II reactions. Uridine 5'-diphospho (UDP)-glucuronosyltransferases (UGTs) are a superfamily of phase II enzymes which have roles in the conjugation of xenobiotics or endogenous compounds, including drugs and bilirubin, with glucuronic acid to make them easier to excrete. The method the human body uses to achieve glucuronidation may be affected by a large interindividual variation due to changes in the sequences of the genes encoding these enzymes. In the last five years, the study of the genetic variants of the UGTs at a molecular level has become important due to its association with several diseases and the ability to predict adverse events due to drug metabolism. In the present review, the structure and the prominent genetic variants of the UGT1A subfamily and their metabolic and clinical implications are described.

Hepatic Parenchymal Injury in Crigler-Najjar Type I

BACKGROUND

Crigler-Najjar syndrome type I (CNI) arises from biallelic variants of UGT1A1 that abrogate uridine diphosphate glucuronosyltransferase (UGT1A1) activity resulting in unconjugated hyperbilirubinemia. Historically, liver parenchyma in CNI was considered structurally and histologically normal. Recent review of CNI liver explants revealed fibrosis. Our aim was to investigate the association between hepatic histology and disease phenotype in CNI.

METHODS

We extracted data from the medical record at the time of liver transplant from 22 patients with CNI at the Children's Hospital of Pittsburgh, and reviewed explant histology. Continuous data were normally distributed, are presented as mean (±1 SD), and analyzed using two-tailed Student t-test. Categorical data were analyzed using the Chi-square test.

RESULTS

Both alanine transaminase (ALT; mean 87.4 IU/L) and aspartate transaminase (AST; mean 54.6 IU/L) were elevated. Nine (41%) of 22 explants had significant fibrosis. Pericentral (n = 5), periportal (n = 2), and mixed (n = 2) patterns of fibrosis occurred. A significant difference in mean age of subjects with fibrotic versus non-fibrotic livers (16.1 years vs 10.5 years; P = 0.02) was seen. There were no indices of synthetic liver dysfunction or portal hypertension. Neither a history of gallstone disease nor excess weight appeared to contribute to the development of fibrosis.

CONCLUSIONS

For the first time, we report a 41% prevalence of clinically silent, yet histologically significant fibrosis among subjects with Crigler-Najjar type 1. Risk for fibrosis appears to accrue with time, indicating that earlier intervention may be prudent whenever considering alternative treatments such as hepatocyte transplant, auxiliary liver transplant, or viral gene therapy.

Clinical UGT1A1 Genetic Analysis in Pediatric Patients: Experience of a Reference Laboratory

BACKGROUND

Neonatal hyperbilirubinemia can be severe or prolonged and warrant exploration into the underlying etiology, which may include genetic assessment of UGT1A1 for inherited disorders (i.e. Crigler-Najjar syndrome or Gilbert syndrome).

METHODS

In our reference laboratory, we performed UGT1A1 gene sequencing analysis on 346 pediatric patients referred for a clinical indication of hyperbilirubinemia.

RESULTS

Males (n = 241) had significantly higher mean total bilirubin concentration compared to females (n = 105) (9.7 and 7.3 mg/dL, respectively, p = 0.042); however, no sex-based difference was observed in frequency of known or suspected reduced function UGT1A1 variants. The presence of two UGT1A1 variants (consistent with Gilbert or Crigler-Najjar syndrome) occurred less frequently in neonates (aged ≤28 days) than older children (aged 1-18 years) (31.3% in neonates vs. 85.1%, p < 0.0001), and among neonates there was no significant difference in mean total bilirubin between those with two UGT1A1 variants and those without (p = 0.47). Three novel variants, including c.337T>G (p.Y113D), c.1037C>A (p.A346E), and c.1469A>C (p.D490A) were identified. Among older children, the most common reason for referral was Gilbert syndrome (83.8%) and UGT1A1 genetic analysis confirmed a diagnosis of Gilbert syndrome in 79.0% of those children.

CONCLUSIONS

Among neonates, a population in which hyperbilirubinemia is common and often of multifactorial etiology, UGT1A1 genetic testing served as a useful clinical tool in ruling in or ruling out inherited hyperbilirubinemia. Here we describe our experience as a reference laboratory in clinical UGT1A1 full gene sequencing. Our results highlight the challenges in predicting the contribution of genetic variation in UGT1A1 to hyperbilirubinemia based on clinical parameters alone, particularly in neonates, and the utility of UGT1A1 full gene sequencing in the evaluation of neonatal and pediatric hyperbilirubinemia.

Genetic polymorphisms of UGT1A1 and susceptibility to anti-tuberculosis drug-induced liver: A RUCAM-based case–control study

Uridine 5’-diphospho-glucuronosyl-transferase 1A1 (UGT1A1) plays an important role in the biliary excretion of bilirubin, suggesting genetic polymorphisms of UGT1A1 may have an impact on bile acid metabolism, which may be related to the development of anti-tuberculosis drug-induced liver injury (ATLI). This study explores the associations between genetic polymorphisms of UGT1A1 and ATLI in a Chinese anti-tuberculosis population. A 1:2 matched case–control study was conducted among 290 ATLI cases and 580 controls, of which causality assessment of ATLI cases was based on the updated Roussel Uclaf Causality Assessment Method (RUCAM). Conditional logistic regression was applied to calculate odds ratio (OR) and 95% confidence intervals (CIs), with weight and use of hepatoprotectant as covariates. The Bonferroni correction was used to adjust P values for multiple testing. Compared with those carrying rs6719561 TT genotype, patients with TC genotype had lower risk of ATLI (adjusted OR = 0.723, 95% CI: 0.531–0.985, P = 0.040). The haplotype TAG (rs3755319-rs2003569-rs4148323) could marginally significantly increase the risk of ATLI (adjusted OR = 5.071, 95% CI: 1.007–25.531, P = 0.049), while haplotype TC (rs4148329-rs6719561) could reduce the risk of ATLI (adjusted OR = 0.719, 95% CI: 0.527–0.982, P = 0.038). Patients with polymorphisms at rs4148328 or rs3755319 were at a reduced risk of moderate and severe liver injury under different genetic models. Based on this case–control study, genetic polymorphisms of UGT1A1 may be associated with susceptibility to ATLI in the Chinese anti-tuberculosis population.

Liver Fibrosis Associated With Crigler-Najjar Syndrome in a Compound Heterozygote: A Case Report

Crigler-Najjar syndrome is a hereditary unconjugated hyperbilirubinemia. Two forms of the disease are recognized. Type I is more severe and results in kernicterus if left untreated, and Type II is less severe and responds to phenobarbital. While Crigler-Najjar syndrome is thought by many to have normal liver histology, few reports of the liver pathology exist. Herein, we present a 19-year-old patient with Crigler-Najjar who underwent liver transplantation. The liver showed marked canalicular cholestasis with portal and variable, delicate, bridging fibrosis. Correlation of the patient's genetic test results and clinical phenotype is presented.

Differences in UGT1A1 gene mutations and pathological liver changes between Chinese patients with Gilbert syndrome and Crigler-Najjar syndrome type II

Diagnosis of Crigler-Najjar syndrome type II (CNS-II) and Gilbert syndrome (GS) based on the serum bilirubin concentration is difficult, because this parameter can fluctuate under certain conditions. The aim of this study was to explore differences in UGT1A1 gene mutations, which cause both CNS and GS, and pathological changes between CNS-II and GS.Ninety-five Chinese patients with hereditary unconjugated hyperbilirubinemia were enrolled in this study. Peripheral blood samples obtained from patients were used to evaluate bilirubin levels and for UGT1A1 gene testing. Percutaneous needle biopsy of the liver and staining of tissue samples with hematoxylin and eosin, Masson trichrome, reticulin, and Perl Prussian blue were performed for 59 patients. The Ishak scoring system was used to assess inflammatory activity and the extent of fibrosis.One hundred ninety-two UGT1A1 mutations at 6 sites were detected in the 95 patients; the most common mutation in GS was c.-3279T>G in the phenobarbital response enhancing motif of the UGT1A1 promoter, whereas the most common mutation in CNS-II was p.G71R. The frequency of heterozygous p.G71R mutations in CNS-II was significantly higher than that in GS (P = .001); however, the frequency of homozygous c.-3279T>G mutations in CNS-II was markedly lower than that in GS (P = .032). Among all patients with multiple mutations, the frequency of p.Y486D was significantly higher in CNS-II than in GS (P = .007). The frequency of compound c.-3279T>G, A(TA)7TAA, and p.G71R mutations in CNS-II was significantly higher than that in GS (P = .001). Among the 59 patients who underwent percutaneous needle biopsy, 20 had iron deposition in the liver. The frequency of hepatic iron deposition in CNS-II was significantly higher than that in GS (P = .002).The linked polymorphic mutations, A(TA)7TAA and c.-3279T>G in UGT1A1, were most strongly associated with GS, whereas mutations in the coding region, especially p.G71R and p.Y486D, were more strongly associated with CNS-II. Iron deposition was more common in liver biopsies from patients with CNS-II than in those with GS.

Germline genetic variants with implications for disease risk and therapeutic outcomes

Genetic testing has multiple clinical applications including disease risk assessment, diagnosis, and pharmacogenomics. Pharmacogenomics can be utilized to predict whether a pharmacologic therapy will be effective or to identify patients at risk for treatment-related toxicity. Although genetic tests are typically ordered for a distinct clinical purpose, the genetic variants that are found may have additional implications for either disease or pharmacology. This review will address multiple examples of germline genetic variants that are informative for both disease and pharmacogenomics. The discussed relationships are diverse. Some of the agents are targeted for the disease-causing genetic variant, while others, although not targeted therapies, have implications for the disease they are used to treat. It is also possible that the disease implications of a genetic variant are unrelated to the pharmacogenomic implications. Some of these examples are considered clinically actionable pharmacogenes, with evidence-based, pharmacologic treatment recommendations, while others are still investigative as areas for additional research. It is important that clinicians are aware of both the disease and pharmacogenomic associations of these germline genetic variants to ensure patients are receiving comprehensive personalized care.

[Repeated yellowing of the skin and sclera for 2 years]

A two-year-old girl was admitted due to repeated yellowing of the skin and sclera for 2 years and had no other specific symptoms or signs. The use of phenobarbital could relieve the symptoms of jaundice. Multiple examinations showed increased indirect bilirubin levels, and the results of aminotransferases and liver imaging were normal. There was no evidence of hemolysis. The analysis of UGT1A1 gene in her family found that this child had double homozygous mutation of c.211G>A(G71R) and c.1456T>G(Y486D), which had been reported as the pathogenic mutation for Gilbert syndrome. Her parents carried double heterozygous mutation of G71R and Y486D and had no symptom of jaundice. The child was diagnosed as having Gilbert syndrome. It is concluded that as for patients with unconjugated hyperbilirubinemia which cannot be explained by liver damage and hemolysis, their family history should be investigated in detail and gene analysis should be performed as early as possible, in order to identify congenital bilirubin metabolic disorders.

Inherited disorders of bilirubin clearance

Inherited disorders of hyperbilirubinemia may be caused by increased bilirubin production or decreased bilirubin clearance. Reduced hepatic bilirubin clearance can be due to defective (i) unconjugated bilirubin uptake and intrahepatic storage, (ii) conjugation of glucuronic acid to bilirubin (e.g., Gilbert syndrome, Crigler-Najjar syndrome, Lucey-Driscoll syndrome, breast milk jaundice), (iii) bilirubin excretion into bile (Dubin-Johnson syndrome), or (iv) conjugated bilirubin re-uptake (Rotor syndrome). In this review, the molecular mechanisms and clinical manifestations of these conditions are described, as well as current approaches to diagnosis and therapy.

Three-dimensional polyacrylamide gel-based DNA microarray method effectively identifies UDP-glucuronosyltransferase 1A1 gene polymorphisms for the correct diagnosis of Gilbert's syndrome

Gilbert's syndrome is a mild genetic liver disorder characterized by unconjugated hyperbilirubinemia due to defects in the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene. The T-3279G mutation in the phenobarbital responsive enhancer module (PBREM), the TA-insertion in the TATA box, creating the A(TA)7TAA motif instead of A(TA)6TAA and the G211A mutation in coding exon 1, particularly in Asian populations, of the human UGT1A1 gene are the three common genotypes found in patients with Gilbert's syndrome. Different approaches for detecting the T-3279G, A(TA)6/7TAA and G211A mutations of the UGT1A1 gene have been described. In this study, to the best of our knowledge, we established a three-dimensional polyacrylamide gel-based DNA microarray method for the first time, in order to study UGT1A1 gene polymorphisms. This method, based on a step-by-step three-dimensional polyacrylamide gel-based DNA microarray protocol, successfully identified all possible genotypes of T-3279G, A(TA)6/7TAA and G211A in 20 patients with hyperbilirubinemia. In addition, sequencing was performed to confirm these results. The data from the current study demonstrate that the three-dimensional polyacrylamide gel microarray method has the potential to be applied as a useful, reliable and cost-effective tool to detect the T-3279G, the A(TA)6/7TAA and the G211A mutations of the UGT1A1 gene in patients with hyperbilirubinemia and thereby aid in the diagnosis of Gilbert's syndrome.

Prolonged Hyperbilirubinemia in a Neonate with a Novel Mutation in the UDP-glucuronosyltransferase 1A1 Gene

The total bilirubin value of a male infant was 385 μmol/l on day 5. Liver function test results were normal and there was no evidence of sepsis and no hemolysis reaction. Phototherapy was administered and on day 8 the patient's total bilirubin level was 255 μmol/l. Intermittent episodes of hyperbilirubinemia occurred without phototherapy, with the total bilirubin level reaching 335 μmol/l on day 19. A 3-day regimen of phenobarbital was administered and on day 24 his total bilirubin level was 180 μmol/l. The patient was discharged. At the age of 2 months, the total bilirubin value was 27 μmol/l. His direct bilirubin value was <15% of total bilirubin in every determination. A family study of the UDP-glucuronosyltransferase(UGT)1A1 gene showed that the infant carries a homozygous mutation at nucleotide -3279 plus compound heterozygous mutations at nucleotides 782 and 1091. The mutation at nucleotide 782 is a novel finding. Gilbert's syndrome was diagnosed.

Identification of Promotor and Exonic Variations, and Functional Characterization of a Splice Site Mutation in Indian Patients with Unconjugated Hyperbilirubinemia

Background

Mild unconjugated hyperbilirubinemia (UH), due to reduced activity of the enzyme uridine diphosphoglucuronate-glucuronosyltransferase family, polypeptide 1 (UGT1A1), is a common clinical condition. Most cases are caused by presence in homozygous form of an A(TA)₇TAA nucleotide sequence instead of the usual A(TA)₆TAA sequence in promoter region of the UGT1A1 gene. In some cases, other genetic variations have been identified which differ between populations. There is need for more data on such genetic variations from India.

Methods

DNA from subjects with unexplained persistent or recurrent UH was tested for the presence of TA promoter insertions. In addition, all five exons and splicing site regions of UGT1A1 gene were sequenced. Several bioinformatics tools were used to determine the biological significance of the observed genetic changes. Functional analysis was done to look for effect of a splice site mutation in UGT1A1.

Results

Of 71 subjects with UH (68 male; median age [range], 26 [16–63] years; serum bilirubin 56 [26–219] μM/L, predominantly unconjugated) studied, 65 (91.5%) subjects were homozygous for A(TA)₇TAA allele, five (7.0%) were heterozygous, and one (1.4%) lacked this change. Fifteen subjects with UH had missense exonic single nucleotide changes (14 heterozygous, 1 homozygous), including one subject with a novel nucleotide change (p.Thr205Asn). Bioinformatics tools predicted some of these variations (p.Arg108Cys, p.Ile159Thr and p.Glu463Val) to be deleterious. Functional characterization of an exonic variation (c.1084G>A) located at a splice site revealed that it results in frameshift deletion of 31 nucleotides and premature truncation of the protein.

Conclusion

Our study revealed several single nucleotide variations in UGT1A1 gene in Indian subjects with UH. Functional characterization of a splice site variation indicated that it leads to disordered splicing. These variations may explain UH in subjects who lacked homozygous A(TA)₇TAA promoter alleles.

X-linked ichthyosis and Crigler-Najjar syndrome I: Coexistence in a male patient with two copy number variable regions of 2q37.1 and Xp22.3

X-linked ichthyosis (XLI) is an X-linked recessive skin disorder generally restricted to males, which arises from mutations in the steroid sulfatase (STS) gene located on Xp22.3. Crigler-Najjar syndrome (CN-I) is a rare autosomal recessive disease caused by the homozygous or compound heterozygous mutations in the UPD-glucuronosyltransferase 1 family, polypeptide A1 (UGT1A1) gene on chromosome 2q37. A male patient was referred to the Department of Medical Genetics with of severe icterus and ichthyosis. The patient and his family members underwent genetic tests related to XLI and CN-I. Quantitative polymerase chain reaction on genomic DNA was performed to determine the gene copy number, while single nucleotide polymorphism array analysis was conducted to identify deletion mutations. Family pedigree analysis showed that the patient and his two cousins were all affected by ichthyosis, which was in accordance with the inheritance pattern of an X-linked recessive disease. In addition, the patient's serum bilirubin concentration (>340 mmol/l) was markedly greater than the normal level. The patient presented with kernicterus and phenobarbital treatment was ineffective. The clinical diagnosis of XLI was confirmed molecularly by laboratory evidence of a maternal 1.61 M deletion (including the STS gene) on ChrXp22.31. Coincidentally, the male patient was also confirmed to carry a rare maternal inherited microdeletion (374 Kb) comprising the entire UGT1A1 gene combined with a paternal UGT1A1 mutation (c.1253delT), a causative event of CN-I. To the best of our knowledge, this study reported for the first time the comorbidity of XLI and CN-I in a male patient. The results suggested that co-occurrence of these two recessive diseases in a patient may be incidental.

UGT1A1 gene mutations and neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations

BACKGROUND

Uridine diphosphoglucuronate-glucuronosyltransferase 1A1 (UGT1A1) gene mutation was shown to be responsible for neonatal hyperbilirubinemia. This study aimed to investigate whether UGT1A1 gene mutation is associated with neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations.

METHODS

Two hundred and eighteen infants with hyperbilirubinemia (118 Heiyi Zhuang, 100 Han) and 190 control subjects (110 Heiyi Zhuang, 80 Han) were enrolled. Polymerase chain reaction and gene sequencing were used to detect the TATA-box and exon 1 of UGT1A1.

RESULTS

(TA)7 insertion mutation, 211G>A (G71R), 686C>A (P229Q), and 189C>T (D63D) were detected. Logistic regression analysis showed odds ratios (OR) of 2.64 (95% confidence interval (CI) 1.64-4.24; P < 0.001) and 0.69 (95%CI 0.43-1.10; P = 0.115) for neonates who carried UGT1A1 G71R and (TA)7 insertion mutation, respectively. G71R homozygosity increased the odds of dangerous bilirubin levels by a factor 34.23, and G71R heterozygosity only by 2.10.

CONCLUSION

We found that UGT1A1 G71R mutation is a risk factor for neonatal hyperbilirubinemia in Guangxi Heiyi Zhuang and Han populations. Meanwhile, the UGT1A1 (TA)7 insertion mutation is not associated with neonatal hyperbilirubinemia in the two ethnic groups.

Outcome and toxicities associated to chemotherapy in children with acute lymphoblastic leukemia and Gilbert syndrome. Usefulness of UGT1A1 mutational screening

BACKGROUND

Acute lymphoblastic leukemia (ALL) is the most frequent cancer in childhood. Although intensive chemotherapy has improved survival in those patients, important side effects, including hyperbilirubinemia, are frequent. Gilbert syndrome (GS) is a frequent condition that causes a reduction in glucuronidation and intermittent hyperbilirubinemia episodes. This could provoke a greater exposure to some cytotoxic agents used in ALL, increasing the risk of toxicity. On the other hand, unexplained hyperbilirubinemia could lead to unnecessary modifications or even treatment withdrawals, which could increase the risk of relapse, but data regarding this in ALL pediatric population are scarce.

METHODS

Retrospective study to analyze toxicity, outcome and treatment modifications related to GS in children diagnosed with ALL.

RESULTS

A total of 23 of 159 patients were diagnosed with GS. They had statistically higher hyperbilirubinemias during all treatment phases (P < 0.0001) and a slower methotrexate clearance when it was administered during a 24-hr infusion at high doses (patients with GS: 74 hr ± 19 vs. patients without GS: 64 hr ± 8; P <  .002). However, no relevant toxicity or delays in treatment were found in them. Finally, changes in treatment due to hyperbilirubinemia were only done in 5 patients with GS.

CONCLUSIONS

Differences in outcome were not found in patients with GS. Universal screening for GS appears to be not necessary in pediatric patients with ALL. However, when hyperbilirubinemia is observed, it must be rule out in order to avoid unnecessary changes in treatment.