Analysis of the UDP-glucuronosyltransferase gene in Portuguese patients with a clinical diagnosis of Gilbert and Crigler–Najjar syndromes (original) (raw)
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A Novel Pathogenic UGT1A1 Variant in a Sudanese Child with Type 1 Crigler-Najjar Syndrome
Drug Metabolism and Disposition, 2018
Uridine diphosphate glucuronosyltransferases (UGTs) are key enzymes responsible for the body's ability to process a variety of endogenous and exogenous compounds. Significant gains in understanding UGT function have come from the analysis of variants seen in patients. We cared for a Sudanese child who showed clinical features of type 1 Crigler-Najjar syndrome (CN-1), namely severe unconjugated hyperbilirubinemia leading to liver transplantation. CN-1 is an autosomal recessive disorder caused by damaging mutations in the gene for UGT1A1, the hepatic enzyme responsible for bilirubin conjugation in humans. Clinical genetic testing was unable to identify a known pathogenic UGT1A1 mutation in this child. Instead, a novel homozygous variant resulting in an in-frame deletion, p.Val275del, was noted. Sanger sequencing demonstrated that this variant segregated with the disease phenotype in this family. We further performed functional testing using recombinantly expressed UGT1A1 with and without the patient variant, demonstrating that p.Val275del results in a complete lack of glucuronidation activity, a hallmark of CN-1. Sequence analysis of this region shows a high degree of conservation across all known catalytically active human UGTs, further suggesting that it plays a key role in the enzymatic function of UGTs. Finally, we note that the patient's ethnicity likely played a role in his variant being previously undescribed and advocate for greater diversity and inclusion in genomic medicine.
Novel missense mutation of the UGT1A1 gene in Thai siblings with Gilbert's syndrome
Pediatrics International, 2002
Background : Gilbert's syndrome is a common inherited disorder of bilirubin metabolism contributing to the development of neonatal jaundice and causing recurrent jaundice after the neonatal period. In the patients with Gilbert's syndrome, mutations have been reported in the promoter and exons of the uridine diphosphateglucuronosyl transferase 1 (UGT1A1) gene on chromsome 2q37, which encodes bilirubin uridine diphosphate-glucuronosyltransferase. However, the genetic basis of Gilbert's syndrome, including its inheritance trait, remains to be clarified. Methods : Patients 1 and 2 were Thai sisters with Gilbert's syndrome. They had a history of prolonged neonatal jaundice and showed recurrent jaundice after their infancy, while the parents showed no symptoms. To search for the mutation in the patients, all exons of the UGT1A1 gene were amplified by polymerase chain reaction (PCR) and sequenced directly. The frequency of the mutation in controls was studied by PCRrestriction enzyme digestion method. Results : The patients were homozygous for a novel single transition of T to C at nucleotide position 247 (exon 1), which would predict a substitution of leucine for phenylalanine at codon 83 of the enzyme protein. No other mutation was detected in any regions except exon 1. The parents with no symptoms showed heterozygosity for the mutation. Among the 110 Japanese controls, no homozygous individuals and three heterozygous individuals for the mutation were identified, giving a mutated allele frequency of 0.0136. Conclusions : A novel missense mutation in the UGT1A1 gene was identified in two Thai siblings with Gilbert's syndrome. The affected family showed that homozygosity for the mutation may lead to apparent symptoms and that the syndrome was inherited as an autosomal recessive trait. The mutation does not explain a high incidence of neonatal jaundice in Japan, because it is very rare in the Japanese population.
Two Different UGT1A1 Mutations causing Crigler-Najjar Syndrome types I and II in an Iranian Family
Journal of gastrointestinal and liver diseases : JGLD, 2015
Crigler-Najjar syndrome type I (CN-1) and type II (CN-2) are rare hereditary unconjugated hyperbilirubinemia disorders. However, there have been no reports regarding the co-existence of CN-1 and CN-2 in one family. We experienced a case of an Iranian family that included members with either CN-1 or CN-2. Genetic analysis revealed a mutation in the bilirubin UDP-glucuronosyltransferase (UGT1A1) gene that resulted in residual enzymatic activity. The female proband developed severe hyperbilirubinemia [total serum bilirubin concentration (TB) = 34.8 mg/dL] with bilirubin encephalopathy (kernicterus) and died after liver transplantation. Her family history included a cousin with kernicterus (TB = 30.0 mg/dL) diagnosed as CN-1. Her great grandfather (TB unknown) and uncle (TB = 23.0 mg/dL) developed jaundice, but without any treatment, they remained healthy as CN-2. The affected cousin was homozygous for a novel frameshift mutation (c.381insGG, p.C127WfsX23). The affected uncle was compou...
Human Mutation, 2005
Crigler-Najjar syndrome types I and II (CN1 and CN2) are usually inherited as autosomal recessive conditions and are characterized by non-hemolytic unconjugated hyperbilirubinaemia. CN1 is the most severe form, associated with the absence of hepatic bilirubin-uridinediphosphoglucuronate glucuronosyltransferase (UGT1A1) activity. CN2 presents intermediate levels of hyperbilirubinaemia as a result of an incomplete deficiency of hepatic UGT1A1 activity. Here, we present the analysis of UGT1A1 gene in 31 unrelated Crigler-Najjar (CN) syndrome patients. This analysis allowed us to identify 22 mutations, 12 of which were no previously described, expanding the spectrum of known UGT1 mutations to 77. Novel mutations, considered pathogenic, including one nonsense mutation, two altered splice sites, one single base deletion and nine missense mutations were identified in coding exons of the UGT1A1 gene and flanking introns. Several novel missense mutations localize in critical domain of UGT1A1 enzyme. In addition, the evaluation of Gilbert-type promoter of UGT1A1 in Crigler-Najjar (CN) syndrome patients was performed. The polymorphisms of the promoter region can modify the UGT1A1 mutation phenotype. This study represents the molecular characterization of the largest cohort of Italian Crigler-Najjar Gilbert syndrome patients studied so far; increase the mutational spectrum of UGT1A1 allelic variants worldwide and provide a new insight useful for clinical diagnosis and genetic counseling.
BioMed research international, 2013
Crigler-Najjar syndrome (CNS) type I and type II are inherited as autosomal recessive conditions that are caused by mutations in the UGT1A1 gene. We present the analysis of UGT1A1 gene in 12 individuals from three different families. This analysis allowed us to identify one novel mutation, which was not previously described. In this study, three families with clinically diagnosed CNS referred from Khuzestan province, southwest Iran, were screened. After signing the informed consent, peripheral blood samples from the patients and their parents were collected in EDTA-containing tube followed by DNA extraction using a routine phenol-chloroform method. All five coding exons and the flanking intronic regions of the bilirubin-UGT were amplified by polymerase chain reaction (PCR) followed by DNA sequencing by Sanger method. From the first family, a 9-month-old boy was homozygous for a deletion mutation of two adjacent nucleotides including one adenosine (A) and one glutamine (G) between nu...
Genetics and Molecular Research, 2014
Gilbert's syndrome is suspected in patients with unconjugated hyperbilirubinemia caused by decreased activity of the UDP-glucuronosyltransferase 1A1 (UGT1A1) gene in the absence of abnormal liver function and hemolysis. The major genetic variants underlying Gilbert's syndrome are TATA-box repeats of the promoter region and exon 1 G211A of the coding region, particularly in Asians. The efficacy of DNA melting curve analysis, however, has not been established for the G211A mutation. For rapid and accurate molecular diagnosis of Gilbert's syndrome, DNA melting curve analysis was evaluated for its genotyping capability not only for TATA-box ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (1): 670-679 (2014) Rapid diagnosis of exon 1 mutant within the UGT1A1 gene repeats of the UGT1A1 promoter, but also for G211A of UGT1A1 exon 1. TA repeats within the TATA-box sequence and the exon 1 G211A mutation of the UGT1A1 gene were analyzed by DNA melting curve analysis. To evaluate the assay reliability, direct sequencing or polyacrylamide gel electrophoresis was used as a comparative method. All homozygous and heterozygous polymorphisms of A(TA) 7 TAA within the TATA-box allele and of exon 1 G211A mutants of the UGT1A1 gene were successfully identified with DNA melting curve analysis. DNA melting curve analysis is, therefore, an effective molecular method for the rapid diagnosis of Gilbert's syndrome, as it detects not only TATA-box polymorphisms but also the exon 1 G211A mutation located within the UGT1A1 gene.
Genetic lesions in the UGT1A1 genes among Gilbert’s syndrome patients from India
Molecular Biology Reports, 2018
The present study was undertaken to investigate genetic variations present in the coding regions of the UGT1A1 gene among the Gilbert's syndrome patients. Analysis of genetic variations was performed by direct DNA sequencing among the patients that do not have any polymorphic variations in the promoter regions of the UGT1A1 gene. We identified seven different sequence variations among Gilbert's Syndrome patients, of which four were novel. Out of seven variants, six missense and one silent single nucleotide substitutions were present in the UGT1A1 gene. In addition, molecular modeling of UGT1A1 (H55R, P152S and N212H) variants suggested a reduced activity of the enzyme. This study demonstrates that different variations present in the UGT1A1 gene and specifically, the H55R variation had a significant effect on bilirubin levels and could be genetic risk factors for hyperbilirubinemia.