Novel missense mutation of the UGT1A1 gene in Thai siblings with Gilbert's syndrome.
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 diphosphate-glucuronosyl 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 PCR-restriction 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.
Sutomo
Retno
R
Department of Development and Aging, Faculty of Medicine, Kobe University Graduate School of Medicine, Japan.
Laosombat
Vichai
V
Sadewa
Ahmad Hamim
AH
Yokoyama
Naoki
N
Nakamura
Hajime
H
Matsuo
Masafumi
M
Nishio
Hisahide
H
D005260:Female; D005878:Gilbert Disease / Q000235:genetics*; D014453:Glucuronosyltransferase / Q000235:genetics*; D006801:Humans; D020125:Mutation, Missense / Q000235:genetics*; D016133:Polymerase Chain Reaction; D013785:Thailand; D000099148:UGT1A1 Enzyme
D014453:Glucuronosyltransferase; D000099148:UGT1A1 Enzyme