Genetic analysis of UGT1A1 gene in a case and her family members with Crigler-Najjar syndrome type Ⅰ / 中华实用儿科临床杂志

ABSTRACT

Objective To test the mutation locus of uridine diphospho-glucuronosyltransferase gene (UGT1A1) in a Chinese patient with Crigler-Najjar syndrome type Ⅰ and her family members,analyzing the genetic characteristics of the pedigree.Methods Genomic DNA was extracted from the patient and her family members and other 50 full-term infants with normal serum bilirubin as a healthy control group.Fifty cases of full-term newborn whose serum bilirubin level were nomal were study as controls.The promoter and all exons of UGT1A1 gene were amplified by the method of polymerase chain reactions (PCR),and mutations were identified by direct sequencing.Results The propositus and her miscarriage sister were homozygous for a nonsense mutation at nucleotide number 715 (715C ＞ T) in exon 1 of gene UGT1A1,substituting of stop codon (TAG) for glutamine (CAG) at position 239 (Q239X).The other 5 members were heterozygous in the same mutation locus.A TA insertion mutation and a G71R mutation in exon 1 were observed in the family members.The patient and her sister were homozygous of A(TA)7TAA mutation while other four were heterozygous.Propositus,grandmother,mother and her younger brother were heterozygous of G71 R mutation.No mutation was found in exons 2-5.No mutation was found in other fifty healthy cases in the healthy control group.Conclusions Q239X homozygous mutations is considered to be the lethal gene in this Crigler-Najjar syndrome family.Collaborative G71 R and A(TA)7TAA mutations may further reduce the enzyme activity of UGT1A1,causing varying degrees of bilirubin disorder.