Genetic Analysis Of UGT1A1 Gene In A Family With Gilbert's Syndrome

[Objective]Gilbert syndrome,a benign form of unconjugated hyperbilirubinemia,is a hereditary dysmetabolism disease and common in clinic.The oversea incidence rate is about 3～10%.The clinical manifestation is intermittent unconjugated nonhemolytic hyperbilirubinemia without hepatic organic disease.Its prognosis is good,requires neither treatment nor long-term medical attention.Clinicians have not known enough about this disease;therefore,the mild hyperbilirubinemia may be mistaken for hepatic jaundice,obstructive jaundice and hemolytic jaundice and received long-term treatment,and causes patient's unwarranted anxiety.So,it is important to make the right diagnosis in time.The study is to detect the gene mutation locus in a Chinese family suffered from Gilbert's syndrome.It is very important to diagnose and understand the differences with other jaundice.[Methods]The patient was a 5-year old boy with jaundice and was treated in Tianjin Children's hospital in May 2007.He was preliminary diagnosed as Gilbert syndrome by medical history,liver function and the result of phenobarbital therapeutic test.Peripheral blood samples were collected from the proband and his four family members,and the genomic DNA was extracted.The Phenobarbital-responsive enhancer module,TATA box and 5 exons of the UGT1A1 gene were amplified by polymerase chain reaction(PCR),and assessed the PCR product by Sepharose Electrophoresis,and analyzed the mutation of the UGT1A1 gene screened by direct DNA sequencing assays.Furthermore,fresh blood samples were collected from all the members to detect the serum biochemical test.[Results]The UDP-glucuronosyltransferase UGTIA1 shows a close relationship with the level of serum bilirubin.The gene sequencing results of proband showed that there was a guanine(G)→adenine(A) homozygous transition at nucleotide 211 leading the substitution of arginine for glycine at position 71 of corresponding coding product(G71R).No mutation was detected in promoter region,the splicing junction sites and the phenobarbital responsive enhancer module of the UGT1A1 gene.The relevant mutation sites of the other family members were sequenced and identified. His father,grandmother and brother had the same Gly71Arg homozygous mutations. His mother had heterozygous mutation.Serum biochemical test showed the levels of serum unconjugated bilirubin of the family members were higher than the normal range.The level of serum unconjugated bilirubin in homozygous mutations was higher than that of in heterozygous mutation.The genotype is in conformity with the phenotype.[Conclusion]1.There is a guanine(G)→adenine(A) homozygous transition at nucleotide 211 in UGT1A1 of this family with Gilbert syndrome,leading the substitution of arginine for glycine at position 71 of corresponding coding product (G71R).No mutation was detected in other sites.2.It is inherited in an autosomal manner.3.Jaundice is one of the important clinical symptom,its etiologies are complicated.Gene diagnosis is objective and accurate,and it provides a new direction for clear diagnose at earlier stage and reduces the patients' unnecessary pains.It is meaningful of clinical application.3.The UDP-glucuronosyltransferase is an important enzyme which plays a critical role in the biological transformation.The reduced expression of UGT1A1 gene will increase the sensitivity of the body to some drugs.Clinical clear diagnosis of Gilbert syndrome is helpful to find these patients who are at a risk for drug toxicities and receive therapy individually.