Results of UGT1A1 gene sequencing in individuals with the Gilbert syndrome phenotype

Aim. To evaluate the effectiveness of automated Sanger sequencing of the UGT1A1 gene to search for pathogenic mutations in individuals with the Gilbert syndrome phenotype.
Materials and methods. Automated Sanger sequencing of exons and part of the promoter in the UGT1A1 gene was carried out for 24 people with unconjugated hyperbilirubinemia, in whom all other causes except for genetic ones were excluded and DNA analysis was performed to determine the number of TA repeats in the promoter of the UGT1A1 gene (rs3064744). Distribution of rs3064744 genotypes in the group was the following: 5 people – 7TA/7TA genotype, 5 people – 6TA/6TA genotype, 12 people – 6TA/7TA genotype, 1 person – 5TA/7TA genotype, 1 person – 6TA/8TA genotype. DNA was isolated using phenol – chloroform extraction or express methods. The sequencing was performed by capillary electrophoresis on the Hitachi 3500 Genetic Analyzer (Applied Biosystems, USA).
Results. Single nucleotide variants of uncertain significance were identified: rs3755319 (in 21 people) and rs28899472 (in three people with the 7TA/7TA genotype of rs3064744) in the promoter of the UGT1A1 gene, rs2125984650 in the first exon of the UGT1A1 gene (in one person with the 5TA/7TA genotype of rs3064744). In two individuals with the 6TA/7TA genotype of rs3064744, gene variants were identified that were pathogenic or likely pathogenic for the Gilbert syndrome according to some sources (rs4148323, rs1273237448).
Conclusion. According to the results of the study, automated Sanger sequencing of the UGT1A1 gene may be the next stage of DNA analysis after determining the rs3064744 genotype for individuals with 6TA/6TA, 6TA/7TA rs3064744 genotypes and suspected Gilbert syndrome.

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