Background: Severe neonatal hyperbilirubinemia or neonatal jaundice (NNJ) characterised by an elevated total serum bilirubin (TSB) level may result in kernicterus or even death. Uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1) is the key enzyme which conjugates bilirubin with glucuronic acid for the subsequent bilirubin excretion. Conversely, constitutive androstane receptor (CAR), encoded by nuclear receptor subfamily 1, group I, member 3 (NR1I3) gene, regulates bilirubin excretion by activating the components of the bilirubin clearance pathway. Thus, genetic variants in UGT1A1 and NR1I3 genes may modulate bilirubin excretion and lead to NNJ. This study aimed to determine the association between UGT1A1 and NR1I3 genetic variants and NNJ development in Malay population by genotyping the DNA isolated from buccal swabs. The accuracy and reliability of the genotyping results produced by buccal DNA was also compared with that of the whole blood DNA.
Methods: Buccal swabs were collected from 232 hyperbilirubinemia and 232 non-hyperbilirubinemia newborns admitted to and/or born in Hospital Universiti Sains Malaysia (HUSM). Hyperbilirubinemia subjects were those with TSB levels ≥250 µmol/L within the first week after birth while non-hyperbilirubinemia subjects were newborns without significant hyperbilirubinemia. The UGT1A1 (c.211G>A) and NR1I3 [MPJ6_1I3008 (G>A), IVS8+116T>G and 540A>G] variants were genotyped by using high resolution melting (HRM) analysis. Binary logistic regression was used to assess the association between variant genotypes and risk of NNJ. Whole blood samples were also collected from 60 subjects and genotyped to compare the HRM genotyping results with that of the buccal swabs.
Results: When compared with wild-type genotype, both heterozygous and homozygous variant genotypes of MPJ6_1I3008 (G>A), IVS8+116T>G and 540A>G were not significantly associated with NNJ. However, the heterozygous genotype (GA) of c.211G>A was found to increase the risk of NNJ (OR: 1.96, 95% CI, 1.13-3.39, P=0.014). Besides, all buccal DNA samples demonstrated 100% genotype call rates and achieved complete genotype concordance with blood DNA samples.
Conclusions: The heterozygous genotype of c.211G>A could be a genetic risk factor of NNJ in Malay population. Since buccal DNA produced complete genotype call and concordance rates, the non-invasive buccal swabs collection can be used as an alternative to blood sampling especially in genetic studies involving paediatric population.
