Molecular basis of phenylketonuria in Serbia: an update

Abstract

Introduction: Phenylketonuria (PKU) is the most frequent inborn disorder of amino acid metabolism caused by variants in human phenylalanine hydroxylase gene (PAH). Methods: In thisstudy (an update for the time period of 10 years, with patientsfrom our previousstudies included) a total of 109 PKU patients from Serbia were analyzed. They were classified into three phenotypic categories in accordance with pre-treatment plasma phenylalanine level: classic PKU, mild PKU and mild hyperphenylalaninemia. For genetic analyses, we combined Sanger sequencing, MLPA and next generation sequencing to identify disease-causing variantsin PAH gene, which were further classified using ACMG classification. Additionally, we used in silico and/or eukaryotic expression studiesto assess the effect of novel genetic variants identified in our patients. Results: Disease-causing variants were identified in 217 of 218 alleles, reaching detection rate of 99.5%. We detected a total of 32 different variants, of which 29 previously described and three novel ones: p.Gln226Lys, p.Pro244His and p.Pro416Leu. In silico and/or eukaryotic expression studies confirmed pathogenic effect of all novel genetic variants. The most frequent variant was p.Leu48Ser (31.2%), followed by p.Arg408Trp (13.8%), p.Ile306Val (9.2%). p.Glu390Gly (5%), p.Pro281Leu (4.6%), and p.Arg261Gln (3.2%). All detected disease-causing variants were classified as pathogenic using ACMG classification. Conclusion: Our study brings the updated spectrum of molecular genetic data, variant classification and detailed phenotypic characteristicsfor PKU patientsfrom Serbia. Therefore, ourstudy contributesto better understanding of molecular landscape of PKU in Europe and to general knowledge on genotype– phenotype correlation in PKU.