Molecular diagnosis of phenylketonuria: From defective protein to disease-causing gene mutation

Abstract

Phenylketonuria (PKU) is the most common inborn error of amino acid metabolism, with an average incidence of 1/10000 in Caucasians. PKU is caused by more than 500 mutations in the phenylalanine hydroxylase gene (PAH) which result in phenylalanine hydroxylase (PAH) enzyme deficiency. Two approaches, in vitro expression analysis of mutant PAH and genotypephenotype correlation study, are used for the assessment of severity of PAH mutations. It has been shown that there is a significant correlation between mutant PAH genotypes and PKU phenotypes. As a result, the molecular diagnosis is completely shifted toward the detection of mutations in the phenylalanine hydroxylase gene. The study of the molecular basis of PKU in Serbia included identification of the spectrum and frequency of PAH mutations in Serbian PKU patients and genotype-phenotype correlation analysis. By using both PCR-RFLP and 'broad range' DGGE/DNA sequencing analysis, the mutation detection rate reached 97%. Thus, the base for molecular diagnosis, genetic counseling and selection of BH4-responsive PKU patients in Serbia was created.

Keywords

• phenylalanine hydroxylase
• phenylalanine hydroxylase gene mutations
• phenotype-genotype correlation
• phenylketonuria
• tetrahydrobiopterin