Mutation analysis of exon 5 of PAH gene in phenylketonuria patients from Golestan Province, Iran

In the phenylalanine hydroxylase (PAH) gene, various mutations are mainly responsible for phenylketonuria (PKU). After thalassemia, PKU is considered as the most common autosomal recessive disease among Iranian population. Therefore, identifying the mutations that cause the disease in this population is of great importance. This study aimed to identify exon 5 mutations of PAH gene in PKU patients from Golestan, the northern province of Iran, and compare these mutations with those onesa found by studies carried out in other parts of the country.

During a one-year period, 25 unrelated PKU patients aged 1-23 years and from different parts of Golestan province were included in the study. Then, their genomic DNAs were extracted from their blood samples and PCR-sequencing method was used to identify the mutations. The sequencing results were analyzed using Chromas and CLC Main Workbench v3.5 software.

In this study, R158Q mutation was detected with a frequency of 6%. This mutation was homozygous in one PKU patient, but it was heterozygous in another one. These patients had cPKU phenotype.

Evaluation of mutations proved to be a useful technique for molecular diagnosis of PKU and identification of disease carriers in the given population. Taking into account the fact that only one exon of PAH gene was explored in this study, however, it is recommended that further studies be conducted to investigate other exons in order for obtaining the complete mutation spectrum of this gene in PKU patients in Golestan province.