Identifying Variable Number of Tandem Repeat Alleles in Phenylalanine Hydroxylase Gene in Patients with Phenylketonuria in Golestan Province, Iran

Golnaz Abedini,Zeinab Khazaei-Koohpar

doi:10.30699/jambs.28.129.198

Abstract

Background and Objective: Phenylketonuria (PKU) is a metabolic disorder that is caused by mutations in the phenylalanine hydroxylase (PAH) gene. The multiplicity of mutations in the PAH gene of PKU leads to the cases, in which the pathogenic mutation cannot be detected. In these cases, the variable number of tandem repeat (VNTR), which is the polymorphic marker associated with the PAH gene, is used to identify PKU carriers. The present study was conducted to investigate the allele frequency of this marker in PKU population of Golestan Province (north of Iran). Materials and Methods: In this cross-sectional descriptive study, 26 non-relative PKU patients (1-23 years old, phenylalanine: 4.5-250 mg/dl) were identified from different regions of Golestan Province within a one-year period (2016). Genomic DNA was then extracted from leukocytes using the high pure PCR template preparation kit (Roche) and the fragments containing the PAH VNTR were evaluated using PCR-sequencing method. Results: PCR products of PAH VNTR alleles produced 334, 454, 484, 514, and 604 bp fragments. They were corresponding to the presence of alleles with 3, 7, 8, 9, and 12 copies of the repeat units, respectively. In addition, the distribution of VNTR alleles was as follows: 28.85, 28.85, 17.3, 19.23, and 5.77. Conclusion: This study is the first report regarding the genetic structure of PKU population using PAH VNTR alleles in Golestan Province. Considering the population diversity in Iran, it is necessary to investigate the frequency and distribution of VNTR alleles in different parts of the country.

Highlights

Phenylketonuria (PKU) is one of the most common inborn errors of amino acid metabolism with an autosomal recessive inheritance pattern [1,2], which was first described by Folling in 1934 [3]
This study is the first report regarding the genetic structure of PKU population using phenylalanine hydroxylase (PAH) variable number of tandem repeats (VNTR) alleles in Golestan Province
After Polymerase Chain Reaction (PCR) reaction, the samples were sequenced to confirm the number of repeats in the VNTR alleles

Summary

Introduction

Phenylketonuria (PKU) is one of the most common inborn errors of amino acid metabolism with an autosomal recessive inheritance pattern [1,2], which was first described by Folling in 1934 [3]. The PAH gene is located on the long (q) arm of chromosome in q22–q24.1 regions. This gene contains exons and 12 introns [6]. The highest prevalence of PKU is reported in this region of the world: 1 per 4,000 in Turkey and 1 per 3627 in Iran. The PAH locus database lists over 800 PAH mutations including missense and nonsense mutations, small and large deletions, as well as small insertions and splicing defects. This gene is located on chromosome of humans. Phenylketonuria (PKU) is a metabolic disorder that is caused by mutations in the phenylalanine hydroxylase (PAH) gene. The present study was conducted to investigate the allele frequency of this marker in PKU population of Golestan Province (north of Iran)

Methods

Results

Discussion

Conclusion