Novel and heteroplasmic mutations in mitochondrial coding genes in iranian patients with familial adenomatous polyposis (fap)

Elham Afkhami,1,* Mohammad mehdi heidari,2 Mehri khatami,3

1. Department of Biology, Faculty of science, Yazd University, Yazd, Iran.
2. Department of Biology, Faculty of science, Yazd University, Yazd, Iran.
3. Department of Biology, Faculty of science, Yazd University, Yazd, Iran.

Abstract

Introduction

familial adenomatous polyposis (fap) is an autosomal dominant inherited disorder and a rare form‌ of colorectal cancer (crc) that represents the most common gastrointestinal polyposis syndrome. generally, cancers start to develop a decade after the appearance of the polyps. it manifests equally in both sexes, and incidence of this disease is in the second decade of life. cytochrome c oxidase subunit i (cox1) is one of three mitochondrial dna (mtdna) encoded subunits (mt-co1, mt-co2, mt-co3) of respiratory complex iv. alteration of the electron transport components by mutations in mtdna may compromise the normal electron flow. this could lead to an increase of bifurcation and generation of superoxidase radicals and increase oxidative stress in various types of cancer cells.

Methods

in this study, 21 iranian patients were investigated for presence of the mutations in mitochondrial coding genes (coxi, d-loop) by pcr and sequencing analysis. the study of pathogenicity of the whole mtdna was accomplished by the human mitochondrial genome database (mitomap).

Results

Our results showed that one patient has a heteroplasmic mutation which is located in mt-co1 gene, (c6433g) that cause change in amino acid (t→s) and according to the results of the in-silico analysis, it was assessed as pathogenic mutation. also, this mutation is novel and has not previously been reported in any other disease. furthermore, one homoplasmic variant (16362t>‌c) in d-loop region was also identified. the bioinformatics’ predictions show that these mutations probably disturb the process of gene expression.

Conclusion

This study is the most comprehensive study in the iran and the results of this study can be used for genetic counseling and prenatal diagnosis and suggest that mutations in mitochondrial coding genes might lead to the production of defective proteins in the respiratory chains, so potentially lead to crc in iranian subjects.

Keywords

Familial adenomatous polyposis, mitochondria, coding genes, mutations.