Cystic fibrosis from genotype to phenotype: review article

Cystic fibrosis (CF) is the most common autosomal recessive genetic disease, which is caused by defection in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. CFTR gene codes chloride channels to modulate the homeostasis of epithelial environments. Defective CFTR affects various organs such as the lungs, pancreas, intestine, liver and skin; however, lung impairment is the main reason for mortality in these patients. About 2000 mutations in this gene have been discovered, but nearly 150 mutations lead to serious symptoms. CFTR mutations are classified into six major classes based on phenotypic manifestations such as structural instability of channels, defective processing, malfunctioning chloride-ion transfers and decreased number of chloride channels in the cell membranes. These cause various symptoms such as respiratory infection, intestinal obstruction, pancreatic exocrine insufficiency and malabsorption. Significant improvements in diagnostic tools and methods such as newborn screening, chloride sweat test and gene sequencing have increased the incidence and the prevalence of CF. Enormous studies have also been done on CF recognition and treatment procedures, which have resulted in 30 years of growth in the life expectancy of the patients. Despite the recent achievements, due to the high complexity of this disease and the involvement of various organs, the available treatments are nonpermanent. In the past few years, new combinatorial drugs have been introduced which potentiate and correct CFTR and ameliorate the CF symptoms. Recently, novel genetic engineering methods like CRISPR/Cas9 and TALEN have been utilized to correct the mutated CFTR gene with high accuracy and eradicate the symptoms. Studying this disease at its distinct levels from subcellular to organs could help to find new treatments. Systematic research in finding common attributes between different states of the disease is very beneficial. Interdisciplinary research groups with various expertise in mathematics, biology and engineering could have a great impact on describing the full picture of the disease and development of new treatment strategies. The main part of this article provides a comprehensive overview of cystic fibrosis with emphasis on the key studies on genetics and their effects on cellular and physiological levels. In this work, conventional and new treatment methods have also been discussed.