Investigation of interleukin-4 (IL-4) and leukotriene C4 synthase (LTC4s) genes in patients with asthma by next generation sequence analysis

Introduction: Asthma is a recurrent chronic inflammatory disease caused by a combination of genetic and environmental risk factors, characterized by increased airway sensitivity to different stimuli and reversible airway obstruction. It is the most common childhood chronic respiratory disease. To date, its prevalence, morbidity and mortality have become increasingly common. Three stages are held responsible for the occurrence of asthma. These are increased airway sensitivity, airway inflammation and reversible airway obstruction. Asthma is considered as a multifactorial disease. The risk of asthma in children of asthmatic parents has long been known and is one of the three major risk factors of the asthma predictive index. Asthma is a complex genetic disease that does not exhibit simple Mendelian inheritance. There are many studies on asthma genetics, but asthma genetics is still not clearly understood. To the best of our knowledge, there are no studies in the literature in which the IL-4 or LTC4S gene have been investigated by the next generation sequence analysis method. In this study, we aimed to reveal the changes in IL-4 and LTC4 genes by the next generation sequencing in patients followed up with asthma diagnosis. Materials and Method: This study is a prospective study conducted on 50 patients who were diagnosed with asthma according to GINA criteria and followed at the Pediatrics Clinic of Düzce University Medical Faculty. DNA isolation was performed from the remaining blood after routine whole blood samples. The targeted gene regions from the isolated DNA samples were amplified and purified using primers specific to these regions and mutations in these regions were determined by targeted next generation sequencing. In addition, demographic, clinical and laboratory data of the patients were recorded. Results: A total of 50 patients, 32 (64%) male and 18 (36%) female, were included in this study. The mean age of the patients was 7.12±3.8 years (1-16 years) and the mean age of onset of symptoms was 2.73±3.2 years (3 months-13 years). Mutations were detected in 31 (62%) of the 50 patients included in our study. Mutations detected in the IL-4 gene were c.-33C>T in intron 1, c.3619 C>A in intron 3, c.23 G>A in exon 4, and c.360+18 C>A in intron 3. Mutations identified in the LTC4S gene were c.312-16 T>C in intron 4, c.230-12 T>C in intron 3, c.59-10 C>A in intron 1, c.-33 C>T in intron 1, and c.361-9 C>A in intron 3. Discussion: Allergic rhinitis and allergic conjunctivitis were the most common comorbidities of asthma. We believed that low MPV might be one of the criteria in the diagnosis of asthma. Total IgE levels were found to be one of the important parameters in the diagnosis of asthma. The probability of acute urticaria in mutation carriers of the IL-4 gene was 5.6 times higher than in non-carriers. The fact that cases with homozygous mutations in the IL-4 gene were worse than those with heterozygous Clinical findings in asthmatic cases showed that IL-4 gene mutations were associated with asthma. In our study, c.312-16 T> C genetic change in intron 4, which is highly observed in LTC4S gene, was associated with asthma. We hope that our study will shed light on larger and controlled studies on the genetic background and pharmacogenetics of asthma.