Association of circadian clock TIMELESS variants and expression with asthma risk in children

Introduction Bronchial asthma is a chronic respiratory disease characterized by airway inflammation, allergen‐induced hypersensitivity and dyspnea. Most asthmatic patients demonstrate oscillations of disease symptoms within 24 hours regulated by circadian clock genes. We hypothesized that these genes may be regulators of childhood asthma risk. Objectives The aim was to investigate whether single‐nucleotide polymorphisms (SNPs) in the circadian clock genes are associated with childhood asthma risk. We also aimed to analyze the mRNA level of clock genes in the blood of asthmatic children and NHBE cells stimulated with IL‐13. Materials and Methods Peripheral blood was collected from 165 asthmatic and 138 healthy Polish children. NHBE cells were culture at the air‐liquid interface (ALI) with IL‐13 as an in vitro model of allergic inflammation. Using TaqMan probes, we genotyped 32 SNPs in: CLOCK, BMAL1, PER3 and TIMELESS. Expression analysis for TIMELESS was performed using real‐time PCR with SYBR Green. For haplotype and genotype statistical analysis we used Haploview 4.2 and STATISTICA version 12, respectively. Gene expression analysis was performed in DataAssist v3.01. Results We found that three polymorphisms in TIMELESS (rs2291739, rs10876890, rs11171856) and two haplotypes (TTTT and CTAC) were associated with asthma risk. We also found significantly decreased expression of TIMELESS in the blood of asthmatic children as compared to the healthy children (P = 0.0289) and in NHBE cells stimulated with IL‐13 (P = 0.0302). Conclusions In our study, we showed for the first time that TIMELESS variants and expression may be associated with childhood asthma.