A total of 300 asthma patients and 418 healthy controls were enrolled. The average ages of asthma patients and controls were 43.6±13.48 and 44.09±13.75 years, respectively. No significant differences in sex, body mass index (BMI) and smoking history were observed between case and control groups (Table 1). Late-onset asthma (age of asthma onset ≥18 years) accounted for 74.3% in the case group.
Association analyses between CDHR3, EMSY SNPs and asthma susceptibility
The characteristics of the selected SNPs are listed in Table S1 and S2. Rs10899234 in EMSY and rs6967330 in CDHR3 were excluded due to their deviation from HWE in the control subjects (P<0.05). The genotyping assays failed for rs12155008, rs41270 and rs448024 in CDHR3.
After adjusting for confounding factors including age, sex, BMI and smoking history, four SNPs were found to be associated with asthma susceptibility (Table 2). The A allele of rs3847076 in CDHR3 was associated with increased susceptibility to asthma under the additive model (P = 0.032, OR = 1.407, 95% CI: 1.030-1.923). For EMSY, both the TC/TT genotype and T allele of rs2508746 were associated with decreased risk of asthma (dominant model: P = 0.019, OR = 0.660, 95% CI: 0.465-0.935; additive model: P = 0.026, OR = 0.718, 95% CI: 0.536-0.961). The TG/TT genotype and T allele of rs12278256 were associated with reduced asthma risk (dominant model: P = 0.033, OR = 0.563, 95% CI: 0.332-1.953; additive model: P = 0.027, OR = 0.558, 95% CI: 0.332-0.937). Finally, the GG genotype of rs1892953 showed an association with increased asthma risk under the recessive model (P = 0.015, OR = 1.667, 95% CI: 1.104-2.518).
Stratified analysis results by gender, smoking status, BMI status and onset age of asthma were shown in Table 3. Allele A of rs3847076 was associated with increased susceptibility to asthma in male subgroup, smoking subgroup, non-overweight subgroup and late onset asthma subgroup (P=0.023, OR=1.869; P=0.009, OR=2.168; P=0.005, OR=1.835 and P=0.023, OR=1.457, respectively). Similarly, rs2508746 TC+TT was related with decreased asthma susceptibility in the non-smoking subgroup, non-overweight subgroup, and late-onset asthma subgroup in dominant model (P=0.014, OR=0.618; P=0.027, OR=0.612 and P=0.016, OR=0.637, respectively). Meanwhile, rs1892953 GG shown increased risk of asthma in the female subgroup, non-smoking subgroup, non-overweight subgroup, and late onset asthma subgroup in recessive model (P=0.038, OR=1.738; P=0.04, OR=1.615; P=0.017, OR=1.910 and P=0.017, OR=1.680, respectively). Rs12278256 T was still associated with decreased asthma susceptibility in female subgroups, non-smoking subgroups, and non-overweight subgroups in additive model (P=0.032, OR=0.465; P=0.02, OR=0.508 and P=0.028, OR=0.481, respectively).
Haplotype and LD analysis
The LD between SNPs of CDHR3 and EMSY was low and those SNPs were divided into eight haplotype blocks with Haploview software (Figures 1 and 2). Only the haplotype consisting of GATCTGAGT in block 1 of EMSY was associated with decreased risk of asthma (P = 0.037, OR = 0.615, 95% CI: 0.388-0.975) (Table 4).
Functional prediction results
Four statistically significant SNPs were predicted using the software RegulomeDB and Haploreg v4 (Table S3). Rs144934374 is strongly linked to rs12278256 and its RegulomeDB scores is lower than that of rs12278256, suggesting that it may be the functional site represented by rs12278256. Acting as promoter histone marks or enhancer histone marks, or affecting DNAse is suggested to be associated with chromatin status, and binding proteins or altering regulatory motifs in ChIP-Seq suggest that transcription levels may be affected. It seems that these four SNPs may have certain effects on chromatin status and transcription level. Rs1892953 appears as an expression quantitative trait loci (eQTL) SNP in thyroid tissue .