Assessing the MUC5B promoter variant in a large cohort of systemic sclerosis-associated interstitial lung disease.

Objective: The common gain-of-function variant rs35705950, located in the promoter of MUC5B gene, has been strongly associated with interstitial lung diseases (ILDs) of different aetiology, such as idiopathic pulmonary fibrosis (IPF) and rheumatoid arthritis-associated ILD (RA-ILD). In this study, we aimed to investigate the association of this variant and its nearby single nucleotide polymorphisms (SNPs) in the largest cohort of systemic sclerosis-associated ILD (SSc-ILD) to date.

Methods: Samples were collected from blood/saliva, followed by DNA extraction and genotyping using SNP arrays. Data for rs35705950 and additional 903 variants within 100 Kb were obtained using genomic imputation. Subsequently, we tested their association in a meta-analysis to increase the consistency of the results, including 10 European ancestry cohorts comprising 2363 patients with SSc-ILD, 3526 SSc patients without ILD and 15 076 controls.

Results: Meta-analysis showed no significant association between rs35705950 and SSc-ILD, either comparing patients with SSc with and without ILD (p value: 0.588, OR: 1.05, 95% CI: 0.87 to 1.27) nor patients with SSc-ILD with controls (p value: 0.061, OR: 1.16, 95% CI: 0.99 to 1.36). Moreover, none of the additional 903 variants tested in the genomic region reached statistical significance.

Conclusion: Despite analysing the largest and most statistically powered SSc-ILD cohort to date, we found no evidence of association between the MUC5B promoter variant rs35705950 and its surrounding SNPs with SSc-ILD. These results suggest that the pathogenic mechanisms underlying SSc-ILD may only partially overlap with those of other similar ILDs, such as IPF or RA-ILD. This highlights the need for further studies regarding their genetic architecture.