Annotation and functional relevance
Significant CpG sites were annotated by GREAT
v3.0.017. We correlated the significant CpG sites we
identified to the expression level of gene nearby (with a region of +/-
250kb) by cis expression quantitative trait DNA methylation
(cis -eQTM) analysis. Blood eQTM was assessed in the BIOS
consortium dataset18. Matched nasal RNA sequencing
data and DNA methylation data was used to perform eQTM analysis for
significant nasal CpG sites and these results were additionally
replicated in the larger collection of nasal brushes obtained in the
PIAMA study19. The genes that were identified in eQTM
analysis were used for pathway analysis by
ConsensusPathDB20. To check if the results of
replicated CpG sites were affected by inhaled corticosteroids (ICS), we
stratified asthma subjects by ICS usage, and compared the
DNA-methylation in the remission group to asthma with ICS and asthma
without ICS group, respectively, by t-test.