Chromosome 5q31 and 17q12-q21 regions show strong genetic association with asthma, however not everyone who carries a risk allele is affected. We hypothesized that inter-individual variation in promoter DNA methylation may modify the risk of asthma development. DNA methylation levels in blood of asthmatic and non-affected individuals from the Saguenay-Lac-Saint-Jean asthma familial collection were analyzed. Our data show that DNA methylation levels at the promoters of SLC22A5, ZPBP2 and GSDMA depend on the local genotype and that variation in DNA methylation at the ZPBP2 and GSDMA promoters may have an effect on asthma predisposition only in females, but not males. (By Dr. Anna K. Naumova, http://jmg.bmj.com/content/early/2015/12/15/jmedgenet-2015-103313 )