Furthermore, a meta-analysis of 375,000individuals recently revealed that migraine loci are enriched for genes expressed invascular and smooth muscle tissues, largely in line with its proposed vascular etiology.40COL22A1, collagen type XXII alpha 1, is part of the collagenprotein family and variants in this gene have been associated with serum creatinine41 and bronchodilator response in asthma,42 although these specific variants did not associate with cerebral blood flowin our study. This evidence concerns the gene COL22A1 and asthma.