DKK1 and migraine disorder: We also visually compared the RNA expression levels of DKK1, PDGFB, GSTA4, FARS2 and CHIC2 to the genes that encode the recent migraine therapeutic target, calcitonin gene-related peptide (CGRP)6, including CALCA and CALCB (Supplementary Fig. 2) across ten HPA brain regions.