CALCA and migraine disorder: They determined the extent of DNA methylation in CALCA, RAMP1, CGRP receptor component protein (CRCP), calcitonin receptor-like receptor (CALCRL), upstream stimulating factor 2 (USF2), and other genes in leukocytes and migraine-related tissues, including dura mater, trigeminal ganglion and trigeminal caudal nucleus.