COL4A1 and migraine disorder: COL4A1 at chr13q34 was shared between migraine and DBP (lead SNP rs13260, PCPASSOC = 8.69 × 10−15 based on SHet statistic) as well as PP (lead SNP rs12875271, PCPASSOC = 6.29 × 10−12 based on SHet statistic).