APEX1 and migraine disorder: Some variants of DNA repair genes, including X-ray repair cross complementing 1 (XRCC1), X-ray repair cross complementing 3 (XRCC3), ERCC excision repair 2, TFIIH core complex helicase subunit (XPD, ERCC2), ERCC excision repair 5, endonuclease (XPG, ERCC5), apurinic/apyrimidinic endodeoxyribonuclease 1 (APE1, APEX1), and 8-oxoguanine DNA glycosylase (hOGG1), involved in the repair of oxidatively damaged DNA, were associated with increased migraine risk [36].