Compared to the donor’s endometrium, the levels of DNA methylation in the promoters of Hoxa10 and Pgr were markedly enhanced in the ectopic lesions and this increase in DNA methylation was suppressed significantly by the DNMT inhibitor treatment (Fig 6D), indicating that DNA methylation is involved, at least in part, in the pathogenesis of endometriosis by affecting target gene expression. The gene discussed is HOXA10; the disease is endometriosis.