background: The causative mechanisms of male infertility are still poorly understood. Mutations in the Methylenetetrahydrofolate reductase (MTHFR) gene have been shown to be involved in male infertility; however, other mechanisms of pathogenesis, like promoter hyper-methylation, could also play a role. Therefore, in this study we compared the methylation status of the promoter region of MTHFR in male patients with non-obstructive azoospermia (NOA) and obstructive azoospermia without anomalies

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... spermatogenesis. methods: DNA from peripheral blood (PB) samples of 50 patients with NOA and 50 fertile men (controls) as well as DNA from testicular biopsies of 32 patients with NOA and five patients with obstructive azoospemia, but normal spermatogenesis, were analyzed by Methylation Specific PCR amplification using primers that hybridize to the CpG island in the promoter region of MTHFR. results: In PB, no differences in the methylation profile of the promoter region of MTHFR were observed between patients and controls. In testis biopsies, hyper-methylation was detected in 53% of the patients with NOA compared with 0% of patients with obstructive azoospermia (P ¼ 0.03). conclusions: These results indicate that hyper-methylation in testis DNA from NOA patients is specific and not due a general methylation defect, and suggest that epigenetic silencing of MTHFR could play a role in azoospermic infertility.