UBC Theses and Dissertations
DNA methylation at imprinted and non-imprinted genes in the sperm of men affected by severe male factor infertility Minor, Agata
Abnormal DNA methylation at imprinted and non-imprinted genes has been associated with spermatogenesis failure. However, little information is available regarding DNA methylation at those genes in men affected by severe male factor infertility. We hypothesized a higher incidence of aberrant DNA methylation would be present in the ejaculate and testicular sperm of men affected by severe male factor infertility compared to that in fertile control men. Furthermore, we hypothesized abnormal DNA methylation would also affect non-imprinted genes in the sperm of men affected by severe oligozoospermia. DNA methylation at the differentially methylated regions (DMRs) of imprinted genes, H19, IG-GTL2 and MEST, was studied in the ejaculate sperm of men affected by severe and very severe oligozoospermia, in the testicular sperm of men affected by obstructive azoospermia (OA) and non-obstructive azoospermia (NOA), and having undergone vasectomy reversal. The results were compared to that in the sperm of control men of proven fertility. Methylation at the DMRs was evaluated by bisulphite sequencing of multiple unique clones, representative of single sperm. DNA methylation was also studied at non-imprinted genes in sperm of men affected by severe and very severe oligozoospermia. DNA methylation was analyzed at 1,505 CpG sites using the Illumina GoldenGate methylation Cancer Panel I with the results at selected CpG sites being confirmed using pyrosequencing. We found the H19 DMR to be most susceptible to methylation abnormalities and the IG-GTL2 DMR to be the most robust. We found a higher incidence of aberrant DNA methylation in the sperm of men affected by severe oligozoospermia, OA and in men undergoing vasectomy reversal compared to control men. The presence of aberrant imprinting in men with obstruction suggests that abnormal methylation at imprinted genes may not only be related to spermatogenesis failure, as seen in patients affected by severe oligozoospermia, but also to changes in testicular environment that may occur in response to obstruction. Lastly, our analysis of a limited number of samples suggests that abnormal DNA methylation in the sperm of men affected by severe oligozoospermia may also affect non-imprinted genes. Our results warrant further analysis of a larger sample size.
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