Global sperm DNA methylation comparison in fertile and infertile men: preliminary results

Abstract viewing session during the 4th NEEM in Riga, Latvia

Wednesday, 15 September 2010- Igor Tsarev and J. Erenpreiss of the Riga Stradins University, Andrology Laboratory (Riga, Latvia) won the second prize for best abstract from Karl Storz during the 4th North Eastern European Meeting (NEEM) recently held in Riga, Latvia.

Titled "Global sperm DNA methylation comparison in fertile and infertile men: Preliminary results," the study bagged one of the six prizes and bested 80 other abstracts submitted to the annual regional conference organised by the Regional Office of the European Association of Urology (EAU). The winning abstract appears below:

DNA methylation is a major epigenetic regulatory mechanism. Several studies have demonstrated significance of immunocytochemically assessed global DNA methylation for normal development of male germ cells and fertilization capability of spermatozoa.

We have elaborated a new, mass-spectrometry based approach for global sperm DNA methylation analysis by assessing methylated to unmethylated deoxycytidine ratio. In this study, we have compared global sperm DNA methylation between two groups of men: donors with proven fertility and males from barren couples with excluded female factor.

Sperm samples from 13 proven fertile donors (with currently pregnant partners) and 31 infertile males were collected, and fresh sperm aliquots were frozen until processed.

Spermatozoa DNA was extracted using protease K treatment, purified with chloroform-isoamyl alcohol solution, and lysed to mononucleotides using DNAze I/nuclease p1 /acid phosphatase treatment protocol elaborated in our laboratory.

Lysis products were stored frozen until analysis. Proportion of 5-methyldeoxycytidine to deoxycitidine was assessed using mass-pectrometry. Mean proportions were compared using two sample t-test.

The results showed that mean proportion of methylated deoxycitidine in male donors group was 8.9% (SD+/-5.5 %, S. E. mean 1.4%), while in infertile male group it was 7.9% (SD+/-6.7%, S. E. mean 1.9%). Two sample t-tests for a difference in means showed no significant statistical difference (p=0.678) in global methylation levels between txo groups.

"We have found that a proportion of methylated deoxycytidine has a tendency to be lower in infertile male group than in donor group, without reaching statistical significance. Further studies including larger number of samples should be carried out to elucidate differences in global sperm DNA methylation levels between fertile and infertile men," the researchers concluded.

Source: I. Tsarev, Ju Erenpreiss, "Global sperm DNA methylation comparison in fertile and infertile men: Preliminary results," Abstract N24, 4th North Eastern European Meeting (NEEM), Riga, Latvia, September 10-11, 2010.

Edited by: JV

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