NEW YORK (Reuters Health) - Men with low concentrations of sperm in their semen may have imprinting defects that could be passed on to offspring as a result of assisted reproductive technologies, according to research in Portugal.

Until now, the potential for congenital syndromes related to imprinting defects associated with such technologies was attributed exclusively to loss of methylation of the maternal allele in the oocyte.

To investigate a possible role of spermatozoa in this process, Dr. Mario Sousa of the University of Porto, Portugal, and colleagues conducted genomic sequencing of spermatozoan DNA from the semen of 27 men with normal sperm counts and from 96 patients with oligozoospermia.

They report in the May 22nd issue of The Lancet that methylation profiles were unaltered in the subjects with normal sperm counts. However, methylation profiles were abnormal in 23 of the 96 oligozoospermic samples.

Dr. Sousa's group suggests that abnormal DNA methyltransferase activity may be the cause of the low sperm counts, and that this condition is transmitted during male infertility treatments and could affect embryonic development.

Lancet 2004;363:1700-1702.

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