Study suggests genetic causes for male infertility

December 13th, 2007 - 4:29 pm ICT by admin  

Washington, Dec 13 (ANI): US researchers have suggested that epigenetics, or the way DNA is processed and expressed, might be the underlying cause for male infertility.

The study, led by Rebecca Sokol, M.D., MPH, professor of obstetrics and gynaecology at the Keck School of Medicine of University of Southern California (USC), is based on the knowledge that a broad epigenetic defect is associated with abnormal semen development.

Epigenetic change, which is defined as in addition to changes in genetic sequence, includes any process that alters gene activity without changing the DNA sequence. Some of these epigenetic changes are inherited from one generation to the next.

This is the first report based on our knowledge that a broad epigenetic defect is associated with abnormal semen development. From our data, it is plausible to speculate that male infertility may be added to the growing list of adulthood diseases that have resulted from foetal origins, Sokol said.

In the study, the researchers studied semen samples from male members of couples attending an infertility clinic.

Using highly specialized molecular biology techniques, the researchers studied the epigenetic state of DNA from each mans sperm.

The scientists found that sperm DNA from men with low sperm counts or abnormal sperm had high levels of methylation, which is one of the ways the body regulates gene expression. However, DNA from normal sperm samples showed no abnormalities of methylation.

DNA methylation results from well-known biochemical alterations that occur during epigenetic reprogramming, which is a normal physiologic process that occurs during embryonic development.

Disturbance of epigenetic programming can result in abnormal gene activity or function, even if there is no change in DNA sequence, Sokol said.

The epigenetic irregularity found in these abnormal sperm samples was present in a high proportion of genes that were studied.

The results suggested that the underlying mechanism for the epigenetic changes might be improper erasure of DNA methylation during epigenetic reprogramming of the male germ line.

If we can identify what causes these changes to the sperm DNA, then we might be able to prevent certain types of male infertility, Sokol said.

This is particularly important because recent animal studies have suggested that epigenetics may have broader implications. Exposures to chemicals as a foetus may lead to adult diseases. Perhaps such exposures may be causing the changes in the sperm DNA that we have identified. Studies to uncover a relationship between chemical exposures and alterations in sperm DNA should shed light on this, Sokol added.

The study is published in Public Library of Science One. (ANI)

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