Increased heat alters specific DNA sequences and proteins that control sperm activity, potentially leading to infertility.
- The optimum temperature for sperm production is just below body temperature, between 32 and 35 degrees Celsius.
- A temperature increase as low as 1 degree above the ideal temperature for sperm production negatively affects male fertility.
In men, the optimum temperature for sperm production is just below body temperature, between 32 and 35 degrees Celsius. The rise in temperature is known to lead to male infertility. This can be the result of too much exposure in hot tubs or hot tubs, wearing too tight clothes, or driving too long in the car. The biological mechanisms of this relationship between heat and infertility were still poorly understood.
One more degree affects sperm
American researchers have discovered the molecular mechanisms that produce DNA damage in sperm as a result of temperature variations. “Previous studies have shown that a temperature increase as small as 1 degree above the ideal temperature for sperm production negatively affects male fertility.”, recalls Diana Libuda, professor in the Department of Biology at the University of Oregon and author of the study. In this study, the results of which were published on October 15 in the journal Current Biology, researchers observed that a 2-degree increase in Caenorhabditis elegans, a small worm, led to a 25-fold increase in DNA damage in developing sperm compared to unexposed sperm. Eggs fertilized by these damaged sperm did not produce offspring.
These results observed in worms need to be confirmed in humans but give an indication of the mechanism induced by heat in spermatozoa. “I think this is a hallmark study because it shows an environmental effect that alters specific DNA sequences and the proteins that control their activityobserved Scott Hawley, an expert in meiosis research who was not involved in the research. The discovery of the researchers is to clearly say what is wrong, at the molecular level, when the production of spermatozoa is altered by heat.”
jumping genes
The article also helps understand how meiosis, the process that produces sex cells, differs between sperm and eggs. Sperm, the smallest cell in a person’s body, form in the billions at temperatures below body temperature and are produced throughout adult life. Eggs, the largest cells in a person’s body, are formed inside, where a constant temperature is maintained, and are only produced for a limited time. “The way eggs and sperm develop differently lies in their control of the ability of mobile DNA elements, also known as ‘jumping genes’ or transposons, to move through the genome, and their sensitivity to heat stress, these mechanisms prevent this movement”, described Nicole A. Kurhanewicz, lead author of the study.
Transposons are DNA segments that move around and modify genetic information by inserting into new positions. They also leave DNA damage. The movement of these “jumping genes” is normally repressed during sperm and egg development. This study reveals that with heat exposure, transposons move specifically in developing sperm. Comparing sperm and egg development to microscopy under normal and heat stress conditions, the researchers found a greater amount of DNA damage in sperm in the second situation.
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