Picture: A man who smokes 
Smoking might also cause
changes in man´s sperm

“Here we are looking at male germline mutations, which are mutations in the DNA of sperm. If inherited, these mutations persist as irreversible changes in the genetic composition of off-spring.” said Carole Yauk, Ph.D., lead author of the study and research scientist in the Mutagenesis Section of Health Canada’s Environmental and Occupational Toxicology Division. “We have known that mothers who smoke can harm their foetuses, and here we show evidence that fathers can potentially damage offspring long before they may even meet their future mate.”

Males, whether they are mouse or man, generate a constant supply of new sperm from self-renewing spermatogonial stem cells. Yauk, along with colleagues studied the spermatogonial stem cells of mature mice that had been exposed to cigarette smoke for either six or 12 weeks to look for alterations in a specific stretch of repeated portions of DNA, called Ms6-hm, which does not contain any known genes. The “smoking” mice were exposed to two cigarettes per day, the equivalent – based on blood levels of tobacco by-products – of an average human smoker.

Yauk and her colleagues found that the rate of Ms6-hm mutations in the smoking mice were 1.4 times higher than that of non-smoking mice at six weeks, and 1.7 times that of non-smoking mice at 12 weeks. “This suggests that damage is related to the duration of exposure, so the longer you smoke the more mutations accumulate and the more likely a potential effect may arise in the offspring,” Yauk said.

While the researchers did not specifically study the protein-coding regions of DNA where genes reside, Yauk notes that previous studies correlate mutations in non-coding regions with those in coding regions, and that some repetitive regions of DNA are associated with genes.

MEDICA.de; Source: American Association for Cancer Research