DNA In Sperm Altered By Cigarette Smoke, Genetic Damage Could Pass To Offspring

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DNA In Sperm Altered By Cigarette Smoke, Genetic Damage Could Pass

To Offspring

http://www.medicalnewstoday.com/medicalnews.php?newsid=72816

The science has long been clear that smoking causes cancer, but new

research shows that children could inherit genetic damage from a

father who smokes.

Canadian researchers have demonstrated in mice that smoking can

cause changes in the DNA sequence of sperm cells, alterations that

could potentially be inherited by offspring. The results of their

study are published in the June 1 issue of Cancer Research, a

journal of the American Association for Cancer Research.

" 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 fetuses, 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 at Health Canada and McMaster University, 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,

according to research previously published by one of the study's co-

authors.

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.

According to Yauk, previous studies have shown that Ms6-hm and

similar locations of non-coding DNA are sensitive to damage from

radiation, mutagenic chemicals and intense industrial air

particulate pollution. 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 (not exam-ined in this study) are associated with

genes.

" It stands to reason that mutations could also interfere with genes,

but our ongoing research looks to clarify the severity of DNA damage

throughout the genome, " said Yauk. " So, while some men say they'll

quit smoking after their child is born, this represents a good

reason to quit well in advance of trying to conceive. "

Among the next steps in gaining a better understanding of the

germline genetic health conse-quences of smoking, Yauk and her

colleagues plan to study how altered DNA manifests itself in the

children and grandchildren of male mice that are exposed to

firsthand smoke. They also plan to study the effects of secondhand

smoke on male mice as well the possibility that the eggs of females

are affected by smoke.