Using genetic data from a group of 1,629 participating couples, scientists in Taiwan have analyzed the impact of paternal smoking on children. The research indicated that when kids are exposed to tobacco smoke by dads that partake, the kids are more likely to have asthma. The scientists showed that changes in immune genes could predict the risk level for asthma development as well. The findings, which have been reported in Frontiers in Genetics, have reinforced what we already know about smoking; when parents smoke, it has an adverse effect on their children’s health. The study may have also revealed biomarkers for the prediction of childhood asthma related to smoking.
"We found that prenatal exposure to paternal tobacco smoking is associated with increased methylation of certain immune genes, which alters how the genetic code is read," said the lead author of the report, Dr. Chih Chiang Wu of Po-Zen Hospital, Taiwan. "This smoking-associated DNA methylation is significantly retained from birth to six years of age, and correlates with [the] development of childhood asthma."
Previous work by other groups has determined that the adverse impacts of tobacco smoke on children are related to epigenetic changes - modifiable chemical tags that adorn the genome and can modify gene expression. Methylation is one of the most common epigenetic tags, for example. This work has shown that smoking-induced epigenetic changes occur in genes that encode for immune system function, and those alterations are connected to an increase in the risk of childhood asthma.
"Twenty-three percent of the fathers [367 dads in the cohort of 1,629 newborns and their parents] were smokers, compared to just three of the mothers [0.2 percent]. This unique disparity provided the perfect opportunity to study the effects of paternal tobacco smoking (PTS) exposure," noted study co-author Dr. Ho Chang Kuo of Kaohsiung Chang Gung Memorial Hospital.
Of all the kids in the study, 1,348 were monitored from birth to eighteen months, and 756 until age six. The risk of childhood asthma was significantly increased in infants who had been exposed to prenatal PTS. As the level of PTS went higher, the methylation of three immune system genes, LMO2, IL10, and GSTM1, also increased.
PTS seems to be influencing the methylation of these three genes and could be implicated in the development of childhood asthma.
"It remains to be determined whether the DNA methylation associated with PTS originated from tobacco smoke exposure in utero, from preconception changes to the father's sperm, or if there is an alternative explanation," noted Dr. Wu. "Preconception paternal smoking has been shown previously to alter sperm DNA methylation, with associated increased asthma risk in offspring."
It may one day be possible to use these methylation patterns to predict who is at risk for getting asthma and reverse course.