Father's nicotine use affects future generations
Mouse study implicates epigenetic changes in paternal sperm DNA. Nick Carne reports.
As if we needed more reasons not to smoke, a new study suggests a father's exposure to nicotine may cause cognitive deficits in his children and even grandchildren.
And this is not more proof of the direct dangers of second-hand smoke. The researchers believe it is due to epigenetic changes in key genes in the father's sperm.
Exposing mothers to nicotine and other components of cigarette smoke is recognised as a significant risk factor for behavioural disorders, including attention deficit hyperactivity disorder (ADHD), in multiple generations of descendants.
Whether the same applies to fathers has been less clear, however, in part because in human studies it has been difficult to separate genetic factors, such as a genetic predisposition to ADHD, from environmental factors, such as direct exposure to cigarette smoke.
In the new study, published in the journal PLOS Biology, researchers from Florida State University and Harvard University in the US exposed male mice to low-dose nicotine in their drinking water during the stage of life in which the mice produce sperm. They then bred these mice with females that had never been exposed to nicotine.
While the fathers were behaviourally normal, offspring of both sexes displayed hyperactivity, attention deficit and cognitive inflexibility. When female, but not male, mice from this generation were bred with nicotine-naïve mates, male offspring displayed fewer, but still significant, deficits in cognitive flexibility.
Analysis of spermatozoa from the original nicotine-exposed males indicated that promoter regions of multiple genes had been epigenetically modified, including the dopamine D2 gene that is critical for brain development and learning, suggesting that these modifications likely contributed to the cognitive deficits in the descendants.
"The fact that men smoke more than women makes the effects in males especially important from a public health perspective,” says Florida’s Pradeep Bhide.
“Our findings underscore the need for more research on the effects of smoking by the father, rather than just the mother, on the health of their children.”