It’s in the Sperm! By Mrs Vera West
It was once proclaimed that there was no transfer of information from the environment to the DNA, and thus not being of an inheritable basis for the characteristics of future offspring. Not so, the science of epigenetics claims. Sperm, for example, are affected by environmental conditions, and may transfer information, especially adverse health effects.
“DNA has long been considered the roadmap to our destiny, the final determinant in our disease risk and longevity. We are told repeatedly that our health is inherited, that our life is already determined by our father and mother’s DNA. While the DNA provides a template, it is not the final arbiter over our health. In the study of epi-genetics, there are environmental factors that influence genetic expression throughout our life. The biochemical influences and stressors in our immediate environment have an impact on our genetic expression. The nurturing a child receives (or doesn’t) has an impact on their genetic expression as they develop. A new study by McGill University finds that this environmental information is also transmitted through non-DNA molecules in the male’s sperm.
Father’s sperm holds secrets to the future vitality of his offspring
A man’s offspring not only inherit his DNA, but they also inherit the biochemical and environmental influences that are encoded in the father’s sperm. These factors precede fertilization and help define the epigenome, or heritable biochemical markers that influence DNA and the proteins that bind it together. Through these mechanisms, a man can make healthy lifestyle decisions that prime his future offspring for healthy genetic expression. Or, a man’s poor dietary decisions prior to conception can negatively impact the child’s well being and disease risk later in life.
McGill University published ground-breaking research in Developmental Cell. The research shows exactly how the molecules in sperm transmit this information at fertilization. This research will open up new avenues of research to better understand disease prevention from one generation to the next. This research can help scientists identify the prospect of childhood disease by simply studying the proteins in the sperm and identifying how certain proteins convey future disease risk.
“The big breakthrough with this study is that it has identified a non-DNA based means by which sperm remember a father’s environment (diet) and transmit that information to the embryo,” says Sarah Kimmins, Ph.D., the senior author on the study and the Canada Research Chair in Epigenetics, Reproduction and Development. “It is remarkable, as it presents a major shift from what is known about heritability and disease from being solely DNA-based, to one that now includes sperm proteins. This study opens the door to the possibility that the key to understanding and preventing certain diseases could involve proteins in sperm.”
Malnourished males transmit health problems through their sperm, at fertilization and beyond.
The researchers investigated the molecular structure of embryos, identifying cells for epigenomic analysis. The researchers manipulated the sperm epigenome by depriving male mice of folate, a key vitamin for embryonic development. Using new epigenetic tools, the researchers were able to trace the effects that these molecules had on proteins that were associated with the DNA. After depriving the male mice of folate, they observed changes to a group of molecules called methyl groups. These molecules are associated with histone proteins, which are a critical component for packing DNA into cells.
The male mice that were deprived of folate ultimately produced sperm that negatively altered the genetic expression of embryos. The malnourished male mice passed on birth defects to their offspring, including deformation of the spine and the skull. These negative changes to the methyl groups on the histones in sperm were not exclusive to the sperm itself. These changes were transmitted at fertilization and caused defects to the developing embryo.
“Our next steps will be to determine if these harmful changes induced in the sperm proteins (histones) can be repaired. We have exciting new work that suggest that this is indeed the case,” adds Kimmins. “The hope offered by this work is that by expanding our understanding of what is inherited beyond just the DNA, there are now potentially new avenues for disease prevention which will lead to healthier children and adults.”
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