Epigenetics…let’s get started.
The text below refers to laboratory results published back in 2011. However, those results are a good example of what epigenetics can mean to our lives. If, after reading the post, you’re more confused than before, don’t worry – even senior scientists working in this field for a long time can be surprised by the experimental results related with epigenetics!
I am writing about a paper published more than a year ago to start a new series called: EpiPosts. More to come soon – how can we resist this topic?!
How long did your grandparents live?
If you are aware that genes we inherit from our ancestors can help us be handsomer, smarter, more athletic or healthier; or even that the proper combination of genes and the right choices in lifestyle can dictate our life expectancy, you should still prepare to be surprised: scientists from Stanford University and Harvard Medical School have discovered that we can inherit more than genetic material from our parents and that such inheritance can augment our longevity. Yes, our parents and grandparents can help us live longer.
Or at least, so it happens in model organisms. The study published back in october 2011 by Greer et al. in Nature, used the nematode Caenorhabditis elegans, a very small and transparent roundworm of great utility in development and ageing research. This simple form of life of about 1mm in length is cherished by researchers as it is easy to grow in the lab and its genes can be manipulated as desired. The short lifespan of two to three weeks was a great advantage for this study. For a while, it was known that the longevity of these worms could be prolonged by removing (or mutating) a gene or a set of genes in the worm genome. Now, scientists asked if the increase in longevity could still be observed when the genes were “put back in place”. Confusing?
Well, it is at least complicated. In other words, what the scientists wanted to know was: can specific events experienced by parents be passed as inheritable traits to their offspring? In this case, the event parental worms went through was the increase in longevity engineered in the laboratory. The genetic alterations introduced to create the extra lifespan were then removed so that the following generations of worms had “lost” the mutations and become “normal” worms again. The results were beyond dispute: the descendants lived longer than descendants of normal unmodified worms up to the third generation. What researchers learnt form this study was that circumstances or events lived by great-grandparents conditioned the lives of the new generation of worms.
The phenomenon behind these observations is epigenetics. Meaning something like “above genetics”, epigenetics refers to changes in the characteristics of an organism that do not alter the genetic code but can affect the behaviour of genes and be passed down through generations. These changes are known to scientists and target well-defined features of the DNA molecules and its associated proteins, rather than the DNA sequence itself. In the case of the worms, the offspring benefited form a lab-induced increase in longevity that occurred at a specific point in time, which was the period of the lives of their great-grandparents. Three generations later, the memory of those early worms was still alive in their descendants.
Epigenetic inheritance is common to higher organisms, including mammals. So, similar processes can occur in humans. In principle, one particular person or generation can be “marked” by specific events or by a certain environment that changes their traits (but not their DNA sequences) to novel ones; the event can pass and the environmental conditions change, but the new traits can persist through generations. In this unexpected way, our existence in the present day can be ruled by past epochs. Who were our ancestors? How did they behave and what did they eat? How long did they live? If we want to understand why we are who we are, it’s in our family tree.