It is widely accepted that characteristics which an organism acquires during one’s life are not imprinted on the genetic material (DNA) and therefore are not transferred to the next generation. It might sound ridiculous but is there a chance that the above statement is not 100% true? Let’s take a look at a couple of facts.
Human’s closest relative, the chimp Scientists all over the globe expected that the chimp genome would be vastly different than the human one. After the end of reading the human and the chimp genome everybody was astonished because of the fact that the genes that make the two species share a 99% similarity meaning that humans and chimps express exactly the same proteins.
If not the genes, then what makes us different? Scientists realized that the answer lies to gene expression regulation rather than genes themselves. In other words the difference is in parts of the genome that don’t control which protein is produced, but rather where, when and how it is produced. Gene expression regulation is not only responsible for cross-species difference but is also the main factor which causes the great variance encountered within a species.
So far, so good Let’s have a look at depression. Scientists have noticed that depression lingers years after a stressful life experience and the main reason for that seems to be something called epigenetic changes, meaning alterations to the chemical groups bound to DNA, which regulate the way genes are expressed. Eric Nestler and his colleagues from the South-western Medical Center of the University of Texas in Dallas subjected a number of mice to an aggressive intruder. All the mice developed long lasting symptoms of depression. Nestler and his team found that in the hippocampus of these mice, methyl groups had been added to the DNA around the gene for the Brain-derived neurotrophic factor BDNF, which is a protein found in the neurons of the central nervous system. That protein helps to support the survival of existing neurons, and encourage the growth of new neurons and synapses. Exposure to stress has been shown to decrease the expression of BDNF. Nestler explains: “Methyl groups tighten the DNA molecule, reducing gene activity. Epigenetic changes to DNA are very stable and people will certainly be very interested in whether stress-induced changes can pass on to the next generation, although there is no evidence that such epigenetic changes occur in eggs or sperm”.
Summarising all the above we can see that gene expression regulation is a key factor for inter as well as intra species variation and stress (being a very common element of our everyday lives) actually causes very stable alterations to the DNA molecule influencing gene expression. There is no evidence that these changes pass on to the next generation although such a fact cannot be confidently ruled out. Furthermore, since our DNA seems to “remember”, one cannot rule out the possibility that epigenetic changes caused to our DNA during our lifetime are transferred to the next generation. Ethically this would be an additional reason to make the best out of our lives having responsibility not only for ourselves but for our offsprings as well.
Konstantinos Vougas is a molecular biologist currently working as a research technician in the Foundation of Biomedical Research of the Academy of Athens in Greece, specializing in proteomics and mass spectrometry. Got his B.Sc from Portsmouth University in 1996 and his PhD from the University of Athens Medical School in 2005. He is primarily interested in bioscience related issues, bioinformatics and the novel communication potential provided by the Internet. Visit his blog at Life Sciences Blog
