We all start our lives in the same way, as one single cell, yet we end up as very diverse human beings with 30 trillion cells and 200 different types all with their own unique function!
All the cells in our body contain exactly the same DNA, yet they are not all alike. A nerve cell is clearly different from a muscle cell or a skin cell. How is it possible that cells with exactly the same blueprint end up being so diverse?
All these interesting questions find its origin in one single term: epigenetics. ‘Epi-‘ from ancient Greek ἐπί means ‘“on top of”, in this context: a layer on top of the genetic code. An additional form of higher control that determines how the genetic blueprint is read.
To understand this concept, we have to zoom in to the nucleus of the cell, which is only 6 µm in diameter, where the genetic material is stored. Here, the 2 meter long DNA sequence wraps around structural molecules, called histones. You can compare this to wrapping 40 km of fine thread around a tennis ball!
DNA and histones are even further compacted into a structure called chromatin. The way in which certain genes are tight up by this packing, makes them inaccessible to being expressed.
The level of this packaging for each gene is controlled by chemical modifications, which are like traffic lights on the different chromosomes. These traffic lights, or epigenetic marks, will determine whether the expression of certain genes is either loosely packed, so ‘on’ (green light) or strongly packed and ‘off’ (red light) and to what extent they are active. This means that for example in nerve cells, a different pattern of traffic lights and thus a different expression of genes can be found than in muscle or skin cells.
Most of these epigenetic marks are stable from generation to generation. This is why a nerve cell will stay a nerve cell when it replicates or divides and doesn’t become a muscle or skin cell all of a sudden. However, many of the epigenetic marks are affected by ageing, the environment and even your own lifestyle. This means, we can say goodbye to the general thought that the activity of genes is stable in living beings. Interestingly, this flexibility to changes offers a great opportunity for medicine, because we may be able to intervene with the activity of some genes from the outside. The hope is that disease causing changes in epigenetic marks can be undone.
To what extend the environment or your lifestyle affects your epigenetic profile is still largely unknown. Also how we can control specific epigenetic marks remains mainly elusive. These questions are currently actively being researched and we expect that more and more will be revealed in the years to come.
Thus, keep in mind that a long healthy life begins with good genes, but the activity of these genes also depends on good habits!
This blog was written by two EpiPredict PhD fellows, Désirée Goubert (UMCG, NL) and Stefania Astrologo (UvA, NL), together with EpiPredict Partner Organisation Biotecture. The EpiPredict consortium (www.EpiPredict.eu) receives funding from the EU Horizon 2020 program under Marie Skłodowska-Curie grant agreement no. 642691.