Epigenetic inheritance of longevity
Long life is inherited without the participation of genes
Kirill Stasevich, CompulentaThe lifespan of roundworms, at least in part, is under epigenetic control: chemical modifications of DNA packaging proteins allow extending the life of three generations of nematodes.
It has long been known that the appearance of an organism is determined not only by genes, but also, so to speak, by an extragenetic "side dish" – chemical modifications of DNA or histone proteins. There is a set of enzymes that work with nitrogenous bases in DNA or with histones – attach and remove methyl groups from them. Depending on the methylation pattern, the activity of the gene that has been processed also changes. Or the gene that the modified histones bind to. All this is included in the concept of the epigenetic code.
Schemes of such modifications are passed down from generation to generation; this gives rise to talk about the epigenetic code and inheritance. For example, the eye color of fruit flies, the color and symmetry of plant flowers are determined by such extragenetic factors transmitted from parent to offspring. But scientists from Stanford University (USA) managed to find something more significant: in their experiments, epigenetic factors determined life expectancy. However, the object of the study was only nematode worms.
In an article published in the journal Nature (Greer et al., Transgenerational epigenetic inheritance of longevity in Caenorhabditis elegans), the authors report that the lifespan of worms depended on how certain histones were methylated. Nothing changed in the "text" of the genes themselves, everything depended only on how they were packaged. More precisely, it depends on whether modified or unmodified histones are involved in their packaging.
But, more importantly, the long-lived worms produced the same offspring. And longevity has been preserved for three generations. That is, we are not talking about a simple change in genetic activity that constantly occurs in any organism, namely, inherited quality.
One of the main mysteries of epigenetics is how such modification schemes are passed down from generation to generation. The fact is that epigenetic markers are cleaned off in the germ cells. But everything speaks in favor of the fact that some memory of them remains. Scientists specializing in epigenetics talk about some metabolites or even RNA molecules that mark the sites of DNA and histone modifications, and then the enzymes of the new organism restore methyl modifications using these labels. Perhaps this is due to the not too long period of such inheritance: by the fourth generation of nematodes, this molecular factor is too much diluted between descendants to maintain the memory of all modifications necessary to increase life expectancy.
Now scientists are trying to reproduce the results obtained in experiments on mice and fish. In more complex organisms, the life span is certainly under more intricate control, but why shouldn't the epigenetic mechanism participate in this?
Prepared based on Nature News: Long life passed down through generations.
Portal "Eternal youth" http://vechnayamolodost.ru20.10.2011