Zones of youth in the DNA
What determines the lifespan of a mouse, alligator, dog or human? A group of scientists from the University of Georgia believes that they have found a new answer to this age-old question.
Emily Bertucci and Benjamin Parrot rely on recently published data on epigenetics, which mediate changes in living organisms caused by modifications of gene expression, rather than changes in the genetic code. Their recent literature review published in the journal Trends in Genetics reports that a significant portion of epigenetic aging occurs in areas with CpG.
CpG is a fragment of DNA in which the elements cytosine (C) and guanine (G) are linked by a phosphate bond (p) and in which the chain is methylated, i.e. the addition of an amplifying chemical code telling it how to function. Methylation can also turn genes on and off.
Scientists have noticed that methylation patterns in vertebrates change with age. These changes can be modeled to create so-called epigenetic clocks, and, for example, to determine the age of an organism based on the results of DNA methylation sequencing in a sample of biomaterial.
The activity occurring in the CpG region determines the fate of the cell. Double-stranded breaks often occur in the genome throughout the life of an organism. These breaks are effectively repaired by proteins and enzymes known as chromatin modifiers.
According to the study, chromatin modifiers are located in the CpG zones and leave them when it is necessary to repair breaks. When chromatin modifiers are moved, gene expression changes and, consequently, the fate of the whole cell.
Scientists have known for many years that species with a longer lifespan (humans, alligators, elephants) have higher CpG levels than, for example, fish and rodents. CPGs in DNA, like a bright beacon, help chromatin modifiers safely return home. They also act as a buffer to keep gene expression unchanged when chromatin modifiers are moved to repair double-stranded DNA breaks.
According to the researchers, in addition to CpG density, environmental factors and stress also affect life expectancy.
Article by E.M.Bertucci et al. Is CpG Density the Link between Epigenetic Aging and Lifespan? published in the journal Trends in Genetics.