Double genome helps to understand human adaptation to cold climate
27 November 2020
Scientists from Lobachevsky University have discovered new factors in mitochondrial and nuclear adaptation to the cold climate
Humankind's early history was a time of hard struggle for survival, when people migrating to new regions had to adapt to new environmental conditions. This era, of course, has not left any written sources, and very few artifacts related to that period have been found. Paradoxically, as it became clear quite recently, this history is encoded within us, in human DNA.
From this perspective, of great informative value is our "second genome", the DNA of mitochondria (the "first" and the main human genome is located in the nucleus of every human cell). Mitochondria that carry this second genome are intracellular organelles are often referred to as the cell's power stations. Mitochondria are believed to have evolved from bacteria that established a symbiotic relationship with eukaryote cells. By analyzing the mutations "recorded" in these "books", scientists were able to reconstruct the emergence of Homo sapiens on the African continent, to identify the "mitochondrial Eve", the hypothetical ancestor of all people living today, and to trace the waves of settlement on our planet in amazing detail.
"Genetic rearrangements are not just 'traces of history', they are the result of natural selection and adaptation to new, often unfriendly, living conditions," explains Professor Claudio Franceschi, head of the megagrant in the field of system medicine for healthy ageing at Lobachevsky University.
"We assumed that migration to colder climates in Europe should have been accompanied primarily by adaptation of cell energy systems, and therefore by simultaneous, interconnected changes in the mitochondrial and nuclear genomes of humans," Claudio Franceschi says of his research.
In a recent paper published in Frontiers in Physiology, the researchers analyzed the interaction (co-evolution) of mitochondrial and certain nuclear genomes in three European populations from different biogeographical and climatic regions: Finland, Great Britain and central Italy.
"One of the main problems in such studies is the astronomical dimension of the data to be analysed," notes another participant in this research, Mikhail Ivanchenko, Lobachevsky University's Vice-Rector for Research. "The number of combinations of the two genomes that had to be tested for the presence of correlated mutations amounted to almost one billion. Of course, a problem like that cannot be solved by exhaustive search."
By using machine learning methods, the researchers have identified synchronous, coordinated rearrangements in nuclear and mitochondrial genes involved in the thermoregulation process. Such changes increased the functionality of skeletal muscles and fat tissue, which was probably the result of adaptation to life in northern Europe. In the future, the methods developed in this study can be used to analyse the interaction and mutual influence of nuclear and mitochondrial genes for a wide variety of biomedical and anthropological applications.
"The significance of the results obtained goes far beyond our original task," believes Professor Franceschi. "By studying the evolutionary mechanisms of the body's adaptation, we can predict resistance to a wide variety of adverse conditions and, ultimately, to the
ageing process. What particular kind of co-mutations in the "double genome" benefits the lucky people who enjoy healthy ageing and active longevity? We expect to lift the veil of secrecy in the near future".
