Unveiling the Secrets of the Woolly Mammoth's Genome
In a groundbreaking discovery, an international team of scientists has successfully reconstructed the first fossilized chromosomes from a woolly mammoth that roamed Siberia 52,000 years ago. Published in the journal Cell, this research offers an unprecedented look into the genome organization of the extinct species, providing valuable insights into their evolution and adaptation. The study, which took a decade to complete, was led by experts from the Baylor College of Medicine in Houston, the University of Copenhagen, the National Center for Genomic Analysis (CNAG), and the Center for Genomic Regulation (CRG) in Barcelona.
Scientists have been able to find and analyze fragments of ancient DNA for forty years, but this is the first time they have been able to collect them all (there are millions of pieces), see how they interact with each other, and organize them into a three-dimensional structure. This allows, for example, to compare in detail the genome of extinct species with other current ones, see the differences and precisely analyze the adaptation of each one to its environment. In other words, better understand evolution from a genetic point of view.
The Technique and Its Implications
The team utilized a method called Hi-C, which detects spatial proximity and interactions between DNA fragments within the cell nucleus. This technique, combined with DNA sequencing, allowed the researchers to create a detailed map of the mammoth's genome, using modern elephants as a model. The analysis revealed that woolly mammoths had 28 chromosomes, the same number as today's Asian and African elephants. However, even a 5% difference in genome behavior can lead to significant changes, such as the development of woolly hair in mammoths, which is absent in elephants.
One of the keys to the study has been finding a sample well enough preserved to be able to analyze it in detail. Under normal conditions, when an animal dies its DNA fragments and disperses. The researchers needed this to not have happened, and so they looked to the Siberian permafrost, where the almost eternal ice could have preserved extinct animals intact. The mammoth that died 52,000 years ago turned out to be the ideal candidate. It kept the hair, hair follicles and cell nuclei almost intact. The analyzes showed that their DNA was broken into millions of pieces, but that the pieces interacted a lot with each other, making the reconstruction of the chromosomes possible.
The discovery also opens new avenues for the study of other extinct species and even ancient human civilizations. The vitrification-like state of the mammoth's chromosomes, achieved through a combination of cold and desiccation, suggests that similar preservation might be found in other specimens. This could potentially include Egyptian mummies, whose mummification process may have preserved their immune systems and adaptations to infectious diseases.
While the research marks a significant step towards the possibility of de-extincting the mammoth through genetic editing, the scientists caution that this is only the beginning. The current study focused solely on the skin of the mammoth, and other organs with different genetic expressions still need to be examined. Ethical considerations also remain a crucial aspect of this ongoing scientific endeavor.
