Finding a 14,300-year-old pet puppy perfectly frozen and preserved in the Siberian permafrost is a big deal. Being able to extract and sequence its DNA is a bigger deal. Being able to extract and sequence its RNA is a HUGE deal – ancient RNA has rarely been found, let alone extracted and sequenced, before. That’s the big news out of Siberia where scientists have done just that on a frozen puppy that still looks almost as cute as it did 14,300-years ago. Good boy!
“Ancient DNA researchers have previously been reluctant to attempt to sequence ancient RNA because it is generally more unstable than DNA, and more prone to enzymatic degradation.”
Dr. Oliver Smith, a specialist in Evolutionary Genomics at the University of Copenhagen and the Natural History Museum of Denmark, explained to Sci-News why we rarely hear about ancient RNA. First, some terminology. RNA is like a single strand copy of a DNA molecule that is used to transfer genetic information from DNA to proteins. A transcriptome is the set of all RNA molecules in one cell or a population of cells, while a genome is the collection of all DNA present in the nucleus and the mitochondria of a somatic (non-reproductive) cell. Because its job is basically done after completing a transfer, RNA is quickly broken down by enzymes – except in one wolf or possibly wolf-dog hybrid pet puppy who had the bad luck to be flash-frozen in what is now Tumat, Siberia, near the end of the Pleistocene era some 14,300 years ago.
“Puppies are very rare, because they have thin bones and delicate skulls.”
Sergei Fyodorov, head of exhibitions at the Mammoth Museum of the North-Eastern Federal University, describes the exciting discovery in 2011. While looking for frozen mammoths, hunters in Tumat found the first known frozen remains of a puppy. With attention focused on that area, they found a second in 2016 that was better preserved with intact skin, fur and internal organs. (Photos here.) Initial research determined that the pups were likely from the same litter and that one had a completely preserved brain (which was removed) and a full belly of twigs and grass which the scientists believed it ate out of desperation after falling into a hole it never escaped from. Once the DNA extraction was completed, Smith and his team decided to try for ancient RNA and were shocked to find it preserved in the pup’s liver, cartilage and muscle tissue.
“To our delight, we found that not only did we find RNA from various tissues, but in some case the signal was so strong that we could distinguish between tissues in a way that makes biological sense.”
Is this a big deal? According to Smith, this puppy’s transcriptome surpassed the next oldest transcriptome by at least 13,000 years. In his study, published recently in PLOS Biology, Smith explains that viruses have RNA genomes and the ability to understand ancient gene regulation will help us better understand our own evolution and the environmental stresses caused by viruses that have impacted it. While not related to its RNA, the fact that this puppy appears to be a wolf-dog hybrid means it was probably a pet at a time long before it was assumed that domestication began.
While it had a sad demise, this puppy now has the distinction of being “man’s best friend” at two separate time in history. Top that, cats!