July 30 (UPI) -- Scientists successfully transcribed RNA sequences from liver tissue belonging to a 14,300-year-old wolf preserved in permafrost.
When researchers found the Pleistocene-era canid -- either a wolf or domesticated wolf-dog hybrid, scientists aren't sure -- they decided to use the animal to prove RNA can survive for thousands of years.
Every living organism's genetic coding exists as a hard copy in the form of DNA. Inside living cells, copies of DNA are translated to produce "live" copies called RNA. The RNA is used to produce the various proteins that power an organism's many biological functions.
Typically, RNA has a relatively short lifespan. DNA is constantly being transcribed and expressed via RNA, but the RNA copies are quickly broken down and recycled. However, scientists have previously identified ancient RNA copies in plant remains, and researchers have long wondered whether recognizable RNA sequences could survive inside well-preserved animal cells.
"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," Oliver Smith of the University of Copenhagen said in a news release. "However, following our recent successes in sequencing ancient RNA from plant material, we speculated that a well-preserved animal specimen, frozen in the permafrost, just might retain enough material to sequence."
Smith and his research partners sequenced RNA copies from the ancient liver tissue and compared them to RNA sequences from modern wolves and dogs. The analysis -- detailed this week in the journal PLOS One -- proved the ancient RNA had not been degraded or corrupted.
Researchers identified liver-specific transcripts in the ancient RNA that matched coding in the RNA of modern wolves and dogs.
Until now, the oldest transcribed RNA was only 1,300 years old. While scientists estimate more frozen tissue samples will reveal suitably preserved RNA, it is unlikely paleontologists will be able to find enough to make paleo-transcriptomics -- large-scale RNA analysis -- a reality. The odds remain stacked against the recovery of ancient, intact RNA.
But even if paleo-transcriptomics is unlikely, researchers suggest RNA analysis could inspire a variety of new scientific endeavors.
"Knowing that RNA acts as an intermediary between DNA and proteins, both of which are more stable, it might be tempting to ask, 'so what?' But we think the future of ancient RNA has great potential," Smith said.
"For example, many of the most clinically relevant viruses around today have RNA genomes, and the RNA stage is often crucial to understanding the intricacies and complexities of gene regulation. This might have repercussions when discussing the environmental stresses and strains that drive evolution."