Remnants of organic molecules found in nuclei of ancient dinosaur cells

A team of scientists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences and the Shandong Tianyu Nature Museum (STM) isolated perfectly preserved cartilage cells in a 125 million dinosaur. years from northeast China that contain nuclei with remnants of organic molecules and chromatin. The study was published in Communications biology.

The dinosaur, called Caudipteryx, was a small omnivore about the size of a peacock with long tail feathers. He roamed the shores of the shallow lakes of Jehol Biota in Liaoning Province during the Lower Cretaceous.

“Geological data has accumulated over the years and has shown that the preservation of fossils in Jehol Biota is exceptional due to the fine volcanic ash that buried the carcasses and preserved them down to the cellular level,” Li said. Zhiheng, associate professor at the IVPP and co-author of this study.

Scientists extracted a piece of distal articular cartilage from the right femur from this specimen, decalcified it, and used different microscopic and chemical methods to analyze it. They realized that all the cells had been mineralized by silicification after the animal’s death. This silicification is very probably what allowed the excellent conservation of these cells.

They also discovered two main types of cells: healthy cells at the time of fossilization and less healthy cells that were porous and fossilized dying. “It is possible that these cells would already die before the animal even dies,” said Alida Bailleul, associate professor at the IVPP and corresponding author of this study.

Cell death is a process that occurs naturally throughout the life of all animals. But being able to place a fossilized cell in a specific location in the cell cycle is fairly new in paleontology. This is one of the objectives of the scientists at the IVPP: to improve cellular imaging in fossils.

Additionally, the team isolated some cells and stained them with a chemical used in biological labs around the world. This purple chemical, called hematoxylin, is known to bind to the nuclei of cells. After staining the dinosaur material, a dinosaur cell showed a purple nucleus with darker purple threads. This means that the 125 million year old dinosaur cell has such a well preserved nucleus that it retains original biomolecules and chromatin strands.

The chromatin found in the cells of all living organisms on Earth is made up of tightly packed DNA molecules. The results of this study thus provide preliminary data suggesting that original dinosaur DNA remains can still be preserved. But to test this accurately, the team needs to do a lot more work and use much more refined chemical methods than the stain they used here.

“Let’s be honest, we’re obviously interested in fossilized cell nuclei because that’s where most of the DNA should be if the DNA was preserved,” Bailleul said. Last year, she published another study reporting exceptional preservation of nuclear and biomolecules in cartilage cells from a Montana dinosaur. “So we have good preliminary data, very interesting data, but we are just starting to understand cellular biochemistry in very old fossils. At this point we need to work more.

The team insists they need to do a lot more analysis and even develop new methods to understand the processes that can allow the preservation of biomolecules in dinosaur cells, because no one has ever succeeded in sequencing the ‘Dinosaur DNA. In the ancient DNA community, sequencing methods are used to confirm whether ancient DNA is preserved in fossils. So far, these methods have only worked for young fossils (not much older than about a million years), but they have never worked for dinosaur material. Dinosaurs are considered far too old to hold any DNA. However, chemical data collected by scientists at IVPP and STM suggests otherwise.

Even though more data needs to be collected, this study clearly shows that 125 million year old fossil dinosaur cells cannot be considered 100% rock. They are not completely “stonified”. Instead, they still contain remnants of organic molecules. Now it is essential to understand precisely what these molecules are, if they hold any biological information and DNA remnants.

– This press release was originally posted on the Chinese Academy of Sciences website

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