A new way that cells can die has been discovered, named erebosis after the Greek word “erebos”, meaning “deep darkness” or “complete darkness”. The phenomenon was observed in the guts of fruit flies, and scientists theorize that it plays a role in the turnover of cells in the gut wall.
“Personally, this work is the most groundbreaking research I have ever done in my life,” said Dr Sa Kan Yoo, who led the research team at the RIKEN Center for Biosystems Dynamics Research, in a statement. The study was published in the journal PLOS Biology.
The dying cells appeared dark under a microscope as they no longer expressed fluorescent proteins, earning the process its seemingly macabre name.
In humans, the lining of the intestines regenerates every five to seven days, helping to maintain stability and function. It has been thought that cells undergo apoptosis – one of the few types of cell death known by science – when they’re ready to vacate the premises. However, these new results suggest otherwise (at least in fruit flies, for now).
“This research was possible due to a really, really miraculous chain of events,” said Dr Yoo in a Twitter thread. “We started research of cell turnover, but the positive control of apoptosis inhibition didn’t work and the project got stuck.”
Researchers were studying an enzyme called Ance in fruit fly enterocytes, the cells that line the intestines. Staining the intestines to make Ance-positive cells show up gave “patchy” results. Then, accidentally, study co-author Hanna M. Ciesielski found that Ance was present in some “weird cells.”
“It took us a few years for us to notice that Ance-labeled cells are dying,” tweeted Yoo. “That moment was a kind of eureka moment for us.”
“Erebotic cells demonstrate accumulation of Ance, flat nuclei and loss of cytoskeleton, adhesion components, and cytoplasmic organelles,” write the team in their paper. “They have no classic feature[s] of apoptosis, necrosis, or autophagy,” other common forms of cell death.
Erebosis was observed to be a gradual march towards death, with a marker of dying cells appearing near the end of the process.
“Small, stem cell-like cells” were often observed beneath or near cells undergoing erebosis, indicating that these young cells were ready to replace their dying brethren in the constant process of gut cell turnover.
As for the dying cells themselves, the researchers theorize that they may serve a function after death. Much like in the skin, the authors propose that erebotic cells may play a structural role, like barrier function.
The authors conclude that erebosis may enable “the continuous flux of the gut tissue without breaching the tissue integrity or arousing immune responses.”
“We are keenly interested in whether erebosis exists in the human gut as well as in fruit flies,” said Yoo.