Joy Lian

Many college students are all too familiar with the drastic effects of stress. But a new Yale study discovered something new: Stress responses in cells have led to different evolutionary development across various mammal species.

A research team of professors and scientists led by ecology and evolutionary biology professor Günter Wagner compared human decidual cells with related cells in mammals, finding that stress responses in decidual cells has helped facilitate evolution. Their work was published in the journal PLOS Biology.

The mammalian decidual cell is a specialized cell in the uterus of many mammals, including humans, said ecology and evolutionary biology professor Eric Erkenbrack, who drafted the publication. Such cells play a role in the reproduction process, are shed or absorbed during menstruation and help potential offspring attach to the mother’s placenta during pregnancy.

The researchers, whose work took place over a year, were most interested in the question of cell identity — the specific differences between cells in certain organisms — particularly the identity of decidual cells and how they evolved.

Erkenbrack, understanding that the study’s vernacular may be difficult to interpret for common readers, took the team’s work to Twitter. In a creative and light-hearted wave of emojis, GIFs and colloquialisms, Erkenbrack condensed a scientific publication into a concise summary for those less scientifically inclined.

Erkenbrack said the thread was well-received.

“Reading a scientific paper is daunting for a layperson,” Erkenbrack said. “And most leave it to someone to translate the paper into layspeak. I thought the results of the paper would be accessible to a broader audience if I successfully condensed the main findings and used a less intimidating terminology.”

The researchers isolated the precursors to decidual cells in opossums and ran tests after adding decidualization media, which spurred the cells to become decidual, allowing them to track how the cells functioned in response to the media.

The cells reacted by shrinking, which the team did not initially connect to stress. Rather, they believed that rapid shrinking within the cell was due to apoptosis, the death of cells that occurs as a normal and controlled part of an organism’s growth and development.

This could not be the case, however, since the cells were not dying at the rate expected from apoptosis.

“The first indication that it was a stress response was just looking at the cells,” Erkenbrack said. “That’s why … we show the morphological response, and at that point we see that the cytoplasm essentially shrinks rapidly around the nucleus, collapses around the nucleus.”

Arun Chavan GRD ’18, an immunobiology postgraduate associate who worked on the project’s methodology and conceptualization, said the research was useful in identifying the evolutionary function of decidual cells. These cells play a key role in the pregnancies of eutherians, a large group of mammals, including placentals, which carry offspring in the womb for a relatively long period.

“These results provide a mechanistic understanding of the early evolution of eutherian pregnancy and also identify the ancestral function of an evolutionary novelty, the decidual cell-type,” Chavan said.

The perhaps unusual research animal used in the experiment — opossums — was chosen by the researchers as a mammal with certain parameters that more ordinary experimental organisms did not provide, according to Erkenbrack.

“We needed to find an organism that had endometrial stromal fibroblasts [a connective tissue located in the uterus] but didn’t undergo the process of [cell] decidualization,” Erkenbrack said. “So when you’re choosing nonmodel organisms to work with, we really had to take into account the evolution [in the nonmodel organism], especially the type of pregnancy.”

The research team will now attempt to expand the number of organisms they wish to study, building on their findings with opossums. They will also compare protein levels among species, which Erkenbrack said will prove a more difficult task.

“The next steps are to look at more mammals,” Erkenbrack said. “So we use a comparative approach … We’re very interested in that because a lot of people haven’t really looked at the protein levels. It’s generally harder to do, and we think that the changes in the protein sequence actually had many dramatic, dramatic changes that led to the decidual cells.”

Opossums are intelligent animals; researchers have found that their memories are more accurate than those of dogs, cats, rats and pigs.

Nick Tabio | nick.tabio@yale.edu

Correction, Sep. 13: The headline of this article has been updated to accurately reflect the study’s finding.