In mouse embryos, sister cells commit suicide in unison

UdeM reproductive biologist Greg FitzHarris and his team show for the first time that sister cells can communicate with each other through a bridge that allows them to die in a coordinated way.

Sister cells are a pair of cells that share the same mother cell. In a new study published in Developmental Cell, researchers led by Université de Montréal (UdeM) professor Greg FitzHarris show how the early mouse embryo gets rid of the defective or unneeded cells in pairs.

“Such a mechanism could serve to ensure the elimination of cells with a common adverse history, such as DNA damage or aneuploidy, an abnormal number of chromosomes in cells known to be one of the main causes of infertility,” said FitzHarris, a researcher at the UdeM-affiliated hospital research centre, the CRCHUM.

In the new study, first author Filip Vasilev, a former postdoctoral fellow in FitzHarris’ laboratory, shows that abscission, the final step of cell division, is delayed in the early mouse embryo, leaving sister cells connected by a stable cytoplasmic bridge.

This bridge between sister cells allows the exchange of molecules that promote apoptosis, the process of programmed cell death in which the body rids itself of unneeded cells.

In humans, apoptosis occurs during early development to eliminate unwanted cells, such as those between the fingers of a developing hand. It also plays an important role in the proper closure of the neural tube—the part of an embryo where the brain and spinal cord develop—and in the normal development of major heart vessels.

Death bridge

“One consequence of this bridge is that sister cells undergo apoptosis in unison,” said FitzHarris. “In other words, if one cell dies, so does its sister. In our study, we have shown that the apoptotic pairing is prevented when the bridge is eliminated. It plays a key role.”

The bridge acts as a true cell-to-cell communication channel, coordinating the clearance of pairs of cells with a similar developmental history.

The question of whether the coordination mechanisms observed by researchers in mice can be extrapolated to humans remains unanswered. FitzHarris’ team is currently studying human embryos.

Science writing: Bruno Geoffroy

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About this study  

“Long-lived cytokinetic bridges coordinate sister-cell elimination in mouse embryos,” by Filip Vasilev under the supervision of Greg FitzHarris et al., was published online Jan. 24, 2025, in Developmental Cell. Funding was provided by the Natural Sciences and Engineering Research Council of Canada, the Canadian Institutes of Health Research and the Fondation Jean-Louis Lévesque. The research was supported by the CRCHUM’s animal facility and the genetic engineering and animal modelling core facility.

About the CHUM Research Centre (CRCHUM)  

Université de Montréal's affiliated hospital research centre, the CRCHUM, is one of North America’s leading hospital research centres. It strives to improve the health of adults through a continuum of research spanning disciplines such as basic science, clinical research and population health. About 2,130 people work at CRCHUM. These include more than 550 researchers and nearly 530 graduate students and postdoctoral fellows. crchum.com 

About Université de Montréal  

Deeply rooted in Montréal and dedicated to its international mission, Université de Montréal is one of the top universities in the French-speaking world. Founded in 1878, Université de Montréal today has 13 faculties and schools, and together with its two affiliated schools, HEC Montréal and Polytechnique Montréal, constitutes the largest centre of higher education and research in Québec and one of the major centres in North America. It brings together 2,300 professors and researchers and has close to 67,000 students. umontreal.ca