Lagging chromosomes among causes of infertility

Almost one in six Canadian couples is affected by infertility.

Almost one in six Canadian couples is affected by infertility.

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A chromosomal discovery could improve the quality of eggs in older patients and thus make it easier for them to become pregnant.

Why do women over 35 have more difficulty conceiving? After discovering one of the causes of age-related female infertility, researchers at the University of Montreal Hospital Research Centre (CRCHUM) suggest that it will be possible in the future to improve the quality of the eggs of older patients by intervening at the cell cycle level.

In a study published in the journal Developmental Cell, CRCHUM researcher Greg FitzHarris and Aleksandar Mihajlovic, a postdoctoral fellow in his lab and first author of the study, reveal in aged mouse eggs (oocytes) that some chromosomes are slower to move during meiosis, a crucial phase of cell division.

These laggards contribute to an uneven chromosomal distribution and therefore to the formation of cells with an abnormal number of chromosomes. This abnormality, called aneuploidy, is one of the major causes of infertility and explains, in part, why older women have difficulty becoming pregnant and carrying a pregnancy to term.

“To give the slowest chromosomes time to reach their destination, we artificially prolonged meiosis with a chemical. Using high-definition imaging techniques, we found that this slowing down before cell division limited aneuploidy,” says Greg FitzHarris, a professor at Université de Montréal.

In the medium term, this discovery, which is still in the basic research stage and conducted in the laboratory on mice, could be used in the clinic to increase the performance of eggs used during in vitro fertilization. Extensive efficacy, safety and security testing will be required before such an approach is adopted.

Almost one in six Canadian couples is affected by infertility. This number has doubled since the 1980s.

About this study

“Distinct classes of lagging chromosome underpin age-related oocyte aneuploidy in mouse,” by Aleksandar Mihajlovic and colleagues, was published August 23, 2021 in Developmental Cell. Funding for the study was provided by the Canadian Institutes of Health Research, the Fonds de recherche du Québec-Santé and the Fondation Jean-Louis Lévesque. 

About the CRCHUM

The CHUM Research Centre (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. More than 2,150 people work at the CRCHUM, including nearly 500 researchers and nearly 650 students and postdoctoral fellows.

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