Institute of Genetics and Cancer

Fresh insight into events behind impaired fertility and genetic disorders

Researchers at the MRC Human Genetics Unit show that the gene Tex19.1 controls events which contribute to the prevention of abnormal chromosome numbers in the egg cells of mice: April 2020


Inheriting the wrong number of chromosomes from your parents is a major cause of human genetic diseases, including Down syndrome. These chromosomal errors are very common in human eggs, and increase dramatically with a mother’s age.

We don’t completely understand why eggs often contain the wrong number of chromosomes, but this appears to be partly caused by eggs pausing their development around the time of birth, maintaining this paused state for decades until the eggs are eventually ovulated and used.

The longer the eggs are paused, the more difficult it is for the eggs to maintain their chromosomes in this suspended state.

In this study, researchers at the MRC Human Genetics Unit studied mice to identify a new set of molecules that act in developing eggs to help maintain chromosomes in their paused state.

The team found that interfering with these molecules causes chromosomes in eggs from young mice to behave more like chromosomes in eggs from old mice. Those mice then passed on the wrong number of chromosomes on to their offspring, also passing on the potential for their offspring to develop genetic disorders.

It is hoped that by understanding how eggs normally try to maintain chromosomes during their prolonged pause, there may be potential in the future for science to improve this process. This could mean reducing how often chromosomal errors arise in eggs, and therefore potentially the likelihood of a mother’s offspring developing a genetic disease.

This study identifies new genes that normally play a role in preventing chromosomal abnormalities from arising in eggs in mice. Further research has the potential to test whether these genes might play a similar role in humans.

Dr Ian AdamsMRC Human Genetics Unit