What does it mean if a quarter of the cells from the placenta carry a genetic abnormality – how likely is it that the child will have cells with this abnormality, too? This is the question we wanted to answer'
- Magdalena Zernicka-Goetz
In a study just published in the journal Nature Communications, scientists show that abnormal cells are eliminated and replaced by healthy cells, repairing – and in some cases completely fixing – the embryo.
Researchers at the Department of Physiology, Development and Neuroscience at Cambridge report a mouse model of aneuploidy, where some cells in the embryo contain an abnormal number of chromosomes. Normally, each cell in the human embryo should contain 23 pairs of chromosomes (22 pairs of chromosomes and one pair of sex chromosomes), but some can carry multiple copies of chromosomes, which can lead of developmental disorders. For example, children born with three copies of chromosome 21 will develop Down’s syndrome.
Pregnant mothers – particular older mothers, whose offspring are at greatest risk of developing such disorders – are offered tests to predict the likelihood of genetic abnormalities. Between the 11th and 14th weeks of pregnancy, mothers may be offered chorionic villus sampling (CVS), a test that involves removing and analysing cells from the placenta. A later test, known as amniocentesis, involves analysing cells shed by the foetus into the surrounding amniotic fluid – this test is more accurate, but is usually carried out during weeks 15-20 of the pregnancy, when the foetus is further developed.
Professor Magdalena Zernicka-Goetz, the study’s senior author, was inspired to carry out the research following her own experience when pregnant with her second child. “I am one of the growing number of women having children over the age of 40 – I was pregnant with my second child when I was 44,” says Professor Zernicka-Goetz.
At the time, a CVS test found that as many as a quarter of the cells in the placenta that joined her and her developing baby were abnormal: could the developing baby also have abnormal cells? When Professor Zernicka-Goetz spoke to geneticists about the potential implications, she found that very little was understood about the fate of embryos containing abnormal cells and about the fate of these abnormal cells within the developing embryos.
Fortunately for Professor Zernicka-Goetz, her son, Simon, was born healthy. “I know how lucky I was and how happy I felt when Simon was born healthy,” she says.
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Image: Chromosomes (cropped)
Credit: Zappys Technology Solutions
Reproduced courtesy of the University of Cambridge
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