How can roundworms help women extend their fertility?
Human eggs begin to mature from the onset of a woman’s first period, meaning they decrease in quality from that point onwards — long before the woman in question is likely to want children. But what if there were a way to delay egg ageing, without losing egg quality?
Researchers at the Hebrew University of Jerusalem have now discovered the switch that may do this — in worms. They’re hopeful this breakthrough, published in the journal Genetics, may help women extend their fertility windows and maintain high egg quality into their 30s and 40s.
Dr Yonatan Tzur and Associate Dr Hanna Achache, along with scientists at Harvard Medical School, studied egg maturation in Caenorhabditis elegans, otherwise known as roundworms. C. elegans has been very helpful in helping scientists understand human genetics, as these worms contain the same number of genes as humans (20,000) and their eggs mature in about one day.
Dr Tzur and his team monitored the changes in each of the worm’s 20,000 genes during egg formation and were able to pinpoint an exact gene (ogr-2) that controls the rhythm of egg maturation. Delving further, the team studied MAP kinase (MAPK), the biochemical switch that turns egg development on and off. When they removed the ogr-2 gene with CRISPR gene-editing technology, MAPK went into overdrive and the worms’ eggs aged very quickly.
“We tested the gene’s role by removing it from the worm’s gene sequence,” Dr Tzur said. “Instantly, these ‘edited’ worms became less fertile and their eggs more closely resembled those of an older worm.”
These findings are significant because ageing egg cells is the main cause of birth defects, miscarriages and infertility in humans. And while in vitro fertilisation (IVF) allows doctors to select the best eggs, women above the age of 35 have a harder time to produce a healthy baby with their own eggs, and for women 42 and older, those chances are close to zero. These statistics, along with the fact that the average age of first-time mothers in the Western world is increasing sharply, means finding the key to slowing down egg maturation is crucial.
Though still in its early stages, Dr Tzur sees two possible applications of his discovery in humans. One is to gently increase the equivalent of ogr-2 in girls via a food additive. This may allow girls to maintain the high quality of young eggs until they’re ready to use them. Another would be to suppress MAPK during IVF cycles. This would help older eggs complete their development and improve women’s chances of having a healthy baby as they get older.
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