UC San Diego researchers say they appear to have discovered a previously unknown cause of female infertility. Their study, performed in mice, is the starting point for determining whether this cause also applies to people.
The cause is a lack of a protein called L2 normally present in female egg cells. Without the protein, the eggs don’t develop normally and can’t be fertilized.
The same protein is also present in human eggs, so it’s highly likely L2 plays the same role in women.
The study was published Monday [Feb. 5] in the journal Developmental Cell. It can be found at j.mp/l2eggs.
An estimated 15 percent of infertility in couples is unexplained. And according to the Centers for Disease Control and Prevention, about 10 percent of women aged 15 to 44, or 6.1 million, have impaired fertility.
The L2 protein is involved in silencing genetic activity in the unfertilized egg, placing it in a quiescent state. That state ends after fertilization in the early embryo. But without L2, genetic activity continues and an embryo cannot be formed.
It’s also possible that L2 plays other roles in preparing the egg that aren’t yet known, Cook-Andersen said. And importantly, multiple causes of infertility can be active at the same time, each reducing the chance for a successful pregnancy.
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