Scientists identify a NEW key cause of female infertility
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- Researchers think a genetic change causes the function of egg cells to differ
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Scientists have discovered a new fundamental cause of female infertility.
Changes in a specific gene called Eif4enif1 have been identified as a driver of a problem with the ovaries that makes conception almost impossible.
Researchers from Tsinghua University in China have found that the tell-tale genetic change causes a problem with egg cells that prevents the ovaries from releasing eggs regularly.
Without the release of eggs - the ovulation process - fertilization cannot occur.
Specifically, the harmful pattern of DNA affects the functioning of the mitochondria within the egg cells - the 'powerhouse' that converts fuel to energy.
The fertility rate among American women has been slowly declining for years. Infertility affects around 48 million couples worldwide, and about one in five women in the US are infertile
Infertility affects around 48 million couples worldwide, and about one in five women in the US are infertile.
In about one to two percent of cases, the problem is caused by the ovaries' failure to release an egg.
Speaking of the findings, Professor Kehkooi Kee, from Tsinghua University in China, who helped lead the study, said the link between Eif4enif1 and mitochondria had not been identified before.
TheWHO estimates one in six adults globally will be affected by infertility in their lifetime, there are regional variations. The Eastern Mediterranean recorded the lowest infertility rate of just 10.7 percent, followed by Africa with 13.1 percent and then Europe with 16.5 percent. The Western Pacific region recorded the highest rate of 23.2 percent, followed by the Americas with 20 percent. No figure was available for the Southeast Asia region due to a lack of quality studies in that area
Medically, problems with the production and release of eggs is known as both primary ovarian insufficiency and premature ovarian insufficiency.
The term premature refers to the fact that the trouble occurs before the menopause - when ovulation naturally stops.
In 2019, the Chinese researchers came across a family with premature ovarian insufficiency who all had changes in the gene Eif4enif1.
The researchers reproduced this genetic change in mice to see how it impacts human fertility.
They allowed the mice to grow up and compared their fertility with mice whose DNA had not been edited.
They found a characteristic pattern of changes in egg mitochondria.
The average number of total follicles - the tiny sacs on the surface of ovaries, which contain developing eggs - was reduced by roughly 40 percent in older and genetically edited mice.
The average number of baby mice in every litter also decreased by a third.
And when grown in a dish, about half of the fertilized eggs did not survive beyond the early stages of development.
When the researchers examined eggs from the less fertile mice under a microscope, they found that the mitochondria were not spread evenly throughout the egg, as they should be, but were clustered together.
It seemed that the misbehaving mitochondria were contributing to the mice's infertility.
The researchers think that restoring proper mitochondrial behavior could improve fertility.
Their next steps will be to see if mitochondrial defects are also seen in the eggs of human patients.
The findings also suggest there is potential for gene-editing drugs that can address the problem and offer an effective treatment.
The study was published in the journal Development.