Clarification: Gene test aims to predict reproductive lifespan

In BioNews 533, we reported on a new study suggesting an association between early ovarian decline and variations in the number of DNA sequence 'CGG' repeats present in a gene called FMR1. Whilst this finding is novel, we would like to clarify that the FMR1 gene has been known for many years, since the presence of excess CGG repeats causes the common genetic condition Fragile X syndrome in boys who inherit the mutation.

The usual number of CGG repeats present in the FMR1 gene is between 10-40, while a repeat number of 55-200 is described as a 'premutation'. This number of repeats causes genetic instability, so a woman carrying a premutation may pass on a 'full mutation' of between 200-1000 repeats, which causes Fragile X syndrome in boys who inherit it. In the latest study, the researchers found that women with fewer or greater than 28-33 repeats had lower levels of anti-Mullerian hormone (AMH), which suggests they have fewer eggs in their ovaries.

It has also been pointed out to us that any future test of ovary function based on this information would also reveal whether a woman is carrying a Fragile X premutation. Since this could give rise to new reproductive implications, the decision to take such a test should therefore not be taken lightly or without full explanation. A corrected version of this story is available online at the link below.