Some studies have found that the FMR1 gene (fragile X mental retardation gene 1) may have control over some aspects of female reproductive health. A new study, published in the journal Reproductive Biomedicine Online, suggests that the gene’s reproductive health impact may be through embryo quality. Let’s dive in.
What is the FMR1 gene?
The FMR1 gene, located on the X chromosome, controls the production of a protein called FMR1 protein (FMRP). This protein helps the synapses in the brain adapt so that we can learn and form memory. It’s also present in the male and female reproductive tissues, primarily in the testes and the ovaries.
The FMR1 gene is most known for the fragile X syndrome, a condition where a DNA segment on the FMR1 gene, called CGG, is repeated too many times (over 200 times) for the gene to properly orchestrate the production of the FMR1 protein. This CGG repeat expansion leads to the fragile X syndrome, characterized by learning problems and intellectual disability.
Most people have the CGG repeats between 10 and 40, and repeats over 55 is considered to be in the premutation range. Once the CGG repeats expand past 200, it’s considered a full mutation.
How does the FMR1 gene affect reproductive health?
Because the FMRP is found in the testes and the ovaries, doctors have long suspected that the FMR1 gene may have some control over male and female reproduction – and it does.
We know that women who have a FMR1 gene premutation (CGG repeats between 55 and 200) have an increased risk of primary ovarian insufficiency, a condition where women reach menopause before 40.
Does the FMR1 gene impact your chance of pregnancy?
While scientists agree that women with FMR1 gene premutation are at a higher risk of losing their ovarian reserve earlier in life, study results are mixed on whether the premutation-range FMR1 gene impacts a woman’s chance of pregnancy. Some studies found that women with FMR1 premutation do have lower chances of pregnancy, while others found no correlation.
Does the FMR1 gene affect embryo quality?
A new study, just published in the journal Reproductive Biomedicine Online, sheds some light on how the FMR1 gene premutations may impact your chance of pregnancy, if at all: through embryo quality. The study authors examined 529 embryos of 39 women who had premutation-range CGG expansion of the FMR1 gene. About half of the embryos inherited the FMR1 gene premutation, while the other half had the FMR1 gene in the normal range.
While the embryos didn’t differ in how they looked under the microscope and how they developed, the embryos that inherited the FMR1 gene premutation were significantly slower to reach the blastocyst stage. They were also less likely to be top-quality embryos at blastocyst stage: While almost 40% of the normal embryos were of top quality, only a quarter of the premutation embryos were of top quality.
A previous study also found that women with FMR1 gene premutations may have embryos that are less likely to reach the blastocyst stage. Embryo quality and their developmental potential have a significant impact on your chance of pregnancy. So, it’s possible that the lower pregnancy rates reported in some studies are due to the FMR1 gene’s impact on embryo quality.
How common is the FMR1 gene premutation?
Scientists estimate that 1 in 4,000 to 6,000 people have a full mutation of the FMR1 gene with CGG repeats over 200. The prevalence can depend on the population and your sex. A study found that 1 in 259 women have a premutation range CGG repeats (more than 55 repeats but below 200); while 1 in 755 men had the FMR1 gene premutation.
How do I know if I have a FMR1 gene mutation?
The only way to find out if you have a mutation on the FMR1 gene is to have a genetic test. Talk to your doctor to determine if you should get an FMR1 gene test. Some fertility centers consider the FMR1 gene test as a part of their initial set of fertility tests.
The cost can vary depending on your insurance, from around $100 to over $1,000. Since changes in the FMR1 gene have an impact on not just you, but also on your family, talking to a genetic counselor may be a good idea so that you understand the full implications. Your doctor can also refer you to a genetic counselor.
Please reach out if we can answer any questions about the FMR1 gene and your fertility. We are with you.
