Many couples who would like to start a family have difficulty doing so. This disappointing and frustrating situation is more common than many people realize, affecting approximately one couple out of six worldwide. Given that female infertility issues receive so much attention, it may surprise some to learn that a couple’s inability to conceive is attributable to male infertility approximately half of the time.
One of the most common reasons for male infertility is azoospermia, a condition of having no sperm in the semen. Azoospermia is present in about 20% of male infertility cases in Europeans and 25% of male infertility cases in Chinese men. There are two main types of azoospermia: obstructive azoospermia and non-obstructive azoospermia (NOA). In obstructive azoospermia, the sperm are blocked by a physical obstruction, such as a vasectomy. In NOA, no physical barrier to sperm delivery is present and the absence of sperm in the semen is usually due to a lack of sperm production.
Recently, a group of researchers from China, led by Zhibin Hu and Jiahua Sha of Nanjing Medical University, reported novel genetic associations with NOA in the journal Nature Genetics. These researchers compared about 3,000 Chinese men diagnosed with NOA to 5,734 Chinese men without the condition. They found that each copy of a C at (equivalent to in the study) was associated with 1.25 times higher odds of NOA and that each copy of a T at (equivalent to in the study) was associated with about 1.4 times higher odds of NOA. They also found a third SNP () associated with NOA, although the effect was slightly smaller than the other two SNPs mentioned above (23andMe does not currently report data on this SNP).
The first of these SNPs () is located near the PRMT6 gene. Some studies suggest that a gene called prmt5, which is related to PRMT6, may be involved in sperm and egg development in fruit flies, mice, and possibly some fish. In humans, the enzyme encoded by PRMT6 may regulate another gene thought to be involved in pairing together chromosomes during the formation of sperm. The second SNP, , is located near the genes PEX10 and MMEL1, both of which have also been associated with male fertility in other animals.
The question of why some couples struggle to conceive is of great personal importance and impact to many, and genetic research is just starting to uncover common genetic variation that may influence human fertility. Many genes and non-genetic factors are likely to be involved in NOA, and many other conditions may contribute to male infertility besides NOA. This study provides insights into some possible genetic factors influencing male infertility in Asian men but more studies are needed to confirm these associations — and find new ones — in other populations.
SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.
Editor’s note: Pending an FDA decision, 23andMe no longer offers new customers access to health reports referred to in this post. Customers who purchased prior to November 22, 2013 will still be able to see their health reports, but those who purchased after that time will not. Those customers will have access to ancestry information as well as access to their uninterpreted raw data.