Lausanne, Switzerland: Researchers in the Netherlands believe they have identified a gene that is involved in causing infertility in men.
Dr Judith Gianotten told the European Society of Human Reproduction and Embryology annual meeting in Lausanne today (Wednesday 4 July) that the ZNF214 gene is probably a candidate gene for impaired spermatogenesis (an inability to make enough sperm cells).
Now they are testing the gene in human testicle cells and mice to discover exactly what role the gene plays in the production (or not) of sperm cells. An understanding of how it works may help researchers in the future to design ways of targeting the gene and developing treatments to men affected by this form of infertility.
Dr Gianotten, a researcher from the Center for Reproductive Medicine at the Amsterdam Academic Medical Center, told the conference that the ZNF214 gene mainly expresses itself in the testis and is located on chromosome 11p15. This part of the chromosome is linked to the Beckwith Wiedemann Syndrome (BWS) – a complex overgrowth disorder, which often involves boys being born with undescended testicles (cryptorchidism) who suffer from infertility as adults1. She said: "For these reasons we hypothesized that ZNF214 could be involved in male subfertility and we decided to test whether this was the case.
"First we investigated whether this gene was associated with impaired spermatogenesis. We found a significantly different distribution of DNA variations in this gene2 in patients with low fertility compared with the control group, which indicated that the gene was indeed associated. So we screened the gene for mutations in men suffering from infertility due to impaired spermatogenesis."
The researchers took DNA from 77 men with very low sperm counts and compared it with DNA from a control group of 65 men with normal sperm counts. In three patients from the infertile group, three new mutations of the ZNF214 gene were found. These mutations were not found amongst the control group.
For two of the patients in whom a mutation was found DNA from their parents was available, and this showed that in both cases the mutation had been inherited from their mothers. All three patients appeared to be normal in every other respect, and none had any symptom of BWS. One of them had a medical history of cryptorchidism.
Dr Gianotten said: "These results suggest that the ZNF214 gene is involved in impaired spermatogenesis, either on its own, or because it causes cryptorchidism which in turn leads to impaired spermatogenesis. In this study only one of the patients in which a mutation was found reported a history of cryptorchidism. This might indicate the involvement of ZNF214 in impaired spermatogenesis on its own. However, it is also possible that ZNF214 is a disease-causing gene for cryptorchidism.
"The fact that the mutation in the gene appears to be inherited from the mother explains how subfertility due to impaired spermatogenesis can be passed on to the next generation. If it was inherited from the father then the mutation would become extinct in the population."
Dr Gianotten said more research was needed to confirm the findings. "At the moment we are preparing studies to see how the gene is expressed in different cell types of human testicles, and we are looking for the identical gene in mice to test the function of the gene and its mutation."
Abstract no: O-210
Notes
1 The Beckwith-Wiedemann Syndrome (BWS) is a congenital disorder which was described by H.R. Wiedemann in 1963 and J.B. Beckwith in 1969. It is characterised by a variety of symptoms, which include enlarged tongues (macroglossia), abdominal wall defects and gigantisms. Children suffering from BWS have an increased risk of developing childhood tumours in their early years, and cryptorchidism is a symptom in the majority of patients; BWS men have a reduced number of children.
2 In other words, the researchers found significant differences in allele frequencies in patients compared with the controls.
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