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In recent years, decreasing counts and quality (motility) of semen have been identified as a possible reason for male infertility. Factors such as hormone-active compounds (so-called endocrine disruptors) released to the environment, chemicals to be found in the home, and sedentary lifestyles have been put forward as possible reasons for the phenomenon.
These de novo mutations are found in every individual and are part of the normal evolution of the genome. Normally, they do not affect the health of individuals. But in some cases they may have a strong effect on gene function and can lead to disease. So far, their role in male infertility had not been studied.
The researchers studied DNA from 108 infertile men, and also from their parents. Comparison of the parental DNA with that of the offspring enabled the identification of the de novo mutations. The researchers found 22 de novo mutations in genes involved in spermatogenesis, which had not previously known to cause infertility in humans.
The researchers will need to screen many more patients and their parents in order to search for patterns in the locations of the novel mutations, and to learn more about the function of the genes that are affected by these mutations. In the meantime it is too early to give the already tested patients a definitive diagnosis.
The de novo mutations leading to infertility can result from errors in DNA that occur during the production of sperm and egg cells of the parents, or during the early development of the embryo. Although by their very nature these spontaneous mutations cannot be predicted, in other diseases patients with a highly similar presentation of a disease (i.e., phenotype) often have mutations in the same gene. This may also apply to the many more infertile men (phenotypes of infertility) in the world who have mutations in the same group of genes as the group of patients that have been studied in the present study..
Eventually, the research will help establish new diagnostic tests, which will be able to provide a patient with a detailed analysis of the reason for his infertility, and allow for personalised care. By establishing the molecular cause of infertility, the risk of transmitting infertility to another generation can be predicted. Infertility is not something you normally inherit from your parents; they were clearly both fertile. But with the introduction of assisted reproductive technologies, infertility may become an inherited disorder in some cases.
See here a sequence on how genetics may affect infertility: