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Infertility passed from father to son

Most people wonder what aspects of themselves they will pass on to their offspring. Will the child have blue eyes, or brown? His big nose; or her pointy chin? There have always been some traits, such as infertility, for which no speculation was necessary - anyone who had a genetic defect making them infertile would not have been able to have kids.

However, with the introduction of assisted reproduction, these rules are changing. David Page from the Whitehead Institute, Cambridge, Massachusetts, and colleagues report in the July issue of Human Reproduction that a specific cause of male infertility - a small genetic deletion on the Y chromosome - can apparently be passed from father to son. Until recently, the deletion has almost always occurred spontaneously in men because it could not be inherited. But now, this genetic defect can be passed on when the child is conceived by an assisted reproduction technique called 'intracytoplasmic sperm injection' or ICSI.

About 2% of all men are infertile because they have little or no fully developed sperm in their semen. In many cases, the molecular cause of the problem is unknown. But the commonest of the identified reasons is a deletion in the part of the Y chromosome called AZFc. ICSI now allows these men to have children. A few spermatozoa are extracted either from the semen or testis, and each sperm is then injected into an individual egg that is implanted in the fallopian tube.

Basic genetics dictates that daughters born to these couples should be perfectly normal because they inherit two X-chromosomes - one from each parent. Boys, though, should inherit the Y-chromosome from their father. In other words, they stand to inherit the deletion that caused the infertility problem in the first place. But until now, no one had tested the babies born by ICSI to see if the boys really do inherit the mutation.

Page's group found three unrelated men with the AZFc deletion who had four sons between them. Examination of the babies' DNA revealed that all of them had, in fact, inherited the Y-chromosome deletion. This implies that, when these children grow up, they will have exactly the same infertility problem as their fathers. Unfortunately, the researchers will only be able to confirm the inheritance of this trait when these babies reach puberty - many years from now.

According to Page's team, the observations "provide a concrete foundation for alerting couples to the likelihood of transmitting infertility-causing Y deletions by ICSI." But more broadly, even for those couples who do not know the exact cause of their infertility, these findings raise important questions about the possibility of passing on infertility to offspring.

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Wunsch, H. Infertility passed from father to son. Nature (1999). https://doi.org/10.1038/news990715-10

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  • DOI: https://doi.org/10.1038/news990715-10

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