Researchers from the University of Southampton in the UK have established that eggs have a protective “checkpoint” that helps to prevent DNA-damaged eggs from being fertilized. Damage to an egg’s DNA can result in infertility, birth defects, and miscarriages. This damage can occur as a result of the natural aging process and also as a result of women taking certain types of medication following chemotherapy, or undergoing radiotherapy. The researchers found that damage to DNA during meiosis, the process that results in the formation of sperm cells and egg cells, activates the spindle assembly checkpoint (SAC) in the maturing egg, known as an oocyte, which prevents it from fully developing and stops it from being fertilized. While the SAC is known to exist in most cells in our body, where it helps to make sure chromosomes are shared equally when a cell divides into two, this checkpoint, uniquely in oocytes, appears to respond to DNA damage in the chromosomes. Lead author of the study Professor Keith Jones, Head of Biological Sciences at the University of Southampton, said, “The discovery of such a checkpoint is an important breakthrough that allows further investigation into what could affect the strength of the checkpoint.” The new work was published online on Novmber 2, 2015 in an open-access article in Nature Communications. The article is titled “DNA Damage-Induced Metaphase I Arrest Is Mediated by the Spindle Assembly Checkpoint and Maternal Age.” “My group aims to go on to understand how the initial DNA damage trigger actually manages to switch-on this checkpoint, because the connection is far from clear.” “However, we already know that a woman’s age is an important factor affecting her fertility, and, as such, it would be important to determine if this checkpoint is reduced by the aging process.
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