Human eggs power down to protect themselves

This image, by Gabriele Zaffagnini from the Centre for Genomic Regulation (CRG), showss a human oocyte fixed and immunostained. Mitochondria are shown in orange and the actin cytoskeleton is shown in green. DNA is shown in light blue.

The image is part of a recent study by the Elvan Böke lab that showed that human eggs slow the activity of their internal waste disposal systems as they mature.

All cells need to do some protein recyclingin order to keep order, but doing so also creates reactive oxygen species (ROS), which can cause damage. Using fluorescent probes in over 100 eggs from 21 healthy donors, the researchers tracked lysosome, proteasome and mitochondrial activity in live egg cells, and found it to be lower than in the surrounding cells.

Together with a previous study from the same lab, this work shows how the immature eggs women are born with (about one to two million) manage to remain healthy enough to support pregnancy for over up to fifty years, by keeping their metabolism – and the damaging secondary effects – low.