The inheritance of a normal and intact number of chromosomes in germ cells, eggs and sperm is essential for the preservation of all species. With age, the risk that the egg will not inherit the normal set of chromosomes increases. This results in so-called aneuploidy, which can mean too many or too few chromosomes. The best-known example is trisomy, also known as Down syndrome in humans. Researchers from the Institute for Genome Stability in Aging and Disease, part of the CECAD Excellence Group for Aging Research at the University of Cologne, have now found that signals from intestinal cells influence significantly the decision whether or not to eliminate damaged eggs in the nematode. C.elegans. The article, “Somatic PMK-1/p38 signaling links environmental stress to germ cell apoptosis and hereditary euploidy” was published in Nature Communication.

The two scientists Dr. Najmeh Soltanmohammadi and Dr. Siyao Wang, in collaboration with the head of the CECAD research group, Professor Dr. Björn Schumacher, studied the stability of genomes in oocytes (egg cells) from C.elegans. In the germ line, the stability of the oocyte chromosomes is closely examined; only intact oocytes survive to be fertilized. The research team has now found that environmental stress responses in the gut lead to the release of a messenger substance that regulates the animal’s germ line. If control by stress responses in the gut is absent, egg quality control fails. Despite the damaged chromosomes, the oocytes survive, more offspring with a defective chromosome number are produced, and aneuploidy occurs. The stress response in the gut reacts both to chromosomal damage in the oocytes and to environmental influences such as increased temperatures.

In humans, the quality of chromosomes in oocytes is also closely monitored and if damaged, the same cell death mechanisms occur as in nematode oocytes. With age, the quality of human oocytes decreases. Environmental influences also play an important role in humans, but how they affect egg quality control is still poorly understood. “This is precisely why new findings on oocyte quality control in the simple nematode are of such importance,” Schumacher said. “We have now shown for the first time how stress responses in the gut control the stability of oocyte chromosomes. Understanding how environmental factors control oocyte quality through such stress responses opens up entirely new possibilities for eliminating harmful influences and preventing malformations.

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