Genetic memory of chromosomal sites

Most biological properties are inherited through genes, with the exception of this rule. Two teams at the University of Geneva (UNIGE) are investigating the location of the centromere, a specific site on the chromosome that is essential for cell division. They found that in the small worm Caenorhabiditis elegans, transmission of these sites to offspring at the correct location is mediated by epigenetic memory mechanisms rather than by genes.These results are published in the journal PLOS Biology..

Organisms, from humans to microscopic worms, inherit physical and sometimes behavioral traits from their parents. Biological trait transmission is usually replicated at each cell division and mediated by DNA containing the gene. However, some traits can be transmitted from generation to generation, independent of the gene. These are epigenetic phenomena.

A transparent organism for observing chromosome segregation

By studying the physical separation of Chromosomes In two daughter cells inside Cell division, UNIGE scientists have been able to identify one such epigenetic process. The team of Florian Steiner, a professor of molecular biology at the University of Geneva and the last author of this study, is investigating the centromere of the nematode Caenorhabditis elegans. These specific chromosomal structures act as anchors to the mechanisms involved in the correct distribution of chromosomes. Daughter cells: Defects in this distribution can cause cell death, but are also frequently observed in cancer cells. “This little worm is transparent and allows us to observe cell division and chromosomal fate live from generation to generation, which makes it very easy for C. elegans to study these processes,” said a researcher at the Department of Molecular Biology. Reinier Prosée explains. First author of the UNIGE Faculty of Science and Research.

Memory transmitted only to the next generation

The location of centromeres on chromosomes is defined by proteins that biologists are studying in both the Florian Steiner group and Professor Monica Gotta of the University School of Medicine. Together, these research groups discovered that proteins find the correct location on the chromosome and define centromeres, thanks to a specific region that acts as a guide. They then created a variant in which DNA lacks the portion of the protein that encodes this “guide” region.

“It was predicted that this mutant would not be feasible because the location of the centromere could not be defined without the guide portion of the protein, which was expected to result in an incorrect distribution of chromosomes,” Florian said. I will explain. Steiner. “But even without this” guide “region, we found that the truncated proteins were properly placed and functioning. Therefore, the worm is perfectly viable! “Reinier Prosée continues. Once the centromere sites are correctly defined in the mother, we know that this information is passed on to the next generation, thanks to the cells “remembering” the correct locations of these sites.”Guide” area protein..

In contrast, the descendants of mutant worms cannot split them. cell Properly and therefore cannot survive. This is because the offspring do not inherit information about the correct location of the centromere site from the mutated mother. This particular epigenetic memory lasts for only one generation and is not transmitted to the next generation. “Here we test the hypothesis to explain the epigenetic mechanism by which this memory is established and persists during development,” concludes Florian Steiner.

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