Like the walls of a house, membranes delimit the different components of eukaryotic cells – nucleus, mitochondria, etc. However, some of these specialized cellular bodies lack an enclosing membrane but still retain their local concentration of proteins and RNA. Stephanie Weber, a professor in McGill University’s Department of Biology, is particularly interested in one of these membraneless organelles: the nucleolus, which presents a different profile in the case of some diseases, such as cancer.

The researcher and her team induced various genetic perturbations in microscopic worms called Caenorhabditis elegans, which have the advantage of being transparent and therefore easy to observe. Using advanced microscopy techniques, she characterized the changes in nucleolus size and assembly dynamics over the nematodes’ short life span (about two weeks). The goal was to gain a better understanding of the mechanisms by which eukaryotic cells control phase separation to regulate the assembly of these membraneless organelles.

While C. elegans has small round nucleoli in the first days of its life, this changes as it ages. The membraneless organelles tend to assemble, leading them to become larger and less abundant. They also synthesize fewer ribosomes, which play a crucial role in the production of proteins. These results, which are transferable to a certain extent to all eukaryotes, contribute to our knowledge of fundamental biology and pave the way for future studies, notably on ribosome synthesis, which lies at the heart of cell proliferation.

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