“Biological emulsions”: What salad dressing can teach us about the internal organization of cells

Like a chest of drawers, our cells are organised into “compartments” where specific functions are carried out. There are two main types of compartments in cells. Some are enclosed by membranes — for example, mitochondria, which produce energy, or the nucleus, which stores genetic material. Others, however, form without membranes; these are called biomolecular condensates, and can be compared to droplets of balsamic vinegar forming in oil — like in a vinaigrette.

The nucleolus — the focus of Professor Lafontaine’s research for the past twenty-five years — is one such biomolecular condensate. Located at the heart of the nucleus, it is responsible for making ribosomes: sophisticated molecular machines that produce all the proteins in our bodies.

This new study unveils the nucleolus’s detailed construction plan and shows, for the first time, that cells can be engineered to build synthetic nucleoli with altered properties.

To visualise this, think of a ribosome as a car made of 84 different parts, and the nucleolus as the factory assembling them. The researchers managed to induce cells to produce extra “factories,” to change the order in which the parts are assembled, and even to split up production into separate factories — something never achieved before in human cells.

This work has important implications for medicine. Ribosome production must be tightly controlled: too many can promote cancer, while too few lead to diseases known as ribosomopathies, which particularly affect blood cell production (especially red blood cells), as well as brain and bone development — other key research areas of Professor Lafontaine’s lab.