The Beginning of Our Skeleton Cells, Picture by Picture

UNIGE scientists have recreated for the first time the assembly film of the human centriole, one of the key structures that make up our cells.

A model of a human centriole cut along its longitudinal axis and viewed from above. © CentrioleLab

Cells have various special structures – such as the nucleus, mitochondria or peroxisomes – known as “organelles”. Tracking their genes and determining their structure is fundamental to understanding the function of cells and the pathologies associated with their dysfunction. Scientists at the University of Geneva ( UNIGE) have combined high-resolution microscopic and kinematic reconstruction methods to see, in motion, the genesis of the human centriole, which is important for the organization of the cellular skeleton, is associated – in the case of dysfunction – with certain cancers, disorders of brain. or retinal diseases. This work, published in the journal Cell, defines the complexity of centriole assembly. It also opens many new avenues for the study of other cell organelles.

Organelle genesis proceeds according to a precise sequence of consecutive protein recruitment events. Viewing this assembly in real time provides a better understanding of the role of these proteins in the structure or function of the organelle. However, obtaining video sequences with sufficient resolution to distinguish such complex microscopic features faces a number of technical limitations.

Cell permeabilization for better diagnosis

This is especially true for the centriole. This nucleus, measuring less than 500 nanometers (half a thousandth of a millimeter), is made up of about 100 different proteins organized into six substructural domains. Until a few years ago, it was not possible to visualize the structure of the centriole in detail. The laboratory of Paul Guichard and Virginie Hamel, co-directors of research in the Department of Molecular and Cell Biology in the Faculty of Science of UNIGE, has changed this situation by using the technique of microscopic magnification. This modern technique enables cells and their components to be slowly inflated without damage, so that they can be observed – using standard microscopes – with very high resolution.

“We were able to put thousands of these randomly taken images back in chronological order, to reconstruct the various steps in the formation of centriole microstructures.”

Obtaining such high-resolution images of centrioles enables complete localization of proteins at a given time but does not provide any information on the arrangement of substructural domains or individual proteins. Marine Laporte, researcher and former teaching fellow in the UNIGE group and first author of the study, used magnification microscopy to analyze the location of 24 proteins in six domains in more than a thousand centrioles at different stages of development.

Rearranging images to put them in motion

”This very tedious work was followed by the construction of artificial kinematics. In other words, we were able to put thousands of these images taken randomly during centriole biogenesis back in chronological order, to reconstruct the various stages of the formation of centriole microstructures, using the computer analysis we developed,” explains Virginie Hamel, co . – research leader.

This unique technique, which combines very high resolution microscopic magnification with kinematic reconstruction, has enabled us to model the first 4D assembly of a human centriole. “Our work will not only increase our understanding of centriole formation, but will also open up incredible prospects in cellular and molecular biology, since this method can be applied to other macromolecules and cellular structures to study their assembly in space and time,” he concludes. . Paul Guichard.