Improved Super-Resolution Microscope Reveals Centriole Structure

If you want to understand the underlying mechanisms of cellular motility and division, then the centriole is the organelle of interest. Each cell has a pair of centrioles, which help to segregate chromosomes during cell division. These special organelles are multi-molecular machines composed of hundreds of proteins, and they have a hidden code of post-translational modifications (PTMs) that contribute to their rigidity or flexibility. Previous electron microscopy studies have revealed the basic structure of centrioles, but PTMs are invisible to the electron microscope—so what do they look like?

Thanks to improved super resolution fluorescence microscope technology developed by EPFL biophysicists, we now have a detailed picture of these nanoscale structures, both isolated and in situ. As expected, the centrioles are shaped like ridged bullets—i.e., they are cylindrical with nine lengthwise ridges, and their diameter tapers off at one end. Given this high degree of organization, the scientists were surprised to find that one PTM actually twists around these ridges. The results were published today in Nature Methods.

“The symmetries of multi-molecular machines often explain how they can perform diverse functions,” says senior author Suliana Manley of EPFL. “PTMs can form a special code that tells proteins where to dock, but they can also stabilize the centriole while forces are pulling during division. We still don’t know why the twist is there, but it offers a clue to how centrioles work. Our study underlines that super-resolution microscopy is an important partner to electron microscopy for structural biology.”

Centrioles are about 100 times smaller than a mammalian cell, and a thousand times smaller than a human hair. So in order to observe them inside of living cells, the researchers had to improve super-resolution microscope technology. Their new super-resolution technology can now be used to study numerous other structures within the cell such as mitochondria or to look at other multi-molecular machines such as viruses.