Associate Professor Tony Poole (University of Otago) explains how electron tomography can be used to build up three-dimensional models of structures in cells. He describes how his PhD student Mike Jennings has used this technique to prepare a 3D model of the primary cilium (an organelle at the cell surface that senses the cell’s surroundings).
Jargon alert: Electron tomography is a technique based on transmission electron microscopy. By collecting images at several different angles, electron tomography makes it possible to build up a high-resolution three-dimensional view of the sample.
ASSOCIATE PROFESSOR TONY POOLE
With electron tomography, once you have your dataset with all the information in it, you can then trace individual elements and you can draw lines along them and map them. And once you’ve done all of that, you then create a model which is basically extracted out of the dataset, and now you have an anatomically accurate three-dimensional image, which you can then manipulate and rotate. It is a lengthy process and it depends really on how much data you want to extract out.
It took my PhD student – and I have to emphasise it was my PhD student’s time, not mine – the best part of two and a half thousand hours or a solid year’s work to extract this data out.
In all, there are 2,200 different elements have been traced by Mike to create the three-dimensional tomographic model. If he wanted to just model the cilium, it would be a lot less, but we want to model the extracellular matrix, which is the mechanical dynamic thing that’s happening around the cell. So it’s quite a challenge, it’s a really challenging electron tomography thing to do. No-one has ever done it before, it’s completely unique.