First-ever images of cell-wide web
Deconvolved confocal image shows pseudocolour representations of fluorescence intensity through a cell [Edinburgh University].
Using confocal microscopy and computer modelling, researchers from the University of Edinburgh, Scotland, have discovered a 'cell-wide web' across which charged calcium molecules carry signals over nanoscale distances.
The latest discovery of this cell-wide network contradicts perceived wisdom that such signals are transmitted via waves, with wave frequency defining the signal.
“The researchers made their discovery by studying the movement of charged calcium molecules inside cells, which are the key messages that carry instructions inside cells,” says Professor Mark Evans from the Centre for Discovery Brain Sciences, University of Edinburgh.
“[Using confocal microscopy] they were able to observe the wiring network with the help of computing techniques similar to those that enabled the first ever image of a black hole to be obtained,” he adds.
As Evan and colleagues write in Nature Communications, the cell-wide web coordinates cellular processes by directing site-specific Ca2+ molecules across distinct cytoplasmic nanocourses that provide discrete lines of communication spanning the entire cell.
The cell nucleus lies at the centre of this network with cytoplasmic nanocourses being demarcated by sarcoplasmic reticulum junctions and Ca2+-pumps.
These sarcoplasmic reticulum junctions, less than 400 nm across, restrict Ca2+ diffusion while the Ca2+-pumps help to segregate signals.
Nuclear invaginations demarcate a releasable Ca2+ store and cytoplasmic nanotubes. a Electron micrographs of artery sections, b Left hand panel shows 3D reconstruction of a deconvolved z stack of confocal images through the nucleus of an arterial myocyte. Right panel, higher threshold and ‘digital surface skin’ applied to select for nuclear invaginations by way of their higher density of labelling for lamin A. c 3D reconstruction of a deconvolved z stack of confocal images from within the lumen of the sarcoplasmic (SR) and nucleoplasmic reticulum (SR) of an arterial myocyte, d Deconvolved confocal z section through the middle of a pulmonary arterial myocyte. Read more here. [Evans et al, Nature Communications 10, Article number: 2299 (2019)]
Images of rat cell images were acquired in one of two ways.
Firstly, the researchers used an Applied Precision Deltavision imaging system consisting of an Olympus IX70 inverted microscope with an oil immersion objective and a Photometric charge-coupled device camera.
Z section (0.2 µm) stacks were taken through cells and images were deconvolved using Softworx acquisition and analysis software, also from Applied Precision.
Alternatively, they used a Nikon A1R + confocal system via a Nikon Eclipse Ti inverted microscope with oil immersion objective.
Image processing and 3D rendering was then carried out using Imaris, Bitplane, with images being deconvolved using Huygens Essential.
Computer models forecast the function of the network and its components, with the researchers also discovering that cells can rapidly rewire their communication networks to change behaviour.
On reaching the cell nucleus, the signals instruct minute changes in structure that release specific genes for expression.
These changes in gene expression further alter the behaviour of the cell.
When, for instance, the cell moves from a steady state into a growth phase, the web is completely reconfigured to transmit signals that switch on the genes needed for growth.
In this way, the cell-wide web is highly flexible and can rapidly reconfigure to deliver different outputs in a manner determined by the information received by and relayed from the nucleus.
Evans and colleagues reckon that by understanding how this this wiring system is controlled could help understand diseases such as pulmonary hypertension and cancer, and could one day open up new treatment opportunities.
Research is published in Nature Communications.