Shooting Messengers

In a hurry for a train, stretchy regions in our leg muscles called sarcomeres contract and expand to pull our bones along. Zooming in further on this mouse muscle, scientists follow molecules on their own journey – messenger RNAs (highlighted in red) are carrying genetic information, used as templates to build proteins. A technique called RNA FISH, spots RNAs travelling from the muscle fibre’s nuclei (where they’re made) to z-disks (blue) at the boundaries between sarcomeres along a muscle myofibre. The RNAs zip along the muscle’s network of microtubules (green) like tube or metro lines (although a billion times smaller). Scientists see patterns of different RNAs at the z-disks, clustering like cosmopolitan crowds of commuters at train stations – perhaps as a way to spread a variety of useful proteins along our muscles, which may be disrupted in myopathies.

Written by John Ankers

Image from work by Lance T. Denes, Chase P. Kelley & Eric T. Wang

Department of Molecular Genetics & Microbiology, Center for NeuroGenetics, Genetics Institute, University of Florida, Gainesville, FL, USA

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in Nature Communications, October 2021

Which pathology is shown here?

A. Antisynthetase syndrome

B. Dermatomyositis

Want Big Muscles?

From a body-builder’s bulging bicep to the tiny flight muscles that keep a fruit fly’s wings beating, muscles are all made from bundles of long fibres divided into short, repeated segments called sarcomeres. When an animal makes a move, interlocking molecules within the sarcomere move past each other and cause the muscle to contract. These images show flight muscle fibres from six fruit flies, each with a different genetic change affecting a structure called the Z-disc (yellow), which marks the end of each sarcomere. Changes in a gene called Zasp affect the size of the Z-disc, in turn affecting the diameter of the fibre and altering the overall size and function of the muscle. Zasp is also involved in setting sarcomere size in the muscles of other animals, including humans. Some of these genetic changes mimic the effects seen in some types of muscle disease (myopathies), pointing towards future treatments.

Written by Kat Arney

Image from work by Nicanor González-Morales and colleagues

Department of Biology, McGill University, Montreal, Canada

Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)

Published in eLife, November 2019