Understanding structure and function of the Z-disc in striated muscle

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Muscles are essential for movement, and the organisation of proteins within the muscle cells is important for muscles to generate this movement. These proteins are organised with very high precision, into building blocks called muscle sarcomeres. The sarcomeres are arranged end to end along the muscle fibre, and the interaction between the two main contractile proteins, actin and myosin organised into filaments within each sarcomere, causes each sarcomere to shorten by a small amount. These small movements are added together along the length of the fibre, to produce a large movement. It is essential that all the sarcomeres work in the same way, to ensure that the sarcomeres contract uniformly, and this is underpinned by the precision engineering of proteins into each sarcomere, ensuring that every sarcomere is the same. At the ends of each sarcomere are complex structures known as Z-discs. These important structures contain over 40 different proteins that both anchor the contractile proteins in the muscle sarcomere, and detect and respond to forces generated by the sarcomere when muscle contracts. However, these structures are very thin. So far no-one has been able to find out how these proteins are arranged within the Z-disc. Light microscopy cannot see inside the Z-discs with enough detail, and while electron microscopy shows the overall Z-disc organisation, it cannot pinpoint where individual proteins are. Without knowing how these proteins are organised, it is difficult to understand how they interact with each other, and how mutations in these proteins lead to muscle disease. In this new research, we plan to use a novel 'super-resolution' light microscopy microscopy, which is able to determine the positions of proteins much more accurately than normal light microscopy. This approach will allow us to pinpoint the positions of individual proteins and uncover their arrangement in the Z-disc. To help us do this, we will also develop novel types of probes to help us label proteins within the Z-disc more precisely. We will also use new ways to analyse the data to help us understand how the proteins are arranged in this structure. Together, we expect that our new techniques will allow us to see inside the Z-disc and understand its complexity for the first time.