Mechanical coordination of mitochondria and myofibril morphogenesis during muscle development and homeostasis
Description: Muscle cells are densely packed with two key organelles that distinguish muscles from other tissues: chains of actively contracting sarcomeres called myofibrils and large quantities of metabolically highly active ATP-producing mitochondria. Such, the energy-consuming myosin motors that are located in the sarcomeres are effectively fuelled with ATP to produce forces that pump body fluids or move an animal. Depending on the physiological requirements of different muscle types, the interplay between myofibrils and mitochondria varies considerably, with the most striking difference comparing the continuously beating aerobic heart, with the powerful but quickly fatiguing glycolytic fast skeletal muscles. Yet, how myofibrils and mitochondria specialisations that cause these metabolic and contractile muscle properties are established in the different muscles is not well understood. Within our MechanoMitoMuscle consortium, we hypothesise that mechanical forces of the assembling myofibrils build-up pressure on the surrounding mitochondria to coordinate the morphogenesis of both and to achieve a suitable metabolic state that matches the muscle type. To study this hypothesis and reveal possible mechanisms of how the morphogenesis of both organelles is coordinated we will combine the synergistic bioinformatics and modelling expertise of mitochondria present in the Habermann team with the muscle cell and developmental biology knowledge of the Schnorrer team. We will utilise the Drosophila flight muscle model to investigate how mitochondria establish their intimate contacts to the assembling myofibrils during development using two-colour live imaging and photoactivation to track mitochondria transport in intact pupae. We will study the role of microtubules during the mitochondria-myofibril intercalation and genetically dissect which motor proteins and mitochondria adaptors are needed (AIM 1). We will then ask how the observed mitochondria metabolic switch during development, from before to after the mitochondria intercalation, is achieved. To do so, we will build the MitoFly metabolic flux model utilising our developmental transcriptomics and proteomics data (AIM2). We will validate the model by metabolic measurements at the key developmental stages and genetically manipulate predicted key mitochondria components to test the predictions. We will perform a genetic screen of a highly curated list of 100 candidate genes to identify transcriptional regulators or mitochondrial effectors that may respond to mechanical pressure. One promising candidate identified is the BTB Zn-finger protein Fallen that re-localises into phase-separated nuclear aggregates upon mechanical pressure. Finally, we will study how mechanical load induced by controlled muscle exercise in adult flying flies can impact mitochondria homeostasis and metabolism during ageing (AIM3). For this, we have built the FlyDome, a behavioural setup that stimulates flight during the fly lifespan. We will bioinformatically integrate transcriptomics, proteomics and metabolomics data during the lifespan of flies, raised under rest or exercise, to build a MitoFly metabolic model for ageing muscles. In conjunction with direct mitochondria protein turnover quantifications using SILAC-based proteomics, we will define key factors or pathways regulating mitochondria turnover. These pathways will be stimulated to test if aged mitochondria can be rejuvenated. Together, our MechanoMitoMuscle consortium will reveal fundamental biological principles of how cell mechanics is coordinated with cell physiology and metabolism to build and maintain a functional tissue. As mitochondria and sarcomere proteins are highly conserved, the gained insights are likely applicable to mammalian muscles and heart. Mechanisms that can explain how mitochondria age build the basis to propose strategies for how mitochondria ageing could be delayed or reversed, with an obvious important impact on our ageing human society.
Funder: Agence Nationale de la Recherche
Amount: €688,700
Funding type: research
Funder scheme: AAPG2023
Start date: 2023-11-01
Investigator: Frank SCHNORRER
Institution: Centre National de la Recherche Scientifique Délégation Provence et Corse_Institut de Biologie du Développement de Marseille
Subfield: Molecular Biology
Domain: Life Sciences
Funded outputs count: 1
Funder award ID: ANR-23-CE13-0027
OpenAlex ID: G2299116273