Unraveling and targeting autophagy defects in rhabdomyolysis – Rhabdophagy

Rhabdomyolysis (RM) is a vital emergency disorder with no specific treatment, characterized by the acute breakdown of skeletal myofibres in response to a triggering factor, e.g. fasting. Our team has been involved in the identification/description of multiple genes associated with RM including LPIN1 and TANGO2. Recently we identified three new RM-related genes: RYR3, VPS13C and ANXA6. All these genes are involved in lipid and/or calcium metabolism. Starvation being a well-known activator of autophagy, we showed that mutations in LPIN1 (published), TANGO2 and RYR3 (submitted) are associated with autophagy impairment. Membrane lipid remodelling and calcium signaling are critically involved in autophagy, and autophagy defects have been associated with muscle diseases. Our aim is to delineate the physiopathology of RM associated with mutations in LPIN1, RYR3, TANGO2, VPS13C or ANXA6 genes and to identify targeted therapeutic candidates using a combination of zebrafish models and primary myoblasts from patients.
To address these hypotheses, we will complete the analysis of the aforementioned mutations effects on calcium flux and cell death (both features being the hallmarks of RM) in primary myoblasts cultured in basal or stress conditions and will investigate if these RM-associated mutations affect the main effectors of autophagy machinery, TFEB signalling and autophagosome membrane composition. As a second objective, zebrafish is an ideal vertebrate model and knockdown of the five orthologous RM genes have been developed with reproducible locomotor defects. We will assess RM parameters and autophagy flux in these in vivo models. Finally, we will test the effect of autophagy activators on the zebrafish RM models using their locomotor properties, muscle ultrastructure and autophagy flux as readouts with hit validation in primary myoblasts. Therefore, this project will advance understanding and therapeutics for RM and related disorders.