Mini-agrin prevents calcium leakage and restores the dystrophin complex.

Aldharee, H.; Mierzejewski, B.; Kerr, A.; Bragg, L.; Bigot, A.; Reinhard, J. R.; Santoleri, S.; Roberts, N.; Das, R.; Mouly, V.; Ruegg, M. A.; Cossu, G.; Galli, F.

doi:10.1101/2025.11.25.690165

bioRxiv · 10.1101/2025.11.25.690165

Mini-agrin prevents calcium leakage and restores the dystrophin complex.

Aldharee, H.·Mierzejewski, B.·Kerr, A.·Bragg, L.·Bigot, A.·Reinhard, J. R.·Santoleri, S.·Roberts, N.·Das, R.·Mouly, V.·Ruegg, M. A.·Cossu, G.·Galli, F.

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Abstract

Muscle cell death in muscular dystrophies depends upon calcium ion (Ca++) leakage through sarcolemma and sarcoplasmic reticulum, triggered by muscle stretch during eccentric contraction. We show here that Ca++ spikes are detected in dystrophic myogenic cells in culture since early differentiation, before sarcomere assembly and contraction. Healthy and genetically corrected dystrophic myotubes do not display Ca++ spikes which are blocked by co-culturing DMD myogenic cells with embryonic mouse motoneurons or treating them with agrin proteoglycan. Same effect is elicited by a muscle spliced, COOH peptide of agrin (termed here mini-agrin) that interacts with dystroglycan, favouring its binding to the basal lamina. Lack of dystrophin in DMD myotubes results in decreased expression of CaV1.1 (CACNA1S), a Ca++ sensor component of the Dihydropyridine Receptor (DHPR) complex, known to regulate Ryanodine Receptor 1 (RyR1). These events explain the emergence of Ca++ spikes. Mini-agrin addition to medium, or lentivector-mediated mini-agrin expression in transplanted cells in vivo, stabilize the expression of CaV1.1 on the membrane. This leads to disappearance of Ca++ spikes and to reappearance of -dystroglycan, -sarcoglycan and n-NOS, indicating the reconstitution of the dystrophin complex in the absence of dystrophin. These findings unveil a novel regulatory mechanism and offer a new therapeutic opportunity for targeting calcium ion influx as a co-treatment strategy.

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Aldharee, H., Mierzejewski, B., Kerr, A., Bragg, L., Bigot, A., Reinhard, J. R., Santoleri, S., Roberts, N., Das, R., Mouly, V., Ruegg, M. A., Cossu, G., Galli, F.. 2025-11-28. Mini-agrin prevents calcium leakage and restores the dystrophin complex.. https://doi.org/10.1101/2025.11.25.690165

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