Authors: Marine Cacheuxa, Ariane Bluma, Muriel Sébastien, Anne Sophie Wozny, Julie Brocard, Kamel Mamchaoui, Vincent Mouly, Nathalie Roux-Buisson, John Rendua, Nicole Monniera, Renée Krivosi, Paul Allen, Arnaud Lacour, Joël Lunardi, Julien Fauré and Isabelle Marty
Background: Central Core Disease (CCD) is a congenital myopathy often resulting from a mutation in RYR1 gene. Mutations in RyR1 can increase or decrease channel activity, or induce a reduction in the amount of protein. The consequences of a single mutation are sometimes multiple and the analysis of the functional effects is complex. Objective: The consequences of the p.Y4864H mutation identified in a CCD patient have been studied regarding both RyR1 function and amount.
Methods: The amount of RyR1 in human and mouse muscles was evaluated using qRT-PCR and quantitative Western blot, and calcium release was studied using calcium imaging on primary cultures. The results were compared between human and mouse.
Results: The p.Y4864H mutation induced an alteration of calcium release, and in addition was associated to a reduction in the amount of RyR1 in the patient’s muscle. This suggests two possible pathophysiological mechanisms: the alteration of calcium release could result from a modification of the channel properties of RyR1 or from a RyR1 reduction. In order to discriminate between the two hypotheses, we used the heterozygous RyR1 knockout (RyR1+/–) mouse model showing a comparable RyR1 protein reduction. No reduction in calcium release was observed in primary muscle culture from these mice, and no muscle weakness was measured.
Conclusions: Because the reduction in the amount of RyR1 protein has no functional consequences in the murine model, the muscle weakness observed in the patient is most likely the result of a modification of the calcium channel function of RyR1 due to the p.Y4864H mutation. Keywords: Ryanodine receptor, Central Core Disease, Malignant Hyperthermia, calcium release