ORAI1 inhibition as an efficient preclinical therapy for tubular aggregate myopathy and Stormorken syndrome. ORAI1 inhibition as an efficient preclinical therapy for tubular aggregate myopathy and Stormorken syndrome

Tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK) are clinically overlapping disorders characterized by childhood-onset muscle weakness and a variable occurrence of multi-systemic signs including short stature, thrombocytopenia, and hyposplenism. TAM/STRMK is caused by gain-of-function mutations in the Ca2+ sensor STIM1 or the Ca2+ channel ORAI1, both regulating Ca2+ homeostasis through the ubiquitous SOCE (store-operated Ca2+ entry) mechanism. Functional experiments in cells have demonstrated that the TAM/STRMK mutations induce SOCE overactivation, resulting in excessive influx of extracellular Ca2+. There is currently no treatment for TAM/STRMK, but SOCE is amenable to manipulation. Here we crossed Stim1R304W/+ mice harboring the most common TAM/STRMK mutation with Orai1R93W/+ mice carrying an ORAI1 mutation partially obstructing Ca2+ influx. Compared with Stim1R304W/+ littermates, Stim1R304W/+Orai1R93W/+ offspring showed a normalization of bone architecture, spleen histology, and muscle morphology, an increase of thrombocytes, and improved muscle contraction and relaxation kinetics. Accordingly, comparative RNA- sequencing detected more than 1200 dysregulated genes in Stim1R304W/+ mice and revealed a major restoration of gene expression in Stim1R304W/+Orai1R93W/+ mice. Altogether, we provide physiological, morphological, functional, and molecular data highlighting the therapeutic potential of ORAI1 inhibition to rescue the multi-systemic TAM/STRMK signs, and we identified myostatin as a suitable biomarker for TAM/STRMK in human and mouse. Overall design: We performed RNA-seq on WT, Stim1R304W/+ (Stim1KI),Orai1+/- (Orai1KO), Orai1R93W/+ (Orai1KI), Stim1R304W/+Orai1R93W/+ (Stim1KIOrai1KI), and Stim1R304W/+Orai1+/-(Stim1KIOrai1KO) tibialis anterior muscle samples