A novel bi-allelic loss-of-function mutation in STIM1 expands the phenotype of STIM1-related diseases

International audience; STIM1, the stromal interaction molecule 1, is the key protein for maintaining calciumconcentration in the endoplasmic reticulum by triggering the Store Operated CalciumEntry (SOCE). Bi-allelic mutations in STIM1 gene are responsible for a loss-offunctionin patients affected with a CRAC channelopathy syndrome in which severecombined immunodeficiency syndrome (SCID-like), autoimmunity, ectodermal dysplasiaand muscle hypotonia are combined. Here, we studied two siblings from a consanguineousSyrian family, presenting with muscle weakness, hyperlaxity, elastic skin,tooth abnormalities, dysmorphic facies, hypoplastic patellae and history of respiratoryinfections. Using exome sequencing, we have identified a new homozygous frameshiftmutation in STIM1: c.685delT [p.(Phe229Leufs*12)], leading to a complete lossof STIM1 protein. In this study, we describe an unusual phenotype linked to STIM1mutations, combining clinical signs usually observed in different STIM1-related diseases.In particular, we confirmed that the complete loss of STIM1 function is notalways associated with severe immune disorders. Altogether, our results broaden thespectrum of phenotypes associated with mutations in STIM1 and opens new perspectiveson the pathological mechanisms associated with a defect in the proteins constitutingthe SOCE complex.