Cutting Edge: Imbalanced Cation Homeostasis in MAGT1-Deficient B Cells Dysregulates B Cell Development and Signaling in Mice

Cation homeostasis, in relation to various immune-suppressive diseases, is a novel field of investigation. Recently, patients with a loss-of-function mutation in magnesium transporter 1 (MAGT1) were reported to present a dysregulated Mg 2+ homeostasis in T lymphocytes. Using Magt1 -knockout mice ( Magt1 −/y ), we show that Mg 2+ homeostasis was impaired in Magt1 −/y B cells and Ca 2+ influx was increased after BCR stimulation, whereas T and NK cell function was unaffected. Consequently, mutant B cells displayed an increased phosphorylation of BCR-related proteins differentially affecting protein kinase C activation. These in vitro findings translated into increased frequencies of CD19 + B cells and marginal zone B cells and decreased frequencies of plasma cells among CD45 + splenocytes in vivo. Altogether, our study demonstrates for the first time, to our knowledge, that abolished MAGT1 function causes imbalanced cation homeostasis and developmental responses in B cells. Therefore, this study might contribute to a further understanding of B cell–related pathologies.