ITPR2 Mediated Calcium Homeostasis in Oligodendrocytes is Essential for Myelination and Involved in Depressive‐Like Behavior in Adolescent Mice

Abstract Ca 2+ signaling is essential for oligodendrocyte (OL) development and myelin formation. Inositol 1,4,5‐trisphosphate receptor type 2 (ITPR2) is an endoplasmic reticulum calcium channel and shows stage‐dependent high levels in postmitotic oligodendrocyte precursor cells (OPCs). The role and potential mechanism of ITPR2 in OLs remain unclear. In this study, it is revealed that loss of Itpr2 in OLs disturbs Ca 2+ homeostasis and inhibits myelination in adolescent mice. Animals with OL‐specific deletion of Itpr2 exhibit anxiety/depressive‐like behaviors and manifest with interrupted OPC proliferation, leading to fewer mature OLs in the brain. Detailed transcriptome profiling and signal pathway analysis suggest that MAPK/ERK‐CDK6/cyclin D1 axis underlies the interfered cell cycle progression in Itpr2 ablated OPCs. Besides, blocking MAPK/ERK pathway significantly improves the delayed OPC differentiation and myelination in Itpr2 mutant. Notably, the resting [Ca 2+ ] i is increased in Itpr2 ablated OPCs, with the elevation of several plasma calcium channels. Antagonists against these plasma calcium channels can normalize the resting [Ca 2+ ] i level and enhance lineage progression in Itpr2‐ ablated OPCs. Together, the findings reveal novel insights for calcium homeostasis in manipulating developmental transition from OPCs to pre‐OLs; additionally, the involvement of OLs‐originated ITPR2 in depressive behaviors provides new therapeutic strategies to alleviate myelin‐associated psychiatric disorders.