Ca2+ influx through ORAI1 and ORAI2 channels regulates chromatin accessibility in CD4+ T cells

Activation of CD4+ T cells by T cell receptor (TCR) signaling results in altered gene expression as a result of epigenetic and transcriptional regulation. A critical TCR signaling pathway in CD4+ T cells is driven by Ca2+ influx across the plasma membrane through Ca2+ release-activated Ca2+ (CRAC) channels that are formed by ORAI1 and ORAI2 proteins. Here we analyzed the effects of suppressing Ca2+ influx in mouse CD4+ T cells on chromatin accessibility by genetically deleting the ORAI1 channel alone or both ORAI1 and ORAI2 channels. CD4+ T cells specific for ovalbumin (OVA) from TCR transgenic OT-II were activated by in vivo exposure to influenza A virus (IAV) expressing OVA neoantigen. Changes in chromatin accessibility of CD4+ T cells in response to IAV-OVA infection were determined by ATAC sequencing Overall design: CD4+ T cells were isolated from wildtype, Orai1fl/fl Cd4Cre OTII (ORAI1 KO) or Orai1fl/fl Cd4Cre Orai2-/- OT-II (ORAI1/2 KO) mice and injected i.v. into TCRalpha-/- host mice. Host mice were left uninfected or infected intranasally with 200 VFU of the mouse-adapted influenza A virus strain PR8-OVA. 8 days post-infection, CD4+ T cells were isolated from mediastinal lymph nodes of host mice for subsequent analysis by ATAC sequencing.