Kidins220 and Aiolos promote thymic iNKT cell development by reducing TCR signals

Development of T cells is controlled by the signal strength of the TCR. The scaffold protein Kinase D-interacting substrate of 220 kDa (Kidins220) binds to the TCR; however, its role in T cell development was unknown. Here, we show that T cell-specific Kidins220 knock-out (T-KO) mice have strongly reduced invariant natural killer T (iNKT) cell numbers and modest decreases in conventional T cells. Enhanced apoptosis due to increased TCR signaling in T-KO iNKT thymocytes of developmental stage 2 and 3 shows that Kidins220 downregulates TCR signaling at these stages. scRNAseq indicated that the transcription factor Aiolos is downregulated in Kidins220-deficient iNKT cells. Analysis of an Aiolos KO demonstrated that Aiolos is a downstream effector of Kidins220 during iNKT cell development. In the periphery, T-KO iNKT cells show reduced TCR signaling upon stimulation with a-galactosylceramide, suggesting that Kidins220 promotes TCR signaling in peripheral iNKT cells. Thus, Kidins220 reduces or promotes signaling dependent on the iNKT cell developmental stage. Overall design: To perform the single-cell RNA sequencing experiments, cells of 4 thymi of Ctrl mice were pooled and the same was done with 4 thymi of T-KO mice. Cells were stained with CD1d tetramers, anti-TCRß, anti-NK1.1, anti-CD44 and anti-CD24 antibodies on ice. Cells were sorted by flow cytometry for TCRß+, CD1dt+, CD24+, NK1.1- cells to obtain stage 0 iNKT cells, and for TCRß+, CD1dt+, NK1.1+, CD24-, CD44+ cells to obtain stage 3 iNKT cells. This was done twice in parallel, to have two replicas each. After sorting, each cell population was barcoded by hash-tagged antibodies (TotalSeqC format, anti-mouse Hashtag 1 to 8; clone M1/42, 30-F11, BioLegend). The antibody concentrations used were 1 ug per million cells. After staining, cells were washed three times in PBS containing 2% BSA and 0.01% Tween 20, followed by centrifugation (300 x g 5 min at 4 °C) and supernatant exchange. Then all 8 populations were pooled (2x stage 0 Ctrl, 2x stage 0 T-KO, 2x stage 3 Ctrl, 2x stage 3 T-KO) for single-cell RNA sequencing.