β-Catenin is required for the differentiation of iNKT2 and iNKT17 cells that augment IL-25-dependent lung inflammation

Abstract

BackgroundInvariant Natural Killer T (iNKT) cells have been implicated in lung inflammation in humans and also shown to be a key cell type in inducing allergic lung inflammation in mouse models. iNKT cells differentiate and acquire functional characteristics during development in the thymus. However, the correlation between development of iNKT cells in the thymus and role in lung inflammation remains unknown. In addition, transcriptional control of differentiation of iNKT cells into iNKT cell effector subsets in the thymus during development is also unclear. In this report we show that β-catenin dependent mechanisms direct differentiation of iNKT2 and iNKT17 subsets but not iNKT1 cells.MethodsTo study the role for β-catenin in lung inflammation we utilize mice with conditional deletion and enforced expression of β-catenin in a well-established mouse model for IL-25-dependen lung inflammation.ResultsSpecifically, we demonstrate that conditional deletion of β-catenin permitted development of mature iNKT1 cells while impeding maturation of iNKT2 and 17 cells. A role for β-catenin expression in promoting iNKT2 and iNKT17 subsets was confirmed when we noted that enforced transgenic expression of β-catenin in iNKT cell precursors enhanced the frequency and number of iNKT2 and iNKT17 cells at the cost of iNKT1 cells. This effect of expression of β-catenin in iNKT cell precursors was cell autonomous. Furthermore, iNKT2 cells acquired greater capability to produce type-2 cytokines when β-catenin expression was enhanced.DiscussionThis report shows that β-catenin deficiency resulted in a profound decrease in iNKT2 and iNKT17 subsets of iNKT cells whereas iNKT1 cells developed normally. By contrast, enforced expression of β-catenin promoted the development of iNKT2 and iNKT17 cells. It was important to note that the majority of iNKT cells in the thymus of C57BL/6 mice were iNKT1 cells and enforced expression of β-catenin altered the pattern to iNKT2 and iNKT17 cells suggesting that β-catenin may be a major factor in the distinct pathways that critically direct differentiation of iNKT effector subsets.ConclusionsThus, we demonstrate that β-catenin expression in iNKT cell precursors promotes differentiation toward iNKT2 and iNKT17 effector subsets and supports enhanced capacity to produce type 2 and 17 cytokines which in turn augment lung inflammation in mice.

Temporal regulation of Wnt/β-catenin signaling is important for invariant NKT cell development and terminal maturation

“…Specific detection of iNKT cells with PBS-57-loaded CD1d tetramers was confirmed by including unloaded tetramers as controls (Fig S1). Consistent with the previous report 24 , we found increased and decreased percentages of CD1d-tetramer positive iNKT cells in CATtg and CAT-KO thymus, respectively and increased numbers of iNKT cells in the CATtg thymus. In the periphery however, there was no significant difference in the iNKT cell percentages or numbers of CATtg spleen, while those of CAT-KO spleen were slightly lower (Fig.…”

“…A previous study of CAT-KO mice showed reduced thymic iNKT cells but developmental stages were not examined 24 . When we examined the stage-wise development of CAT-KO iNKT cells in the thymus, an increase in the percentage but not the cell number of Stage 0 cells was observed, but the rest of stages were comparable to WT (Fig 1E).…”

“…Different branches of TGF-β signaling have been shown to work together to control early, intermediate and late differentiation of iNKT cells 11 . Other factors that have been reported to play a role in iNKT cell maturation are RelA 12 , Itk 13 , Calcineurin 14 , Id2 15 and CYLD 16 including transcriptional regulators PLZF 17, 18 , T-bet 19, 20 , c-Myc 21, 22 , EGR-2 14 , IRF-1 23 and β-Catenin 24 .…”

“…However, the role of Wnt/β-Catenin signaling in the development of innate T cells is not clearly understood. Recently, β-Catenin was demonstrated to be important for controlling iNKT cell numbers and balancing the iNKT effector subsets 24 . However, what is not clear so far is if β-Catenin expression changes during iNKT cell development and if that in turn contributes to the acquisition of effector functions.…”

Caught in a Wnt storm: Complexities of Wnt signaling in hematopoiesis

“…Important work from the Gounari group highlighted a role of Wnt/β-catenin in TCRβ-selection (18,19) and in leukemia (20). Misra Sen and coworkers published many reports on the importance of Tcf1, β-catenin and Wnt signaling in thymocyte survival, positive selection and development of NK T cells (21)(22)(23)(24)(25)(26)(27)(28). Interestingly, thymic epithelial cells (TECs), which are the niche cells for developing T cells, are also regulated by Wnt signals, as TECs are specified by a direct Wnt target gene the transcription factor FoxN1 (29).…”