An in vitro model of acute horizontal basal cell activation reveals gene regulatory networks underlying the nascent activation phase

While horizontal basal cells (HBCs) make minor contributions to olfactory epithelium (OE) regeneration during homeostatic conditions, they possess a potent, latent capacity to activate and subsequently regenerate the OE following severe injury. Activation requires, and is mediated by, the downregulation of the transcription factor (TF) TP63. In this paper, we describe the cellular processes that drive the nascent stages of HBC activation. The compound phorbol 12-myristate 13-acetate (PMA) induces a rapid loss in TP63 protein and rapid enrichment of HOPX and the nuclear translocation of RELA, previously identified as components of HBC activation. Using bulk RNA sequencing (RNA-seq), we find that PMA-treated HBCs pass through various stages of activation identifiable by transcriptional regulatory signatures that mimic stages identified in vivo. These temporal stages are associated with varying degrees of engraftment and differentiation potential in transplantation assays. Together, these data show that our in vitro HBC activation system models physiologically relevant features of in vivo HBC activation and identifies new candidates for mechanistic testing. •Treating HBCs with PMA induces the rapid degradation of TP63 protein•PMA-treated HBCs express previously identified in vivo activation genes•Analysis of PMA-treated HBC gene networks reveals candidate activation genes•PMA treatment unlocks HBC engraftment and partial differentiation potential Barrios-Camacho et al. develop an in vitro model of nascent horizontal basal cells (HBCs) activation. Transcriptomic profiling of HBCs at various stages of activation reveals discrete gene regulatory networks also seen in the in vivo injury context. Despite initiating activation gene signatures, HBCs can regress and re-establish dormancy markers. Further, activated HBCs differ in engraftment and differentiation responses when transplanted.