Phospho-regulation of ATOH1 Is Required for Plasticity of Secretory Progenitors and Tissue Regeneration

Abstract

SummaryThe intestinal epithelium is largely maintained by self-renewing stem cells but with apparently committed progenitors also contributing, particularly following tissue damage. However, the mechanism of, and requirement for, progenitor plasticity in mediating pathological response remain unknown. Here we show that phosphorylation of the transcription factor Atoh1 is required for both the contribution of secretory progenitors to the stem cell pool and for a robust regenerative response. As confirmed by lineage tracing, Atoh1+ cells (Atoh1(WT)CreERT2 mice) give rise to multilineage intestinal clones both in the steady state and after tissue damage. In a phosphomutant Atoh1(9S/T-A)CreERT2 line, preventing phosphorylation of ATOH1 protein acts to promote secretory differentiation and inhibit the contribution of progenitors to self-renewal. Following chemical colitis, Atoh1+ cells of Atoh1(9S/T-A)CreERT2 mice have reduced clonogenicity that affects overall regeneration. Progenitor plasticity maintains robust self-renewal in the intestinal epithelium, and the balance between stem and progenitor fate is directly coordinated by ATOH1 multisite phosphorylation.

Atoh1 + secretory progenitors possess renewal capacity independent of Lgr5 + cells during colonic regeneration

“…Upon injury, however, both colonic and intestinal Atoh1 + cells expand to renew the epithelium, consistent with plasticity required for crypt regeneration. Our observations are consistent with the recent findings reported by two other groups demonstrating that Atoh1 + secretory cells are able to contribute to colonic regeneration post-colitis (Ishibashi et al, 2018;Tomic et al, 2018). Thus, a subset of Atoh1 + cells in the colon can renew the epithelium during normal homeostasis, whereas in the small intestine, Atoh1 + cells behave similarly to intestinal Dll1 + progenitors cells that are short-lived and only lineage trace upon epithelial injury (van Es et al, 2012).…”

“…Complementing the recent findings showing that phosphorylation of ATOH1 regulates the plasticity of secretory progenitors (Tomic et al, 2018), we found that renewal by Atoh1 + cells is independent of Lgr5 + stem cells and that Atoh1 + cells are multipotent in terms of their renewal capacity. This is demonstrated by their ability to give rise to colonic organoids in vitro, as well as to lineage trace in vivo in the absence of Lgr5 + cells by DT ablation during regeneration.…”

“…Notably, we and others have also reported that Lgr5 + stem cells are highly sensitive to epithelial injury induced by radiation or colitis Asfaha et al, 2015;Ishibashi et al, 2018), suggesting that an Lgr5negative cell population is responsible, at least in part, for colonic regeneration. More recently, work by two groups suggested that secretory cells marked by the transcription factor Atoh1 contribute to colonic epithelial repair (Ishibashi et al, 2018 andTomic et al, 2018). However, neither study directly addressed whether Atoh1 + cells are dependent on Lgr5 + stem cells for this epithelial repair.…”

CyclinD1 controls development of cerebellar granule cell progenitors through phosphorylation and stabilization of ATOH1

“…Many studies have suggested that phosphorylation of ATOH1 affects its protein stability (Aragaki et al, 2008;Cheng et al, 2016;Forget et al, 2014;Klisch et al, 2017;Tomic et al, 2018;Tsuchiya et al, 2007;Xie et al, 2017). Among previously reported phosphorylation sites, S52, S56, tyrosine (Y)78, S193, S328, S334 and S339 of mouse ATOH1 are believed to participate in the protein stability.…”

“…It was previously suggested that CCND1 and CDK4 are involved in phosphorylation of ATOH1 in HEK293T cells (Tomic et al, 2018). However, it remained unclear whether CCND1/CDK4 directly phosphorylates ATOH1 or whether ATOH1 phosphorylation by CCND1/CDK4 participates in stabilization of ATOH1.…”