A28 SHP-1 REGULATES INTESTINAL EPITHELIUM HOMEOSTASIS BY CONTROLLING ACTIVATION OF BOTH PI3K/AKT AND WNT/β-CATENIN PATHWAYS

Abstract

Background

Shp-1 is a tyrosine phosphatase highly expressed in hematopoietic cells and involved in the control of proliferation and differentiation. This phosphatase is also expressed at lower levels in epithelial cells such as intestinal epithelium. Our previous results showed that loss of epithelial Shp-1 leads to an intestinalomegaly associated with increased epithelial cell proliferation. We also noticed that the PI3K/Akt and Wnt/β-catenin pathways were both hyperactivated in IECs from these mice in comparison to controls (Leblanc Faseb J 2017).

Aims

However, the role of Shp-1 in this epithelium still remains poorly characterized. So we wanted to determine the contribution of hyperactive PI3K/Akt pathway in these phenotypic alterations.

Methods

To determine the contribution of hyperactive PI3K/Akt pathway, we generated mice with a specific deletion of Pten in IEC (Pten^IEC-KO mice) and carefully compared their intestinal phenotype with Shp-1^IEC-KO mice.

Results

Interestingly, both Shp-1^IEC-KO and Pten^IEC-KO mice develop similar intestinal phenotype: increased proliferation rate, intestinalomegaly and increased Goblet cell number. However, Paneth cell maturation is impaired in Shp-1^IEC-KO mice but not in Pten^IEC-KO mice. Indeed, decreased gene expression of Lyz1 and an expansion of intermediate cells are observed in Shp-1^IEC-KO mice. Since Paneth cells constitute the niche for Lgr5 stem cells in intestinal crypts, we analyzed stem cell activity ex vivo, in enteroids isolated from Shp-1^IEC-KO, Pten^IEC-KO and their control littermates. Surprisingly, we observed striking difference in enteroid development: Pten^IEC-KO enteroids grow very well and develop many protrusions in comparison to their respective controls. However, while proliferation is increased in Shp-1^IEC-KO enteroids, their morphogenesis is clearly impaired; diminution of R-spondin in the culture medium rescues de novo crypt formation in Shp-1-deficient organoids.

Conclusions

Our results indicate that loss of Shp-1 in IEC phenocopies many defects that are observed in Pten^IEC-KO mice, including intestinalomegaly and abnormal Goblet cell differentiation. However, defects in Paneth cell maturation observed in Shp-1^IEC-KO mice is probably triggered by the hyperactivation of Wnt/β-catenin signaling observed in these mice.

Funding Agencies

NSERC