Transcriptional corepressor MTG16 regulates small intestinal crypt proliferation and crypt regeneration after radiation-induced injury

Abstract

Myeloid translocation genes (MTGs) are transcriptional corepressors implicated in development, malignancy, differentiation, and stem cell function. While MTG16 loss renders mice sensitive to chemical colitis, the role of MTG16 in the small intestine is unknown. Histological examination revealed that Mtg16(-/-) mice have increased enterocyte proliferation and goblet cell deficiency. After exposure to radiation, Mtg16(-/-) mice exhibited increased crypt viability and decreased apoptosis compared with wild-type (WT) mice. Flow cytometric and immunofluorescence analysis of intestinal epithelial cells for phospho-histone H2A.X also indicated decreased DNA damage and apoptosis in Mtg16(-/-) intestines. To determine if Mtg16 deletion affected epithelial cells in a cell-autonomous fashion, intestinal crypts were isolated from Mtg16(-/-) mice. Mtg16(-/-) and WT intestinal crypts showed similar enterosphere forming efficiencies when cultured in the presence of EGF, Noggin, and R-spondin. However, when Mtg16(-/-) crypts were cultured in the presence of Wnt3a, they demonstrated higher enterosphere forming efficiencies and delayed progression to mature enteroids. Mtg16(-/-) intestinal crypts isolated from irradiated mice exhibited increased survival compared with WT intestinal crypts. Interestingly, Mtg16 expression was reduced in a stem cell-enriched population at the time of crypt regeneration. This is consistent with MTG16 negatively regulating regeneration in vivo. Taken together, our data demonstrate that MTG16 loss promotes radioresistance and impacts intestinal stem cell function, possibly due to shifting cellular response away from DNA damage-induced apoptosis and towards DNA repair after injury.

MTG16 is a tumor suppressor in colitis-associated carcinoma

“…To date, we have learned a great deal about the biological functions of MTG16 through the analysis of Mtg16 -/-mouse phenotypes. In addition to hematopoietic stem cell defects (20), these mice have increased enterocyte proliferation, altered intestinal differentiation, protection against radiation enteritis (12), and develop severe colitis after DSS-induced injury (10), indicating that MTG16 is a key contributor to intestinal epithelial homeostasis.…”

“…Furthermore, both Mtgr1 -/-and Mtg16 -/-mice have increased enterocyte proliferation with an expansion of transit-amplifying cell populations and skewed lineage allocation, indicative of disrupted intestinal homeostasis (12,15,16). When colitis was induced with dextran sodium sulfate (DSS), both Mtgr1 -/-and Mtg16 -/-mice were more sensitive to injury in comparison with wild-type (WT) mice, demonstrating that MTGs are required for maintaining intestinal integrity when the epithelium is challenged (10,13).…”

“…Recent work has implicated the myeloid translocation genes (MTGs) in intestinal inflammation, stem cell function, and epithelial repair -all processes contributing to the development of CAC (9)(10)(11)(12)(13). The MTG family includes MTG16 (CBFA2T3), MTGR1 (CBFA2T2), and MTG8 (RUNX1T1) (14).…”

Using 3D Organoid Cultures to Model Intestinal Physiology and Colorectal Cancer

“…In addition to genetic disease models, organoid modeling has been applied to investigate intestinal injuries, such as radiation enteritis. These irradiation models involve both organoids generated from irradiated mice as well as direct organoid irradiation in order to identify modifiers of sensitivity, intestinal viability, stem cell function, and repair following radiation treatment [47–49]. …”

Myeloid translocation genes differentially regulate colorectal cancer programs

“…A portion of Mtg8 −/− mice fail to develop the midgut 22 , Mtgr1 −/− mice have pan-secretory lineage loss 17 , and Mtg16 −/− mice have decreased goblet cells indices 23 . Moreover, both Mtgr1 −/− and Mtg16 −/− mice have augmented intestinal epithelial proliferation 17,23–25 , further suggesting dysregulated stem cell programs. The mechanism underlying their intestinal phenotypes is not deduced, but may reflect alterations in Wnt or Notch signaling levels.…”