The transcriptional corepressor MTGR1 regulates intestinal secretory lineage allocation

Abstract

Notch signaling largely determines intestinal epithelial cell fate. High Notch activity drives progenitors toward absorptive enterocytes by repressing secretory differentiation programs, whereas low Notch permits secretory cell assignment. Myeloid translocation gene-related 1 (MTGR1) is a transcriptional corepressor in the myeloid translocation gene/Eight-Twenty-One family. Given that Mtgr1(-/-) mice have a dramatic reduction of intestinal epithelial secretory cells, we hypothesized that MTGR1 is a key repressor of Notch signaling. In support of this, transcriptome analysis of laser capture microdissected Mtgr1(-/-) intestinal crypts revealed Notch activation, and secretory markers Mucin2, Chromogranin A, and Growth factor-independent 1 (Gfi1) were down-regulated in Mtgr1(-/-) whole intestines and Mtgr1(-/-) enteroids. We demonstrate that MTGR1 is in a complex with Suppressor of Hairless Homolog, a key Notch effector, and represses Notch-induced Hairy/Enhancer of Split 1 activity. Moreover, pharmacologic Notch inhibition using a γ-secretase inhibitor (GSI) rescued the hyperproliferative baseline phenotype in the Mtgr1(-/-) intestine and increased production of goblet and enteroendocrine lineages in Mtgr1(-/-) mice. GSI increased Paneth cell production in wild-type mice but failed to do so in Mtgr1(-/-) mice. We determined that MTGR1 can interact with GFI1, a transcriptional corepressor required for Paneth cell differentiation, and repress GFI1 targets. Overall, the data suggest that MTGR1, a transcriptional corepressor well characterized in hematopoiesis, plays a critical role in intestinal lineage allocation.

Transcriptional Regulation by ATOH1 and its Target SPDEF in the Intestine

“…We defined the ATOH1 targetome as the 658 genes in the colon and 193 genes in the ileum with significantly enriched expression in ATOH1-positive cells that also were bound by ATOH1 (Figure 5 A , Supplementary Table 9). Consistent with the concept that ATOH1 functions as a key transcription factor for differentiation of the intestinal epithelium, several ATOH1 target genes were known to be involved in intestinal secretory lineage differentiation and function, such as Notch ligands Dll1 and Dll4 ; transcription factors Spdef ,17, 18 Sox9 ,39, 40 Gfi1 ,19, 41 and Creb3l1 42 ; transcription co-repressors Cbfa2t2 and Cbfa2t3 43, 44, 45, 46; and secretory lineage-specific genes such as Best2 , Spink4 , Muc2 , Sct , EphB3 , Xbp1 , and Clca3 17, 47, 48, 49. To gain broader insight into ATOH1 target genes in the intestines, we performed GO analysis using DAVID.…”

MTG16 is a tumor suppressor in colitis-associated carcinoma

“…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).…”

Myeloid translocation genes differentially regulate colorectal cancer programs

“…As the ChIP-seq data also suggested preferential Notch regulation by MTGR1, and because we previously determined that the secretory lineage deficiency observed in the Mtgr1 −/− intestine was rescued by Notch inhibition 24 , we next determined if Notch signaling was perturbed in Mtgr1 −/− tumors. As active Notch signaling will increase absorptive enterocyte production at the expense of secretory lineages, we stained tumors with periodic acid Schiff (PAS) to identify goblet cells.…”

“…Mtg8 −/− mice demonstrate a severe mid-gut deletion phenotype 22 ; Mtgr1 −/− mice have pan-secretory cell loss and are smaller than wild-type mice 17 ; and Mtg16 −/− mice have decreased goblet cell indices 23 . The mechanisms underlying these various phenotypes remain unclear, although there are reports that MTGR1 directly binds to TCF4, competing for β-catenin occupancy and that it interacts with CSL in repressing Notch signaling 24,35 . However, evidence that MTGs occupy Wnt/Notch targets in the gut has been lacking.…”

“…qPCR was then performed using SYBR Green (Biorad) with primers for Gapdh (Realtimeprimers). Primers for CgA and Muc2 were previously described 24 . Primers for Ascl2 , Axin2 , c-Myc , and Klf4 were purchased from RealtimePrimers.…”