KLF4 gene expression is inhibited by the notch signaling pathway that controls goblet cell differentiation in mouse gastrointestinal tract

Abstract

In Kruppel-like factor (KLF)-4-deficient mice, colonic goblet cell numbers are significantly reduced. Goblet cell development is regulated by the Notch signaling pathway. The aim of this study was to examine whether Notch represses KLF4 expression to regulate goblet cell differentiation. We first detected that KLF4 gene expression was upregulated in a human progastrin-overexpressing mouse model where goblet cell hyperplasia has been observed. We then found that mice treated with a γ-secretase inhibitor (compound E, 10 μmol/kg) for 24 h, which inhibits the Notch signaling pathway, had significantly increased KLF4 mRNA levels in small intestine and colon, accompanied by an increased number of KLF4-expressing cells at the bottom of crypts in small intestine and colon. In a colon cancer cell line (HCT116 cells), KLF4 promoter activity was inhibited by a constitutively active form of Notch1 (ICN1) by transient cotransfection assays. This inhibition was significantly compromised by a dominant-negative RBPjk, a repressive mediator of the Notch signaling pathway. An ICN1-responsive element was then mapped in the human KLF4 promoter between −151 and −122 nucleotides upstream of the transcriptional start site. It was also found that an intact ICN1-responsive element is required for ICN1 to inhibit KLF4 promoter activity by transient cotransfection assays. Our findings thus reveal a possible mechanism by which KLF4 is inhibited by Notch, which controls goblet cell differentiation in mouse gastrointestinal tract.

Function of KLF4 in Stem Cell Biology

“…KLF4 is proposed as the downstream target of Notch signaling pathway and KLF4 promoter activity is inhibited by Notch, but the relationship between the Notch signaling pathway and KLF4 appears dependent on different cellular contexts. Our early work and that of others suggest that KLF4 is inhibited by Notch in the gastrointestinal tract [107,109,110]. Recently, downregulation of Notch1 gene expression in keratinocytes by KLF4 has also been reported [111].In our current study on breast CSCs, we found that the expression of Notch1, Notch2 and Jagged1 were significantly decreased in KLF4 knockdown cells, and upregulated by overexpression of KLF4.…”

“…ICN then translocates to the nucleus where it displaces corepressor complexes that are prebound with CSL. The following recruitment of coactivators, including Mastermind-like proteins and CBP/p300, then activates gene expression of downstream target genes [107].…”

Regulation of the Potential Marker for Intestinal Cells, Bmi1, by β-Catenin and the Zinc Finger Protein KLF4

“…We have shown that KLF4 induced goblet cell differentiation in colon cancer xenografts (5); this is consistent with the role of KLF4 in Bmi1 repression. The expression of KLF4 is also regulated by Notch pathway in the intestine (41,42); it will be interesting to learn if Notch signaling interacts with Bmi1 in the intestine. The demonstrated role of Bmi1 in xenograft tumor growth is consistent with previous report that overexpressed KLF4 inhibited xenograft tumor growth (5) and with the finding that KLF4 inhibits Bmi1 as we discussed above.…”

Emerging Roles of Krüppel-Like Factor 4 in Cancer and Cancer Stem Cells

“…KLF4 is highly expressed in the post-mitotic cells in both gut and skin (Zheng et al, 2009). Downregulation of KLF4 in gastric cancer, colon adenomas, intestinal adenomas, prostate cancer, esophageal cancer, and lung cancer may contribute to malignant transformation and cellular hyperproliferation, which is consistent with its role in growth inhibition and cell cycle arrest (Choi et al, 2006).…”

“…Recently, it has also been reported that KLF4 is expressed in ESCs, and forced expression of a combination of four transcription factors, including Oct4, c-myc, Sox2, and KLF4, can reprogram fibroblasts into iPSCs that are similar to ESCs, suggesting that KLF4 is critical for the maintenance of stem cells (Wernig et al, 2007). In addition, forced expression of KLF4 can inhibit ES cells from differentiating into erythroid progenitors, and can increase their ability to generate secondary embryoid bodies, indicating a role of KLF4 in maintaining the self-renewal capacity (Zheng et al, 2009). Also, it has been demonstrated that KLF4 plays a crucial role in cellular invasion and migration during embryogenesis (Garvey et al, 2010).…”