Abstract
Colorectal cancer (CRC) and inflammatory bowel disease (IBD) are two major health problems that are increasing worldwide. More than 7400 people die from CRC in the Nordic countries alone, and more than 1 in 350 people are afflicted with IBD in the western part of the world. Dysregulation of colonic homeostasis has been linked to the development and severity of both diseases. A large number of genes and several molecular signalling pathways are involved in maintaining the homeostasis. A network of transcription factors controls the expression of the colonic genes. Caudal type homeobox 2 (CDX2) is an intestinal-specific transcription factor that plays a central rolein this network, and it regulates many genes important for homeostasis. The dysregulation of CDX2 has been associated with the development and severity of CRC and IBD.
The goal of the thesis is to increase our knowledge about CDX2s role in
colonic homeostasis, by identifying CDX2 target genes important for the colonic
epithelium. Two potential CDX2 target genes, YAP1 and IL33 were identified by
analyzing ChIP-Seq data from Caco-2 and LS174T colon epithelial cell lines. Both genes are expressed in many tissues and their role in most tissues are well described. However, their function in the colonic epithelium is not well understood. Investigating their connection with the intestinal specific transcription factor CDX2 will enable a deeper understanding of their role in colonic epithelium.
In paper I of this thesis, CDX2 was shown to transcriptionally regulate YAP1 promoter activity in Caco-2 cells, partly through an identified intragenic enhancer. By using a CDX2 inducible colon epithelial cell line described in paper III, it was possible to demonstrate that the YAP1 protein level was increased by CDX2 induction.
In paper II, IL33 was found to be a target gene for CDX2 in LS174T colon epithelial cells. Furthermore, it was found that CDX2 was indispensable for IL33 promoter activity in LS174T cells, and that induction of CDX2 in the colonic epithelial cell model caused a dose-dependent increase in the IL33 mRNA level.
Paper III describes a novel method for developing an inducible CDX2
knockout LS174T based cell line. This cell line expresses no endogenous CDX2 protein, but CDX2 expression can be induced using doxycycline. In addition, paper I and II demonstrated how the identification of novel CDX2 target genes is possible using the LS174TCDX2-/- cell model.
In summary, YAP1 and IL33 were identified as novel CDX2 target genes
with importance for colonic homeostasis. It is hypothesized, that the regulation by CDX2 contributes to a YAP1 and IL33 intestinal-specific expression pattern that define their role in the colon homeostasis. Furthermore, it is likely that other transcription factors in the colon play a role in the transcriptional regulation of YAP1 and IL33.
The goal of the thesis is to increase our knowledge about CDX2s role in
colonic homeostasis, by identifying CDX2 target genes important for the colonic
epithelium. Two potential CDX2 target genes, YAP1 and IL33 were identified by
analyzing ChIP-Seq data from Caco-2 and LS174T colon epithelial cell lines. Both genes are expressed in many tissues and their role in most tissues are well described. However, their function in the colonic epithelium is not well understood. Investigating their connection with the intestinal specific transcription factor CDX2 will enable a deeper understanding of their role in colonic epithelium.
In paper I of this thesis, CDX2 was shown to transcriptionally regulate YAP1 promoter activity in Caco-2 cells, partly through an identified intragenic enhancer. By using a CDX2 inducible colon epithelial cell line described in paper III, it was possible to demonstrate that the YAP1 protein level was increased by CDX2 induction.
In paper II, IL33 was found to be a target gene for CDX2 in LS174T colon epithelial cells. Furthermore, it was found that CDX2 was indispensable for IL33 promoter activity in LS174T cells, and that induction of CDX2 in the colonic epithelial cell model caused a dose-dependent increase in the IL33 mRNA level.
Paper III describes a novel method for developing an inducible CDX2
knockout LS174T based cell line. This cell line expresses no endogenous CDX2 protein, but CDX2 expression can be induced using doxycycline. In addition, paper I and II demonstrated how the identification of novel CDX2 target genes is possible using the LS174TCDX2-/- cell model.
In summary, YAP1 and IL33 were identified as novel CDX2 target genes
with importance for colonic homeostasis. It is hypothesized, that the regulation by CDX2 contributes to a YAP1 and IL33 intestinal-specific expression pattern that define their role in the colon homeostasis. Furthermore, it is likely that other transcription factors in the colon play a role in the transcriptional regulation of YAP1 and IL33.
| Translated title of the contribution | Transskriptionel regulering af YAP1 og IL33 af CDX2 i epitelceller fra kolon |
|---|---|
| Original language | English |
| Place of Publication | Roskilde |
|---|---|
| Publisher | Roskilde Universitet |
| Number of pages | 173 |
| Publication status | Published - 29 Aug 2018 |