The role of Hes genes in intestinal development, homeostasis and tumor formation
ABSTRACT Notch signaling regulates intestinal development, homeostasis and tumorigenesis, but its precise downstream mechanism remains largely unknown. Here we found that inactivation of the Notch effectors Hes1, Hes3 and Hes5, but not Hes1 alone, led to reduced cell proliferation, increased secretory cell formation and altered intestinal structures in adult mice. However, in Apc mutation-induced intestinal tumors, inactivation of Hes1 alone was sufficient for reducing tumor cell proliferation and inducing differentiation of tumor cells into all types of intestinal epithelial cells, but without affecting the homeostasis of normal crypts owing to genetic redundancy. These results indicated that Hes genes cooperatively regulate intestinal development and homeostasis and raised the possibility that Hes1 is a promising target to induce the differentiation of tumor cells.
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ABSTRACT: The transcription factor Hes3 is a component of a signaling pathway that supports the growth of neural stem cells with profound consequences in neurodegenerative disease models. Here we explored whether Hes3 also regulates pancreatic islet cells. We showed that Hes3 is expressed in human and rodent pancreatic islets. In mouse islets it co-localizes with alpha and beta cell markers. We employed the mouse insulinoma cell line MIN6 to perform in vitro characterization and functional studies in conditions known to modulate Hes3 based upon our previous work using neural stem cell cultures. In these conditions, cells showed elevated Hes3 expression and nuclear localization, grew efficiently and showed higher evoked insulin release responses, compared to serum-containing conditions. They also exhibited higher expression of the transcription factor Pdx1 and insulin. Further, they were responsive to pharmacological treatments with the GLP-1 analog Exendin-4 which increased nuclear Hes3 localization. We employed a transfection approach to address specific functions of Hes3. Hes3 RNA interference opposed cell growth and affected gene expression as revealed by DNA microarrays. Western blotting and PCR approaches specifically showed that Hes3 RNA interference opposes the expression of Pdx1 and insulin. Hes3 overexpression (using a Hes3-GFP fusion construct) confirmed a role of Hes3 in regulating Pdx1 expression. Hes3 RNA interference reduced evoked insulin release. Mice lacking Hes3 exhibited increased islet damage by streptozotocin. These data suggest roles of Hes3 in pancreatic islet function.Journal of Biological Chemistry 11/2014; 289(51). DOI:10.1074/jbc.M114.590687 · 4.60 Impact Factor
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ABSTRACT: Hes genes, encoding basic helix-loop-helix (HLH) transcriptional repressors, are mammalian homologues of Drosophila hairy and Enhancer of split genes, both of which are required for normal neurogenesis in Drosophila. There are seven members in the human Hes family, Hes1-7, which are expressed in many tissues and play various roles mainly in development. All Hes proteins have three conserved domains: basic HLH (bHLH), Orange, and WRPW domains. The basic region binds to target DNA sequences, while the HLH region forms homo- and heterodimers with other bHLH proteins, the Orange domain is responsible for the selection of partners during heterodimer formation, and the WRPW domain recruits corepressors. Hes1, Hes5, and Hes7 are known as downstream effectors of canonical Notch signaling, which regulates cell differentiation via cell-cell interaction. Hes factors regulate many events in development by repressing the expression of target genes, many of which encode transcriptional activators that promote cell differentiation. For example, Hes1, Hes3, and Hes5 are highly expressed by neural stem cells, and inactivation of these genes results in insufficient maintenance of stem cell proliferation and prematurely promotes neuronal differentiation. Recently, it was shown that the expression dynamics of Hes1 plays crucial roles in proper developmental timings and fate-determination steps of embryonic stem cells and neural progenitor cells. Here, we discuss some key features of Hes factors in development and diseases.Current Topics in Developmental Biology 01/2014; 110C:263-283. DOI:10.1016/B978-0-12-405943-6.00007-5 · 4.21 Impact Factor
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ABSTRACT: The intestinal mucosa undergoes a continual process of proliferation, differentiation and apoptosis, which is regulated by multiple signaling pathways. Notch signaling is critical for the control of intestinal stem cell maintenance and differentiation. However, the precise mechanisms involved in the regulation of differentiation are not fully understood. Previously, we have shown that tuberous sclerosis 2 (TSC2) positively regulates the expression of the goblet cell differentiation marker, MUC2, in intestinal cells. Using transgenic mice constitutively expressing a dominant negative TSC2 allele, we observed that TSC2 inactivation increased mTORC1 and Notch activities, and altered differentiation throughout the intestinal epithelium, with a marked decrease in the goblet and Paneth cell lineages. Conversely, treatment of mice with either Notch inhibitor dibenzazepine (DBZ) or mTORC1 inhibitor rapamycin significantly attenuated the reduction of goblet and Paneth cells. Accordingly, knockdown of TSC2 activated, whereas knockdown of mTOR or treatment with rapamycin decreased, the activity of Notch signaling in the intestinal cell line LS174T. Importantly, our findings demonstrate that TSC2/mTORC1 signaling contributes to the maintenance of intestinal epithelium homeostasis by regulating Notch activity.Cell Death & Disease 02/2015; 6(2):e1631. DOI:10.1038/cddis.2014.588 · 5.18 Impact Factor