HDAC1 Regulates The Expression Of Intestinal Stem Cell Marker Genes And The Role Of MicroRNA-31 In Colon Tumors

Intestinal epithelia is the most proliferative tissue and continuously regenerates from a small pool of stem cells residing at the bottom of crypts.The identity and location of intestinal epithelial stem cells(ISCs)have been intensively explored.Two populations of stem cells were recognized in intestine,which were rapid cycling crypt basal columnar cells(CBCs)and slow cycling label retaining "+4" cells.CBCs were marked by Lgr5,Olfm4,Troy and Ascl2 expression,whereas "+4" cells express Hopx,Bmi1,Lrig1,Msi1 and mTert.Histone acetylation is a key epigenetic mechanism in controlling various cellular processes,including chromatin remodeling,gene expression and cell fate determination.Dynamic changes in histone acetylation are controlled by two classes of enzymes,namely histone acetyltransferases(HATs)and histone deacetylases(HDACs).HDACs have been implied playing an important role in intestinal homeostasis.However,the role of HDACs in regulating transcription of genes encoding markers of ISCs is still unclear.ISCs express several markers,including Lgr5,Ascl2,Hopx,Bmi1 and Tnfrsf19 that are functionally important for ISC fate determination,chronic intestinal inflammation and colon cancer.In this study,we sought to investigate the role of HDACs in regulating the transcription of these stem cell markers.By treating primary colonic epithelial cells(PCECs)with different HDAC inhibitors,our results show that HDAC1 participates in modulating stem cell markers Lgr5,Ascl2,Hopx,Tnfrsf19 and Bmi1 expression in PCECs through regulating histone deacetylation.Inhibiting HDAC1 leads to accumulation of H3K27 ac in the promoter region of Lgr5,Ascl2 and Tnfrsf19,and dramatically increases the expression of these genes.Thus,our study identified a previously unrecognized role of HDAC1 in regulating expression of intestinal stem cell markers,suggesting an important epigenetic mechanism through which HDAC1 modulates the expression of functional genes critical for intestinal stem cell homeostasisCancers are complex diseases,with disorders in gene structure and gene expression.Micro RNA deregulation is frequently found in human colorectal cancers(CRCs),but little is known about why these mi RNAs are aberrantly expressed and to which extent they are involved in tumor progression in vivo.mi R-31 is a highly evolutionarily conserved mi RNA and is mainly expressed in epithelial tissue especially in stomach and small intestine.In this study,we report that mi R-31 expression is transcriptionally activated in CRC.And we established Mir31 conditional knockout in intestinal epithelial cells and global knockout mouse.Both Mir31 conditional knockout and global knockout mice are viable without obvious abnormality but develop more tumors in AOM/DSS induced colitis associated cancer model.Mir31 deletion affects cell adhesion and migration both in vivo and in vitro.Together,we illustrated the gene structure of mi R-31 in mouse,and identified mi R-31 as a tumor suppressor in CRC.