title: Epigenetic modulation of intestinal cholesterol transporter Niemann-Pick C1-like 1 (NPC1L1) gene expression by DNA methylation.
abstract: Intestinal NPC1L1 transporter is essential for cholesterol absorption and the maintenance of cholesterol homeostasis in the body. NPC1L1 is differentially expressed along the gastrointestinal tract with very low levels in the colon as compared with the small intestine. This study was undertaken to examine whether DNA methylation was responsible for segment-specific expression of NPC1L1. Treatment of mice with 5-azacytidine (i.p.) resulted in a significant dose-dependent increase in NPC1L1 mRNA expression in the colon. The lack of expression of NPC1L1 in the normal colon was associated with high levels of methylation in the area flanking the 3-kb fragment upstream of the initiation site of the mouse NPC1L1 gene in mouse colon as analyzed by EpiTYPER® MassARRAY®. The high level of methylation in the colon was observed in specific CpG dinucleotides and was significantly decreased in response to 5-azacytidine. Similar to mouse NPC1L1, 5-azacytidine treatment also increased the level of human NPC1L1 mRNA expression in the intestinal HuTu-80 cell line in a dose- and time-dependent manner. Silencing the expression of DNA methyltransferase DNMT1, -2, -3A, and -3B alone by siRNA did not affect NPC1L1 expression in HuTu-80 cells. However, the simultaneous attenuation of DNMT1 and -3B expression caused a significant increase in NPC1L1 mRNA expression as compared with control. Also, in vitro methylation of the human NPC1L1 promoter significantly decreased NPC1L1 promoter activity in human intestinal Caco2 cells. In conclusion, our data demonstrated for the first time that DNA methylation in the promoter region of the NPC1L1 gene appears to be a major mechanism underlying differential expression of NPC1L1 along the length of the gastrointestinal tract.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Pooja
authors.initials: P
authors.lastname: Malhotra
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Vinay
authors.initials: V
authors.lastname: Soni
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Anoop
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Arivarasu N
authors.initials: AN
authors.lastname: Anbazhagan
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Amish
authors.initials: A
authors.lastname: Dudeja
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Seema
authors.initials: S
authors.lastname: Saksena
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Ravinder K
authors.initials: RK
authors.lastname: Gill
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612; Jesse Brown Veterans Affairs Medical Center, University of Illinois at Chicago, Chicago, Illinois 60612.
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Dudeja
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois 60612; Jesse Brown Veterans Affairs Medical Center, University of Illinois at Chicago, Chicago, Illinois 60612. Electronic address: walrefai@uic.edu.
authors.forename: Waddah A
authors.initials: WA
authors.lastname: Alrefai
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D018938:Caco-2 Cells; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D019175:DNA Methylation / Q000187:drug effects / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D008565:Membrane Proteins / Q000096:biosynthesis* / Q000235:genetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics
chemical_list: D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C410800:NPC1L1 protein, human; C482445:Npc1l1 protein, mouse; D012333:RNA, Messenger; D001374:Azacitidine
keywords: DNA Methylation; Epithelial Cell; Intestinal Epithelium; Plasma Membrane; Transporter