title: hnRNP I inhibits Notch signaling and regulates intestinal epithelial homeostasis in the zebrafish.
abstract: Regulated intestinal stem cell proliferation and differentiation are required for normal intestinal homeostasis and repair after injury. The Notch signaling pathway plays fundamental roles in the intestinal epithelium. Despite the fact that Notch signaling maintains intestinal stem cells in a proliferative state and promotes absorptive cell differentiation in most species, it remains largely unclear how Notch signaling itself is precisely controlled during intestinal homeostasis. We characterized the intestinal phenotypes of brom bones, a zebrafish mutant carrying a nonsense mutation in hnRNP I. We found that the brom bones mutant displays a number of intestinal defects, including compromised secretory goblet cell differentiation, hyperproliferation, and enhanced apoptosis. These phenotypes are accompanied by a markedly elevated Notch signaling activity in the intestinal epithelium. When overexpressed, hnRNP I destabilizes the Notch intracellular domain (NICD) and inhibits Notch signaling. This activity of hnRNP I is conserved from zebrafish to human. In addition, our biochemistry experiments demonstrate that the effect of hnRNP I on NICD turnover requires the C-terminal portion of the RAM domain of NICD. Our results demonstrate that hnRNP I is an evolutionarily conserved Notch inhibitor and plays an essential role in intestinal homeostasis.
authors.affiliation: Center for Cell and Development Biology, The Research Institute at Nationwide Children's Hospital, Columbus, Ohio, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.forename: Chin Yee
authors.initials: CY
authors.lastname: Chan
authors.forename: Bo
authors.initials: B
authors.lastname: Jiang
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Yu
authors.forename: Guo-Zhang
authors.initials: GZ
authors.lastname: Zhu
authors.forename: Yiping
authors.initials: Y
authors.lastname: Chen
authors.forename: John
authors.initials: J
authors.lastname: Barnard
authors.forename: Wenyan
authors.initials: W
authors.lastname: Mei
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000378:metabolism*; D006801:Humans; D007413:Intestinal Mucosa / Q000166:cytology / Q000378:metabolism*; D007422:Intestines / Q000166:cytology; D051379:Mice; D009865:Oocytes / Q000378:metabolism; D051880:Receptors, Notch / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D015398:Signal Transduction; D014982:Xenopus laevis; D015027:Zebrafish / Q000378:metabolism
chemical_list: D034441:Heterogeneous-Nuclear Ribonucleoproteins; D051880:Receptors, Notch