Notch signaling promotes the generation of EphrinB1-positive intestinal epithelial cells.
OBJECTIVE
The intestinal epithelium consists of EphB2-positive proliferative basal cryptic cells and EphrinB1-positive, postmitotic differentiated cells. We investigated the effects of Notch signaling on formation of the EphB2-EphrinB1 boundary using mouse and tissue culture models.


METHODS
We created mice in which Mind bomb-1 (Mib1), an essential E3 ubiquitin ligase that activates Notch ligands, was inactivated specifically in the intestinal epithelia (Vil-Cre;Mib1(f/f)); Notch is, therefore, inactivated in this tissue. We also studied the effects of different inhibitors on intestinal epithelial cells (IEC-6) that express activated Notch. Tissues and cells were analyzed by immunohistochemical and immunoblot analyses.


RESULTS
The intestinal epithelia of Vil-Cre;Mib1(f/f) mice had reduced numbers of EphrinB1-positive cells, compared with controls, but increases in EphB2-positive cells; beta-catenin was activated in these cells. These phenotypes were reversed by expression of a constitutively active form of Notch1. In the IEC-6 cells, Notch signaling activated the expression of EphrinB1 in an Hes1-independent manner, but down-regulated the expression of EphB2 through the GSK3beta-mediated inhibition of beta-catenin.


CONCLUSIONS
Notch signaling regulates formation of the EphB2-EphrinB1 boundary in the mouse intestinal epithelium.
Koo
Bon-Kyoung
BK
Department of Biological Sciences, Seoul National University, Silim-dong, Gwanak-gu, Seoul, South Korea.
Lim
Hyoung-Soo
HS
Chang
Hee Jin
HJ
Yoon
Mi-Jeong
MJ
Choi
Yongwook
Y
Kong
Myung-Phil
MP
Kim
Cheol-Hee
CH
Kim
Jin-Man
JM
Park
Jae-Gahb
JG
Kong
Young-Yun
YY