title: Smad3 contributes to positioning of proliferating cells in colonic crypts by inducing EphB receptor protein expression.
abstract: Deficiency of Smad3, an intracellular mediator of TGF-β, was shown to significantly accelerate re-epithelialization of the colonic mucosa. This study was performed to investigate the molecular mechanisms by which Smad3 controls colonic epithelial cell proliferation and crypt formation. Smad3(ex8/ex8) C57BL/6 mice were used in this study and wild-type littermates served as controls. The number of proliferating cells in the isolated colonic epithelium of Smad3(-/-) mice was significantly increased compared to that in wild-type littermates. Protein levels of the cell cycle inhibitors p21 and p27 were significantly decreased, while that of c-Myc was increased in the isolated colonic epithelium from Smad3(-/-) mice. In the colonic tissue of wild-type mice, cell proliferation was restricted to the bottom of the crypts in accordance with nuclear β-catenin staining, whereas proliferating cells were located throughout the crypts in Smad3(-/-) mice in accordance with nuclear β-catenin staining, suggesting that Smad3 is essential for locating proliferating cells at the bottom of the colonic crypts. Notably, in Smad3(-/-) mice, there was loss of EphB2 and EphB3 receptor protein expression, critical regulators of proliferating cell positioning, while EphB receptor protein expression was confirmed at the bottom of the colonic crypts in wild-type mice. These observations indicated that disturbance of the EphB/ephrin B system brings about mispositioning of proliferating cells in the colonic crypts of Smad3(-/-) mice. In conclusion, Smad3 is essential for controlling number and positioning of proliferating cells in the colonic crypts and contributes to formation of a "proliferative zone" at the bottom of colonic crypts in the normal colon.
authors.affiliation: Department of Clinical Cell Biology (F5), Graduate School of Medicine, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba-shi 260-8670, Japan.
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Furukawa
authors.forename: Toru
authors.initials: T
authors.lastname: Sato
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Katsuno
authors.forename: Tomoo
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Noguchi
authors.forename: Atsuko
authors.initials: A
authors.lastname: Tokumasa
authors.forename: Kotaro
authors.initials: K
authors.lastname: Yokote
authors.forename: Osamu
authors.initials: O
authors.lastname: Yokosuka
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Saito
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D003106:Colon / Q000166:cytology / Q000502:physiology*; D007413:Intestinal Mucosa / Q000166:cytology / Q000502:physiology*; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D014176:Protein Biosynthesis; D036104:Receptor, EphA2 / Q000096:biosynthesis; D036121:Receptor, EphA3 / Q000096:biosynthesis; D036081:Receptors, Eph Family / Q000096:biosynthesis*; D051900:Smad3 Protein / Q000235:genetics / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000502:physiology
chemical_list: D019394:Ki-67 Antigen; C498355:Mki67 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; D036104:Receptor, EphA2; D036121:Receptor, EphA3; D036081:Receptors, Eph Family