title: Oligodendrocyte lineage transcription factor 2 inhibits the motility of a human glial tumor cell line by activating RhoA.
abstract: The basic helix-loop-helix transcription factor, oligodendrocyte lineage transcription factor 2 (OLIG2), is specifically expressed in the developing and mature central nervous system and plays an important role in oligodendrogenesis from neural progenitors. It is also expressed in various types of glial tumors, but rarely in glioblastoma. Although we previously showed that OLIG2 expression inhibits glioma cell growth, its role in tumorigenesis remains incompletely understood. Here, we investigated the effect of OLIG2 expression on the migration of the human glioblastoma cell line U12-1. In these cells, OLIG2 expression is controlled by the Tet-off system. Induction of OLIG2 expression inhibited both the migration and invasiveness of U12-1 cells. OLIG2 expression also increased the activity of the GTPase RhoA as well as inducing the cells to form stress fibers and focal adhesions. Experiments using short interfering RNA against p27(Kip1) revealed that up-regulation of the p27(Kip1) protein was not essential for RhoA activation, rather it contributed independently to the decreased motility of OLIG2-expressing U12-1 cells. Alternatively, semiquantitative reverse transcription-PCR analysis revealed that mRNA expression of RhoGAP8, which regulates cell migration, was decreased by OLIG2 expression. Furthermore, expression of C3 transferase, which inhibits Rho via ADP ribosylation, attenuated the OLIG2-induced inhibition of cell motility. Imaging by fluorescence resonance energy transfer revealed that in U12-1 cells lacking OLIG2, the active form of RhoA was localized to protrusions of the cell membrane. In contrast, in OLIG2-expressing cells, it lined almost the entire plasma membrane. Thus, OLIG2 suppresses the motile phenotype of glioblastoma cells by activating RhoA.
authors.affiliation: Department of Molecular Pathobiology, Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan.
authors.forename: Kouichi
authors.initials: K
authors.lastname: Tabu
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Ohba
authors.forename: Tadaki
authors.initials: T
authors.lastname: Suzuki
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Makino
authors.forename: Taichi
authors.initials: T
authors.lastname: Kimura
authors.forename: Akiko
authors.initials: A
authors.lastname: Ohnishi
authors.forename: Mieko
authors.initials: M
authors.lastname: Sakai
authors.forename: Takuya
authors.initials: T
authors.lastname: Watanabe
authors.forename: Shinya
authors.initials: S
authors.lastname: Tanaka
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Sawa
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D016543:Central Nervous System Neoplasms / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000378:metabolism; D005910:Glioma / Q000737:chemistry / Q000235:genetics / Q000473:pathology*; D006801:Humans; D009419:Nerve Tissue Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D000076104:Oligodendrocyte Transcription Factor 2; D034741:RNA, Small Interfering / Q000494:pharmacology; D015854:Up-Regulation; D020742:rhoA GTP-Binding Protein / Q000032:analysis / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D020690:GTPase-Activating Proteins; D009419:Nerve Tissue Proteins; D000076104:Oligodendrocyte Transcription Factor 2; D034741:RNA, Small Interfering; D020742:rhoA GTP-Binding Protein; C405708:OLIG2 protein, human; C085379:rho GTPase-activating protein