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Identification of an epigenetically silenced gene, RFX1, in human glioma cells using restriction landmark genomic scanning


To identify the CpG islands differentially methylated in human glioma, we performed restriction landmark genomic scanning with a CpG methylation-sensitive enzyme. We found 12 spots, the intensity of which was entirely lost or decreased in both the human glioma tissues examined as compared with that in matched normal lymphocytes, indicating aberrant methylation of these CpG islands in gliomas. The expression of RFX1, one of the genes associated with the methylated CpG islands, was frequently decreased in human glioma cell lines and tissues. We also demonstrated that the isolated CpG island located in the seventh intron of the RFX1 gene had enhancer activity and was hypermethylated in all of the glioma tissues and cell lines analysed, but not in normal brains or lymphocytes. Treatment of glioma cells with a demethylating agent, 5-azacytidine, resulted in the expression of RFX1, indicating that the silencing of the RFX1 gene may be attributable to its methylation. RFX1 has been implicated in transcriptional downregulation of the proto-oncogene c-myc. By expression of the RFX1 gene, the cellular proliferative activity of glioma cells was suppressed. Taken together, these results suggest that the RFX1 gene may be epigenetically silenced in human gliomas and involved in glioma tumorigenesis.

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We thank Mr Muramatsu and Mr Iizuka (Keio University School of Medicine) for their technical support. We are also grateful to Dr W Reith (University of Geneva Medical School) for providing us with the pHRFX1 plasmid. This work was supported by grants from grant-in-aid for Scientific Research from the Japanese Ministry of Education, Culture, Sports, Science and Technology (MT), the Keio University Medical Science Fund (MT), and grand-in-aid for Scientific Research on Priority Areas from the Japanese Ministry of Education, Culture, Sports, Science and Technology (MU).

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Correspondence to Masahiro Toda.

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Ohashi, Y., Ueda, M., Kawase, T. et al. Identification of an epigenetically silenced gene, RFX1, in human glioma cells using restriction landmark genomic scanning. Oncogene 23, 7772–7779 (2004).

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  • glioma
  • RLGS
  • RFX1
  • methylation
  • epigenetics

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