Expression of a rlf/L-myc minigene inhibits differentiation of embryonic stem cells and embroid body formation.
Rearrangements of the L-myc proto-oncogene with the cellular gene rlf occur in a subset of human small cell lung carcinoma (SCLC) resulting in the expression of a fusion protein. To investigate whether expression of such a rlf/L-myc fusion protein could contribute to the development of SCLC we constructed a chimeric minigene where the rlf first exon and the L-myc second and third exon are under the control of the rlf promoter thereby recapitulating the events of the rearrangement. Attempts to generate transgenic mice with this minigene showed that mouse embryos containing high copy numbers of the rlf/L-myc minigene fail to develop, suggesting that the expression of a rlf/L-myc fusion protein interferes with early differentiation processes. To investigate the nature of this potential embryonic lethality further, we transfected the rlf/L-myc construct stably into embryonic stem (ES) cells. Transfected ES lines that express the rlf/L-myc construct do not show a higher proliferation rate than the parental ES line but fail to properly develop embroid bodies. In addition, outgrowth and differentiation of cells from embroid bodies was severely impaired in ES cells expressing the rlf/L-myc construct when compared to normal ES cells, again suggesting an interference of rlf/L-myc expression with proper differentiation. Expression of a rlf/L-myc fusion may therefore be of critical importance in tumorigenesis by blocking differentiation and thereby allowing continued proliferation of cells and the acquisition of further mutations leading to a fully malignant tumor.
Institut für Molekularbiologie und Tumorforschung, Philipps Universität Marburg, Germany.
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MacLean-Hunter
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Mäkelä
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Grzeschiczek
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Alitalo
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Möröy
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics*; D002455:Cell Division; D004622:Embryo, Mammalian / Q000166:cytology; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics*; D013234:Stem Cells / Q000166:cytology*
C000715470:MAS1 protein, human; D009838:Oligodeoxyribonucleotides; D000090063:Proto-Oncogene Mas; D016271:Proto-Oncogene Proteins c-myc