title: Analysis of C-MYC function in normal cells via conditional gene-targeted mutation.
abstract: Germline inactivation of c-myc in mice causes embryonic lethality. Therefore, we developed a LoxP/Cre-based conditional mutation approach to test the role of c-myc in mouse embryonic fibroblasts (MEFs) and mature B lymphocytes. Cre expression resulted in reduced proliferation of wild-type MEFs, but c-Myc-deficient MEFs showed a further reduction. In contrast to fibroblasts, Cre expression had no apparent affect on wild-type B cell proliferation. Deletion of both c-Myc genes in B cells led to severely impaired proliferation in response to anti-CD40 plus IL-4. However, treated cells did upregulate several early activation markers but not CD95 or CD95 ligand. We discuss these findings with respect to potential c-Myc functions in proliferation and apoptosis and also discuss potential limitations in the Cre-mediated gene inactivation approach.
authors.affiliation: Howard Hughes Medical Institute and Children's, Hospital, Center for Blood Research and Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
authors.forename: I M
authors.initials: IM
authors.lastname: de Alboran
authors.forename: R C
authors.initials: RC
authors.lastname: O'Hagan
authors.forename: F
authors.initials: F
authors.lastname: Gärtner
authors.forename: B
authors.initials: B
authors.lastname: Malynn
authors.forename: L
authors.initials: L
authors.lastname: Davidson
authors.forename: R
authors.initials: R
authors.lastname: Rickert
authors.forename: K
authors.initials: K
authors.lastname: Rajewsky
authors.forename: R A
authors.initials: RA
authors.lastname: DePinho
authors.forename: F W
authors.initials: FW
authors.lastname: Alt
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D019013:CD40 Antigens / Q000276:immunology; D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002478:Cells, Cultured; D050760:Cyclin-Dependent Kinase Inhibitor p27; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism; D016193:G1 Phase; D018390:Gene Targeting; D015847:Interleukin-4 / Q000276:immunology / Q000494:pharmacology; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008934:Mitogens / Q000276:immunology / Q000494:pharmacology; D009154:Mutation; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D016192:Resting Phase, Cell Cycle; D025521:Tumor Suppressor Proteins
chemical_list: D019013:CD40 Antigens; C493961:Cdkn1b protein, mouse; D018797:Cell Cycle Proteins; D008869:Microtubule-Associated Proteins; D008934:Mitogens; D016271:Proto-Oncogene Proteins c-myc; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015847:Interleukin-4; D018844:Cyclin-Dependent Kinases