title: Flavin mononucleotide-based fluorescent proteins function in mammalian cells without oxygen requirement.
abstract: Usage of the enhanced green fluorescent protein (eGFP) in living mammalian cells is limited to aerobic conditions due to requirement of oxygen during chromophore formation. Since many diseases or disease models are associated with acute or chronic hypoxia, eGFP-labeling of structures of interest in experimental studies might be unreliable leading to biased results. Thus, a chromophore yielding a stable fluorescence under hypoxic conditions is desirable. The fluorescence of flavin mononucleotide (FMN)-based fluorescent proteins (FbFPs) does not require molecular oxygen. Recently, the advantages of FbFPs for several bacterial strains and yeasts were described, specifically, their usage as a real time fluorescence marker in bacterial expression studies and their ability of chromophore formation under anaerobic conditions. Our objective was to verify if FbFPs also function in mammalian cells in order to potentially broaden the repertoire of chromophores with ones that can reliably be used in mammalian studies under hypoxic conditions. In the present study, we demonstrate for the first time, that FbFPs can be expressed in different mammalian cells, among them murine neural stem cells during proliferative and differentiated stages. Fluorescence intensities were comparable to eGFP. In contrast to eGFP, the FbFP fluorescence did not decrease when cells were exposed to defined hypoxic conditions neither in proliferating nor in differentiated cells. Thus, FbFPs can be regarded as an alternative to eGFP in studies that target cellular structures which are exposed to hypoxic conditions.
authors.affiliation: Department of Neurology and Epileptology, Hertie Institute for Clinical Brain Research, Eberhard-Karls-University, Tübingen, Baden-Württemberg, Germany. Janine.Walter@googlemail.com
authors.forename: Janine
authors.initials: J
authors.lastname: Walter
authors.forename: Sascha
authors.initials: S
authors.lastname: Hausmann
authors.forename: Thomas
authors.initials: T
authors.lastname: Drepper
authors.forename: Michael
authors.initials: M
authors.lastname: Puls
authors.forename: Thorsten
authors.initials: T
authors.lastname: Eggert
authors.forename: Marcel
authors.initials: M
authors.lastname: Dihné
mesh_terms: D000818:Animals; D016466:CHO Cells; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D048429:Cell Size; D006224:Cricetinae; D005486:Flavin Mononucleotide / Q000378:metabolism*; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D008164:Luminescent Proteins / Q000378:metabolism; D008322:Mammals / Q000378:metabolism*; D051379:Mice; D058953:Neural Stem Cells / Q000166:cytology / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D014162:Transfection; D019076:Transgenes / Q000235:genetics
chemical_list: D008164:Luminescent Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D005486:Flavin Mononucleotide; D010100:Oxygen