title: Control of gene expression using a red- and far-red light-responsive bi-stable toggle switch.
abstract: Light-triggered gene expression systems offer an unprecedented spatiotemporal resolution that cannot be achieved with classical chemically inducible genetic tools. Here we describe a protocol for red light-responsive gene expression in mammalian cells. This system can be toggled between stable ON and OFF states by short pulses of red and far-red light, respectively. In the protocol, CHO-K1 cells are transfected to allow red light-inducible expression of the secreted alkaline phosphatase (SEAP) reporter, and gene expression is tuned by illumination with light of increasing wavelengths. As a starting point for elaborate red light-responsive gene expression, we outline the reversible activation of gene expression and describe how a spatial pattern can be 'printed' on a monolayer of cells by using a photomask. The core protocol requires only 4 d from seeding of the cells to reporter quantification, and other than light-emitting diode (LED) illumination boxes no elaborate equipment is required.
authors.affiliation: Faculty of Biology, University of Freiburg, Freiburg, Germany.
authors.forename: Konrad
authors.initials: K
authors.lastname: Müller
authors.affiliation: Faculty of Biology, University of Freiburg, Freiburg, Germany.
authors.forename: Matias D
authors.initials: MD
authors.lastname: Zurbriggen
authors.affiliation: 1] Faculty of Biology, University of Freiburg, Freiburg, Germany. [2] Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg, Germany.
authors.forename: Wilfried
authors.initials: W
authors.lastname: Weber
mesh_terms: D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D005786:Gene Expression Regulation / Q000528:radiation effects*; D008027:Light; D019076:Transgenes / Q000528:radiation effects*