RT Journal Article SR Electronic T1 A genetically encoded biosensor for visualising hypoxia responses in vivo JF Biology Open JO Biology Open FD Company of Biologists SP 296 OP 304 DO 10.1242/bio.018226 VO 6 IS 2 A1 Misra, Tvisha A1 Baccino-Calace, Martin A1 Meyenhofer, Felix A1 Rodriguez-Crespo, David A1 Akarsu, Hatice A1 Armenta-Calderón, Ricardo A1 Gorr, Thomas A. A1 Frei, Christian A1 Cantera, Rafael A1 Egger, Boris A1 Luschnig, Stefan YR 2017 UL http://bio.biologists.org/content/6/2/296.abstract AB Cells experience different oxygen concentrations depending on location, organismal developmental stage, and physiological or pathological conditions. Responses to reduced oxygen levels (hypoxia) rely on the conserved hypoxia-inducible factor 1 (HIF-1). Understanding the developmental and tissue-specific responses to changing oxygen levels has been limited by the lack of adequate tools for monitoring HIF-1 in vivo. To visualise and analyse HIF-1 dynamics in Drosophila, we used a hypoxia biosensor consisting of GFP fused to the oxygen-dependent degradation domain (ODD) of the HIF-1 homologue Sima. GFP-ODD responds to changing oxygen levels and to genetic manipulations of the hypoxia pathway, reflecting oxygen-dependent regulation of HIF-1 at the single-cell level. Ratiometric imaging of GFP-ODD and a red-fluorescent reference protein reveals tissue-specific differences in the cellular hypoxic status at ambient normoxia. Strikingly, cells in the larval brain show distinct hypoxic states that correlate with the distribution and relative densities of respiratory tubes. We present a set of genetic and image analysis tools that enable new approaches to map hypoxic microenvironments, to probe effects of perturbations on hypoxic signalling, and to identify new regulators of the hypoxia response.