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Advances in live-cell imaging have been accelerated by the development of various fluorescent indicators. However, indicators that are suitable for multicolor imaging remain a challenge to develop. Herein, we have developed a single fluorescent protein (FP)-based indicator using a semirational molecular design and a molecular evolution approach. We first inserted a ligand-binding domain into the vicinity of an FP chromophore to convert the conformational change induced by ligand binding into a change in fluorescence intensity. We then optimized the linker regions between the FP and the ligand-binding domain to greatly expand the dynamic range (F/F 0 ) of the indicator. Our design and optimization methods are highly versatile and can be used to develop any single FP-based indicators, which will further advance the utility of live-cell imaging.

Adenosine triphosphate (ATP) provides energy for the regulation of multiple cellular processes in living organisms. Capturing the spatiotemporal dynamics of ATP in single cells is fundamental to our understanding of the mechanisms underlying cellular energy metabolism. However, it has remained challenging to visualize the dynamics of ATP in and between distinct intracellular organelles and its interplay with other signaling molecules. Using single fluorescent proteins, multicolor ATP indicators were developed, enabling the simultaneous visualization of subcellular ATP dynamics in the cytoplasm and mitochondria of cells derived from mammals, plants, and worms. Furthermore, in combination with additional fluorescent indicators, the dynamic interplay of ATP, cAMP, and Ca 2+ could be visualized in activated brown adipocyte. This set of indicator tools will facilitate future research into energy metabolism., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

cAMP is a common second messenger that is involved in various physiological processes. To expand the colour palette of available cAMP indicators, we developed a red cAMP indicator named "Pink Flamindo" (Pink Fluorescent cAMP indicator). The fluorescence intensity of Pink Flamindo increases 4.2-fold in the presence of a saturating dose of cAMP, with excitation and emission peaks at 567 nm and 590 nm, respectively. Live-cell imaging revealed that Pink Flamindo is effective for monitoring the spatio-temporal dynamics of intracellular cAMP generated by photoactivated adenylyl cyclase in response to blue light, and in dual-colour imaging studies using a green Ca 2+ indicator (G-GECO). Furthermore, we successfully monitored the elevation of cAMP levels in vivo in cerebral cortical astrocytes by two-photon imaging. We propose that Pink Flamindo will facilitate future in vivo, optogenetic studies of cell signalling and cAMP dynamics.

Fluorescent probes are valuable tools for visualizing the spatiotemporal dynamics of molecules in living cells. Here we developed a genetically encoded antibody probe with antigen-dependent fluorescence intensity called "Flashbody". We first created a fusion of EGFP to the single chain variable region fragment (scFv) of antibody against seven amino acids of the bone Gla protein C-terminus (BGPC7) called BGP Fluobody, which successfully showed the intracellular localization of BGPC7-tagged protein. To generate BGP Flashbody, circularly permuted GFP was inserted in between two variable region fragments, and the linkers were optimized, resulting in fluorescence intensity increase of 300% upon binding with BGPC7 in a dose-dependent manner. Live-cell imaging using BGP Flashbody showed that BGPC7 fused with cell penetrating peptide was able to enter through the plasma membrane by forming a nucleation zone, while it penetrated the nuclear membrane with different mechanism. The construction of Flashbody will be possible for a range of antibody fragments and opens up new possibilities for visualizing a myriad of molecules of interest.

Here we describe the development of a single fluorescent protein (FP)-based cGMP indicator, Green cGull, based on the cGMP binding domain from mouse phosphodiesterase 5α. The dynamic range of Green cGull was enhanced to a 7.5-fold fluorescence change upon cGMP binding by optimization of the amino acid linkers between the cGMP binding domain and FP. Green cGull has excitation and emission peaks at 498 and 522 nm, respectively, and specifically responds to cGMP in a dose-dependent manner. Live cell imaging analysis revealed that addition of a nitric oxide (NO) donor induced different cGMP kinetics and was cell-type dependent. We also found that the NO donor induced an increase of intracellular cGMP, while intracellular Ca 2+ exhibited a complex profile, as revealed by dual-color imaging of cGMP and Ca 2+ . The results suggest that Green cGull sheds new light on understanding the complex interactions between various signaling molecules by multicolor imaging and that our systematic strategy for expanding the dynamic range of single-FP-based indicators is valuable to generate indicators for molecules of interest.

Accurate clinical staging is crucial for adequate risk-adapted treatment in Hodgkin lymphoma (HL) to prevent patients from under- or over-treatment. Within the latest German Hodgkin Study Group trial generation, diagnostic findings such as histopathology, computerized tomography imaging and clinical risk factors were re-evaluated by expert panels. Here, we retrospectively analysed 5965 patients and identified 399 in who major discordant findings changed their first-line treatment allocation. Histopathology review did not confirm the initial diagnosis of HL in 87 patients. Treatment allocation was revised in 312 of the remaining 5878 patients: 176 were assigned to a higher and 128 to a lower risk group, respectively; the correct treatment group remained unclear in 8 patients. Cases of revised treatment allocation accounted for 9·8%, 6·0%, 0·8%, and 14·8% of patients initially assigned to the HD13, HD14, HD15 trials and stage IA lymphocyte-predominant HL project, respectively. Most revisions were due to wrong application of clinical stage (20·5% of 312 patients with revised treatment group), histological subtype (9·0%) or the risk factors ≥3 involved areas (46·8%) or large mediastinal mass (9·3%). In conclusion, centralized review by experienced experts changed risk-adapted first-line treatment in a relevant proportion of HL patients. Quality control measures clearly improve the accuracy of treatment and should be implemented in clinical practice., (© 2015 John Wiley & Sons Ltd.)

Purpose: The introduction of BEACOPP(escalated) (escalated-dose bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone) has significantly improved tumor control and overall survival in patients with advanced-stage Hodgkin lymphoma. However, this regimen has also been associated with higher treatment-related mortality (TRM). Thus, we analyzed clinical course and risk factors associated with TRM during treatment with BEACOPP(escalated)., Patients and Methods: In this retrospective analysis, we investigated incidence, clinical features, and risk factors for BEACOPP(escalated)-associated TRM in the German Hodgkin Study Group trials HD9, HD12, and HD15., Results: Among a total of 3,402 patients, TRM of 1.9% (64 of 3,402) was mainly related to neutropenic infections (n = 56; 87.5%). Twenty of 64 events occurred during the first course of BEACOPP(escalated) (31.3%). Higher risk of TRM was seen in patients age ≥ 40 years with poor performance status (PS) and in patients age ≥ 50 years. PS and age were then used to construct a new risk score; those with a score ≥ 2 had TRM of 7.1%, whereas patients who scored 0 or 1 had TRM of 0.9%., Conclusion: The individual risk of TRM associated with BEACOPP(escalated) can be predicted by a simple algorithm based on age and PS. High-risk patients should receive special clinical attention.