Biology subjects

Wen, G.

Publications and source records attributed to Wen, G..

3 recordsLinked to original sources

bioRxiv2020

HiFi-SIM: reconstructing high-fidelity structured illumination microscope images

Structured illumination microscopy (SIM) has been a widely-used super-resolution (SR) fluorescence microscopy technique, but artifacts often appear in reconstructed SR images which reduce its fidelity and might cause misinterpretation of biological structures. We present HiFi-SIM, a high-fidelity SIM reconstruction algorithm, by engineering the effective point spread function (PSF) into an ideal form. HiFi-SIM can effectively reduce commonly-seen artifacts without loss of fine structures and improve the axial sectioning. Since results of HiFi-SIM are not sensitive to used PSF and reconstruction parameters, it lowers the requirements for dedicated PSF calibration and complicated parameter adjustment, thus promoting SIM as a daily imaging tool.

biophysics↗

bioRxiv2020

Astrocytes express DMT1 and transferrin receptors, which transport iron thus activating Ca2+ signalling: possible role in neuroprotection against iron overload?

ABSTRACTIron is the fundamental element for numerous physiological functions. Reduced ferrous (Fe2+) and oxidized ferric (Fe3+) are the two ionized iron states in the living organisms. In the cell membrane, divalent metal ion transporter 1 (DMT1) is responsible for cellular uptake of Fe2+, whereas transferrin receptors (TFR) carry transferrin (TF)-bound Fe3+. In this study we performed, for the first time, detailed analysis of the action of Fe ions on cytoplasmic free calcium ion concentration ([Ca2+]i) in astrocytes. Using qPCR and immunocytochemistry we identified DMT1 and TFR in astrocytes in primary cultures, in acutely isolated astrocytes and in brain tissue preparations; in situ both DMT1 and TFR are concentrated in astroglial perivascular endfeet. Administration of Fe2+ or Fe3+ in low μM concentrations evoked Ca2+ signals in astrocytes in vitro and in vivo. Iron ions triggered increase in [Ca2+]i by acting through two distinct molecular cascades. Uptake of Fe2+ by DMT1 inhibited astroglial Na+-K+-ATPase (NKA), which led to an elevation in cytoplasmic Na+ concentration (as measured by SBFI probe), thus reversing Na+/Ca2+ exchanger (NCX) thereby generating Ca2+ influx. Uptake of Fe3+ by TF-TFR stimulated phospholipase C to produce inositol 1,4,5-trisphosphate (InsP3), thus trigering InsP3 receptor-mediated Ca2+ release from the endoplasmic reticulum. Iron-induced Ca2+ signals promote astroglial release of arachidonic acid and prostaglandin E2 cytokines by activating cytosolic phospholipase A2 (cPLA2) and NF-κB signalling cascade. In summary, these findings reveal new mechanisms of iron-induced astrocytic signalling operational in conditions of iron overload, in response to which astrocytes actively accumulate excessive iron and activate neuroprotective pathways.Competing Interest StatementThe authors have declared no competing interest.View Full Text

molecular biology↗

bioRxiv2019

Evaluation of direct grafting strategies in Expansion Microscopy

High resolution fluorescence microscopy is a key tool in the elucidation of biological fine-structure, providing insights into the distribution and interactions of biomolecular systems down to the nanometer scale. Expansion microscopy is a recently developed approach to achieving nanoscale resolution in optical imaging. In the experiment, biological samples are embedded in a hydrogel, which is isotropicaly swollen. This physically pulls labels apart, allowing more of them to be resolved. However, in the gelation and swelling process, two factors combine to reduce the signal in the final image; signal dilution and the polymerization reaction, which can damage some fluorophores. Here, we show a chemical linking approach that allows covalent grafting of biomolecular target and reporter in expansion microscopy. Through the combination of a targeting ligand, a reporter moiety and a polymerizable group in a single linker, complex constructs can be prepared in a single, labelling step. We show application of this new series of molecules in the targeting of the cell cytoskeleton, a first example of lipid membranes in expansion microscopy; direct immunostaining with primary and secondary antibodies, and direct grafting of ISH probes and signal amplification initiators (HCR and RollFISH). Our probes allow direct, multiplexed targeting of the cellular blueprint and enable a range of novel imaging approaches in combination with expansion microscopy.

biophysics↗