Biology subjects

Steffens, H.

Publications and source records attributed to Steffens, H..

4 recordsLinked to original sources

bioRxiv2024

MINFLUX fluorescence nanoscopy in biological tissue

Optical imaging access to nanometer-level protein distributions in intact tissue is a highly sought-after goal, as it would provide visualization in physiologically relevant contexts. Under the unfavorable signal-to-background conditions of increased absorption and scattering of the excitation and fluorescence light in the complex tissue medium, super-resolution fluorescence microscopy methods are severely challenged in attaining precise localization of molecules. We reasoned that the typical use of a confocal detection pinhole in MINFLUX nanoscopy, suppressing background and providing optical sectioning, should facilitate the detection and resolution of single fluorophores even amid scattering and optically challenging tissue environments. Here, we investigated the performance of MINFLUX imaging for different synaptic targets and fluorescent labels in tissue sections of the mouse brain. Single fluorophores were localized with a precision of < 5 nm at up to 80 {micro}m sample depth. MINFLUX imaging in two color channels allowed to probe PSD95 localization relative to the spine head morphology, while also visualizing presynaptic VGlut clustering and AMPA receptor clustering at the post-synapse. Our two-dimensional (2D) and three-dimensional (3D) two-color MINFLUX results in tissue, with < 10 nm 3D fluorophore localization, open up new avenues to investigate protein distributions on the single-synapse level in fixed and living brain slices.

biophysics↗

bioRxiv2024

Autonomous bioluminescence emission from transgenic mice

The bacterial bioluminescence system can be applied to produce autonomous bioluminescence in mammalian cells. Until now, the system has only been stably inserted into cells cultured in vitro. Here we report the generation of an autobioluminescent transgenic mouse line constitutively expressing the genes of the bacterial bioluminescence system, enabling substrate-free in vivo luminescence imaging of a living mammal.

bioengineering↗

bioRxiv2020

Environmental enrichment enhances precision and remodeling speed of synaptic nanoarchitecture revealed by crosstalk free two-color in vivo STED nanoscopy

Synaptic plasticity underlies long-lasting structural and functional changes to brain circuitry and its experience-dependent remodeling can be fundamentally enhanced by environmental enrichment. It is unknown, however, whether and how environmental enrichment alters the morphology and dynamics of individual synapses. Here, we present a virtually crosstalk free, two-color in vivo STED microscope to simultaneously superresolve the dynamics of endogenous PSD95 of the post-synaptic density and spine geometry. With environmental enrichment, the size distributions of PSD95 and spine head sizes were sharper than in controls, indicating that synaptic strength is set more precisely with environmental enrichment. Spine head geometry and PSD95 assemblies were highly dynamic but their changes correlated only mildly. With environmental enrichment, the topography of the PSD95 nanoorganization was more dynamic; changes in size were smaller than in mice housed in standard cages and depended linearly on their original size. Thus, two-color in vivo time-lapse imaging of synaptic nanoorganization uncovers a unique synaptic nanoplasticity associated with the enhanced learning capabilities under environmental enrichment.

neuroscience↗

bioRxiv2020

Chronic in vivo STED nanoscopy uncovers multiple drivers of shape volatility in stable cortical spines

Excitatory synapses on dendritic spines of pyramidal neurons are considered a central memory locus. To foster both continuous adaption as well as the storage of long-term information, spines need to be plastic and stable at the same time. Here we advanced in vivo STED nanoscopy to superresolve distinct features of dendritic spines (head size, neck length and width) in mouse neocortex for up to one month. While LTP-dependent changes predict highly correlated modifications of spine geometry, we find both, uncorrelated dynamics, as well as correlated changes, indicating multiple independent drivers of spine remodeling. The magnitude of this remodeling suggests substantial fluctuations in synaptic strength, and is exaggerated in a mouse model of neurodegeneration. Despite this high degree of volatility, all spine features also exhibit persistent components that are maintained over long periods of time. Thus, at the nanoscale, stable dendritic spines exhibit a delicate balance of stability and volatility.

neuroscience↗