Biology subjects

Selhuber-Unkel, C.

Publications and source records attributed to Selhuber-Unkel, C..

4 recordsLinked to original sources

bioRxiv2025

Model of integrin binding as a function of light-induced variations in forces exerted on cells via RGD-terminated, photoswitchable azobenzene surfaces

Photo-responsive biomaterials are attractive because of the ability to non-invasively alter and control the material properties, thus allowing control over the cell response at the interface with the bioamaterial surface. While in silico mathematical models have been implemented for simulating single-cell force spectroscopy (SCFS) experiments on static and some dynamic biomaterials, these models have yet to be extended to light-responsive biointerfaces. So here, we develop a mathematical model that describes and predicts the strength of integrin-mediated cell adhesions to a photoswitchable biomaterial surface. The fluctuating biomaterial comprises photoswitchable azobenzene attached to a glass surface and terminated with peptide c(RGDfK). Upon irradiation with light at 530 nm, the azobenzenes rapidly fluctuate between an extended and contracted conformation, leading to a change in the length of the azobenzene that stimulates integrins bound to c(RGDfK). The mathematical model mimics the nascent adhesion and spatial fluctuations in the extra-cellular matrix (ECM) and is calibrated using single-cell force microscopy retraction curves. It relies on spring-based mechanics to describe the stretch and deformation of a cell and ensembles of integrins when applied to a fluctuating biomaterial. We use the model to simulate retraction curves and the proportion of bound integrins on the surface as the material fluctuates. Additionally, we use the model to predict SCFS retraction curves for varying experimental conditions. This includes the length of time the cell (attached to the tip of the atomic force microscopy cantilever) is kept in contact with the biomaterial before retraction, and for varying frequency of light-induced movement of the azobenzene conformations. These model outcomes provide an attractive route to integrate and rigorously control certain experimental variables, thus accelerating experimental design of the study of cell adhesion to light-responsive biomaterials. Furthermore the model complements experiments by providing estimates of variables that are experimentally inaccessible. Thus, the outcomes of the model provide a valuable resource to aid in the interpretation and design of light-responsive biointerface functionalities.

biophysics↗

bioRxiv2024

Morphology-dependent entry kinetics and spread of influenza A virus

Influenza A viruses (IAV) display a broad variety of morphologies ranging from spherical to long filamentous virus particles. These diverse phenotypes are believed to allow the virus to overcome various immunological and pulmonary barriers during entry into the airway epithelium and influence the viral entry pathway. Remarkably, lab-adapted IAV strains lost this morphological variance and exhibit preferred spherical morphology. However, it remains unclear which factors lead to this lab-adapted preference and which pulmonary defense factors are responsible for the preferred filamentous morphology in physiological settings. In this study, we established fluorescent reporter viruses with spherical or filamentous morphology but with the same surface glycoproteins. We developed a correlative fluorescence and scanning electron microscopy workflow to analyze the impact of viral morphology on cell-to-cell spread and identify conditions under which IAV with either spherical or filamentous morphology confer an advantage. Our findings demonstrate that filamentous IAV cell-to-cell spread is significantly slower in various cell lines, which can explain the predominant spherical morphology in lab-adapted strains. This observation is consistent with delayed entry kinetics of filamentous viruses structurally analyzed by cellular cryo-electron tomography. We found that cellular junction integrity and mucin do not exert morphology-dependent inhibition of IAV cell-to-cell spread. On the other hand, filamentous virions confer an advantage under the pressure exerted by neutralizing antibodies against hemagglutinin.

microbiology↗

bioRxiv2023

2-photon laser printing to mechanically stimulate multicellular systems in 3D

Most biological activities take place in 3D environments, where cells communicate with each other in various directions and are located in a defined, often microstructured, space. To investigate the effect of defined cyclic mechanical forces on a multicellular system, we develop a sub-millimeter sized stretching device for mechanical stimulation of a structurally restricted, soft multicellular microenvironment. For the stretching device, a multimaterial 3D microstructure made of PDMS and gelatine-based hydrogel is printed via 2-photon polymerization (2PP) method. The printed structures are first characterized microscopically and mechanically to study the effect of different printing parameters. With 2PP, organotypic cell cultures are then directly printed into the hydrogel structures to achieve true 3D cell culture systems. These are mechanically stimulated with a cantilever by indenting the stretching device at a defined point. As a most important result, the cells in the 3D organotypic cell culture change morphology and actin orientation when exposed to cyclic mechanical stretch, even within short timescales of just 30 minutes. As a proof of concept, we encapsulated a Medaka retinal organoid in the same structure to demonstrate that even preformed organoids can be stimulated by our method. The results demonstrate the power of 2PP to manufacturing multifunctional soft devices for mechanically controlling multicellular systems at micrometer resolution and thus mimicking mechanical stress situations, as they occur in vivo.

biophysics↗

bioRxiv2023

Microbes as part of ancestral neuronal circuits: Bacterial produced signals affect neurons controlling eating behavior in Hydra

Although recent studies indicate the impact of microbes on the central nervous systems and behavior, it remains unclear how the relationship between the functionality of the nervous system, behavior and the microbiota arise. We studied the eating behavior of Hydra, a host that has a simple nervous system and a low-complexity microbiota. To identify the neuronal subpopulations involved, we used a subpopulation specific cell ablation system and calcium imaging. The role of the microbiota was uncovered by reducing the diversity of the natural microbiota. Here, we demonstrate that different neuronal subpopulations are functioning together to control the eating behavior. The microbiota participates in control of the eating behavior since germ-free or mono-colonized animals have drastic difficulties in mouth opening. This was restored by adding a full complement of the microbiota. In summary, we provide a mechanistic explanation of how the eating behavior is controlled in Hydra and how microbes can affect the neuronal circuit. Highlights- Multiple neuronal modules and their networks control complex behavior in an animal lacking a central nervous system. - Its associated microbes participate in these neuronal circuits and influence the eating behavior. - Disorganization of the microbiota negatively impacts this eating behavior. - Glutamate participates in an evolutionary ancient interkingdom language.

animal behavior and cognition↗