Open Access

Manipulation of neuronal or muscular activity by optogenetics or other stimuli can be directly linked to the analysis of Caenorhabditis elegans (C. elegans) body length. Thus, WormRuler was developed as an open-source video analysis toolbox that offers video processing and data analysis in one application. Utilizing this novel tool, the super red-shifted channelrhodopsin variant, ChrimsonSA, was characterized in C. elegans. Expression and activation of ChrimsonSA in GABAergic motor neurons results in their depolarization and therefore elongation of body length, the extent of which providing information about the strength of neuronal transmission.

Clb2 is a conserved mitotic B-type cyclin, the levels of which are finely controlled to drive progression through the cell cycle. While it is known that CLB2 transcription and Clb2 protein degradation are important for precise control of its expression, it remains unclear whether the synthesis of Clb2 is also regulated. To address whether and how Clb2 expression levels respond to cell growth changes and adapt cell cycle progression, we combined single-cell and single-molecule imaging methods to measure CLB2 mRNA and protein expression throughout the Saccharomyces cerevisiae cell cycle. We found that the CLB2 mRNA was efficiently localized to the yeast bud as soon as this compartment was formed, but strikingly the Clb2 protein accumulated in the mother nucleus. The CLB2 mRNA localization in the yeast bud by the She2-3 complex did not control protein localization but rather promoted CLB2 translation. Moreover, CLB2 mRNA bud localization and protein synthesis were coupled and dependent on a single secondary structure -a ZIP code-located in the coding sequence. In a CLB2 ZIP code mutant, mRNA localization was impaired and Clb2 protein synthesis decreased, resulting in changes in cell cycle distribution and increased size of daughter cells at birth. Finally, while in WT cells the Clb2 protein concentration followed bud growth, this relationship was impaired in the ZIP code mutant. We propose that S. cerevisiae couples the control of CLB2 mRNA bud localization and protein synthesis to coordinate cell growth and cell cycle progression. This mechanism extends our knowledge of CLB2 expression regulation, and constitutes a novel function for mRNA localization.

Mitochondria are dynamic organelles exhibiting diverse shapes. While the variation of shapes, ranging from spheres to elongated tubules, and the transition between them, are clearly seen in many cell types, the molecular mechanisms governing this morphological variability remain poorly understood. Here, we propose a novel shaping mechanism based on the interplay between the inner and outer mitochondrial membranes. Our biophysical model suggests that the difference in surface area, arising from the pulling of the inner membrane into cristae, correlates with mitochondrial elongation. Analysis of live cell super-resolution microscopy data supports this correlation, linking elongated shapes to the extent of cristae in the inner membrane. Knocking down cristae shaping proteins further confirms the impact on mitochondrial shape, demonstrating that defects in cristae formation correlate with mitochondrial sphericity. Our results suggest that the dynamics of the inner mitochondrial membrane are important not only for simply creating surface area required for respiratory capacity, but go beyond that to affect the whole organelle morphology. This work explores the biophysical foundations of individual mitochondrial shape, suggesting potential links between mitochondrial structure and function. This should be of profound significance, particularly in the context of disrupted cristae shaping proteins and their implications in mitochondrial diseases.

Highlights • Denervation induces mushroom spine loss and AMPAR redistribution to the surface • GRIP1 and ephrinB2 mediate homeostatic mechanisms after lesion • Stimulation with the ephrinB2 receptor EphB4 promotes a surface shift of AMPARs • AMPARs surface shift restores impaired spine recovery after lesion in GRIP1 mutants Summary Despite decades of work, much remains elusive about molecular events at the interplay between physiological and structural changes underlying neuronal plasticity. Here, we combined repetitive live imaging and expansion microscopy in organotypic brain slice cultures to quantitatively characterize the dynamic changes of the intracellular versus surface pools of GluA2-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) across the different dendritic spine types and the shaft during hippocampal homeostatic plasticity. Mechanistically, we identify ephrinB2 and glutamate receptor interacting protein (GRIP) 1 as mediating AMPAR relocation to the mushroom spine surface following lesion-induced denervation. Moreover, stimulation with the ephrinB2 specific receptor EphB4 not only prevents the lesion-induced disappearance of mushroom spines but is also sufficient to shift AMPARs to the surface and rescue spine recovery in a GRIP1 dominant-negative background. Thus, our results unravel a crucial role for ephrinB2 during homeostatic plasticity and identify a potential pharmacological target to improve dendritic spine plasticity upon injury.

The increasing incidence of infected skin wounds poses a major challenge in clinical practice, especially when conventional antibiotic therapy fails. In this context, bacteriophages emerged as promising alternatives for the treatment of antibiotic-resistant bacteria. However, clinical implementation remains hampered by the lack of efficient delivery approaches to infected wound tissue. In this study, bacteriophage-loaded electrospun fiber mats were successfully developed as next-generation wound dressings for the treatment of infected wounds. We employed a coaxial electrospinning approach, creating fibers with a protective polymer shell, enveloping bacteriophages in the core while maintaining their antimicrobial activity. The novel fibers exhibited a reproducible fiber diameter range and morphology, while the mechanical fiber properties were ideal for application onto wounds. Further, immediate release kinetics for the phages were confirmed as well as the biocompatibility of the fibers with human skin cells. Antimicrobial activity was demonstrated against Staphylococcus aureus and Pseudomonas aeruginosa and the core/shell formulation maintained the bacteriophage activity for 4 weeks when stored at − 20 °C. Based on these promising characteristics, our approach holds great potential as a platform technology for the encapsulation of bioactive bacteriophages to enable the translation of phage therapy into clinical application.