Dynamic interplay of microtubule and actomyosin forces drive tissue extension.

In order to shape a tissue, individual cell-based mechanical forces have to be integrated into a global force pattern. Over the last decades, the importance of actomyosin contractile arrays, which are the key constituents of various morphogenetic processes, has been established for many tissues. Recent studies have demonstrated that the microtubule cytoskeleton mediates folding and elongation of the epithelial sheet during Drosophila morphogenesis, placing microtubule mechanics on par with actin-based processes.

The Microtubule Minus-End Binding Protein Patronin Is Required for the Epithelial Remodeling in the Abdomen.

In the developing abdomen, the epithelial tissue displays extensive cytoskeletal remodeling. In stark contrast to the spatio-temporal control of the actin cytoskeleton, the regulation of microtubule architecture during epithelial morphogenesis has remained opaque. In particular, its role in cell motility remains unclear.

Astrocytes in stress accumulate lipid droplets.

When the brain is in a pathological state, the content of lipid droplets (LDs), the lipid storage organelles, is increased, particularly in glial cells, but rarely in neurons. The biology and mechanisms leading to LD accumulation in astrocytes, glial cells with key homeostatic functions, are poorly understood. We imaged fluorescently labeled LDs by microscopy in isolated and brain tissue rat astrocytes and in glia-like cells in Drosophila brain to determine the (sub)cellular localization, mobility, and content of LDs under various stress conditions characteristic for brain pathologies.

Using migrating cells as probes to illuminate features in live embryonic tissues.

The biophysical and biochemical properties of live tissues are important in the context of development and disease. Methods for evaluating these properties typically involve destroying the tissue or require specialized technology and complicated analyses. Here, we present a novel, noninvasive methodology for determining the spatial distribution of tissue features within embryos, making use of nondirectionally migrating cells and software we termed "Landscape," which performs automatized high-throughput three-dimensional image registration.

The Mechanical Role of Microtubules in Tissue Remodeling.

During morphogenesis, tissues undergo extensive remodeling to get their final shape. Such precise sculpting requires the application of forces generated within cells by the cytoskeleton and transmission of these forces through adhesion molecules within and between neighboring cells. Within individual cells, microtubules together with actomyosin filaments and intermediate filaments form the composite cytoskeleton that controls cell mechanics during tissue rearrangements.

Polarized microtubule dynamics directs cell mechanics and coordinates forces during epithelial morphogenesis.

Coordinated rearrangements of cytoskeletal structures are the principal source of forces that govern cell and tissue morphogenesis. However, unlike for actin-based mechanical forces, our knowledge about the contribution of forces originating from other cytoskeletal components remains scarce. Here, we establish microtubules as central components of cell mechanics during tissue morphogenesis.

Regulation of cell polarity by cell adhesion receptors.

The ability of cells to polarize is an intrinsic property of almost all cells and is required for the devlopment of most multicellular organisms. To develop cell polarity, cells integrate various signals derived from intrinsic as well as extrinsic sources. In the recent years, cell-cell adhesion receptors have turned out as important regulators of cellular polarization.

Automated analysis of filopodial length and spatially resolved protein concentration via adaptive shape tracking.

Filopodia are dynamic, actin-rich structures that transiently form on a variety of cell types. To understand the underlying control mechanisms requires precise monitoring of localization and concentration of individual regulatory and structural proteins as filopodia elongate and subsequently retract. Although several methods exist that analyze changes in filopodial shape, a software solution to reliably correlate growth dynamics with spatially resolved protein concentration along the filopodium independent of bending, lateral shift, or tilting is missing.

Polarized trafficking provides spatial cues for planar cell polarization within a tissue.

Planar cell polarity, the polarization of cells within the plane of the epithelium, orthogonal to the apical-basal axis, is essential for a growing list of developmental events, and - over the last 15 years - has evolved from a little-studied curiosity in Drosophila to the subject of a substantial research enterprise. In that time, it has been recognized that two molecular systems are responsible for polarization of most tissues: Both the "core" Frizzled system and the "global" Fat/Dachsous/Four-jointed system produce molecular asymmetry within cells, and contribute to morphological polarization. In this review, we discuss recent findings on the molecular mechanism that links "global" directional signals with local coordinated polarity.

Force-control at cellular membranes.

Force-regulation at cellular membranes relies on dynamic molecular platforms that integrate intra- and extracellular signals to control cell shape and function. To correctly respond to a continuously changing environment, activity of these platforms needs to be tightly controlled in space and time. Over the last few years, curvature-dependent mechano-chemical signal translation—a receptor-independent signaling mechanism where physical forces at the plasma membrane trigger nanoscale membrane deformations that are then translated into chemical signal transduction cascades—has emerged as a new signaling principle that cells use to regulate forces at the membrane.

Dynamic recruitment of the curvature-sensitive protein ArhGAP44 to nanoscale membrane deformations limits exploratory filopodia initiation in neurons.

In the vertebrate central nervous system, exploratory filopodia transiently form on dendritic branches to sample the neuronal environment and initiate new trans-neuronal contacts. While much is known about the molecules that control filopodia extension and subsequent maturation into functional synapses, the mechanisms that regulate initiation of these dynamic, actin-rich structures have remained elusive. Here, we find that filopodia initiation is suppressed by recruitment of ArhGAP44 to actin-patches that seed filopodia.

Microtubules provide directional information for core PCP function.

Planar cell polarity (PCP) signaling controls the polarization of cells within the plane of an epithelium. Two molecular modules composed of Fat(Ft)/Dachsous(Ds)/Four-jointed(Fj) and a 'PCP-core' including Frizzled(Fz) and Dishevelled(Dsh) contribute to polarization of individual cells. How polarity is globally coordinated with tissue axes is unresolved.

Prickle/spiny-legs isoforms control the polarity of the apical microtubule network in planar cell polarity.

Microtubules (MTs) are substrates upon which plus- and minus-end directed motors control the directional movement of cargos that are essential for generating cell polarity. Although centrosomal MTs are organized with plus-ends away from the MT organizing center, the regulation of non-centrosomal MT polarity is poorly understood. Increasing evidence supports the model that directional information for planar polarization is derived from the alignment of a parallel apical network of MTs and the directional MT-dependent trafficking of downstream signaling components.

Regulation of PCP by the Fat signaling pathway.

Planar cell polarity (PCP) in epithelia, orthogonal to the apical-basal axis, is essential for numerous developmental events and physiological functions. Drosophila model systems have been at the forefront of studies revealing insights into mechanisms regulating PCP and have revealed distinct signaling modules. One of these, involving the atypical cadherins Fat and Dachsous and the ectokinase Four-jointed, appears to link the direction of cell polarization to the tissue axes.

A universal analysis tool for the detection of asymmetric signal distribution in microscopic images.

Background: Polarization of tissue is achieved by asymmetric distribution of proteins and organelles within individual cells. However, existing quantitative assays to measure this asymmetry in an automated and unbiased manner suffer from significant limitations.

Results: Here, we report a new way to assess protein and organelle localization in tissue based on correlative fluorescence analysis.

STED Super-resolution Microscopy in Tissue and in Mammalian Cells.

Far-field super-resolution microscopy is a rapidly emerging method that is opening up opportunities for biological imaging beyond the optical diffraction limit. We have implemented a Stimulated Emission Depletion (STED) microscope to image single dye, cell, and tissue samples with 50-80 nm resolution. First, we compare the STED performance imaging single molecules of several common dyes and report a novel STED dye.

Asymmetric homotypic interactions of the atypical cadherin flamingo mediate intercellular polarity signaling.

Acquisition of planar cell polarity (PCP) in epithelia involves intercellular communication, during which cells align their polarity with that of their neighbors. The transmembrane proteins Frizzled (Fz) and Van Gogh (Vang) are essential components of the intercellular communication mechanism, as loss of either strongly perturbs the polarity of neighboring cells. How Fz and Vang communicate polarity information between neighboring cells is poorly understood.

Global Analysis of the Hortaea werneckii proteome: studying steroid response in yeast.

The response of the halophilic black yeast Hortaea werneckii to the steroid hormone progesterone has been studied at the protein level using fluorescent two-dimensional differential gel electrophoresis (2D-DIGE) technology in combination with mass spectrometry. Data on protein identification from this study reveal molecular mechanisms of the response to progesterone. In particular, the overexpression of Pck2 and Pac2 in the stimulated cells indicates the interactions of progesterone with the cell growth and reproduction signaling pathways.

Ammodytoxin, a secretory phospholipase A2, inhibits G2 cell-cycle arrest in the yeast Saccharomyces cerevisiae.

Ammodytoxin (Atx), an sPLA2 (secretory phospholipase A2), binds to g and e isoforms of porcine 14-3-3 proteins in vitro. 14-3-3 proteins are evolutionarily conserved eukaryotic regulatory proteins involved in a variety of biological processes, including cell-cycle regulation. We have now shown that Atx binds to yeast 14-3-3 proteins with an affinity similar to that for the mammalian isoforms.

Mass spectrometry and database search in the analysis of proteins from the fungus Pleurotus ostreatus.

Tandem mass spectrometry is a method of choice for rapid analysis in proteomics. Identification and characterization of proteins from organisms with sequenced genomes is today a routine procedure as will be identification of proteins from organisms with unsequenced genomes with new developing tools. Here, we report the use of isotopic labeling with electrospray ionisation (ESI)-tandem mass spectrometry for de novo sequencing in combination with database search taking advantage of different programs for identification of fungal proteins.

Murine monoclonal antibodies directed against human recombinant Macrophage Migration Inhibitory Factor.

Macrophage Migration Inhibitory Factor (MIF) is a crucial component of the immune system acting together with glucocorticosteroids to regulate immunity and inflammation. Understanding of its many putative functions and action mechanisms is still ambiguous. Due to the newest findings that a local MIF expression is up regulated in allograft rejection and in glomerulonephritis, an interest in MIF research is increasing and is focused on possibilities of anti-MIF treatment.