Actomyosin-based Self-organization of cell internalization during C. elegans gastrulation

Background: Gastrulation is a key transition in embryogenesis; it requires self-organized cellular coordination, which has to be both robust to allow efficient development and plastic to provide adaptability. Despite the conservation of gastrulation as a key event in Metazoan embryogenesis, the morphogenetic mechanisms of self-organization (how global order or coordination can arise from local interactions) are poorly understood. Results: We report a modular structure of cell internalization in Caenorhabditis elegans gastrulation that reveals mechanisms of self-organization. Cells that internalize during gastrulation show apical contractile flows, which are correlated with centripetal extensions from surrounding cells. These extensions converge to seal over the internalizing cells in the form of rosettes. This process represents a distinct mode of monolayer remodeling, with gradual extrusion of the internalizing cells and simultaneous tissue closure without an actin purse-string. We further report that this self-organizing module can adapt to severe topological alterations, providing evidence of scalability and plasticity of actomyosin-based patterning. Finally, we show that globally, the surface cell layer undergoes coplanar division to thin out and spread over the internalizing mass, which resembles epiboly. Conclusions: The combination of coplanar division-based spreading and recurrent local modules for piecemeal internalization constitutes a system-level solution of gradual volume rearrangement under spatial constraint. Our results suggest that the mode of C. elegans gastrulation can be unified with the general notions of monolayer remodeling and with distinct cellular mechanisms of actomyosin-based morphogenesis

Chiral Forces Organize Left-Right Patterning in C. elegans by Uncoupling Midline and Anteroposterior Axis

SummaryLeft-right (LR) patterning is an intriguing but poorly understood process of bilaterian embryogenesis. We report a mechanism for LR patterning in C. elegans in which the embryo uncouples its midline from the anteroposterior (AP) axis. Specifically, the eight-cell embryo establishes a midline that is tilted rightward from the AP axis and positions more cells on the left, allowing subsequent differential LR fate inductions. To establish the tilted midline, cells exhibit LR asymmetric protrusions and a handed collective movement. This process, termed chiral morphogenesis, involves differential regulation of cortical contractility between a pair of sister cells that are bilateral counterparts fate-wise and is activated by noncanonical Wnt signaling. Chiral morphogenesis is timed by the cytokinetic furrow of a neighbor of the sister pair, providing a developmental clock and an unexpected signaling interaction between the contractile ring and the adjacent cells

Magnetofection potentiates gene delivery to cultured endothelial cells

Modification of cellular functions by overexpression of genes is increasingly practised for research of signalling pathways, but restricted by limitations of low efficiency. We investigated whether the novel technique of magnetofection (MF) could enhance gene transfer to cultured primary endothelial cells. MF of human umbilical vein endothelial cells (HUVEC) increased transfection efficiency of a luciferase reporter gene up to 360-fold compared to various conventional transfection systems. In contrast, there was only an up to 1.6-fold increase in toxicity caused by MF suggesting that the advantages of MF outbalanced the increase in toxicity. MF efficiently increased transfection efficiency using several commercially available cationic lipid transfection reagents and polyethyleneimine (PEI). Using PEI, even confluent HUVEC could be efficiently transfected to express luciferase activity. Using a green fluorescent protein vector maximum percentages of transfected cells amounted up to 38.7% while PEI without MF resulted in only 1.3% transfected cells. Likewise, in porcine aortic endothelial cells MF increased expression of a luciferase or beta-galactosidase reporter, reaching an efficiency of 37.5% of cells. MF is an effective tool for pDNA transfection of endothelial cells allowing high efficiencies. It may be of great use for investigating protein function in cell culture experiments

Higher plant diversity enhances soil stability in disturbed alpine ecosystems

Plant diversity is hypothesised to increase soil stability by increasing the diversity of root types. To test this hypothesis, we took soil cores from machine-graded ski slopes and from the adjacent undisturbed vegetation as a control. We quantified aggregate stability as an indicator for soil stability in relation to (1) abiotic soil properties, (2) above-ground vegetation characteristics and (3) root parameters. From the three groups of variables, the number of plant species, root density (RD) and sand content showed the highest correlation with soil aggregate stability and explained 54% of its variance. In variance partitioning, the number of plant species was the most relevant factor explaining 19% of the variance in aggregate stability. Further, it explained another 11% through shared effects with RD and sand content. An additional 8% was explained through the shared influence with sand content. Plant species showing the highest correlation with overall diversity were from different functional groups (grasses, forbs and shrubs), meaning that beneficial effects can not only be assigned to one specific functional group, but to the combination of several groups. Our data demonstrate the positive effect of plant diversity on aggregate stability. We suggest that high plant diversity is one of the most relevant factors for enhancing soil stability at disturbed sites at high elevatio

New ideas for knowledge management in product development projects

Due to their high complexity, product development processes should be expected to be a highly rewarding field for the application of knowledge management systems. Nonetheless, such systems are rarely used in practice. One important reason is that the extra effort of writing down knowledge is widely perceived as slowing down the actual design work without offering visible benefits. Also, writing documents is typically not a favourite pastime of technicians and engineers. There is a high inhibition threshold due to the expectation that the text within a document is well structured and formulated. Furthermore, documents as knowledge carriers require additional effort to retrieve the knowledge: Often the user has to screen several complete documents to find the piece of information he/she is looking for. Full text searches can help, but quite frequently lead to irrelevant information or miss out an important passages because different words were used. So, economically speaking, knowledge management does not yield sufficient return on investment. The authors claim that this can be changed when • knowledge capturing is not a separate activity, but is integrated in the daily design work, • knowledge is integrated into a comprehensive representation of the design and the ongoing design process, • knowledge capturing can be done with very low effort, • knowledge retrieval is very efficient, i.e. the user finds relevant information quickly and reliably, • the captured knowledge can be automatically processed in order to extract different views and to create reports for different purposes. It will be shown that a system that handles a large number of small notes is able to fulfil these requirements. Writing a small note on an adhesive paper is surely the easiest and most popular way of putting down knowledge. The rising popularity of Blogs and Wiki systems for documentation purposes, even in business, shows that people are willing to put down and to share knowledge if they can do it in small portions

Structuring complexity for tailoring research contributions to sustainable development: a framework

Research aiming at generating effective contributions to sustainable development faces particular complexity related challenges. This article proposes an analytical framework disentangling and structuring complexity issues with which research for sustainable development is confronted. Based on theoretical conceptions from fields like policy sciences and transdisciplinary research as well as on an in-depth analysis of the concept of sustainable development, three meta-perspectives on research for sustainable development are introduced and elaborated. The first perspective focuses on notions of sustainable development, sorting out the problem of unclear or ambiguous interpretations of the general sustainability objectives in specific contexts. The second perspective introduces a broad conception of the policy process representing the way societal change towards sustainable development is brought about. It supports identifying those academic and non-academic actors and stakeholders that are relevant for coming up with effective knowledge contributions. The third perspective identifies different forms of knowledge that are needed to tackle sustainability problems as well as the significance of their mutual interrelations. How the framework perspectives support reflecting on the fundamental complexity issues research for sustainable development is confronted with is illustrated using a case example from natural scientific research in the field of land use. We argue that meeting the complexity inherent in the concept of sustainable development requires joint learning in policy processes, working out shared visions being in line with the core objectives of sustainable development and generating knowledge about empirical, normative and pragmatic aspect

Coherent many-body spin dynamics in a long-range interacting Ising chain

Coherent many-body quantum dynamics lies at the heart of quantum simulation and quantum computation. Both require coherent evolution in the exponentially large Hilbert space of an interacting many-body system. To date, trapped ions have defined the state of the art in terms of achievable coherence times in interacting spin chains. Here, we establish an alternative platform by reporting on the observation of coherent, fully interaction-driven quantum revivals of the magnetization in Rydberg-dressed Ising spin chains of atoms trapped in an optical lattice. We identify partial many-body revivals at up to about ten times the characteristic time scale set by the interactions. At the same time, single-site-resolved correlation measurements link the magnetization dynamics with inter-spin correlations appearing at different distances during the evolution. These results mark an enabling step towards the implementation of Rydberg atom based quantum annealers, quantum simulations of higher dimensional complex magnetic Hamiltonians, and itinerant long-range interacting quantum matter.Comment: 11 pages, 9 figure