Faculty Opinions recommendation of Large-scale curvature sensing by directional actin flow drives cellular migration mode switching.

Traditional energy saving methods for engineering vehicle cannot raise the effect on a large scale if there are no major technology breakthrough. Hybrid system has the potential of improving fuel economy by operating the engine in an optimum efficiency range and it has been successfully applied in engineering vehicles. So equipping engineering vehicle with the hybrid system provides a new way to achieve energy savings. Simulation results of vehicles based on backward modelling shows that the energy control strategy can achieve a variety of reasonable operating mode switching and meet the vehicle at power.

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Microtopographical guidance of macropinocytic signaling patches

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2110281118 ◽

2021 ◽

Vol 118 (50) ◽

pp. e2110281118

Author(s):

Gen Honda ◽

Nen Saito ◽

Taihei Fujimori ◽

Hidenori Hashimura ◽

Mitsuru J. Nakamura ◽

...

Keyword(s):

Immune Cells ◽

Large Scale ◽

Nanometer Scale ◽

Distinct Mode ◽

Structured Surfaces ◽

Curvature Sensing ◽

Quantitative Image ◽

Membrane Protrusions ◽

Particle Ingestion ◽

Micrometer Scale

In fast-moving cells such as amoeba and immune cells, dendritic actin filaments are spatiotemporally regulated to shape large-scale plasma membrane protrusions. Despite their importance in migration, as well as in particle and liquid ingestion, how their dynamics are affected by micrometer-scale features of the contact surface is still poorly understood. Here, through quantitative image analysis of Dictyostelium on microfabricated surfaces, we show that there is a distinct mode of topographical guidance directed by the macropinocytic membrane cup. Unlike other topographical guidance known to date that depends on nanometer-scale curvature sensing protein or stress fibers, the macropinocytic membrane cup is driven by the Ras/PI3K/F-actin signaling patch and its dependency on the micrometer-scale topographical features, namely PI3K/F-actin–independent accumulation of Ras-GTP at the convex curved surface, PI3K-dependent patch propagation along the convex edge, and its actomyosin-dependent constriction at the concave edge. Mathematical model simulations demonstrate that the topographically dependent initiation, in combination with the mutually defining patch patterning and the membrane deformation, gives rise to the topographical guidance. Our results suggest that the macropinocytic cup is a self-enclosing structure that can support liquid ingestion by default; however, in the presence of structured surfaces, it is directed to faithfully trace bent and bifurcating ridges for particle ingestion and cell guidance.

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scASK: A novel ensemble framework for classifying cell types based on single-cell RNA-seq data

10.1101/2020.06.07.138271 ◽

2020 ◽

Author(s):

Bo Liu ◽

Fang-Xiang Wu ◽

Xiufen Zou

Keyword(s):

Single Cell ◽

Large Scale ◽

Poor Performance ◽

Cell Types ◽

Mode Switching ◽

Rna Seq ◽

Adaptive Slicing ◽

Large Scale Data ◽

Data Adaptive ◽

Computational Analyses

ABSTRACTThe Human Cell Atlas (HCA) is a large project that aims to identify all cell types in the human body. The dimension reduction and clustering for identification of cell types from single-cell RNA-sequencing (scRNA-seq) data have become foundational approaches to HCA. The major challenges of current computational analyses are of poor performance on large scale data and sensitive to initial data. We present a new ensemble framework called Adaptive Slice KNNs (scASK) to address the challenges for analysing scRNA-seq data with high dimensionality. scASK consists of three innovational modules, called DAS (Data Adaptive Slicing), MCS (Meta Classifiers Selecting) and EMS (Ensemble Mode Switching), respectively, which facilitate scASK to approximate a bias-variance tradeoff beyond classification. Thirteen real scRNA-seq datasets are used to evaluate the performance of scASK. Compared with five popular classification algorithms, our experimental results indicate that scASK achieves the best accuracy and robustness among all competing methods. In conclusion, adaptive slicing is an effective structural reduction procedure, and meanwhile scASK provides novel and robust ensemble framework especially for classifying cell types based on scRNA-seq data. scASK is publically available at https://github.com/liubo2358/scASKcmd.

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High Throughput strategies Aimed at Closing the GAP in Our Knowledge of Rho GTPase Signaling

Cells ◽

10.3390/cells9061430 ◽

2020 ◽

Vol 9 (6) ◽

pp. 1430

Author(s):

Manel Dahmene ◽

Laura Quirion ◽

Mélanie Laurin

Keyword(s):

High Throughput ◽

Protein Interactions ◽

Rho Gtpases ◽

High Throughput Screening ◽

Large Scale ◽

Rho Gtpase ◽

Cellular Migration ◽

Cell Junctions ◽

System Level ◽

Culture Models

Since their discovery, Rho GTPases have emerged as key regulators of cytoskeletal dynamics. In humans, there are 20 Rho GTPases and more than 150 regulators that belong to the RhoGEF, RhoGAP, and RhoGDI families. Throughout development, Rho GTPases choregraph a plethora of cellular processes essential for cellular migration, cell–cell junctions, and cell polarity assembly. Rho GTPases are also significant mediators of cancer cell invasion. Nevertheless, to date only a few molecules from these intricate signaling networks have been studied in depth, which has prevented appreciation for the full scope of Rho GTPases’ biological functions. Given the large complexity involved, system level studies are required to fully grasp the extent of their biological roles and regulation. Recently, several groups have tackled this challenge by using proteomic approaches to map the full repertoire of Rho GTPases and Rho regulators protein interactions. These studies have provided in-depth understanding of Rho regulators specificity and have contributed to expand Rho GTPases’ effector portfolio. Additionally, new roles for understudied family members were unraveled using high throughput screening strategies using cell culture models and mouse embryos. In this review, we highlight theses latest large-scale efforts, and we discuss the emerging opportunities that may lead to the next wave of discoveries.

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Large-scale curvature sensing by epithelial monolayers depends on active cell mechanics and nuclear mechanoadaptation

10.1242/prelights.23824 ◽

2020 ◽

Author(s):

Grace Lim

Keyword(s):

Cell Mechanics ◽

Large Scale ◽

Active Cell ◽

Curvature Sensing ◽

Epithelial Monolayers

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Large-scale curvature sensing by epithelial monolayers depends on active cell mechanics and nuclear mechanoadaptation

10.1101/2020.07.04.187468 ◽

2020 ◽

Author(s):

Marine Luciano ◽

Shi-Lei Xue ◽

Winnok H. De Vos ◽

Lorena Redondo Morata ◽

Mathieu Surin ◽

...

Keyword(s):

Cell Mechanics ◽

Large Scale ◽

Chromatin Condensation ◽

Active Cell ◽

Epithelial Tissue ◽

Hippo Signaling ◽

Curvature Sensing ◽

Epithelial Monolayers ◽

Substrate Curvature

AbstractWhile many tissues fold in vivo in a highly reproducible and robust way, epithelial folds remain difficult to reproduce in vitro, so that the effects and underlying mechanisms of local curvature on the epithelial tissue remains unclear. Here, we photoreticulated polyacrylamide hydrogels though an optical photomask to create corrugated hydrogels with isotropic wavy patterns, allowed us to show that concave and convex curvatures affect cellular and nuclear shape. By culturing MDCK epithelial cells at confluency on corrugated hydrogels, we showed that the substrate curvature leads to thicker epithelial zones in the valleys and thinner ones on the crest, as well as corresponding density, which can be generically explained by a simple 2D vertex model, leading us to hypothesize that curvature sensing could arise from resulting density/thickness changes. Additionally, positive and negative local curvatures lead to significant modulations of the nuclear morphology and positioning, which can also be well-explained by an extension of vertex models taking into account membrane-nucleus interactions, where thickness/density modulation generically translate into the corresponding changes in nuclear aspect ratio and position, as seen in the data. Consequently, we find that the spatial distribution of Yes associated proteins (YAP), the main transcriptional effector of the Hippo signaling pathway, is modulated in folded epithelial tissues according to the resulting thickness modulation, an effect that disappears at high cell density. Finally, we showed that these deformations are also associated with changes of A-type and B-type lamin expression, significant chromatin condensation and to lower cell proliferation rate. These findings show that active cell mechanics and nuclear mechanoadaptation are key players of the mechanistic regulation of epithelial monolayers to substrate curvature, with potential application for a number of in vivo situations.

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Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1

International Astronomical Union Colloquium ◽

10.1017/s0252921100031493 ◽

1999 ◽

Vol 173 ◽

pp. 243-248

Author(s):

D. Kubáček ◽

A. Galád ◽

A. Pravda

Keyword(s):

Image Processing ◽

Large Scale ◽

Harvard College ◽

Oak Ridge ◽

Large Scale Structures ◽

Short Period Comet ◽

Short Period ◽

Scale Structures ◽

Harvard College Observatory ◽

Period Comet

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.

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Evolution of Large-Scale Coronal Structures

International Astronomical Union Colloquium ◽

10.1017/s0252921100024945 ◽

1994 ◽

Vol 144 ◽

pp. 29-33

Author(s):

P. Ambrož

Keyword(s):

Magnetic Field ◽

Field Line ◽

Large Scale ◽

Coronal Magnetic Field ◽

Source Surface ◽

Solar Cycles ◽

Characteristic Relationship ◽

The Magnetic Field ◽

Coronal Structures

AbstractThe large-scale coronal structures observed during the sporadically visible solar eclipses were compared with the numerically extrapolated field-line structures of coronal magnetic field. A characteristic relationship between the observed structures of coronal plasma and the magnetic field line configurations was determined. The long-term evolution of large scale coronal structures inferred from photospheric magnetic observations in the course of 11- and 22-year solar cycles is described.Some known parameters, such as the source surface radius, or coronal rotation rate are discussed and actually interpreted. A relation between the large-scale photospheric magnetic field evolution and the coronal structure rearrangement is demonstrated.

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Large-scale Motion of Solar Filaments

International Astronomical Union Colloquium ◽

10.1017/s0252921100064502 ◽

2000 ◽

Vol 179 ◽

pp. 205-208

Author(s):

Pavel Ambrož ◽

Alfred Schroll

Keyword(s):

Magnetic Flux ◽

Proper Motion ◽

Time Scale ◽

Large Scale ◽

Accuracy Of Measurements ◽

Solar Filaments ◽

General Movement ◽

Scale Motion ◽

Velocity Scatter

AbstractPrecise measurements of heliographic position of solar filaments were used for determination of the proper motion of solar filaments on the time-scale of days. The filaments have a tendency to make a shaking or waving of the external structure and to make a general movement of whole filament body, coinciding with the transport of the magnetic flux in the photosphere. The velocity scatter of individual measured points is about one order higher than the accuracy of measurements.

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