Cadherin Switch during EMT in Neural Crest Cells Leads to Contact Inhibition of Locomotion via Repolarization of Forces

Contact inhibition of locomotion (CIL) is the process through which cells move away from each other after cell-cell contact, and it contributes to malignant invasion and developmental migration. Various cell types exhibit CIL, whereas others remain in contact after collision and may form stable junctions. To investigate what determines this differential behavior, we study neural crest cells, a migratory stem cell population whose invasiveness has been likened to cancer metastasis. By comparing pre-migratory and migratory neural crest cells, we show that the switch from E- to N-cadherin during EMT is essential for acquisition of CIL behavior. Loss of E-cadherin leads to repolarization of protrusions, via p120 and Rac1, resulting in a redistribution of forces from intercellular tension to cell-matrix adhesions, which break down the cadherin junction. These data provide insight into the balance of physical forces that contributes to CIL in cells in vivo.</p

Sub-diffraction error mapping for localisation microscopy images

Assessing the quality of localisation microscopy images is highly challenging due to the difficulty in reliably detecting errors in experimental data. The most common failure modes are the biases and errors produced by the localisation algorithm when there is emitter overlap. Also known as the high density or crowded field condition, significant emitter overlap is normally unavoidable in live cell imaging. Here we use Haar wavelet kernel analysis (HAWK), a localisation microscopy data analysis method which is known to produce results without bias, to generate a reference image. This enables mapping and quantification of reconstruction bias and artefacts common in all but low emitter density data. By avoiding comparisons involving intensity information, we can map structural artefacts in a way that is not adversely influenced by nonlinearity in the localisation algorithm. The HAWK Method for the Assessment of Nanoscopy (HAWKMAN) is a general approach which allows for the reliability of localisation information to be assessed

Speaking vocabulary of first grade children

Thesis (Ed.M.)--Boston Universit

A Global Ecological Classification of Coastal Segment Units to Complement Marine Biodiversity Observation Network Assessments

A new data layer provides Coastal and Marine Ecological Classification Standard (CMECS) labels for global coastal segments at 1 km or shorter resolution. These characteristics are summarized for six US Marine Biodiversity Observation Network (MBON) sites and one MBON Pole to Pole of the Americas site in Argentina. The global coastlines CMECS classifications were produced from a partitioning of a 30 m Landsat-derived shoreline vector that was segmented into 4 million 1 km or shorter segments. Each segment was attributed with values from 10 variables that represent the ecological settings in which the coastline occurs, including properties of the adjacent water, adjacent land, and coastline itself. The 4 million segments were classified into 81,000 coastal segment units (CSUs) as unique combinations of variable classes. We summarize the process to develop the CSUs and derive summary descriptions for the seven MBON case study sites. We discuss the intended application of the new CSU data for research and management in coastal areas

The effect of mechanical load on dermal fibroblast collagen deposition and organisation

During dermal wound healing, resident cells are constantly exposed to mechanical forces from surrounding tissue movement. It is hypothesised that these forces contribute to increased human dermal fibroblast collagen deposition and alignment, and that this external mechanical signal is transduced to the cell nucleus via the cell surface receptors integrins. To address this hypothesis, two in vitro mechanical loading systems have been employed: a 2-dimensional system to load dermal fibroblasts in monolayer culture and a 3-dimensional system to load cells within a collagen gel. The effect of mechanical load in the presence of serum or growth factors on procollagen synthesis and deposition was determined in each system. It was found that mechanical load alone in either system had no effect on procollagen synthesis. However, in the presence of 10% fetal calf serum or TGFB, both loading regimens lead to a highly significant stimulation of procollagen synthesis. Levels of the enzyme procollagen c-proteinase, critical in the formation of insoluble collagen fibrils, were also increased in response to load, whereas the procollagen c-proteinase enhancer protein was not. In the 3-dimensional system there was also alignment of collagen fibrils in response to load, and this was shown to be dependent on the load-induced increase in collagen synthesis. The involvement of integrins in load-induced procollagen synthesis in the 2-dimensional system was investigated. Integrin α1β1 was shown to be increased at the cell surface in loaded cultures, and important in basal procollagen synthesis. α2β1 was transiently increased at the cell surface by mechanical load, and was specifically involved in mediating load-induced collagen synthesis and deposition. α5βl was not involved in collagen synthesis is this system. These data demonstrate that mechanical load and growth factors act synergistically to enhance human dermal fibroblast collagen synthesis, deposition and re-organisation, and that these phenomena are in part regulated by specific integrins. The elucidation of these mechanisms has furthered the understanding of fibroblast responses to mechanical load, and may assist in the development of novel therapeutic strategies to treat pathologies involving enhanced dermal scarring

Dissecting cell adhesion architecture using advanced imaging techniques

Cell adhesion to extracellular matrix proteins or to other cells is essential for the control of embryonic development, tissue integrity, immune function and wound healing. Adhesions are tightly spatially regulated structures containing over one hundred different proteins that coordinate both dynamics and signaling events at these sites. Extensive biochemical and morphological analysis of adhesion types over the past three decades has greatly improved understanding of individual protein contributions to adhesion signaling and, in some cases, dynamics. However, it is becoming increasingly clear that these diverse macromolecular complexes contain a variety of protein sub-networks, as well as distinct sub-domains that likely play important roles in regulating adhesion behavior. Until recently, resolving these structures, which are often less than a micron in size, was hampered by the limitations of conventional light microscopy. However, recent advances in optical techniques and imaging methods have revealed exciting insight into the intricate control of adhesion structure and assembly. Here we provide an overview of the recent data arising from such studies of cell:matrix and cell:cell contact and an overview of the imaging strategies that have been applied to study the intricacies and hierarchy of proteins within adhesions