Drosophila gastrulation: analysis of cell shape changes in living embryos by three-dimensional fluorescence microscopy

Development ◽  
1991 ◽  
Vol 112 (2) ◽  
pp. 365-370 ◽  
Author(s):  
Z. Kam ◽  
J.S. Minden ◽  
D.A. Agard ◽  
J.W. Sedat ◽  
M. Leptin
Keyword(s):  
Cell Shape ◽  
Three Dimensional ◽  
Time Lapse ◽  
Second Phase ◽  
Fluorescent Markers ◽  
Ventral Furrow ◽  
Cell Shapes ◽  
Cell Shape Changes ◽  
Two Phases ◽  
Shape Changes

The first event of Drosophila gastrulation is the formation of the ventral furrow. This process, which leads to the invagination of the mesoderm, is a classical example of epithelial folding. To understand better the cellular changes and dynamics of furrow formation, we examined living Drosophila embryos using three-dimensional time-lapse microscopy. By injecting fluorescent markers that visualize cell outlines and nuclei, we monitored changes in cell shapes and nuclear positions. We find that the ventral furrow invaginates in two phases. During the first ‘preparatory’ phase, many prospective furrow cells in apparently random positions gradually begin to change shape, but the curvature of the epithelium hardly changes. In the second phase, when a critical number of cells have begun to change shape, the furrow suddenly invaginates. Our results suggest that furrow formation does not result from an ordered wave of cell shape changes, contrary to a model for epithelial invagination in which a wave of apical contractions causes invagination. Instead, it appears that cells change their shape independently, in a stochastic manner, and the sum of these individual changes alters the curvature of the whole epithelium.

Cell shape changes during gastrulation in Drosophila

Development ◽  
1990 ◽  
Vol 110 (1) ◽  
pp. 73-84 ◽  
Author(s):  
M. Leptin ◽  
B. Grunewald
Keyword(s):  
Cell Fate ◽  
Cell Shape ◽  
Multilayered Structure ◽  
Second Phase ◽  
Specific Cell ◽  
Ventral Furrow ◽  
Correct Execution ◽  
Cell Shape Changes ◽  
Two Phases ◽  
Shape Changes

The first morphogenetic movement during Drosophila development is the invagination of the mesoderm, an event that folds a one-layered epithelium into a multilayered structure. In this paper, we describe the shape changes and behaviour of the cells participating in this process and show how mutations that change cell fate affect this behaviour. We divide the formation of the mesodermal germ layer into two phases. During the first phase, the ventral epithelium folds into a tube by a series of concerted cell shape changes (ventral furrow formation). Based on the behaviour of cells in this phase, we conclude that the prospective mesoderm is not a homogeneous cell population, but consists of two subpopulations. Each subpopulation goes through a distinctive sequence of specific cell shape changes which together mediate the invagination of the ventral furrow. In the second phase, the invaginated tube of mesoderm loses its epithelial character, the mesoderm cells disperse, divide and then spread out along the ectoderm to form a single cell layer. To test how ventral furrow formation depends on cell fates in the mesoderm and in neighbouring cells we alter these fates genetically using maternal and zygotic mutations. These experiments show that some of the aspects of cell behaviour specific for ventral furrow cells are part of an autonomous differentiation programme. The force driving the invagination is generated within the region of the ventral furrow, with the lateral and dorsal cell populations contributing little or none of the force. Two known zygotic genes that are required for the formation of the mesoderm, twist and snail, are expressed in ventral furrow cells, and the correct execution of cell shape changes in the mesoderm depends on both. Finally, we show that the region where the ventral furrow forms is determined by the expression of mesoderm-specific genes, and not by mechanical or other epigenetic properties of the egg.

scholarly journals Cellular structure image classification with small targeted training samples

2019 ◽  
Author(s):  
Dali Wang ◽  
Zheng Lu ◽  
Yichi Xu ◽  
Zi Wang ◽  
Chengcheng Li ◽  
...  
Keyword(s):  
Deep Learning ◽  
Image Classification ◽  
Cell Shape ◽  
Time Lapse ◽  
Training Dataset ◽  
Generative Adversarial Networks ◽  
Training Samples ◽  
Cell Shapes ◽  
Cell Shape Changes ◽  
Shape Changes

AbstractMotivationCell shapes provide crucial biology information on complex tissues. Different cell types often have distinct cell shapes, and collective shape changes usually indicate morphogenetic events and mechanisms. The identification and detection of collective cell shape changes in an extensive collection of 3D time-lapse images of complex tissues is an important step in assaying such mechanisms but is a tedious and time-consuming task. Machine learning provides new opportunities to automatically detect cell shape changes. However, it is challenging to generate sufficient training samples for pattern identification through deep learning because of a limited amount of images and annotations.ResultWe present a deep learning approach with minimal well-annotated training samples and apply it to identify multicellular rosettes from 3D live images of the Caenorhabditis elegans embryo with fluorescently labelled cell membranes. Our strategy is to combine two approaches, namely, feature transfer and generative adversarial networks (GANs), to boost image classification with small training samples. Specifically, we use a GAN framework and conduct an unsupervised training to capture the general characteristics of cell membrane images with 11,250 unlabelled images. We then transfer the structure of the GAN discriminator into a new Alex-style neural network for further learning with several dozen labelled samples. Our experiments showed that with 10-15 well-labelled rosette images and 30-40 randomly selected non-rosette images our approach can identify rosettes with over 80% accuracy and capture over 90% of the model accuracy achieved with a training dataset that is five times larger. We also established a public benchmark dataset for rosette detection. This GAN-based transfer approach can be applied to study other cellular structures with minimal training [email protected], [email protected]

Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations

Development ◽  
1991 ◽  
Vol 112 (3) ◽  
pp. 775-789 ◽  
Author(s):  
D. Sweeton ◽  
S. Parks ◽  
M. Costa ◽  
E. Wieschaus
Keyword(s):  
Cell Shape ◽  
Time Course ◽  
Drosophila Embryo ◽  
Second Phase ◽  
Rapid Phase ◽  
Apical Constriction ◽  
Posterior Midgut ◽  
Ventral Furrow ◽  
Two Phases ◽  
Shape Changes

The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.

scholarly journals Mathematical modelling in cell migration: tackling biochemistry in changing geometries

2020 ◽  
Vol 48 (2) ◽  
pp. 419-428
Author(s):  
Björn Stinner ◽  
Till Bretschneider
Keyword(s):  
Cell Migration ◽  
Molecular Motors ◽  
Cell Shape ◽  
Reaction Diffusion ◽  
Level Line ◽  
External Signal ◽  
Interface Capturing ◽  
Cell Shapes ◽  
Cell Shape Changes ◽  
Shape Changes

Directed cell migration poses a rich set of theoretical challenges. Broadly, these are concerned with (1) how cells sense external signal gradients and adapt; (2) how actin polymerisation is localised to drive the leading cell edge and Myosin-II molecular motors retract the cell rear; and (3) how the combined action of cellular forces and cell adhesion results in cell shape changes and net migration. Reaction–diffusion models for biological pattern formation going back to Turing have long been used to explain generic principles of gradient sensing and cell polarisation in simple, static geometries like a circle. In this minireview, we focus on recent research which aims at coupling the biochemistry with cellular mechanics and modelling cell shape changes. In particular, we want to contrast two principal modelling approaches: (1) interface tracking where the cell membrane, interfacing cell interior and exterior, is explicitly represented by a set of moving points in 2D or 3D space and (2) interface capturing. In interface capturing, the membrane is implicitly modelled analogously to a level line in a hilly landscape whose topology changes according to forces acting on the membrane. With the increased availability of high-quality 3D microscopy data of complex cell shapes, such methods will become increasingly important in data-driven, image-based modelling to better understand the mechanochemistry underpinning cell motion.

scholarly journals Hyperactivation of the folded gastrulation pathway induces specific cell shape changes

Development ◽  
1998 ◽  
Vol 125 (4) ◽  
pp. 589-597 ◽  
Author(s):  
P. Morize ◽  
A.E. Christiansen ◽  
M. Costa ◽  
S. Parks ◽  
E. Wieschaus
Keyword(s):  
Cell Shape ◽  
Inducible Promoter ◽  
Specific Cell ◽  
Apical Surface ◽  
Apical Constriction ◽  
Cellular Effects ◽  
Ventral Furrow ◽  
Cell Shape Changes ◽  
Shape Changes

During Drosophila gastrulation, mesodermal precursors are brought into the interior of the embryo by formation of the ventral furrow. The first steps of ventral furrow formation involve a flattening of the apical surface of the presumptive mesodermal cells and a constriction of their apical diameters. In embryos mutant for folded gastrulation (fog), these cell shape changes occur but the timing and synchrony of the constrictions are abnormal. A similar phenotype is seen in a maternal effect mutant, concertina (cta). fog encodes a putative secreted protein whereas cta encodes an (alpha)-subunit of a heterotrimeric G protein. We have proposed that localized expression of the fog signaling protein induces apical constriction by interacting with a receptor whose downstream cellular effects are mediated by the cta G(alpha)protein. <P> In order to test this model, we have ectopically expressed fog at the blastoderm stage using an inducible promoter. In addition, we have examined the constitutive activation of cta protein by blocking GTP hydrolysis using both in vitro synthesized mutant alleles and cholera toxin treatment. Activation of the fog/cta pathway by any of these procedures results in ectopic cell shape changes in the gastrula. Uniform fog expression rescues the gastrulation defects of fog null embryos but not cta mutant embryos, arguing that cta functions downstream of fog expression. The normal location of the ventral furrow in embryos with uniformly expressed fog suggests the existence of a fog-independent pathway determining mesoderm-specific cell behaviors and invagination. Epistasis experiments indicate that this pathway requires snail but not twist expression.

scholarly journals 3D viscoelastic drag forces drive changes to cell shapes during organogenesis in the zebrafish embryo

2021 ◽  
Author(s):  
Paula C. Sanematsu ◽  
Gonca Erdemci-Tandogan ◽  
Himani Patel ◽  
Emma M. Retzlaff ◽  
Jeffrey D. Amack ◽  
...  
Keyword(s):  
Cell Shape ◽  
Shape Change ◽  
New Physics ◽  
Tissue Mechanics ◽  
List Type ◽  
Drag Forces ◽  
Velocity Gradients ◽  
Cell Shapes ◽  
Cell Shape Changes ◽  
Shape Changes

AbstractThe left-right organizer in zebrafish embryos, Kupffer’s Vesicle (KV), is a simple organ that undergoes programmed asymmetric cell shape changes that are necessary to establish the left-right axis of the embryo. We use simulations and experiments to investigate whether 3D mechanical drag forces generated by the posteriorly-directed motion of the KV through the tailbud tissue are sufficient to drive such shape changes. We develop a fully 3D vertex-like (Voronoi) model for the tissue architecture, and demonstrate that the tissue can generate drag forces and drive cell shape changes. Furthermore, we find that tailbud tissue presents a shear-thinning, viscoelastic behavior consistent with those observed in published experiments. We then perform live imaging experiments and particle image velocimetry analysis to quantify the precise tissue velocity gradients around KV as a function of developmental time. We observe robust velocity gradients around the KV, indicating that mechanical drag forces must be exerted on the KV by the tailbud tissue. We demonstrate that experimentally observed velocity fields are consistent with the viscoelastic response seen in simulations. This work also suggests that 3D viscoelastic drag forces could be a generic mechanism for cell shape change in other biological processes.Highlightsnew physics-based simulation method allows study of dynamic tissue structures in 3Dmovement of an organ through tissue generates viscoelastic drag forces on the organthese drag forces can generate precisely the cell shape changes seen in experimentPIV analysis of experimental data matches simulations and probes tissue mechanicsGraphical abstract

Mechanisms of early Drosophila mesoderm formation

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 23-31 ◽  
Author(s):  
Maria Leptin ◽  
José Casal ◽  
Barbara Grunewald ◽  
Rolf Reuter
Keyword(s):  
Cell Shape ◽  
Cell Populations ◽  
Genetic Screens ◽  
Germ Band ◽  
Posterior Midgut ◽  
Ventral Furrow ◽  
Mesoderm Formation ◽  
Cell Shape Changes ◽  
Shape Changes ◽  
Different Parts

Several morphogenetic processes occur simultaneously during Drosophila gastrulation, including ventral furrow invagination to form the mesoderm, anterior and posterior midgut invagination to create the endoderm, and germ band extension. Mutations changing the behaviour of different parts of the embryo can be used to test the roles of different cell populations in gastrulation. Posterior midgut morphogenesis and germ band extension are partly independent, and neither depends on mesoderm formation, nor mesoderm formation on them. The invagination of the ventral furrow is caused by forces from within the prospective mesoderm (i. e. the invaginating cells) without any necessary contribution from other parts of the embryo. The events that lead to the cell shape changes mediating ventral furrow formation require the transcription of zygotic genes under the control of twist and snail. Such genes can be isolated by molecular and genetic screens.

Regulatory network for cell shape changes during Drosophila ventral furrow formation

2006 ◽  
Vol 239 (1) ◽  
pp. 49-62 ◽  
Author(s):  
Julio Aracena ◽  
Mauricio González ◽  
Alejandro Zuñiga ◽  
Marco A. Mendez ◽  
Verónica Cambiazo
Keyword(s):  
Regulatory Network ◽  
Cell Shape ◽  
Ventral Furrow ◽  
Cell Shape Changes ◽  
Shape Changes

scholarly journals Erythrocyte morphology reflects the transbilayer distribution of incorporated phospholipids.

1989 ◽  
Vol 108 (4) ◽  
pp. 1375-1385 ◽  
Author(s):  
D L Daleke ◽  
W H Huestis
Keyword(s):  
Cell Morphology ◽  
Cell Shape ◽  
Shape Change ◽  
Cell Protein ◽  
Second Phase ◽  
Erythrocyte Morphology ◽  
Intracellular Magnesium ◽  
Cell Shape Changes ◽  
Protein Sulfhydryl Groups ◽  
Shape Changes

The transbilayer distribution of exogenous phospholipids incorporated into human erythrocytes is monitored through cell morphology changes and by the extraction of incorporated 14C-labeled lipids. Dilauroylphosphatidylserine (DLPS) and dilauroylphosphatidylcholine (DLPC) transfer spontaneously from sonicated unilamellar vesicles to erythrocytes, inducing a discocyte-to-echinocyte shape change within 5 min. DLPC-induced echinocytes revert slowly (t1/2 approximately 8 h) to discocytes, but DLPS-treated cells revert rapidly (10-20 min) to discocytes and then become invaginate stomatocytes. The second phase of the phosphatidylserine (PS)-induced shape change, conversion of echinocytes to stomatocytes, can be inhibited by blocking cell protein sulfhydryl groups or by depleting intracellular ATP or magnesium (Daleke, D. L., and W. H. Huestis. 1985. Biochemistry. 24:5406-5416). These cell shape changes are consistent with incorporation of phosphatidylcholine (PC) and PS into the membrane outer monolayer followed by selective and energy-dependent translocation of PS to the membrane inner monolayer. This hypothesis is explored by correlating cell shape with the fraction of the exogenous lipid accessible to extraction into phospholipid vesicles. Upon exposure to recipient vesicles, DLPC-induced echinocytes revert to discoid forms within 5 min, concomitant with the removal of most (88%) of the radiolabeled lipid. On further incubation, 97% of the foreign PC transfers to recipient vesicles. Treatment of DLPS-induced stomatocytes with acceptor vesicles extracts foreign PS only partially (22%) and does not affect cell shape significantly. Cell treated with inhibitors of aminophospholipid translocation (sulfhydryl blockers or intracellular magnesium depletion) and then incubated with either DLPS or DLPC become echinocytic and do not revert to discocytic or stomatocytic shape for many hours. On treatment with recipient vesicles, these echinocytes revert to discocytes in both cases, with concomitant extraction of 88-99% of radiolabeled PC and 86-97% of radiolabeled PS. The accessibility of exogenous lipids to extraction is uniformly consistent with the transbilayer lipid distribution inferred from cell shape changes, indicating that red cell morphology is an accurate and sensitive reporter of the transbilayer partitioning of incorporated exogenous phospholipids.

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