scholarly journals Shuttling of Dorsal by Cactus: mechanism and implications

2019 ◽  
Author(s):  
Allison E. Schloop ◽  
Sophia Carrell-Noel ◽  
Gregory T. Reeves
Keyword(s):  
Cell Types ◽  
Bmp Signaling ◽  
Previous Literature ◽  
Drosophila Embryo ◽  
Morphogen Gradient ◽  
Facilitated Diffusion ◽  
Morphogen Gradients ◽  
Binding Partner ◽  
Early Drosophila Embryo ◽  
Gradient Formation

AbstractIn a developing animal, morphogen gradients act to pattern tissues into distinct domains of cell types. However, despite their prevalence in development, morphogen gradient formation is a matter of debate. In our recent publication, we showed that the Dorsal/NF-κB morphogen gradient, which patterns the DV axis of the early Drosophila embryo, is partially established by a mechanism of facilitated diffusion. This mechanism, also known as “shuttling,” occurs when a binding partner of the morphogen facilitates the diffusion of the morphogen, allowing it to accumulate at a given site. In this case, the inhibitor Cactus/IκB facilitates the diffusion of Dorsal/NF-κB. In the fly embryo, we used computation and experiment to not only show that shuttling occurs in the embryo, but also that it enables the viability of embryos that inherit only one copy of dorsal maternally. Here we further discuss our evidence behind the shuttling mechanism, the previous literature data explained by the mechanism, and how it may also be critical for robustness of development. Finally, we describe an interaction between Dorsal and BMP signaling that is likely affected by shuttling.

scholarly journals A translational block to HSPG synthesis permits BMP signaling in the early Drosophila embryo

Development ◽  
2008 ◽  
Vol 135 (6) ◽  
pp. 1039-1047 ◽  
Author(s):  
D. J. Bornemann ◽  
S. Park ◽  
S. Phin ◽  
R. Warrior
Keyword(s):  
Bmp Signaling ◽  
Drosophila Embryo ◽  
Early Drosophila Embryo ◽  
Translational Block

scholarly journals Dorsal/NF-κB exhibits a dorsal-to-ventral mobility gradient in the Drosophila embryo

2018 ◽  
Author(s):  
Hadel Al Asafen ◽  
Natalie M. Clark ◽  
Thomas Jacobsen ◽  
Rosangela Sozzani ◽  
Gregory T. Reeves
Keyword(s):  
Dna Binding ◽  
Nuclear Export ◽  
Developmental Process ◽  
Ventral Side ◽  
Correlation Spectroscopy ◽  
Drosophila Embryo ◽  
Morphogen Gradient ◽  
Biophysical Parameters ◽  
Quantitative Measurements ◽  
Gradient Formation

AbstractMorphogen-mediated patterning is a highly dynamic developmental process. To obtain an accurate understanding of morphogen gradients, biophysical parameters such as protein diffusivities must be quantified in vivo. The dorsal-ventral (DV) patterning of early Drosophila embryos by the NF-κB homolog Dorsal (Dl) is an excellent system for understanding morphogen gradient formation. Dl gradient formation is controlled by the inhibitor Cactus/IκB (Cact), which regulates the nuclear import and diffusion of Dl protein. However, quantitative measurements of spatiotemporal Dl movement are currently lacking. Here, we use scanning fluorescence correlation spectroscopy to quantify the mobility of Dl. We find that the diffusivity of Dl varies along the DV axis, with lowest diffusivities on the ventral side, and the DV asymmetry in diffusivity is exclusive to the nuclei. Moreover, we also observe that nuclear export rates are lower in the ventral and lateral regions of the embryo. Both cross correlation spectroscopy measurements and a computational model of Dl/DNA binding suggest that DNA binding of Dl, which is more prevalent on the ventral side of the embryo, is correlated to a lower diffusivity and nuclear export rate. We propose that the variation in Dl/DNA binding along the DV axis is dependent on Cact binding Dl, which prevents Dl from binding DNA in dorsal and lateral regions of the embryo. Thus, our results highlight the complexity of morphogen gradient dynamics and the need for quantitative measurements of biophysical interactions in such systems.

scholarly journals Cyto-architecture constrains the spread of photoactivated tubulin in the syncytial Drosophila embryo

2020 ◽  
Vol 64 (4-5-6) ◽  
pp. 275-287
Author(s):  
Sameer Thukral ◽  
Bivash Kaity ◽  
Bipasha Dey ◽  
Swati Sharma ◽  
Amitabha Nandi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Nuclear Division ◽  
The Body ◽  
Drosophila Embryo ◽  
Morphogen Gradient ◽  
Cytoplasmic Domains ◽  
Microtubule Network ◽  
Drosophila Embryogenesis ◽  
Gradient Formation ◽  
Kinetics Of

Drosophila embryogenesis begins with nuclear division in a common cytoplasm forming a syncytial cell. Morphogen gradient molecules spread across nucleo-cytoplasmic domains to pattern the body axis of the syncytial embryo. The diffusion of molecules across the syncytial nucleo-cytoplasmic domains is potentially constrained by association with the components of cellular architecture. However, the extent of restriction has not been examined. Here we use photoactivation (PA) to generate a source of cytoplasmic or cytoskeletal molecules in order to monitor the kinetics of their spread in the syncytial Drosophila embryo. Photoactivated PA-GFP and PA-GFP-Tubulin generated within a fixed anterior area diffused along the antero-posterior axis. These molecules were enriched in the cortical cytoplasm above the yolk-filled center, suggesting that the cortical cytoplasm is phase separated from the yolk-filled center. The length scales of diffusion were extracted using exponential fits under steady state assumptions. PA-GFP spread a greater distance as compared to PA-GFP-Tubulin. Both molecules were more restricted when generated in the center of the embryo. The length scale of spread for PA-GFP-Tubulin increased in mutant embryos containing short plasma membrane furrows and a disrupted tubulin cytoskeleton. PA-GFP spread was unaffected by cyto-architecture perturbation. Taken together, these data show that PA-GFP-Tubulin spread is restricted by its incorporation in the microtubule network and intact plasma membrane furrows. This photoactivation based analysis of protein spread allows for interpretation of the dependence of gradient formation on syncytial cyto-architecture.

scholarly journals Systems biology derived source-sink mechanism of BMP gradient formation

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Joseph Zinski ◽  
Ye Bu ◽  
Xu Wang ◽  
Wei Dou ◽  
David Umulis ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Systems Biology ◽  
Bmp Signaling ◽  
Morphogen Gradient ◽  
Wild Type ◽  
Morphogenetic Protein ◽  
Gradient Formation ◽  
Source Sink ◽  
Bmp Antagonist ◽  
Prevailing View

A morphogen gradient of Bone Morphogenetic Protein (BMP) signaling patterns the dorsoventral embryonic axis of vertebrates and invertebrates. The prevailing view in vertebrates for BMP gradient formation is through a counter-gradient of BMP antagonists, often along with ligand shuttling to generate peak signaling levels. To delineate the mechanism in zebrafish, we precisely quantified the BMP activity gradient in wild-type and mutant embryos and combined these data with a mathematical model-based computational screen to test hypotheses for gradient formation. Our analysis ruled out a BMP shuttling mechanism and a bmp transcriptionally-informed gradient mechanism. Surprisingly, rather than supporting a counter-gradient mechanism, our analyses support a fourth model, a source-sink mechanism, which relies on a restricted BMP antagonist distribution acting as a sink that drives BMP flux dorsally and gradient formation. We measured Bmp2 diffusion and found that it supports the source-sink model, suggesting a new mechanism to shape BMP gradients during development.

scholarly journals Patterning and growth control in vivo by an engineered GFP gradient

Science ◽  
2020 ◽  
Vol 370 (6514) ◽  
pp. 321-327 ◽  
Author(s):  
Kristina S. Stapornwongkul ◽  
Marc de Gennes ◽  
Luca Cocconi ◽  
Guillaume Salbreux ◽  
Jean-Paul Vincent
Keyword(s):  
Fluorescent Protein ◽  
Growth Control ◽  
Positional Information ◽  
Morphogen Gradient ◽  
Length Scale ◽  
Wild Type ◽  
Morphogen Gradients ◽  
Gradient Formation ◽  
Green Fluorescent

Morphogen gradients provide positional information during development. To uncover the minimal requirements for morphogen gradient formation, we have engineered a synthetic morphogen in Drosophila wing primordia. We show that an inert protein, green fluorescent protein (GFP), can form a detectable diffusion-based gradient in the presence of surface-associated anti-GFP nanobodies, which modulate the gradient by trapping the ligand and limiting leakage from the tissue. We next fused anti-GFP nanobodies to the receptors of Dpp, a natural morphogen, to render them responsive to extracellular GFP. In the presence of these engineered receptors, GFP could replace Dpp to organize patterning and growth in vivo. Concomitant expression of glycosylphosphatidylinositol (GPI)–anchored nonsignaling receptors further improved patterning, to near–wild-type quality. Theoretical arguments suggest that GPI anchorage could be important for these receptors to expand the gradient length scale while at the same time reducing leakage.

scholarly journals Cyto-architecture constrains a photoactivation induced tubulin gradient in the syncytial Drosophila embryo

2019 ◽  
Author(s):  
Sameer Thukral ◽  
Bivash Kaity ◽  
Bipasha Dey ◽  
Swati Sharma ◽  
Amitabha Nandi ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Nuclear Division ◽  
The Body ◽  
Drosophila Embryo ◽  
Morphogen Gradient ◽  
Cytoplasmic Domains ◽  
Microtubule Network ◽  
Cellular Architecture ◽  
Gradient Formation ◽  
Kinetics Of

AbstractDrosophila embryogenesis begins with nuclear division in a common cytoplasm forming a syncytial cell. Morphogen gradient molecules spread across nucleo-cytoplasmic domains to pattern the body axis of the syncytial embryo. The diffusion of molecules across the syncytial nucleo-cytoplasmic domains is potentially constrained by association with the components of cellular architecture, however the extent of restriction has not been examined so far. Here we use photoactivation (PA) to generate a source of cytoplasmic or cytoskeletal molecules in order to monitor the kinetics of their spread in the syncytial Drosophila embryo. Photoactivated PA-GFP and PA-GFP-Tubulin within a fixed anterior area diffused along the antero-posterior axis. These molecules were enriched in cortical cytoplasm above the yolk-filled center suggesting that the cortical cytoplasm is phase separated from the yolk-filled center. The length scales of diffusion were extracted using exponential fits under steady state assumptions. PA-GFP spread to greater distance as compared to PA-GFP-Tubulin. Both gradients were steeper and more restricted when generated in the center of the embryo probably due to a higher density of nucleo-cytoplasmic domains. The length scale of diffusion for PA-GFP-Tubulin gradient increased in mutant embryos containing short plasma membrane furrows and disrupted tubulin cytoskeleton. The PA-GFP gradient shape was unaffected by cyto-architecture perturbation. Taken together, these data show that PA-GFP-Tubulin gradient is largely restricted by its incorporation in the microtubule network and intact plasma membrane furrows. This photoactivation based analysis of protein spread across allows for interpretation of the dependence of gradient formation on the syncytial cyto-architecture.

scholarly journals Preformation and epigenesis converge to specify primordial germ cell fate in the early Drosophila embryo

PLoS Genetics ◽  
2022 ◽  
Vol 18 (1) ◽  
pp. e1010002
Author(s):  
Megan M. Colonnetta ◽  
Yogesh Goyal ◽  
Heath E. Johnson ◽  
Sapna Syal ◽  
Paul Schedl ◽  
...  
Keyword(s):  
Cell Fate ◽  
Germ Plasm ◽  
Primordial Germ Cells ◽  
Primordial Germ Cell ◽  
Bmp Signaling ◽  
Drosophila Embryo ◽  
Animal Development ◽  
Early Drosophila Embryo ◽  
Bmp Pathway ◽  
Necessary And Sufficient

A critical step in animal development is the specification of primordial germ cells (PGCs), the precursors of the germline. Two seemingly mutually exclusive mechanisms are implemented across the animal kingdom: epigenesis and preformation. In epigenesis, PGC specification is non-autonomous and depends on extrinsic signaling pathways. The BMP pathway provides the key PGC specification signals in mammals. Preformation is autonomous and mediated by determinants localized within PGCs. In Drosophila, a classic example of preformation, constituents of the germ plasm localized at the embryonic posterior are thought to be both necessary and sufficient for proper determination of PGCs. Contrary to this longstanding model, here we show that these localized determinants are insufficient by themselves to direct PGC specification in blastoderm stage embryos. Instead, we find that the BMP signaling pathway is required at multiple steps during the specification process and functions in conjunction with components of the germ plasm to orchestrate PGC fate.

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