scholarly journals Dynamics of Spaetzle morphogen shuttling in the Drosophila embryo shapes pattern

2018 ◽  
Author(s):  
Neta Rahimi ◽  
Inna Averbukh ◽  
Shari Carmon ◽  
Eyal D. Schejter ◽  
Naama Barkai ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Dynamic Environment ◽  
Drosophila Embryo ◽  
Morphogen Gradients ◽  
Extracellular Milieu ◽  
Early Embryos

AbstractEstablishment of morphogen gradients in the early Drosophila embryo is challenged by a diffusible extracellular milieu, and rapid nuclear divisions that occur at the same time. To understand how a sharp gradient is formed within this dynamic environment, we followed the generation of graded nuclear Dorsal (Dl) protein, the hallmark of pattern formation along the dorso-ventral axis, in live embryos. We show that a sharp gradient is formed through extracellular, diffusion-based morphogen shuttling that progresses through several nuclear divisions. Perturbed shuttling in wntD mutant embryos results in a flat activation peak and aberrant gastrulation. Re-entry of Dl into the nuclei at each cycle refines the signaling output, by guiding graded accumulation of the T48 transcript that drives patterned gastrulation. We conclude that diffusion-based ligand shuttling, coupled with dynamic readout, establishes a refined pattern within the diffusible environment of early embryos.

Homeostatic balance between dorsal and cactus proteins in the Drosophila embryo

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 135-148 ◽  
Author(s):  
S. Govind ◽  
L. Brennan ◽  
R. Steward
Keyword(s):  
Direct Interaction ◽  
Drosophila Embryo ◽  
Loss Of Function ◽  
Wild Type ◽  
Wild Type Embryo ◽  
Cleavage Stage ◽  
Dorsoventral Axis ◽  
Maternal Effect Gene ◽  
Early Embryos ◽  
Effect Gene

The maternal-effect gene dorsal encodes the ventral morphogen that is essential for elaboration of ventral and ventrolateral fates in the Drosophila embryo. Dorsal belongs to the rel family of transcription factors and controls asymmetric expression of zygotic genes along the dorsoventral axis. The dorsal protein is cytoplasmic in early embryos, possibly because of a direct interaction with cactus. In response to a ventral signal, dorsal protein becomes partitioned into nuclei of cleavage-stage syncytial blastoderms such that the ventral nuclei have the maximum amount of dorsal protein, and the lateral and dorsal nuclei have progressively less protein. Here we show that transgenic flies containing the dorsal cDNA, which is driven by the constitutively active hsp83 promoter, exhibits rescue of the dorsal- phenotype. Transformed lines were used to increase the level of dorsal protein. Females with dorsal levels roughly twice that of wild-type produced normal embryos, while a higher level of dorsal protein resulted in phenotypes similar to those observed for loss-of-function cactus mutations. By manipulating the cactus gene dose, we found that in contrast to a dorsal/cactus ratio of 2.5 which resulted in fully penetrant weak ventralization, a cactus/dorsal ratio of 3.0 was acceptable by the system. By manipulating dorsal levels in different cactus and dorsal group mutant backgrounds, we found that the relative amounts of ventral signal to that of the dorsal-cactus complex is important for the elaboration of the normal dorsoventral pattern. We propose that in a wild-type embryo, the activities of dorsal and cactus are not independently regulated; excess cactus activity is deployed only if a higher level of dorsal protein is available. Based on these results we discuss how the ventral signal interacts with the dorsal-cactus complex, thus forming a gradient of nuclear dorsal protein.

scholarly journals Decoding of position in the developing neural tube from antiparallel morphogen gradients

Science ◽  
2017 ◽  
Vol 356 (6345) ◽  
pp. 1379-1383 ◽  
Author(s):  
Marcin Zagorski ◽  
Yoji Tabata ◽  
Nathalie Brandenberg ◽  
Matthias P. Lutolf ◽  
Gašper Tkačik ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Cell Fate ◽  
Neural Tube ◽  
Target Gene ◽  
Ex Vivo ◽  
Data Link ◽  
Cell Fate Decisions ◽  
Morphogen Gradients ◽  
Positional Identity ◽  
Mechanistic Basis

Like many developing tissues, the vertebrate neural tube is patterned by antiparallel morphogen gradients. To understand how these inputs are interpreted, we measured morphogen signaling and target gene expression in mouse embryos and chick ex vivo assays. From these data, we derived and validated a characteristic decoding map that relates morphogen input to the positional identity of neural progenitors. Analysis of the observed responses indicates that the underlying interpretation strategy minimizes patterning errors in response to the joint input of noisy opposing gradients. We reverse-engineered a transcriptional network that provides a mechanistic basis for the observed cell fate decisions and accounts for the precision and dynamics of pattern formation. Together, our data link opposing gradient dynamics in a growing tissue to precise pattern formation.

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.

Neither the homeodomain nor the activation domain of Bicoid is specifically required for its down-regulation by the Torso receptor tyrosine kinase cascade

Development ◽  
1996 ◽  
Vol 122 (11) ◽  
pp. 3499-3508 ◽  
Author(s):  
Y. Bellaiche ◽  
R. Bandyopadhyay ◽  
C. Desplan ◽  
N. Dostatni
Keyword(s):  
Dna Binding ◽  
Tyrosine Kinase ◽  
Receptor Tyrosine Kinase ◽  
Chimeric Protein ◽  
Drosophila Embryo ◽  
Activation Domain ◽  
Down Regulation ◽  
Dna Binding Sites ◽  
Early Embryos ◽  
Kinase Cascade

Bicoid (Bcd) is a maternal morphogen responsible for patterning the head and thorax of the Drosophila embryo. Correct specification of head structure, however, requires the activity of the Torso receptor tyrosine kinase cascade, which also represses expression of Bcd targets at the most anterior tip of the embryo. Here, we investigate the role of both the homeodomain (HD) and the activation domain of Bcd in the anterior repression of its targets. When a Bcd mutant protein whose HD has been replaced by the Gal4 DNA-binding domain is expressed in early embryos, a reporter gene driven by Gal4 DNA-binding sites is first activated in an anterior domain and then repressed from the anterior pole. The down-regulation of Bcd-Gal4 activity requires torso function but does not depend on endogenous bcd activity, indicating that the Bcd protein alone and none of its targets is required to mediate the effect of torso. Functional analysis of a chimeric protein, whose activation domain has been replaced by a generic activation domain, indicates that the activation domain of Bcd is also not specifically required for its down-regulation by Torso. We propose that Torso does not affect the ability of Bcd to bind DNA, but instead directs modification of Bcd or of a potential Bcd co-factor, which renders the Bcd protein unable to activate transcription.

scholarly journals Pattern Formation by Graded and Uniform Signals in the Early Drosophila Embryo

2012 ◽  
Vol 102 (3) ◽  
pp. 427-433 ◽  
Author(s):  
Jitendra S. Kanodia ◽  
Hsiao-Lan Liang ◽  
Yoosik Kim ◽  
Bomyi Lim ◽  
Mei Zhan ◽  
...  
Keyword(s):  
Pattern Formation ◽  
Drosophila Embryo ◽  
Early Drosophila Embryo

scholarly journals Bacterial “Conversations” and Pattern Formation

2017 ◽  
Author(s):  
Sarangam Majumdar ◽  
Sisir Roy ◽  
Rodolfo Llinas
Keyword(s):  
Pattern Formation ◽  
Quorum Sensing ◽  
Burgers Equation ◽  
Water Movement ◽  
Reaction Diffusion ◽  
Dynamical Behaviour ◽  
Signal Molecules ◽  
Extracellular Milieu ◽  
Long Time ◽  
Coordinated Water

AbstractIt has long been recognized that certain bacterial groups exhibit cooperative behavioral patterns. Bacteria accomplish such communication via exchange of extracellular signaling molecules called pheromones(autoinducer or quorum sensing molecules). As the bacterial culture grows, signal molecules are released into extracellular milieu accumulate, changing water fluidity. Under such threshold conditions swimming bacterial suspensions impose a coordinated water movement on a length scale of the order 10 to 100 micrometers compared with a bacterial size of the order of 3 micrometers.Here, we investigate the non-local hydrodynamics of the quorum state and pattern formation using forced Burgers equation with Kwak transformation. Such approach resulted in the conversion of the Burgers equation paradigm into a reaction-diffusion system. The examination of the dynamics of the quorum sensing system, both analytically as well as numerically result in similar long-time dynamical behaviour.

Pattern formation under the control of the terminal system in the Drosophila embryo

Development ◽  
1990 ◽  
Vol 110 (2) ◽  
pp. 621-628 ◽  
Author(s):  
J. Casanova
Keyword(s):  
Pattern Formation ◽  
Tyrosine Kinase ◽  
Protein A ◽  
Primary Response ◽  
The Body ◽  
Drosophila Embryo ◽  
Tyrosine Kinase Receptor ◽  
Terminal System ◽  
Gap Genes

The specification of the most anterior and posterior domains of the Drosophila embryo depends on the activity of the torso protein, a putative tyrosine kinase receptor. Localized torso activity at the poles of the embryo generates graded information that specifies distinct portions of the body. The primary response to the terminal signal in the posterior end of the embryo is likely to be the activation of the gap genes huckebein and tailless. Here I address the question of how the graded maternal signal generates different elements of the pattern at the posterior end of the embryo and what role huckebein and tailless activities may play in this process. These experiments show that distinctly localized activities of huckebein and tailless are responsible for the appropriate expression of other genes known to be under the control of the terminal system. Moreover, they suggest that different elements of the terminal pattern can be specified in response to distinct levels of graded tailless activity.

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