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1.
PLoS Biol ; 22(8): e3002775, 2024 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-39178318

RESUMEN

Germ cell apoptosis in Caenorhabditis elegans hermaphrodites is a physiological process eliminating around 60% of all cells in meiotic prophase to maintain tissue homeostasis. In contrast to programmed cell death in the C. elegans soma, the selection of germ cells undergoing apoptosis is stochastic. By live-tracking individual germ cells at the pachytene stage, we found that germ cells smaller than their neighbors are selectively eliminated through apoptosis before differentiating into oocytes. Thus, cell size is a strong predictor of physiological germ cell death. The RAS/MAPK and ECT/RHO/ROCK pathways together regulate germ cell size by controlling actomyosin constriction at the apical rachis bridges, which are cellular openings connecting the syncytial germ cells to a shared cytoplasmic core. Enhancing apical constriction reduces germ cell size and increases the rate of cell death while inhibiting the actomyosin network in the germ cells prevents their death. We propose that actomyosin contractility at the rachis bridges of the syncytial germ cells amplifies intrinsic disparities in cell size. Through this mechanism, the animals can adjust the balance between physiological germ cell death and oocyte differentiation.


Asunto(s)
Actomiosina , Apoptosis , Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Células Germinativas , Animales , Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiología , Actomiosina/metabolismo , Células Germinativas/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Oocitos/metabolismo , Tamaño de la Célula , Diferenciación Celular
2.
J Exp Biol ; 224(15)2021 08 01.
Artículo en Inglés | MEDLINE | ID: mdl-34338301

RESUMEN

Understanding how extrinsic factors modulate genetically encoded information to produce a specific phenotype is of prime scientific interest. In particular, the feedback mechanism between abiotic forces and locomotory organs during morphogenesis to achieve efficient movement is a highly relevant example of such modulation. The study of this developmental process can provide unique insights on the transduction of cues at the interface between physics and biology. Here, we take advantage of the natural ability of adult zebrafish to regenerate their amputated fins to assess its morphogenic plasticity upon external modulations. Using a variety of surgical and chemical treatments, we could induce phenotypic responses to the structure of the fin. Through the ablation of specific rays in regenerating caudal fins, we generated artificially narrowed appendages in which the fin cleft depth and the positioning of rays bifurcations were perturbed compared with normal regenerates. To dissect the role of mechanotransduction in this process, we investigated the patterns of hydrodynamic forces acting on the surface of a zebrafish fin during regeneration by using particle tracking velocimetry on a range of biomimetic hydrofoils. This experimental approach enabled us to quantitatively compare hydrodynamic stress distributions over flapping fins of varying sizes and shapes. As a result, viscous shear stress acting on the distal margin of regenerating fins and the resulting internal tension are proposed as suitable signals for guiding the regulation of ray growth dynamics and branching pattern. Our findings suggest that mechanical forces are involved in the fine-tuning of the locomotory organ during fin morphogenesis.


Asunto(s)
Hidrodinámica , Pez Cebra , Adaptación Fisiológica , Aletas de Animales , Animales , Mecanotransducción Celular , Proteínas de Pez Cebra
3.
J Exp Biol ; 221(Pt 4)2018 02 20.
Artículo en Inglés | MEDLINE | ID: mdl-29246971

RESUMEN

The caudal fins of adult zebrafish are supported by multiple bony rays that are laterally interconnected by soft interray tissue. Little is known about the fin's mechanical properties that influence bending in response to hydrodynamic forces during swimming. Here, we developed an experimental setup to measure the elastic properties of caudal fins in vivo by applying micro-Newton forces to obtain bending stiffness and a tensional modulus. We detected overall bending moments of 1.5×10-9-4×10-9 N m2 along the proximal-distal axis of the appendage showing a non-monotonous pattern that was not due to the geometry of the fin itself. Surgical disruption of the interray tissues along the proximal-distal axis revealed no significant changes to the overall bending stiffness, which we confirmed by determining a tensional modulus of the interray tissue. Thus, the biophysical values suggest that the flexibility of the fin during its hydrodynamic performance predominantly relies on the mechanical properties of the rays.


Asunto(s)
Aletas de Animales/fisiología , Fisiología/métodos , Natación/fisiología , Pez Cebra/fisiología , Animales , Fenómenos Biomecánicos , Hidrodinámica
4.
Development ; 139(17): 3221-31, 2012 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-22833127

RESUMEN

The regulation of organ size constitutes a major unsolved question in developmental biology. The wing imaginal disc of Drosophila serves as a widely used model system to study this question. Several mechanisms have been proposed to have an impact on final size, but they are either contradicted by experimental data or they cannot explain a number of key experimental observations and may thus be missing crucial elements. We have modeled a regulatory network that integrates the experimentally confirmed molecular interactions underlying other available models. Furthermore, the network includes hypothetical interactions between mechanical forces and specific growth regulators, leading to a size regulation mechanism that conceptually combines elements of existing models, and can be understood in terms of a compression gradient model. According to this model, compression increases in the center of the disc during growth. Growth stops once compression levels in the disc center reach a certain threshold and the compression gradient drops below a certain level in the rest of the disc. Our model can account for growth termination as well as for the paradoxical observation that growth occurs uniformly in the presence of a growth factor gradient and non-uniformly in the presence of a uniform growth factor distribution. Furthermore, it can account for other experimental observations that argue either in favor or against other models. The model also makes specific predictions about the distribution of cell shape and size in the developing disc, which we were able to confirm experimentally.


Asunto(s)
Drosophila/crecimiento & desarrollo , Discos Imaginales/crecimiento & desarrollo , Modelos Biológicos , Transducción de Señal/fisiología , Alas de Animales/crecimiento & desarrollo , Animales , Fenómenos Biomecánicos , Forma de la Célula/fisiología , Simulación por Computador , Discos Imaginales/citología , Tamaño de los Órganos/fisiología , Presión
5.
Development ; 137(3): 499-506, 2010 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-20081194

RESUMEN

Apical cell surfaces in metazoan epithelia, such as the wing disc of Drosophila, resemble polygons with different numbers of neighboring cells. The distribution of these polygon numbers has been shown to be conserved. Revealing the mechanisms that lead to this topology might yield insights into how the structural integrity of epithelial tissues is maintained. It has previously been proposed that cell division alone, or cell division in combination with cell rearrangements, is sufficient to explain the observed epithelial topology. Here, we extend this work by including an analysis of the clustering and the polygon distribution of mitotic cells. In addition, we study possible effects of cellular growth regulation by mechanical forces, as such regulation has been proposed to be involved in wing disc size regulation. We formulated several theoretical scenarios that differ with respect to whether cell rearrangements are allowed and whether cellular growth rates are dependent on mechanical stress. We then compared these scenarios with experimental data on the polygon distribution of the entire cell population, that of mitotic cells, as well as with data on mitotic clustering. Surprisingly, we observed considerably less clustering in our experiments than has been reported previously. Only scenarios that include mechanical-stress-dependent growth rates are in agreement with the experimental data. Interestingly, simulations of these scenarios showed a large decrease in rearrangements and elimination of cells. Thus, a possible growth regulation by mechanical force could have a function in releasing the mechanical stress that evolves when all cells have similar growth rates.


Asunto(s)
Células Epiteliales/citología , Mitosis , Estrés Mecánico , Animales , Proliferación Celular , Tamaño de la Célula , Simulación por Computador , Drosophila , Modelos Teóricos , Alas de Animales/citología
6.
PLoS Comput Biol ; 7(4): e1002025, 2011 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-21490725

RESUMEN

Non-intermingling, adjacent populations of cells define compartment boundaries; such boundaries are often essential for the positioning and the maintenance of tissue-organizers during growth. In the developing wing primordium of Drosophila melanogaster, signaling by the secreted protein Hedgehog (Hh) is required for compartment boundary maintenance. However, the precise mechanism of Hh input remains poorly understood. Here, we combine experimental observations of perturbed Hh signaling with computer simulations of cellular behavior, and connect physical properties of cells to their Hh signaling status. We find that experimental disruption of Hh signaling has observable effects on cell sorting surprisingly far from the compartment boundary, which is in contrast to a previous model that confines Hh influence to the compartment boundary itself. We have recapitulated our experimental observations by simulations of Hh diffusion and transduction coupled to mechanical tension along cell-to-cell contact surfaces. Intriguingly, the best results were obtained under the assumption that Hh signaling cannot alter the overall tension force of the cell, but will merely re-distribute it locally inside the cell, relative to the signaling status of neighboring cells. Our results suggest a scenario in which homotypic interactions of a putative Hh target molecule at the cell surface are converted into a mechanical force. Such a scenario could explain why the mechanical output of Hh signaling appears to be confined to the compartment boundary, despite the longer range of the Hh molecule itself. Our study is the first to couple a cellular vertex model describing mechanical properties of cells in a growing tissue, to an explicit model of an entire signaling pathway, including a freely diffusible component. We discuss potential applications and challenges of such an approach.


Asunto(s)
Biología Computacional/métodos , Drosophila melanogaster/metabolismo , Proteínas Hedgehog/metabolismo , Animales , Comunicación Celular , Clonación Molecular , Simulación por Computador , Cruzamientos Genéticos , Homocigoto , Mitosis , Modelos Biológicos , Modelos Estadísticos , Transducción de Señal , Estrés Mecánico , Alas de Animales/fisiología
7.
Mech Dev ; 124(4): 318-26, 2007 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-17293093

RESUMEN

For animal development it is necessary that organs stop growing after they reach a certain size. However, it is still largely unknown how this termination of growth is regulated. The wing imaginal disc of Drosophila serves as a commonly used model system to study the regulation of growth. Paradoxically, it has been observed that growth occurs uniformly throughout the disc, even though Decapentaplegic (Dpp), a key inducer of growth, forms a gradient. Here, we present a model for the control of growth in the wing imaginal disc, which can account for the uniform occurrence and termination of growth. A central feature of the model is that net growth is not only regulated by growth factors, but by mechanical forces as well. According to the model, growth factors like Dpp induce growth in the center of the disc, which subsequently causes a tangential stretching of surrounding peripheral regions. Above a certain threshold, this stretching stimulates growth in these peripheral regions. Since the stretching is not completely compensated for by the induced growth, the peripheral regions will compress the center of the disc, leading to an inhibition of growth in the center. The larger the disc, the stronger this compression becomes and hence the stronger the inhibiting effect. Growth ceases when the growth factors can no longer overcome this inhibition. With numerical simulations we show that the model indeed yields uniform growth. Furthermore, the model can also account for other experimental data on growth in the wing disc.


Asunto(s)
Drosophila melanogaster/anatomía & histología , Drosophila melanogaster/crecimiento & desarrollo , Modelos Biológicos , Alas de Animales/anatomía & histología , Alas de Animales/crecimiento & desarrollo , Animales , Proteínas de Drosophila/fisiología , Tamaño de los Órganos/fisiología , Pupa/anatomía & histología
8.
Lab Chip ; 18(9): 1359-1368, 2018 05 01.
Artículo en Inglés | MEDLINE | ID: mdl-29652050

RESUMEN

Live-imaging of C. elegans is essential for the study of conserved cellular pathways (e.g. EGFR/Wnt signaling) and morphogenesis in vivo. However, the usefulness of live imaging as a research tool has been severely limited by the need to immobilize worms prior to and during imaging. Conventionally, immobilization is achieved by employing both physical and chemical interventions. These are known to significantly affect many physiological processes, and thus limit our understanding of dynamic developmental processes. Herein we present a novel, easy-to-use microfluidic platform for the long-term immobilization of viable, normally developing C. elegans, compatible with image acquisition at high resolution, thereby overcoming the limitations associated with conventional worm immobilization. The capabilities of the platform are demonstrated through the continuous assessment of anchor cell (AC) invasion and distal tip cell (DTC) migration in larval C. elegans and germ cell apoptosis in adult C. elegans in vivo for the first time.


Asunto(s)
Caenorhabditis elegans/crecimiento & desarrollo , Rastreo Celular/instrumentación , Dispositivos Laboratorio en un Chip , Técnicas Analíticas Microfluídicas/instrumentación , Animales , Apoptosis , Caenorhabditis elegans/citología , Rastreo Celular/métodos , Diseño de Equipo , Células Germinativas/citología , Larva/citología , Larva/crecimiento & desarrollo
9.
Lab Chip ; 18(12): 1802, 2018 06 12.
Artículo en Inglés | MEDLINE | ID: mdl-29808900

RESUMEN

Correction for 'Long-term C. elegans immobilization enables high resolution developmental studies in vivo' by Simon Berger et al., Lab Chip, 2018, 18, 1359-1368.

10.
Nat Cell Biol ; 19(6): 653-665, 2017 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-28530658

RESUMEN

The hierarchical organization of properly sized blood vessels ensures the correct distribution of blood to all organs of the body, and is controlled via haemodynamic cues. In current concepts, an endothelium-dependent shear stress set point causes blood vessel enlargement in response to higher flow rates, while lower flow would lead to blood vessel narrowing, thereby establishing homeostasis. We show that during zebrafish embryonic development increases in flow, after an initial expansion of blood vessel diameters, eventually lead to vessel contraction. This is mediated via endothelial cell shape changes. We identify the transforming growth factor beta co-receptor endoglin as an important player in this process. Endoglin mutant cells and blood vessels continue to enlarge in response to flow increases, thus exacerbating pre-existing embryonic arterial-venous shunts. Together, our data suggest that cell shape changes in response to biophysical cues act as an underlying principle allowing for the ordered patterning of tubular organs.


Asunto(s)
Forma de la Célula , Endoglina/metabolismo , Células Endoteliales/metabolismo , Hemodinámica , Mecanotransducción Celular , Proteínas de Pez Cebra/metabolismo , Animales , Malformaciones Arteriovenosas/genética , Malformaciones Arteriovenosas/metabolismo , Malformaciones Arteriovenosas/fisiopatología , Endoglina/deficiencia , Endoglina/genética , Predisposición Genética a la Enfermedad , Células Endoteliales de la Vena Umbilical Humana/metabolismo , Humanos , Factores de Transcripción de Tipo Kruppel/genética , Factores de Transcripción de Tipo Kruppel/metabolismo , Ratones Noqueados , Mutación , Neovascularización Fisiológica , Fenotipo , Flujo Sanguíneo Regional , Estrés Mecánico , Factores de Tiempo , Pez Cebra/embriología , Pez Cebra/genética , Pez Cebra/metabolismo , Proteínas de Pez Cebra/genética
11.
Phys Rev E Stat Nonlin Soft Matter Phys ; 74(2 Pt 1): 023901, 2006 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-17025493

RESUMEN

In a recent paper, Houchmandzadeh [Phys. Rev. E 72, 061920 (2005)] introduce a correlated bigradient model in order to explain the robust scaling of the boundary of hunchback (hb) expression in the early Drosophila embryo. In particular, they stress that recent experiments by Lucchetta [Nature (London) 434, 1134 (2005)], where embryos whose anterior and posterior halves develop at different temperatures still show excellent precision in the hb boundary, are in good agreement with such a model. We would like to show here that this conclusion is unwarranted. This is because the experiments of Lucchetta were done at different temperatures from those studied in the model. Since in other temperature combinations the model does not produce precise boundaries and there are no systematic trends in these deviations, a comparison to the experiment is not possible. Furthermore, we would like to point out that any correlated bigradient model should also take into account the fluctuations of the bicoid profile within an embryo. When forming correlated bigradients of experimental profiles from an online library, we observe that these intraembryo variations destroy robustness of the hb boundary even in the wild-type situation.


Asunto(s)
Tipificación del Cuerpo/fisiología , Proteínas Portadoras/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/embriología , Drosophila melanogaster/fisiología , Embrión no Mamífero/fisiología , Regulación del Desarrollo de la Expresión Génica/fisiología , Morfogénesis/fisiología , Factores de Transcripción/metabolismo , Animales , Simulación por Computador , Modelos Biológicos , Distribución Tisular
12.
Biochem Mol Biol Educ ; 33(5): 325-9, 2005 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-21638593

RESUMEN

The building of models to explain data and make predictions constitutes an important goal in molecular biology research. To give students the opportunity to practice such model building, two digital cases had previously been developed in which students are guided to build a model step by step. In this article, the development and initial evaluation of a third digital case is described. It concerns the selection of bristles during Drosophila development. To mimic a real research situation in a more realistic way, students are given much more freedom while building their models and can thus follow their own model-building approach. At the same time, however, students are provided with a sufficient amount of support to ensure that they can build their models without the requirement of intensive supervision.

13.
Dev Cell ; 33(5): 535-48, 2015 Jun 08.
Artículo en Inglés | MEDLINE | ID: mdl-25982676

RESUMEN

In epithelia, specialized tricellular junctions (TCJs) mediate cell contacts at three-cell vertices. TCJs are fundamental to epithelial biology and disease, but only a few TCJ components are known, and how they assemble at tricellular vertices is not understood. Here we describe a transmembrane protein, Anakonda (Aka), which localizes to TCJs and is essential for the formation of tricellular, but not bicellular, junctions in Drosophila. Loss of Aka causes epithelial barrier defects associated with irregular TCJ structure and geometry, suggesting that Aka organizes cell corners. Aka is necessary and sufficient for accumulation of Gliotactin at TCJs, suggesting that Aka initiates TCJ assembly by recruiting other proteins to tricellular vertices. Aka's extracellular domain has an unusual tripartite repeat structure that may mediate self-assembly, directed by the geometry of tricellular vertices. Conversely, Aka's cytoplasmic tail is dispensable for TCJ localization. Thus, extracellular interactions, rather than TCJ-directed intracellular transport, appear to mediate TCJ assembly.


Asunto(s)
Animales Modificados Genéticamente/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Embrión no Mamífero/citología , Epitelio/crecimiento & desarrollo , Uniones Intercelulares/fisiología , Uniones Estrechas/fisiología , Animales , Animales Modificados Genéticamente/genética , Animales Modificados Genéticamente/crecimiento & desarrollo , Proteínas de Drosophila/genética , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Embrión no Mamífero/metabolismo , Epitelio/metabolismo , Immunoblotting , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Mutación/genética , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Transporte de Proteínas , Secuencias Repetitivas de Aminoácido
14.
Elife ; 4: 05864, 2015 May 06.
Artículo en Inglés | MEDLINE | ID: mdl-25946108

RESUMEN

Morphogenesis emerges from complex multiscale interactions between genetic and mechanical processes. To understand these processes, the evolution of cell shape, proliferation and gene expression must be quantified. This quantification is usually performed either in full 3D, which is computationally expensive and technically challenging, or on 2D planar projections, which introduces geometrical artifacts on highly curved organs. Here we present MorphoGraphX ( www.MorphoGraphX.org), a software that bridges this gap by working directly with curved surface images extracted from 3D data. In addition to traditional 3D image analysis, we have developed algorithms to operate on curved surfaces, such as cell segmentation, lineage tracking and fluorescence signal quantification. The software's modular design makes it easy to include existing libraries, or to implement new algorithms. Cell geometries extracted with MorphoGraphX can be exported and used as templates for simulation models, providing a powerful platform to investigate the interactions between shape, genes and growth.


Asunto(s)
Algoritmos , Arabidopsis/ultraestructura , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Programas Informáticos , Animales , Anisotropía , Arabidopsis/genética , Arabidopsis/crecimiento & desarrollo , Cassia/genética , Cassia/crecimiento & desarrollo , Cassia/ultraestructura , Proliferación Celular , Forma de la Célula , Drosophila melanogaster/genética , Drosophila melanogaster/crecimiento & desarrollo , Drosophila melanogaster/ultraestructura , Flores/genética , Flores/crecimiento & desarrollo , Flores/ultraestructura , Frutas/genética , Frutas/crecimiento & desarrollo , Frutas/ultraestructura , Expresión Génica , Procesamiento de Imagen Asistido por Computador/estadística & datos numéricos , Imagenología Tridimensional/instrumentación , Imagenología Tridimensional/estadística & datos numéricos , Solanum lycopersicum/genética , Solanum lycopersicum/crecimiento & desarrollo , Solanum lycopersicum/ultraestructura , Microscopía Confocal , Microtúbulos/genética , Microtúbulos/ultraestructura , Morfogénesis/genética , Desarrollo de la Planta/genética , Imagen de Lapso de Tiempo/instrumentación , Imagen de Lapso de Tiempo/métodos , Imagen de Lapso de Tiempo/estadística & datos numéricos
16.
PLoS One ; 8(10): e76171, 2013.
Artículo en Inglés | MEDLINE | ID: mdl-24204600

RESUMEN

Control of cessation of growth in developing organs has recently been proposed to be influenced by mechanical forces acting on the tissue due to its growth. In particular, it was proposed that stretching of the tissue leads to an increase in cell proliferation. Using the model system of the Drosophila wing imaginal disc, we directly stretch the tissue finding a significant increase in cell proliferation, thus confirming this hypothesis. In addition, we characterize the growth over the entire growth period of the wing disc finding a correlation between the apical cell area and cell proliferation rate. PACS NUMBERS: 87.19.lx, 87.18.Nq, 87.80.Ek, 87.17.Ee, 87.85.Xd.


Asunto(s)
Drosophila/crecimiento & desarrollo , Fenómenos Mecánicos , Alas de Animales/crecimiento & desarrollo , Animales , Tamaño de los Órganos , Alas de Animales/citología
17.
PLoS One ; 7(10): e47594, 2012.
Artículo en Inglés | MEDLINE | ID: mdl-23091633

RESUMEN

In developmental biology, the sequence of gene induction and pattern formation is best studied over time as an organism develops. However, in the model system of Drosophila larvae this oftentimes proves difficult due to limitations in imaging capabilities. Using the larval wing imaginal disc, we show that both overall growth, as well as the creation of patterns such as the distinction between the anterior(A) and posterior(P) compartments and the dorsal(D) and ventral(V) compartments can be studied directly by imaging the wing disc as it develops inside a larva. Imaged larvae develop normally, as can be seen by the overall growth curve of the wing disc. Yet, the fact that we can follow the development of individual discs through time provides the opportunity to simultaneously assess individual variability. We for instance find that growth rates can vary greatly over time. In addition, we observe that mechanical forces act on the wing disc within the larva at times when there is an increase in growth rates. Moreover, we observe that A/P boundary formation follows the established sequence and a smooth boundary is present from the first larval instar on. The division of the wing disc into a dorsal and a ventral compartment, on the other hand, develops quite differently. Contrary to expectation, the specification of the dorsal compartment starts with only one or two cells in the second larval instar and a smooth boundary is not formed until the third larval instar.


Asunto(s)
Drosophila/crecimiento & desarrollo , Discos Imaginales/crecimiento & desarrollo , Alas de Animales/crecimiento & desarrollo , Animales , Expresión Génica , Larva/genética , Larva/crecimiento & desarrollo , Morfogénesis/genética
18.
Mech Dev ; 126(11-12): 942-9, 2009 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-19748573

RESUMEN

Morphogenesis, the process by which all complex biological structures are formed, is driven by an intricate interplay between genes, growth, as well as intra- and intercellular forces. While the expression of different genes changes the mechanical properties and shapes of cells, growth exerts forces in response to which tissues, organs and more complex structures are shaped. This is exemplified by a number of recent findings for instance in meristem formation in Arabidopsis and tracheal tube formation in Drosophila. However, growth not only generates forces, mechanical forces can also have an effect on growth rates, as is seen in mammalian tissues or bone growth. In fact, mechanical forces can influence the expression levels of patterning genes, allowing control of morphogenesis via mechanical feedback. In order to study the connections between mechanical stress, growth control and morphogenesis, information about the distribution of stress in a tissue is invaluable. Here, we applied stress-birefringence to the wing imaginal disc of Drosophila melanogaster, a commonly used model system for organ growth and patterning, in order to assess the stress distribution present in this tissue. For this purpose, stress-related differences in retardance are measured using a custom-built optical set-up. Applying this method, we found that the stresses are inhomogeneously distributed in the wing disc, with maximum compression in the centre of the wing pouch. This compression increases with wing disc size, showing that mechanical forces vary with the age of the tissue. These results are discussed in light of recent models proposing mechanical regulation of wing disc growth.


Asunto(s)
Drosophila melanogaster/fisiología , Drosophila melanogaster/efectos de la radiación , Elasticidad/efectos de la radiación , Luz , Estrés Mecánico , Alas de Animales/fisiología , Alas de Animales/efectos de la radiación , Animales , Proteínas de Drosophila/metabolismo , Larva/crecimiento & desarrollo , Transducción de Señal , Alas de Animales/crecimiento & desarrollo
19.
J Theor Biol ; 234(1): 13-9, 2005 May 07.
Artículo en Inglés | MEDLINE | ID: mdl-15721032

RESUMEN

During embryonic development, a spatial pattern is formed in which proportions are established precisely. As an early pattern formation step in Drosophila embryos, an anterior-posterior gradient of Bicoid (Bcd) induces hunchback (hb) expression (Nature 337 (1989) 138; Nature 332 (1988) 281). In contrast to the Bcd gradient, the Hb profile includes information about the scale of the embryo. Furthermore, the resulting hb expression pattern shows a much lower embryo-to-embryo variability than the Bcd gradient (Nature 415 (2002) 798). An additional graded posterior repressing activity could theoretically account for the observed scaling. However, we show that such a model cannot produce the observed precision in the Hb boundary, such that a fundamentally different mechanism must be at work. We describe and simulate a model that can account for the observed precise generation of the scaled Hb profile in a highly robust manner. The proposed mechanism includes Staufen (Stau), an RNA binding protein that appears essential to precision scaling (Nature 415 (2002) 798). In the model, Stau is released from both ends of the embryo and relocalizes hb RNA by increasing its mobility. This leads to an effective transport of hb away from the respective Stau sources. The balance between these opposing effects then gives rise to scaling and precision. Considering the biological importance of robust precision scaling and the simplicity of the model, the same principle may be employed more often during development.


Asunto(s)
Drosophila/embriología , Desarrollo Embrionario , Modelos Biológicos , Animales , Tipificación del Cuerpo/genética , Proteínas de Unión al ADN/genética , Drosophila/anatomía & histología , Drosophila/genética , Proteínas de Drosophila/genética , Desarrollo Embrionario/genética , Regulación del Desarrollo de la Expresión Génica , Proteínas de Unión al ARN/genética , Factores de Transcripción/genética
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