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Morphogenesis: Emergence of shape to bring functionality to tissues
Morphogenesis: Emergence of shape to bring functionality to tissues
The following images show part of the diversity of forms that tissues and cells acquire to fulfil a given function. Tissues that transport information or liquids throughout the body form long cellular processes; for instance, neurons (yellow) or tracheal tubes (blue/red). We study the mechanisms that cells use to build such structures. In doing this we also incorporate studying what is the contribution of factors that are external to the cells: The image on the right also shows how neurons and tracheal tubes associate with other tissues like muscles, and we are interested in studying how these interactions contribute to tissue shape changes.
Find out more: When life takes shape
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Cells and tissues encode more information than what we can see at any given time point. This is illustrated with the image on the left. This image shows a group of structures known as 'imaginal discs'. These structures are present in the larvae of insects, and even though they do not have an obvious function at this stage, they constantly receive patterning signals from other cells and tissues. These become crucial during metamorphosis, as the discs grow to form all the parts of the adult body. There is a disc for each leg, eye, antenna and even wing of the adult fly.
To build complex shapes, tissues integrate this information from their surroundings. These cues comprise ligands that activate signaling pathways, forces exerted by other cells or tissues, metabolic modifications and other mechanisms. Altogether, they are converted into subcellular responses that allow proper morphogenesis. Our aim is to dissect how external factors are integrated during tissue morphogenesis.
Related application: Celldiscoverer 7 with LSM900
Subcellular mechanisms of embryonic development
Subcellular mechanisms of embryonic development
Execution of shape changes require structural proteins. Many of these proteins are secreted to the extracellular space to support tissues, whereas others provide stability within the cell. The following images show aspects of how this happens in different contexts. The image below shows a pupa; an animal in the process of metamorphosis. At this stage many tissues of the adult fly have already formed, even though the animal is traslucid and immobile, developing within its case. Nevertheless we can tag proteins to visualise their distribution within the animal. In blue we can see a protein named 'Dumpy', which is present in the surface of all insects. Dumpy constitutes part of the barrier from the inner part of the animal to the outside world. In fact, similar proteins also shield human oocytes. Studying how Dumpy is secreted in different tissues has allowed us to understand basic principles of cell biology, and what happens to the embryo when these processes fail. The image in the center shows cells of the wing primordium and the different colours label parts of the subcellular machinery required to secrete proteins: In pink and cyan, the endoplasmic reticulum (ER) and in white the ER exit sites. The image on the right shows the same subcellular machinery but now in green, and following very different distribution in a tracheal cell (pink/red) and in the underlying muscle where it forms green stripes.
Related note: A giant called Dumpy*
Related note: Wings without wings*
Also here: Tráfico vesicular en la formación de traqueolas en Drosophila melanogaster*
Also here: Tráfico vesicular en la formación de traqueolas en Drosophila melanogaster*
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Cooperation between tissues during development
Cooperation between tissues during development
In order to change shape, many times tissues deform their surroundings, even if these surroundings are other tissues. The image on the left shows two groups of very different cells. The small ones on the edges are epidermal cells, whereas the center ones constitute a tissue called 'amnioserosa'. For the epidermis to completely cover the surface of the embryo it must stretch over the amnioserosa, until it seals at the dorsal midline of the animal. Throughout this process the amnioserosa acts as a signalling center that orchestrates the process, and it also contributes forces that fine-tune the remodelling and sealing of the epidermis. The interplay between these two tissues has been a very useful model to understand tissue interaction and its relevance during development.
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