Many patterns of cell and tissue organization are specified during development by gradients of morphogens, substances that assign different cell fates at different concentrations. Gradients form by morphogen transport from a localized site, but whether this occurs by simple diffusion or by more elaborate mechanisms is unclear. We attempt to resolve this controversy by analyzing recent data in ways that appropriately capture the complexity of systems in which transport, receptor interaction, endo- and exocytosis, and degradation occur together. We find that diffusive mechanisms of morphogen transport are much more plausible-and nondiffusive mechanisms much less plausible-than has generally been argued. Moreover, we show that a class of experiments, endocytic blockade, thought to effectively distinguish between diffusive and nondiffusive transport models actually fails to draw useful distinctions.
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Trends Cell Biol
January 2025
Living Systems Institute, University of Exeter, Exeter, UK. Electronic address:
Cellular communication through the dissemination of signal molecules is vital for tissue organisation and homeostasis. The mechanisms of signal spreading can include binding-protein-assisted transport, long membrane protrusions known as cytonemes, and exovesicles. Recent research indicates that cytonemes and exovesicles can not only transport ligands but also facilitate the regulated distribution of receptors, thereby enabling signal transduction in cells lacking endogenous receptors.
View Article and Find Full Text PDFBull Math Biol
January 2025
School of Mathematics, University of Minnesota, Minneapolis, USA.
Spatial distributions of morphogens provide positional information in developing systems, but how the distributions are established and maintained remains an open problem. Transport by diffusion has been the traditional mechanism, but recent experimental work has shown that cells can also communicate by filopodia-like structures called cytonemes that make direct cell-to-cell contacts. Here we investigate the roles each may play individually in a complex tissue and how they can jointly establish a reliable spatial distribution of a morphogen.
View Article and Find Full Text PDFElife
December 2024
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom.
The endoplasmic reticulum (ER), the largest cellular compartment, harbours the machinery for the biogenesis of secretory proteins and lipids, calcium storage/mobilisation, and detoxification. It is shaped as layered membranous sheets interconnected with a network of tubules extending throughout the cell. Understanding the influence of the ER morphology dynamics on molecular transport may offer clues to rationalising neuro-pathologies caused by ER morphogen mutations.
View Article and Find Full Text PDFFront Plant Sci
November 2024
Department for Plant Physiology, Institute for Biological Research "Siniša Stanković" - National Institute of Republic of Serbia, University of Belgrade, Belgrade, Serbia.
Common centaury ( Rafn) is a medicinal plant species with vigorous morphogenic potential . The process of spontaneous shoot regeneration in a solid root culture is characteristic for this plant species. In this context, the aim of this work was to investigate the dynamic changes of endogenous phytohormones and carbohydrates content in root explants at different time points (0, 2, 4, 7, 14, 21, 28, and 60 days) during spontaneous centaury morphogenesis .
View Article and Find Full Text PDFAdv Mater
October 2024
Institute of Biofunctional Polymer Materials/Max Bergmann Center of Biomaterials Dresden, Leibniz Institute of Polymer Research Dresden, Hohe Str. 6, 01069, Dresden, Germany.
Concentration gradients of soluble signaling molecules-morphogens-determine the cellular organization in tissue development. Morphogen-releasing microgels have shown potential to recapitulate this principle in engineered tissue constructs, however, with limited control over the molecular cues in space and time. Inspired by the functionality of sulfated glycosaminoglycans (sGAGs) in morphogen signaling in vivo, a library of sGAG-based microgels is developed and designated as µGel Units to Instruct Development (µGUIDEs).
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