Extracellular interactions and ligand degradation shape the nodal morphogen gradient.
The correct distribution and activity of secreted signaling proteins called morphogens is required for many developmental processes. Nodal morphogens play critical roles in embryonic axis formation in many organisms. Models proposed to generate the Nodal gradient include diffusivity, ligand processing, and a temporal activation window. But how the Nodal morphogen gradient forms in vivo remains unclear. Here, we have measured in vivo for the first time, the binding affinity of Nodal ligands to their major cell surface receptor, Acvr2b, and to the Nodal inhibitor, Lefty, by fluorescence cross-correlation spectroscopy. We examined the diffusion coefficient of Nodal ligands and Lefty inhibitors in live zebrafish embryos by fluorescence correlation spectroscopy. We also investigated the contribution of ligand degradation to the Nodal gradient. We show that ligand clearance via degradation shapes the Nodal gradient and correlates with its signaling range. By computational simulations of gradient formation, we demonstrate that diffusivity, extra-cellular interactions, and selective ligand destruction collectively shape the Nodal morphogen gradient.
Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.|Department of Biological Sciences, National University of Singapore, Singapore, Singapore.
Yin
Y
Wang
Department of Chemistry, Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore.
Xi
X
Wang
Department of Biological Sciences, National University of Singapore, Singapore, Singapore.|Department of Chemistry, Centre for Bioimaging Sciences, National University of Singapore, Singapore, Singapore.
Thorsten
T
Wohland
Division of Biomedical Sciences, Warwick Medical School, University of Warwick, Coventry, United Kingdom.
Karuna
0000-0002-0729-1977
K
Sampath
D030301:Activin Receptors, Type II / Q000378:metabolism; D000818:Animals; D055458:Left-Right Determination Factors / Q000378:metabolism; D009024:Morphogenesis; D055456:Nodal Signaling Ligands / Q000378:metabolism*; D011485:Protein Binding; D059748:Proteolysis; D013050:Spectrometry, Fluorescence; D015027:Zebrafish / Q000196:embryology*; D029961:Zebrafish Proteins / Q000378:metabolism
D055458:Left-Right Determination Factors; D055456:Nodal Signaling Ligands; D029961:Zebrafish Proteins; D030301:Activin Receptors, Type II; C505425:acvr2ba protein, zebrafish
Nodal; developmental biology; gradient; inhibitor; morphogen; receptor; stem cells; zebrafish