Grand Séminaire d'Institut

Mardi 2 Avril 2024 à 11h00.

Wnt ligands diffusion and polarity transfer in /C. elegans/ embryos

''
Multiple developmental processes are under the control of signaling molecules that spread and control tissue patterning or cell fates during animal development. The spatial and temporal dynamics of the spreading of these molecules is often not known, yet it determines the length scales and time frames of the activity of these signals. It is often proposed that the diffusion of morphogens establishes a concentration gradient, even though there are very few measurements of this gradient /in vivo/, and to a few exceptions, the modes of dispersion of morphogens in tissue remain unclear. We use /C elegans/ embryos to study the mobility of Wnt ligands, an evolutionary conserved family of signaling proteins. We demonstrated that Wnts are expressed in the posterior half of the embryo and used quantitative live imaging on endogenously tagged ligands. We could measure that ligands can diffuse throughout the tissue in a timescale shorter than the cell cycle and measured their diffusion coefficient with Fluorescence Correlation Spectroscopy (FCS). We combined our experimental measurements with numerical simulations to prove that the diffusion of the ligands is fast enough to polarize target cells in the anterior half of the embryo, at distance from the source of Wnt. Our results support a diffusion based long-range Wnt signaling, which is consistent with the dynamics of developmental processes.

''