Fig. 7: Modulation of TNFR-Wgn and model.

a, b Dorso-lateral views of a stage 14 embryos. a FGF-Bnl accumulates in intracellular vesicles that also contain TNFR-Wgn and FGFR-Btl particularly in the terminal cells (grey square). More TNFR-Wgn vesicles are detected at the tip of DBs (white arrow) compared to the base (yellow square). b In TNFR-wgn mutants, FGF-Bnl is detected in more cells of the DBs (yellow arrows). c–f Dorso-lateral views of a stage 14 embryos. c TNFR-Wgn vesicles are more abundant at the tip of the branches. d When the endocytic maturation is compromised, TNFR-Wgn is found also at high levels in the stalk cells at the base (blue arrows). e, f The overexpression of FGF-Bnl leads to an increased accumulation of TNFR-Wgn protein. g Model. TNFR-Wgn protein is constantly trafficking and can form a complex with FGFR-Btl receptor. Through this interaction, TNFR-Wgn promotes FGFR-Btl degradation. In the wild type, the terminal cell receives huge amounts of FGF-Bnl ligand (due to source proximity), activating FGFR-Btl, which leads to activation of the ERK pathway and to transcriptional DSRF activation. This activation can bypass the negative effect of TNFR-Wgn. The stalk cell receives lower levels of FGF-Bnl ligand, leading to a weaker activation of the pathway. This, combined with the negative effect of TNFR-Wgn, prevents DSRF activation. When TNFR-Wgn is overexpressed, it promotes FGFR-Btl degradation, preventing DSRF activation in spite of the presence of high levels of FGF-Bnl ligand. This also leads to lower levels of FGFR-Btl. When TNFR-Wgn activity is lost, FGFR-Btl degradation decreases, and FGFR-Btl levels increase. Under these conditions, weak activation of the FGFR-Btl in stalk cells can lead to DSRF activation. Scale bar: (a, b) 10 μm; (c) 5 μm; (d–f) 20 μm. Source data are provided as a Source Data file.