Fig. 2: Disturbing Dpp diffusion without affecting niche-GSC signal.

A Schematics of the design to trap Dpp on the surface of hub cells using Morphotrap. The anti-GFP nanobody, vhhGFP4 (blue circle), is fused to transmembrane domains of either mouse CD8 (mCD8-Morphotrap) or Nrv1 basolateral scaffold protein (Nrv-Morphotrap). BFP; tagBFP fluorescent protein. B Expected outcome of hub-driven expression of Morphotrap in the background of mGL-dpp homozygous fly rescued by pPA dpp 8391/X. C Histone H3-GFP expressed under the hub-specific driver, fasIIIGal4. D, F Representative images of homozygous mGL-dpp fly rescued by pPA dpp 8391/X without (D) or with (E) fasIIIGal4 driven Nrv-Morphotrap expression or with (F) fasIIIGal4 driven mCD8-Morphotrap expression. Hub is encircled by red broken lines. G, H Hub area from homozygous mGL-dpp fly rescued by pPA dpp 8391/X without (G) or with (H) fasIIIGal4 driven Nrv-Morphotrap expression. I–K pMad staining of GSCs after trapping Dpp using indicated Morphotrap lines. The fasIIIGal4 driver was used. White broken lines encircle GSCs. L Quantification of pMad intensity in GSCs (relative to CCs) of fasIIIGal4 driven Nrv-Morphotrap or mCD8-Morphotrap expressing testes in mGL-dpp homozygous background rescued by pPA dpp 8391/X. P-values were calculated by Dunnett’s multiple comparisons tests. n indicates the number of scored GSCs. Box plots show 25–75% (box), minimum to maximum (whiskers) with all data points. Source data are provided as a Source Data file. M Live testis tip of homozygous mGL-dpp fly rescued by pPA dpp 8391/X expressing Nrv-Morphotrap under the germline specific driver, nosGal4. Trapped mGL-Dpp signal is seen on the surface of early germ cells (white arrowheads). N, O pMad staining shows emerging pMad positive germ cells (arrowheads in O) outside of the niche of homozygous mGL-dpp fly rescued by pPA dpp 8391/X, without (O) or with (N) the expression of Nrv-Morphotrap under the germline specific driver, nosGal4. pMad positive germ cells are normally only seen in GSCs and immediate descendants around the hub (arrowheads in N). White broken lines encircle GSCs. All scale bars represent 10 μm. Asterisks indicate the hub. Live tissues were used for C–H, M and fixed samples were used for I–K, N, O.