Fig. 5. Anterior Osk, specifically long Osk, recruits endosomal proteins and stimulates endocytosis in Drosophila. (A-D) Rbsn-5 localization at the oocyte anterior without (A) or with expression of osk-bcd 3' UTR (B), osk(M1L)-bcd 3' UTR (C) or osk(M139L)-bcd 3' UTR (D). Rbsn-5 accumulated in the anterior of oocytes expressing the intact osk-bcd 3' UTR or osk(M139L)-bcd 3' UTR transgenes, but not the osk(M1L)-bcd 3' UTR transgene (arrowheads). (E-J) Rab5 (E,F), Rab11 (G,H) and Rab7 (I,J) localization at the oocyte anterior without (E,G,I) or with long Osk expression (F,H,J). Rab5, Rab11 and Rab7 all accumulated at the oocyte anterior when long Osk was expressed (arrowheads). (K,L) Incorporation of FM4-64 in stage 9 oocytes without (K) or with long Osk expression (L). Ectopic dye incorporation was observed at the oocyte anterior in the presence of long Osk (arrowheads). (M,N) Kin-βgal localization without (M) or with long Osk expression (N). No ectopic Kin-βgal signal was detected at the anterior pole of the osk(M139L)-bcd 3' UTR oocyte (arrowheads). DNA was counterstained with DAPI (cyan) in all images. Scale bars: 20 µm.