Fig. 6. Ectopic anchoring of Osk to the entire oocyte cortex requires Long Osk. Ectopic overexpression of the two Osk isoforms (A) and Short Osk alone (B) from the UAS-osk-K10 3'UTR and UAS-oskM1R-K10 3'UTR transgenes, respectively, in wild-type ovaries. When both isoforms are expressed (A), Osk is readily detected along the entire cortex of oocytes of stages 7/8 to 10. When only Short Osk is expressed (B), no cortical staining is observed other than at the posterior pole, where endogenous Osk (Long and Short) is expressed and localized. In both cases, the brightness of the immunostaining in the subcortical region of the nurse cells reveals the massive overproduction of Osk isoforms. (C) Analysis of overexpressed Osk isoforms produced from the transgenic ovaries by western blotting.