Figure 3. Oskar mRNA dynamics in Staufen mutant oocytes.

Molecular beacon cocktail was microinjected in a nurse cell (A) or an oocyte (C) of egg chambers mutant for Staufen protein. oskar mRNA was imaged over approximately 50 minutes. (A) oskar mRNA particles were tracked in two (a) and three (b) dimensions. The end point of each particle track highlighted in the 2D colored panel is represented by circle. (B) High resolution 3D tracking of wild-type oocyte where velocity and trend of flow of osk particles is overlaid on the oocyte by arrows, as compared to Stau mutant. Large arrows represent faster velocities and stronger flows, whilst smaller arrows represent slower velocities. Osk particles seem to have a posterior bias, which concentrates at the posterior tip with both flows then seeming to “rebound” from the posterior to the center creating a strong central anterior flow. Since osk in wild-type is captured at the posterior, this effect is minimized. In Stau mutants, where osk is not captured at the posterior, this anterior flow dominates and osk eventually acquires an anterior localization. (C) The first and last time point frames (green&yellow) (panel I and II, respectively) are merged with the time projection image (red) to indicate the position of the particles at the beginning and the end of the tracked paths inside the oocyte. Tracks of several particles are traced by white dotted line. The black arrowheads indicated the beginning (in panel I) and end (in panel II) points of those particles defining the tracks. Oskar mRNA is distributed throughout the oocyte including at the posterior and anterior of the oocyte (white arrowheads). No crescent-like localization is observed as in wild type oocytes (B). (D) The tracking data shows the particles over the time course as they appear to retreat toward the anterior once they reach the posterior as if they are no longer anchored there. See Movies S6. Posterior is oriented to the right. Scale bar is 25 µm. N = 23.