Fig. 2. rab6^D23D egg chambers form open syncytia. (A-C) Egg chambers stained to reveal F-actin (phalloidin, red) and all membranes (FM4-64, green). rab6^D23D clones are distinguished by the absence of nuclear GFP (blue). In wild-type stage-7 egg chambers (A), actin cytoskeleton and plasma membranes overlap (arrow). A membranous continuum decorating a nucleus (^*) appears to span the ring canals, linking adjacent cells (arrowhead). (B,C) In mildly affected rab6^D23D egg chambers (B), remaining plasma membranes and actin delimit two nurse cell `open' syncytia (arrow). Within these syncytia, clusters of actin debris and ring canals are embedded in dense membranous material (arrowhead in bottom syncytium; not visible in the upper syncytium in this focal plane). The membranous continuum passes through the ring canals in the remaining plasma membranes separating the large open syncytia and the oocyte. In strongly affected rab6^D23D egg chambers (C), all compartmentalization by actin and plasma membrane is lost, and nurse cell nuclei lie in a common cytoplasm containing a single central cluster of ring canals, membranes and actin debris (arrowhead). The nurse cell nuclei (^*) found in the syncytia away from the membranes appear disconnected from the membranous continuum (B,B') and are occasionally stripped of vesicular material (C,C').