Figure 4. rab11-null epithelial cells arrest differentiation early, but continue to divide through s6 or 7, while sec-15 null cells arrest differentiation early and are targeted for programmed cell death.

(A–C) Confocal images of wildtype s9 egg chambers immunostained for (A) Rab11 (red), (B) Nuf (green), or (C) Sec15 (red). Magnified views are shown at the bottom of each panel. (D) Mosaic s6 egg chamber immunostained for nGFP (green) and Fas3 (red) 4–6 days ACI. The asterisks point to rab11-null cells still embedded in the epithelium. A cluster of 3 or 4 rab11-null cells that have delaminated from the epithelium and invaded the germline cyst is enclosed in the dashed white line. All of the rab11-null cells over-express Fas3 consistent with an early arrest of epithelial cell differentiation (see Text). The arrow points to a wildtype polar cell, which also over-expresses Fas3. (D′) Light micrograph of egg chamber shown in (D). (E) Mosaic s4/5 egg chamber immunostained for nGFP (green), E-cad (red) and phospho-histone 3 (PH3) (blue) 3 days ACI, with rab11-null cells enclosed by the dashed white lines. The asterisk marks a dividing (PH3-positive) rab11-null cell, while the arrows point to two dividing wildtype cells. (F) Mosaic s7 egg chamber immunostained as in (E), with rab11-null cells enclosed by the dashed white lines. (F′) Magnified view of the region bracketed in (F), where a pair of dividing rab11-null (PH3-positive) cells are clearly evident. (G) Mosaic sec15-null s6/7 egg chamber immunostained for nGFP (green) and Fas3 (red) 2 days ACI. All of the sec15-null (GFP-negative) cells over-express Fas3 again consistent with an early arrest of epithelial cell differentiation. The yellow dashed line highlights a gap in the follicle cell epithelium, presumably due to PCD of sec15-null cells. (H) Mosaic sec15-null s6/7 egg chamber immunostained for nGFP (green) and counterstained for activated caspase-3 two days (red) ACI. The arrow points to an apoptotic sec15-null cell.