DRP1 down-regulation inhibits mitochondrial fission and maintains proliferation in the postmitotic follicle cell layer. (A) Drosophila follicle cell lineage during different developmental stages of the ovariole. (B, left) Microirradiation of TMRE-labeled mitochondria in nonclonal (containing UbiGFP) and drp1^KG clones (lacking UbiGFP) was performed at white points. (right) This caused rapid loss of all TMRE signal only in drp1^KG clones (with clustered mitochondria) after irradiation (arrows point to the effect on TMRE signal). (C) drp1^KG clonal follicle cells in a S8 egg chamber. Nonclonal cells express UbiGFP, whereas drp1^KG clones lack UbiGFP. Red lines demarcate the boundary between patterned zones. The arrow points to proliferating drp1^KG PFC clones. Hoechst (blue) stains nuclei. (D) drp1^KG PFC clones (lacking UbiGFP) show BrdU incorporation in an S10 egg chamber. (E) drp1^KG PFC clones (lacking UbiGFP) show pH3-positive cells. Hoechst stains nuclei. (F) Quantification of pH3-positive nuclei in background follicle cells versus drp1^KG PFC and MBC clones in postmitotic egg chambers. Error bar indicates standard deviation. White lines define the clone boundary, and the dotted lines outline the egg chambers. WT, wild type. Bars, 10 µm.