Boi functions in apical cells to regulate FSC proliferation. (A) Ptc expression (green) in wild-type (WT) germarium. Apical cells (red, anti-Hh) and FSC location (arrowhead) are indicated. (B and C) Boi (green) localizes predominantly to apical cells (brackets) in WT (B) but not boi^e mutant (C) germaria. FSCs are indicated (arrowheads). (D and E) UAS-boi^RNAi expression in apical cells reduces Boi levels. Boi (left), GFP (center), and germ cells (right, anti-Vasa) are labeled. WT germaria (D) express Boi but lack GFP. UAS-boi^RNAi/UAS-GFP; babGal4/+ germaria (E) lose Boi and gain GFP in apical cells. (F) Mean cell number in the first stalk for each genotype is shown. Significant differences relative to control (109-30/+ or babGal4/+) are indicated (*, P < 0.000002). (G) Mean numbers of dividing FSCs (PH3+) per germarium are shown. Significant differences relative to control (109-30/+ or babGal4/+) are indicated (*, P < 0.007). Error bars represent SEM.