Figure 4. lin-28 Mutants Exhibit Reduced Fertility.

(A) Schematic drawing of the germarium with its two stem cell clusters, i.e. germline stem cells (GSCs) and follicular stem cells (FSCs), and of an ovariole composed of a string of egg chambers of increasing maturation stages. The last egg chamber is composed of a large oocyte with its karyosome (kary.) at the posterior pole, and the 15 nurse cells at the anterior pole. (B) While w¹¹¹⁸ female flies laid 18.8 eggs per day, lin-28^dF30/+25.1 eggs per day and lin-28^dF101/+24.8 eggs per day, lin-28^{dF3 0} and lin-28^dF101 mutant flies laid respectively 5.5 and 5.2 eggs per day (n = 10; p<0.05). (C) Comparison of whole ovaries revealed increased auto-fluorescence in homozygous ovaries. The auto-fluorescence is localized at the oocyte portion of the eggs (asterisk), therefore indicating an increased number of eggs between stages 7 to 10, compared to controls. In addition, the visualization of nuclei in single ovarioles revealed an accumulation of supernumerary nurse cells in lin-28^dF30 and lin-28^dF101 stage 8 egg chambers. (D) 75.4% and 78.1% of homozygous lin-28^dF30 and lin-28^dF101 egg chambers displayed abnormal egg chambers, compared to 16.9% of the w¹¹¹⁸ and 13.8% and 12.7% of the heterozygous lin-28^{dF3 0/+ and} lin-28^dF101/+ ovarioles (n = 65). Scale bars represent 100 µm.