Figure 4.

APOL1 G0 and G1 induced age-related changes in nephrocyte cell size and cell number. (A) Adult fly nephrocytes (and smaller cardiomyocytes) expressing GFP (green, the majority concentrated in nucleus) at days 1, 8, and 15 postemergence. Nephrocytes of control flies (carrying Dot-GAL4 driver without UAS-APOL1 transgene) were unchanged with respect to cell size and cell number from day 1 through day 15. Nephrocyte-specific expression of APOL1-G0 and G1 proteins, by contrast, was associated as flies aged with progressively increased cell size and decreased cell numbers. Arrows indicate cell debris among intact nephrocytes expressing APOL1 G1 at days 8 and 15. (B) Quantification of adult nephrocyte cell size at days 1, 8, and 15 postemergence. Size is indicated relative to day 1 control nephrocytes. G0 and G1 forms of APOL1 were both associated with progressively increased cell size, with G1 inducing a greater degree of cell enlargement. The size of control nephrocytes did not change significantly over the course of the experiment. (C) Quantification of adult nephrocyte cell numbers at days 1, 8, and 15. Cell numbers are indicated relative to control nephrocytes. G0 and G1 forms of APOL1 were both associated with progressively decreased cell numbers, but with G1 inducing greater reduction. The number of control nephrocytes did not change significantly over the course of the experiment. For quantification, ≥20 nephrocytes were analyzed from each of three female flies per genotype. The results are presented as mean±SD. Statistical significance (*) was defined as P<0.05.