Figure 2.

Expression of APOL1 G0 and G1 increases the function of nephrocytes in young adult transgenic flies. (A) ANF-RFP red fluorescent fusion protein in nephrocytes of 1-day-old (1 day postemergence) adult flies. Left panels (MHC-ANF-RFP) show RFP with dotted lines indicating nephrocyte cell outlines. Right panels (MHC-ANF-RFP Hand-GFP) show merged RFP fluorescence and GFP reporter fluorescence (green, mostly nuclear). Control flies carried MHC-ANF-RFP, Hand-GFP, and Dot-GAL4 driver (without UAS-APOL1 transgene). Dot>APOL1-G0 and Dot>APOL1-G1 flies carried MHC-ANF-RFP, Hand-GFP, and Dot-GAL4 driver–directing nephrocyte-specific expression of the indicated APOL1 transgene. (B) Quantification of nephrocyte RFP fluorescence, relative to control value. 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. (C) AgNO₃ sequestration by nephrocytes of 1-day-old adult flies. Left panels show bright field views of AgNO₃ taken up by nephrocytes with dotted lines indicating cell outlines. Right panels show Hand-GFP reporter fluorescence in nephrocytes (green, mostly nuclear), with dotted lines indicating cell outlines. (D) Quantification of nephrocyte AgNO₃ levels, relative to control value. 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. (E) Adult survival curves for control (without UAS-APOL1 transgene) and Dot enhancer–directed APOL1 transgene expressing flies. Nephrocyte expression of both G0 and G1 forms of APOL1 caused early mortality, although G1 expression was more toxic.