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Kidney Week

Abstract: FR-PO1023

A Modifier Genetic Screen for APOL1 in Drosophila Nephrocytes Identified Potential Therapeutic Targets That Rescue the Renal Toxicity of APOL1

Session Information

Category: Genetic Diseases of the Kidney

  • 1002 Genetic Diseases of the Kidney: Non-Cystic

Author

  • Han, Zhe, Children's National Health System, Washington, District of Columbia, United States
Background

African Americans are at higher risk for developing chronic kidney diseases due to APOL1 risk alleles (RA), but the treatment is lacking. We generated a Drosophila model of APOL1 nephropathy by expressing APOL1-G1 in nephrocytes, which share striking similarities with podocytes. APOL1-G1 expression in nephrocytes led to loss of renal function and cell death, providing a platform to identify genes that modifies APOL1 renal toxicity.

Methods

We designed and performed a modifier genetic screen for APOL1 in Drosophila, by crossing thousands of transgenic RNAi lines to a master line that carries four transgenes: a nephrocyte-specific driver (Dot-Gal4), a nephrocyte function readout (MHC-ANF-RFP), a marker (Hand-GFP) and the UAS-APOL1-G1 over a balancer chromosome. We examined and compared the effects of silencing each individual gene in nephrocytes, with or without APOL1-G1. We also used a human kidney cell line to validate our findings.

Results

We identified ~20 genes (out of ~1000) that could modify the APOL1-G1 toxicity in nephrocytes. Silencing of these genes alone in nephrocytes did not generate a phenotype, but the toxicity was increased in a synergistic manner together with APOL1-G1, suggesting that these genes could antagonize APOL1-G1 toxicity when over-expressed. We therefore generated transgenic lines to over-express these genes in nephrocytes. We discovered that two of these genes, when over-expressed with APOL1-G1, could rescue the functional defects of nephrocytes caused by APOL1-G1 expression. We further tested these two genes in a human kidney cell line, and found that they encode proteins that co-localize and directly bind to APOL1. Furthermore, expression of these two genes in human kidney cells significantly rescued the cell death caused by APOL1-G1 expression.

Conclusion

Our findings suggest that the Drosophila genetic screen can be used to identify modifier genes for APOL1 renal toxicity. Our data suggest that an evolutionarily conserved genetic network mediates the renal toxicity of APOL1-RA. Using Drosophila genetic screen and cultured human kidney cells, we discovered two genes that antagonize the renal toxicity of APOL1-G1 in both fly nephrocytes and human kidney cells, as potential therapeutic targets for APOL1 nephropathy.

Funding

  • NIDDK Support