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Abstract: SA-PO990

Transcriptional Profiling of Induced Pluripotent Stem Cell (iPSC)-Derived Podocytes Comparing APOL1 Risk Variants

Session Information

Category: Glomerular Diseases

  • 1403 Podocyte Biology

Authors

  • Haines, Lauren, Cleveland Clinic, Cleveland, Ohio, United States
  • Tran, Uyen, Cleveland Clinic, Cleveland, Ohio, United States
  • Sedor, John R., Cleveland Clinic, Cleveland, Ohio, United States
  • O'Toole, John F., Cleveland Clinic, Cleveland, Ohio, United States
  • Wessely, Oliver, Cleveland Clinic, Cleveland, Ohio, United States
Background

African Americans of sub-Saharan ancestry have a 3.5-fold increased risk for end-stage kidney disease compared to populations of European descent due to, in part, two high-risk variants G1 and G2 in the apolipoprotein L1 (APOL1) gene. Individuals with two high-risk alleles are predisposed to kidney disease through an undetermined mechanism. We sought to determine if APOL1 expression in high-risk human induced pluripotent stem cell (iPSC)-derived podocytes causes transcriptional differences compared to reference APOL1 iPSC-derived podocytes.

Methods

We utilized iPSC-derived podocytes engineered with APOL1 reference (G0) and high-risk (G1, G2) variant genotypes. Our lab has also developed a protocol to directly differentiate these iPSCs into podocyte populations that express APOL1 with IFN-γ stimulation. To characterize the transcriptional impact of APOL1 variants, we performed mRNA-sequencing on G0/G0, G1/G1, and G2/G2 podocytes either untreated or treated with IFN-γ. EdgeR was used for differential gene expression and further analyzed by principal component analysis, gene ontology enrichment, and Gene Set Enrichment Analysis.

Results

Variant APOL1 iPSC lines differentiate into podocyte populations using our protocol, express APOL1 with IFN-γ stimulation, and do not demonstrate differential cell death. Transcriptome principal component analysis shows both untreated (lacking APOL1 expression) and, unexpectedly, IFN-γ treated (with APOL1 expression) podocytes are not statistically different between reference and high-risk genotypes. The majority of variance (68%) results from IFN-γ treatment and the upregulation of more than 400 genes (2-fold change, FDR 0.05). Furthermore, the few differentially expressed genes between reference and high-risk podocytes could not be assigned a functional role using pathway analysis methods.

Conclusion

We were not able to identify an APOL1-specific transcriptome response between reference and high-risk APOL1 iPSC-derived podocytes. Variant-dependent differences may be overshadowed by the robust transcriptional response to INF-γ used for APOL1 induction. This supports the need to induce APOL1 expression without inflammatory stimulation in order to assess the effect of APOL1 variants on podocyte biology.

Funding

  • NIDDK Support