Novel Variant of ARHGEF18 Increases Susceptibility to Adriamycin-Induced Podocyte Injury

Background: Diabetic kidney disease (DKD) is a leading cause of end-stage kidney disease (ESKD) however, therapies have been limited due to disease heterogeneity. Using deep learning we recently identified a novel nonsynonymous disease-causing variant within the Rho GTPase regulatory gene ARHGEF18 associated with higher risk of ESKD. Overexpression of ARHGEF18 in human podocytes led to impairments in focal adhesion architecture, cytoskeletal dynamics, cellular motility, and RhoA/Rac1 activation. Here, we further validate the pathophysiology observed in vitro using a transgenic mouse model. Methods: Publicly available KPMP snRNA-seq data was analyzed using Seurat. We created a transgenic mouse line using CRISPR-Cas9 knock-in system to introduce a global G>A point mutation on the mouse Arhgef18 gene (A1268T), replicating the human rs117824875 variant. We performed retroorbital Adriamycin (ADR) injections in male mice aged 11-13 weeks at 15 mg/kg and urine was collected at baseline and after 1 week to measure the urinary albumin-creatinine ratio (UACR). Results: We previously showed that rs117824875 led to a pathological accumulation of ARHGEF18 in immortalized podocytes due to increased protein stability, suggesting that increased levels of ARHGEF18 are detrimental to podocytes. Podocyte snRNA-seq data from the KPMP database showed an increased expression of ARHGEF18 in DKD as well as CKD patients (Figure 1A). In our transgenic mouse model, we observed a significant increase in UACR in the A1268T mice compared to the WT at one-week after ADR injections (Figure 1B). PAS staining and transmission electron microscopy showed increased glomerular area and podocyte foot process effacement, respectively in the A1268T mutant mice compared to the WT (Figure 1C-D). Conclusion: Our data shows that A1268T transgenic mouse model showed increased susceptibility to ADR induced kidney injury. Targeted degradation strategies could be developed as a therapeutic option for management of DKD and CKD.