Kidney Week

Abstract: FR-PO0171

Proximal Tubule Pax8 Inactivation Protects Against Ischemic Kidney Injury

Session Information

• AKI: Mechanisms - 2
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Beamish, Jeffrey A., University of Michigan, Ann Arbor, Michigan, United States

Jeffrey A. Beamish, MD, PhD

• Telang, Asha Claire, University of Michigan, Ann Arbor, Michigan, United States

Asha Claire Telang

• Ference-Salo, Jenna T., University of Michigan, Ann Arbor, Michigan, United States

Jenna T. Ference-Salo

• Dressler, Greg R., University of Michigan, Ann Arbor, Michigan, United States

Greg R. Dressler, PhD

• Wan, Ma, National Institute of Environmental Health Sciences, Durham, North Carolina, United States

Ma Wan, PhD

• Delker, Don, National Institute of Environmental Health Sciences, Durham, North Carolina, United States

Don Delker, PhD

• Watts, Jason A., National Institute of Environmental Health Sciences, Durham, North Carolina, United States

Jason A. Watts, MD, PhD

Background

The molecular mechanisms that drive cell fate decisions after acute kidney injury (AKI) remain poorly understood. Pax2 and Pax8 are homologous transcription factors upregulated in the proximal tubule during AKI recovery and may help determine cell fate. However, the individual contributions of Pax2 and Pax8 are poorly defined. This project aimed to dissect the specific roles of Pax2 and Pax8 in AKI pathogenesis and recovery.

Methods

Mice with conditional Pax2 or Pax8 were crossed with the phosphoenolpyruvate carboxykinase Cre driver to generate proximal-tubule-specific Pax2 or Pax8 mutants and wild-type (WT) controls. Kidneys from uninjured mice were subjected to single-nucleus RNA sequencing (snRNA-seq). Mice were also subjected to unilateral ischemia-reperfusion injury (IRI) with contralateral nephrectomy. Response to injury was assessed by serum BUN and histologic injury. Cleavage under targets and tagmentation (CUT&Tag) was used to determine chromatin localization of Pax8, RNA Polymerase II, and various histone marks (H3K4me3, H3K27me3, H3K27ac) 6 h following IRI.

Results

Analysis of snRNA-seq data revealed that Pax8 mutants, but not Pax2 mutants, developed a population of proximal tubule cells with gene expression changes that mimic preconditioning (Gene Set Enrichment Analysis, P_adj < 3x10^-6). Histologically, these mutant cells lacked Pax8 protein and were localized to the proximal tubule S3 segment. Pax8 mutant mice were protected from IRI relative to WT controls (48 h BUN: 31 vs 79 mg/dL, P = 1x10^-3), but Pax2 mutants were not (62 vs 79 mg/dL, P = 0.33). Histologic injury was less severe in Pax8 mutants. CUT&Tag in WT mice 6 h after IRI revealed dynamic Pax8 chromatin occupancy following injury. Loss of Pax8 occupancy at distal regulatory elements was linked to decreased H3K27ac, a mark of active enhancers. Expression of the set of genes near Pax8-depleted loci was reduced following injury compared with genes near unchanged Pax8-bound loci (1.3-fold decrease, P = 3x10^-10). This set of Pax8 gene targets was enriched with genes altered in the resilient Pax8 mutant mice (P_adj < 8x10^-3).

Conclusion

Inactivation of Pax8, but not Pax2, drives proximal tubule resilience to ischemic kidney injury. Dynamic changes in Pax8 chromatin occupancy early after injury may mediate adaptive responses to AKI.

Funding

• NIDDK Support

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025216y57s0