Defining immunomodulatory mechanisms in autosomal recessive polycystic kidney disease - PROJECT SUMMARY/ABSTRACT Autosomal recessive polycystic kidney disease (ARPKD) is a severe fibrocystic disorder of the kidney and liver. In the United States, ~120 neonates with ARPKD survive each year, and most progress to kidney failure in early childhood. Nearly all cases result from biallelic loss-of-function variants in PKHD1, which encodes fibrocystin (FPC), a transmembrane protein essential for tubular epithelial differentiation. Despite its discovery over two decades ago, FPC biology is poorly understood, and no targeted therapies exist. A major barrier is the lack of an animal model that develops kidney cysts: all Pkhd1 single knockout mice reproduce liver lesions but not kidney disease. Guided by preliminary experimental data in transgenic zebrafish, the candidate found that deleting both Pkhd1 and its ancestral paralog Pkhd1L1 generates a novel double knockout (DKO) mouse that uniquely recapitulates human ARPKD kidney pathology, including distal tubular dilatation, immune infiltration, and fibrosis. In mice, Pkhd1 is strongly expressed in collecting ducts, while Pkhd1L1 is minimal in epithelia but enriched in immune cells, particularly T lymphocytes. These complementary patterns support a model in which Pkhd1 and Pkhd1L1 cooperate to integrate epithelial differentiation with immune signaling. Using the DKO model, human ARPKD tissues, and datasets, the candidate will test the hypothesis that disruption of epithelial– immune networks drives ARPKD pathogenesis and progression. Aim 1 will define the timing of cyst initiation, nephron segment of origin, and immune infiltration in DKO kidneys, validated in human kidney tissue. Aim 2 will test whether immune-mediated transcriptomic alterations drive disease progression using single-cell RNA sequencing of DKO kidneys, integrated with human ARPKD kidney datasets. Aim 3 will determine whether Pkhd1L1 acts within nephron epithelia or T cells by lineage-specific deletion on a Pkhd1-deficient background, compared to the DKO. The candidate is a Pediatric Nephrology Attending Physician at Children’s National Hospital and an Assistant Professor at George Washington University, with >75% protected research time, strong institutional support, and a structured career development plan. Training will focus on mouse genetics, single-cell and spatial transcriptomics, and immune–epithelial biology, under a multidisciplinary mentorship team. This proposal is significant because it reframes ARPKD from an epithelial-only disorder to one in which epithelial–immune interactions are central to disease progression. It is innovative in employing a novel DKO model, integrating developmental phenotyping with single-cell transcriptomics, and testing cell lineage- specific gene requirements. The expected impact is to establish the first mechanistic framework for immune involvement in ARPKD, lay the foundation for immune-bases therapies, and prepare the candidate for independence as a physician–scientist bridging PKD biology, developmental biology, and immunology.
