EXOCYST INACTIVATION IN UROTHELIAL CELLS LEADS TO FN14 UPREGULATION AND CELL DEATH IN A MOUSE MODEL OF PRENATAL URETER OBSTRUCTIONS
Date
2022
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Abstract
Congenital obstructive nephropathy (CON) is the leading cause of chronic kidney disease(CKD) and end-stage renal disease in children. This disorder is usually detected as
hydronephrosis by prenatal ultrasounds. The most common cause of CON is obstruction at the
ureteropelvic junction (UPJ), where the renal pelvis transitions to the upper ureter. EXOC5 is the
central stabilizing subunit of the exocyst, an octameric protein complex that regulates exocytosis
of secretory vesicles to the plasma membrane. The Fogelgren laboratory previously generated
a novel EXOC5-conditional knockout (EXOC5-CKO) mouse using the Cre/loxP technology to
inactivate EXOC5 in ureteric bud-derived epithelial cells. The EXOC5-CKO mice had severe
bilateral UPJ obstructions, hydronephrosis, and succumbed to neonatal death. In these mice,
UPJ obstruction was preceded by failure of urothelial stratification and cell death at E17.5,
followed by a fibroproliferative response by the underlying mesenchyme. By transcriptomic
microarray, we identified the Fn14 gene as being robustly upregulated in the EXOC5-CKO
embryonic ureter at E16.5. Fn14 is a transmembrane tumor necrosis factor (TNF) receptor
superfamily member with a single known ligand, TWEAK, which can activate different pathways
depending on cell context, including programmed cell death. We demonstrated that ureter
obstructions can be rescued in EXOC5-CKO mice by administering a pan-caspase inhibitor zVAD-fmk at E16.5. We also found inhibited urothelial stratification alone did not drive cell death
during ureter development. Instead, exocyst-perturbed urothelial cells in vivo and in vitro have
disrupted autophagy which activated NF-κB signaling and cell death. To study the role of Fn14
in renal and urological diseases, we generated a global Fn14-knockout (KO) mouse using
CRISPR-Cas9 gene editing. Fn14-KO mice had ameliorated renal pathology in a cisplatininduced CKD model. Our findings support the hypothesis that urothelial cell death is a critical
event leading to UPJO pathogenesis and that Fn14 signaling contributes to cell death in renal
and urological pathologies.
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Cellular biology, Developmental biology, Molecular biology, exocyst, Fn14, ureter, urothelium
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135 pages
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