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Kidney Week

Abstract: SA-PO783

Differential Regulation of MYC Expression by PKHD1/Pkhd1 in Human and Mouse Kidneys: Phenotypic Implications for Recessive Polycystic Kidney Disease

Session Information

Category: Genetic Diseases of the Kidneys

  • 1201 Genetic Diseases of the Kidneys: Cystic

Authors

  • Harafuji, Naoe, Children's National Hospital, Washington, District of Columbia, United States
  • Yang, Chaozhe, Children's National Hospital, Washington, District of Columbia, United States
  • Caldovic, Ljubica, Children's National Hospital, Washington, District of Columbia, United States
  • Thiruvengadam, Girija, Children's National Hospital, Washington, District of Columbia, United States
  • Gordish-Dressman, Heather, Children's National Hospital, Washington, District of Columbia, United States
  • Thompson, Robert Griffin, The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Bell, Phillip Darwin, The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Rosenberg, Avi Z., Johns Hopkins University, Baltimore, Maryland, United States
  • Bebok, Zsuzsanna M., The University of Alabama at Birmingham Heersink School of Medicine, Birmingham, Alabama, United States
  • Guay-Woodford, Lisa M., Children's National Hospital, Washington, District of Columbia, United States
Background

ARPKD (MIM 263200) is caused by mutations in PKHD1, which encodes FPC. We previously showed that: 1) MYC/Myc is overexpressed in human ARPKD and mouse Cys1cpk/cpk (cpk) kidneys, but not in several Pkhd1 mutants; 2) the FPC C-terminal domain (FPC-CTD) upregulates, while cystin downregulates, the MYC/Myc P1 promoter; 3) mouse and human FPC-CTD differ in subcellular localization (Yang, 2021). Here we present new data from informatic analyses and FPC-CTD overexpression in mouse and human renal epithelia.

Methods

Evo-devo mammalian organ database was queried for developmental expression patterns of cystogenes. ClustalOmega and WebLOGO3 were used to analyze the vertebrate FPC conservation. Immunoblotting and qRT-PCR were used to quantify proteins and mRNA.

Results

PKHD1 mRNA expression peaked before CYS1 mRNA in fetal human kidney; in contrast, Cys1 mRNA expression peaked before Pkhd1 mRNA in the developing mouse kidney. Developmental expression patterns of MYC/Myc mRNA were similar in human and mouse kidneys, peaking in early fetal development and gradually decreased thereafter. Sequence alignment of 102 vertebrate FPCs revealed higher conservation score of the extracellular (1.9) than the intracellular cytoplasmic (1.5) domain. Cys1 mRNA and cystin protein were downregulated by 80% and 70%, respectively, in mIMCD-3 cells stably overexpressing mFPC-CTD. Stable hFPC-CTD overexpression in TERT immortalized human renal epithelial (hTERT-HRE) cells was unsuccessful, suggesting cytotoxicity. Transient hFPC-CTD overexpression in hTERT-HRE cells did not alter cystin expression.

Conclusion

Higher expression of Cys1 vs. Pkhd1 in the developing mouse kidney and the suppression of Myc expression by cystin could contribute to the low renal MYC expression in Pkhd1 mutant mice. In contrast, the relatively lower levels of CYS1 vs. PKHD1 in developing human kidney may preclude a cystin-driven protective effect for renal cystogenesis. In addition, the low cross-species conservation of the FPC-CTD suggests functional differences that may contribute to differing susceptibilities to PKHD1/Pkhd1 mutations and the disparate renal phenotypes.

Funding

  • NIDDK Support