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Kidney Week

Abstract: FR-PO987

Mice Lacking Pkhd1 Exons 3-67 Develop Biliary but Not Renal Abnormalities

Session Information

Category: Genetic Diseases of the Kidney

  • 1001 Genetic Diseases of the Kidney: Cystic

Authors

  • Menezes, Luis F., NIDDK, National Institute of Health, Bethesda, Maryland, United States
  • Zhou, Fang, NIDDK, National Institute of Health, Bethesda, Maryland, United States
  • Kurashige, Mahiro, NIDDK, National Institute of Health, Bethesda, Maryland, United States
  • Outeda, Patricia, University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Watnick, Terry J., University of Maryland School of Medicine, Baltimore, Maryland, United States
  • Germino, Gregory G., NIDDK, National Institute of Health, Bethesda, Maryland, United States
Background

Autosomal recessive polycystic kidney disease (ARPKD; OMIM 263200) is caused by mutations in PKHD1 and is characterized by cysts/dilations in kidney collecting ducts, liver biliary cysts and portal fibrosis. While orthologous mouse models of ARPKD reproduce the liver phenotype, the kidney disease is mild, of low penetrance and strain-dependent. It was suggested that Pkhd1 alternative splicing could compensate for the lack of full-length Pkhd1. Here we tested if genomic deletion of most of the Pkhd1 locus could exacerbate the renal pathology.

Methods

We had previously generated two Pkhd1 mouse models: Pkhd1flox3-4, with loxP sites flanking exons 3-4; and Pkhd1flox67HA , with loxP sites flanking the last exon (67). We bred mice carrying Pkhd1del3-4/del67 alleles to Ddx4-Cre mice, a transgenic line with cre activity in embryonic germ cells of males and females. Starting with 6 independent Pkhd1del3-4/del67 vs. Ddx4-Cre crosses, we obtained 9 heterozygous Pkhd1del3-67 mutants, and started 4 independent founder lines, which were bred separately to homozygosis, generating a total of 28 Pkhd1del3-67/del3-67 (4 to 12 per founder) with overlapping phenotypes. Subsequent generations were allowed to interbreed across founder-lines. A total of 84 Pkhd1del3-67/del3-67 were harvested between 30 and 440 days at approximately 10-day intervals, and two animals were allowed to age to 620 days. Animal body, liver and kidney weights were measured; kidneys and livers were visually inspected. In a subset of samples we measured eye weight and embedded kidney, liver and eyes for histological analysis.

Results

None of the animals had abnormal kidney size or macroscopic appearance, and histologic analysis confirmed absence of dilated tubules. In contrast, all analyzed animals had some degree of liver pathology, characterized by biliary cysts, duct proliferation and variable degrees of periportal fibrosis and cholangitis. Large coledochal and pancreatic cysts, and ascitis were occasionally observed. Additional phenotypes included ophthalmic pathology.

Conclusion

Compensation by alternative splice variants cannot explain the mild kidney phenotype in orthologous ARPKD mouse models. Further studies are required to determine if Pkhd1 or other sequences in the deleted genomic region are responsible for the additional unexpected phenotypes.

Funding

  • NIDDK Support