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Abstract: SA-PO784

Spontaneously Occurring Pkhd1 Mutation (Pkhd1cyli/cyli) with Altered Renal mRNA Processing and Hormonally Sensitive Hepato-Biliary 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
  • Yu, Weiying, Children’s National Hospital, Washington, District of Columbia, United States
  • Gordish-Dressman, Heather, Children’s National Hospital, Washington, District of Columbia, 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 a hereditary hepato-renal fibrocystic disorder that causes early childhood morbidity and mortality. Mutations in the PKHD1 gene, which encodes fibrocystin/polyductin complex (FPC), causes all typical forms of ARPKD. Several mouse strains carrying diverse, genetically-engineered disruptions in the orthologous Pkhd1 gene do not exhibit the classic ARPKD renal phenotype. Here we present the phenotypic and molecular characterization of new mouse model with a spontaneous recessive Pkhd1 mutation which causes isolated cystic liver (cyli) disease.

Methods

A backcross mating scheme and MIT microsatellite makers were used map the cyli mutation. DNA sequencing was used to identify the cyli mutation. Kidneys and livers were harvested for HE histology. Pkhd1 mRNA and FPC protein expression were analyzed by RT-PCR, qRT-PCR, Oxford Nanopore sequencing, and immunoblotting.

Results

We mapped the cyli mutation to Chromosome 1 and identified an insertion/deletion mutation within Pkhd1 exon 48, which was predicted to result in a premature termination codon (UGA). Pkhd1cyli/cyli (cyli) mice exhibited progressive hepato-biliary pathology and longitudinal analysis revealed that pregnancy exacerbated liver disease severity in female mutants. Renal cystic disease was not observed in mutants aged to 6-months. Abundance of Pkhd1 mRNA was lower in cyli than in wild-type kidneys. Several alternatively spliced Pkhd1 transcripts, all containing exon 48, were detected in cyli kidneys. We identified an AAAAAT motif in exon 48 immediately upstream of the cyli mutation that could enable ribosomal frameshifting and nonsense mediated decay (NMD) escape.

Conclusion

The cyli mutation caused cystic liver similar to the hepato-biliary disease in human ARPKD. The low abundance of Pkhd1 transcripts in cyli kidneys suggests an escape from NMD. Ribosomal frameshifting could allow production of sufficient amounts of FPC for renoprotection in the cyli mouse. Further analysis will be required to assess differences in ribosomal frameshifting activity in renal epithelia from the cyli mouse and humans with truncating PKHD1 exon 48 mutations.

Funding

  • NIDDK Support