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Heterozygous Pkhd1C642* mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

ABSTRACT: Heterozygosity for human polycystic kidney and hepatic disease 1 ( PKHD1) mutations was recently associated with cystic liver disease and radiographic findings resembling medullary sponge kidney (MSK). However, the relevance of these associations has been tempered by a lack of cystic liver or renal disease in heterozygous mice carrying Pkhd1 gene trap or exon deletions. To determine whether heterozygosity for a smaller Pkhd1 defect can trigger cystic renal disease in mice, we generated and characterized mice with the predicted truncating Pkhd1C642* mutation in a region corresponding to the middle of exon 20 cluster of five truncating human mutations (between PKHD1G617fs and PKHD1G644*). Mouse heterozygotes or homozygotes for the Pkhd1C642* mutation did not have noticeable liver or renal abnormalities on magnetic resonance images during their first weeks of life. However, when aged to ~1.5 yr, the Pkhd1C642* heterozygotes developed prominent cystic liver changes; tissue analyses revealed biliary cysts and increased number of bile ducts without signs of congenital hepatic fibrosis-like portal field inflammation and fibrosis that was seen in Pkhd1C642* homozygotes. Interestingly, aged female Pkhd1C642* heterozygotes, as well as homozygotes, developed radiographic changes resembling MSK. However, these changes correspond to proximal tubule ectasia, not an MSK-associated collecting duct ectasia. In summary, by demonstrating that cystic liver and kidney abnormalities are triggered by heterozygosity for the Pkhd1C642* mutation, we provide important validation for relevant human association studies. Together, these investigations indicate that PKHD1 mutation heterozygosity (predicted frequency 1 in 70 individuals) is an important underlying cause of cystic liver disorders and MSK-like manifestations in a human population.

SUBMITTER: Shan D

PROVIDER: S-EPMC6442377 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Heterozygous Pkhd1<sup>C642*</sup> mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

Shan Dan D Rezonzew Gabriel G Mullen Sean S Roye Ronald R Zhou Juling J Chumley Phillip P Revell Dustin Z DZ Challa Anil A Kim Harrison H Lockhart Mark E ME Schoeb Trenton R TR Croyle Mandy J MJ Kesterson Robert A RA Yoder Bradley K BK Guay-Woodford Lisa M LM Mrug Michal M

American journal of physiology. Renal physiology 20190102 3

Heterozygosity for human polycystic kidney and hepatic disease 1 ( PKHD1) mutations was recently associated with cystic liver disease and radiographic findings resembling medullary sponge kidney (MSK). However, the relevance of these associations has been tempered by a lack of cystic liver or renal disease in heterozygous mice carrying Pkhd1 gene trap or exon deletions. To determine whether heterozygosity for a smaller Pkhd1 defect can trigger cystic renal disease in mice, we generated and chara ...[more]

PMID: 30600684

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Project description:Autosomal recessive polycystic kidney disease (ARPKD) results from mutations in the human PKHD1 gene. Both this gene, and its mouse ortholog, Pkhd1, are primarily expressed in renal and biliary ductal structures. The mouse protein product, fibrocystin/polyductin complex (FPC), is a 445-kDa protein encoded by a 67-exon transcript that spans >500 kb of genomic DNA. In the current study, we observed multiple alternatively spliced Pkhd1 transcripts that varied in size and exon composition in embryonic mouse kidney, liver, and placenta samples, as well as among adult mouse pancreas, brain, heart, lung, testes, liver, and kidney. Using reverse transcription PCR and RNASeq, we identified 22 novel Pkhd1 kidney transcripts with unique exon junctions. Various mechanisms of alternative splicing were observed, including exon skipping, use of alternate acceptor/donor splice sites, and inclusion of novel exons. Bioinformatic analyses identified, and exon-trapping minigene experiments validated, consensus binding sites for serine/arginine-rich proteins that modulate alternative splicing. Using site-directed mutagenesis, we examined the functional importance of selected splice enhancers. In addition, we demonstrated that many of the novel transcripts were polysome bound, thus likely translated. Finally, we determined that the human PKHD1 R760H missense variant alters a splice enhancer motif that disrupts exon splicing in vitro and is predicted to truncate the protein. Taken together, these data provide evidence of the complex transcriptional regulation of Pkhd1/PKHD1 and identified motifs that regulate its splicing. Our studies indicate that Pkhd1/PKHD1 transcription is modulated, in part by intragenic factors, suggesting that aberrant PKHD1 splicing represents an unappreciated pathogenic mechanism in ARPKD. Key messages: Multiple mRNA transcripts are generated for Pkhd1 in renal tissues Pkhd1 transcription is modulated by standard splice elements and effectors Mutations in splice motifs may alter splicing to generate nonfunctional peptides.

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Heterozygous Pkhd1C642* mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

Publications

Heterozygous Pkhd1<sup>C642*</sup> mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

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Heterozygous Pkhd1C642* mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

Publications

Heterozygous Pkhd1&lt;sup&gt;C642*&lt;/sup&gt; mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Heterozygous Pkhd1<sup>C642*</sup> mice develop cystic liver disease and proximal tubule ectasia that mimics radiographic signs of medullary sponge kidney.