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Role of genetic modifiers in an orthologous rat model of ARPKD.

ABSTRACT: Human data and animal models of autosomal recessive polycystic kidney disease (ARPKD) suggest that genetic factors modulate the onset and severity of the disease. We report here for the first time that ARPKD susceptibility is attenuated by introgressing the mutated Pkhd1 disease allele from the polycystic kidney (PCK) rat onto the FHH (Fawn-Hooded Hypertensive) genetic background. Compared with PCK, the FHH.Pkhd1 strain had significantly decreased renal cyst formation that coincided with a threefold reduction in mean kidney weights. Further analysis revealed that the FHH. Pkhd1 is protected from increased blood pressure as well as elevated plasma creatinine and blood urea nitrogen levels. On the other hand, liver weight and biliary cystogenesis revealed no differences between PCK and FHH.Pkdh1, indicating that genes within the FHH genetic background prevent the development of renal, but not hepatic, manifestations of ARPKD. Microarray expression analysis of kidneys from 30-day-old PCK rats revealed increased expression of genes previously identified in PKD renal expression profiles, such as inflammatory response, extracellular matrix synthesis, and cell proliferation genes among others, whereas the FHH.Pkhd1 did not show activation of these common markers of disease. This newly developed strain can serve as a tool to map modifier genes for renal disease in ARPKD and provides further insight into disease variability and pathophysiology.

SUBMITTER: O'Meara CC

PROVIDER: S-EPMC3774585 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Role of genetic modifiers in an orthologous rat model of ARPKD.

O'Meara Caitlin C CC Hoffman Matthew M Sweeney William E WE Tsaih Shirng-Wern SW Xiao Bing B Jacob Howard J HJ Avner Ellis D ED Moreno Carol C

Physiological genomics 20120605 15

Human data and animal models of autosomal recessive polycystic kidney disease (ARPKD) suggest that genetic factors modulate the onset and severity of the disease. We report here for the first time that ARPKD susceptibility is attenuated by introgressing the mutated Pkhd1 disease allele from the polycystic kidney (PCK) rat onto the FHH (Fawn-Hooded Hypertensive) genetic background. Compared with PCK, the FHH.Pkhd1 strain had significantly decreased renal cyst formation that coincided with a three ...[more]

PMID: 22669842

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Project description:Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in the PKHD1 gene in both humans and the orthologous PCK rat model. Although ARPKD results solely from PKHD1 mutations, the disease onset and severity are highly variable, indicating that other unknown genetic risk factor(s) modify ARPKD-associated phenotypes. To identify genetic modifiers of ARPKD severity, we created two genetically distinct Pkhd1 congenic rat strains on the Fawn-Hooded Hypertensive (FHH) and the Dahl S (SS) rat backgrounds (denoted FHH.Pkhd1 and SS.Pkhd1, respectively) that harbor the PCK-derived Pkhd1 allele. The FHH.Pkhd1 and SS.Pkhd1 strains had lower renal cyst formation at 30 days-of-age (5±2% and 8±2% cystic, respectively; P<0.001) compared to the PCK kidneys (26±4% cystic), which coincided with significantly reduced kidney weights in the FHH.Pkhd1 and SS.Pkhd1. Liver cyst formation and liver weight did not differ between PCK, FHH.Pkhd1, and SS.Pkhd1. These data indicated that the PCK genome harbors genetic modifier(s) of ARPKD severity that are not present in the FHH and SS genomes. Using high density SNP array genotyping and microarray expression analysis, we identified 50 potential modifiers of ARPKD severity in the PCK rat. Of these candidates, a damaging nonsynonymous variant in Nphp4 stood out as the most likely candidate based on variant segregation, protein modeling, network analysis, and gene ontology. Nphp4 is widely associated with the autosomal recessive cilliopathy and nephronopthisis, but had not been previously implicated in the molecular or cellular pathophysiology of ARPKD. Collectively, these data provide genetic evidence of disease modifier(s) in the PCK model of ARPKD and prioritized multiple candidates, including NPHP4, for further investigation in ARPKD pathogenesis. In this study, we used microarray to analyze transcript expression in the kidneys of 30 day old SD (n=4), PCK (n=4), FHH (n=4), FHH.Pkhd1 (n=4), SS (n=4), and SS.Pkhd1 (n=4). Samples were pooled and the pooled samples were run in triplicate. The 30 day timepoint was chosen because the differences in renal cyst formation between PCK, FHH.Pkhd1, and SS.Pkhd1 were greatest at this timepoint. To account for genetic strain differences that do not contribute to ARPKD severity, gene expression of each cystic rat strain was compared to its parental strain.

Project description:Radiation therapy is used in ~50% of cancer patients to reduce the risk of recurrence and in some cases improve survival. Despite these benefits, doses can be limited by toxicity in multiple organs, including the heart. The underlying causes and biomarkers of radiation-induced cardiotoxicity are currently unknown, prompting the need for experimental models with inherent differences in sensitivity and resistance to the development of radiation-induced cardiotoxicity. We have identified the parental SS (Dahl salt-sensitive/Mcwi) rat strain to be a highly-sensitized model of radiation-induced cardiotoxicity. In comparison, substitution of rat chromosome 3 from the resistant BN (Brown Norway) rat strain onto the SS background (SS-3BN consomic) significantly attenuated radiation-induced cardiotoxicity. SS-3BN rats had less radiation-induced cardiotoxicity than SS rats, as measured by survival, pleural and pericardial effusions, echocardiogram parameters, and histological damage. Mast cells, previously shown to have predominantly protective roles in radiation-induced cardiotoxicity, were increased in the more resistant SS-3BN hearts postradiation. RNA sequencing from SS and SS-3BN hearts at 1 wk postradiation revealed 5,098 differentially expressed candidate genes across the transcriptome and 350 differentially expressed genes on rat chromosome 3, which coincided with enrichment of multiple pathways, including mitochondrial dysfunction, sirtuin signaling, and ubiquitination. Upstream regulators of enriched pathways included the oxidative stress modulating transcription factor, Nrf2, which is located on rat chromosome 3. Nrf2 target genes were also differentially expressed in the SS vs. SS-3BN consomic hearts postradiation. Collectively, these data confirm the existence of heritable modifiers in radiation-induced cardiotoxicity and provide multiple biomarkers, pathways, and candidate genes for future analyses. NEW & NOTEWORTHY This novel study reveals that heritable genetic factors have the potential to modify normal tissue sensitivity to radiation. Gene variant(s) on rat chromosome 3 can contribute to enhanced cardiotoxicity displayed in the SS rats vs. the BN and SS-3BN consomic rats. Identifying genes that lead to understanding the mechanisms of radiation-induced cardiotoxicity represents a novel method to personalize radiation treatment, as well as predict the development of radiation-induced cardiotoxicity.

Project description:Human autosomal recessive polycystic kidney disease (ARPKD) produces kidneys which are massively enlarged due to multiple cysts, hypertension, and congenital hepatic fibrosis characterized by dilated bile ducts and portal hypertension. The PCK rat is an orthologous model of human ARPKD with numerous fluid-filled cysts caused by stimulated cellular proliferation in the renal tubules and hepatic bile duct epithelia, with interstitial fibrosis developed in the liver. We previously reported that a peroxisome proliferator activated receptor (PPAR)-? full agonist ameliorated kidney and liver disease in PCK rats. Telmisartan is an angiotensin receptor blocker (ARB) used widely as an antihypertensive drug and shows partial PPAR-? agonist activity. It also has nephroprotective activity in diabetes and renal injury and prevents the effects of drug-induced hepatotoxicity and hepatic fibrosis. In the present study, we determined whether telmisartan ameliorates progression of polycystic kidney and fibrocystic liver disease in PCK rats. Five male and 5 female PCK and normal control (+/+) rats were orally administered 3 mg/kg telmisartan or vehicle every day from 4 to 20 weeks of age. Treatment with telmisartan decreased blood pressure in both PCK and +/+ rats. Blood levels of aspartate amino transferase, alanine amino transferase and urea nitrogen were unaffected by telmisartan treatment. There was no effect on kidney disease progression, but liver weight relative to body weight, liver cystic area, hepatic fibrosis index, expression levels of Ki67 and TGF-?, and the number of Ki67- and TGF-?-positive interstitial cells in the liver were significantly decreased in telmisartan-treated PCK rats. Therefore, telmisartan ameliorates congenital hepatic fibrosis in ARPKD, possibly through the inhibition of signaling cascades responsible for cellular proliferation and interstitial fibrosis in PCK rats. The present results support the potential therapeutic use of ARBs for the treatment of fibrocystic liver disease in ARPKD patients.

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Role of genetic modifiers in an orthologous rat model of ARPKD.

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Role of genetic modifiers in an orthologous rat model of ARPKD.

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