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Mapping genetic modifiers of radiation-induced cardiotoxicity to rat chromosome 3.

ABSTRACT: 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-3^BN consomic) significantly attenuated radiation-induced cardiotoxicity. SS-3^BN 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-3^BN hearts postradiation. RNA sequencing from SS and SS-3^BN 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-3^BN 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-3^BN 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.

SUBMITTER: Schlaak RA

PROVIDER: S-EPMC6620678 | biostudies-literature |

REPOSITORIES: biostudies-literature

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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.

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Mapping genetic modifiers of radiation-induced cardiotoxicity to rat chromosome 3.

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