Characterization of biological pathways associated with a 1.37 Mbp genomic region protective of hypertension in Dahl S rats

Abstract

The goal of the present study was to narrow a region of chromosome 13 to only several genes and then apply unbiased statistical approaches to identify molecular networks and biological pathways relevant to blood-pressure salt sensitivity in Dahl salt-sensitive (SS) rats. The analysis of 13 overlapping subcongenic strains identified a 1.37 Mbp region on chromosome 13 that influenced the mean arterial blood pressure by at least 25 mmHg in SS rats fed a high-salt diet. DNA sequencing and analysis filled genomic gaps and provided identification of five genes in this region, Rfwd2, Fam5b, Astn1, Pappa2, and Tnr. A cross-platform normalization of transcriptome data sets obtained from our previously published Affymetrix GeneChip dataset and newly acquired RNA-seq data from renal outer medullary tissue provided 90 observations for each gene. Two Bayesian methods were used to analyze the data: 1) a linear model analysis to assess 243 biological pathways for their likelihood to discriminate blood pressure levels across experimental groups and 2) a Bayesian graphical modeling of pathways to discover genes with potential relationships to the candidate genes in this region. As none of these five genes are known to be involved in hypertension, this unbiased approach has provided useful clues to be experimentally explored. Of these five genes, Rfwd2, the gene most strongly expressed in the renal outer medulla, was notably associated with pathways that can affect blood pressure via renal transcellular Na(+) and K(+) electrochemical gradients and tubular Na(+) transport, mitochondrial TCA cycle and cell energetics, and circadian rhythms.

Combined linkage and association analysis identifies rare and low frequency variants for blood pressure at 1q31

“…These three genes harbor four non-synonymous variants and demonstrate a consistent protective effect on PP in the FBPP. ASTN1 and its two upstream genes RFWD2 and PAPPA2 have been shown to be strongly expressed in the renal outer medulla and show protective effects on HTN in Dahl S rats [43,44], consistent with what we observed with humans in this study. This effect may be mediated through pathways that affect BP via renal transcellular Na and K electrochemical gradients and tubular Na transport, mitochondrial TCA cycle and cell energetics, and circadian rhythms [43].…”

“…ASTN1 and its two upstream genes RFWD2 and PAPPA2 have been shown to be strongly expressed in the renal outer medulla and show protective effects on HTN in Dahl S rats [43,44], consistent with what we observed with humans in this study. This effect may be mediated through pathways that affect BP via renal transcellular Na and K electrochemical gradients and tubular Na transport, mitochondrial TCA cycle and cell energetics, and circadian rhythms [43]. For humans, we used the GTEx database [34] to search for the expression domains of the four genes: ASTN1 is mainly expressed in the brain; and, SEC16B is highly expressed in the kidney and liver ( Supplementary Fig.…”

Report of the National Heart, Lung, and Blood Institute Working Group on Sex Differences Research in Cardiovascular Disease

“…33 More complex statistical analyses to evaluate the impact of expression changes on molecular networks and alteration of disease phenotype are also warranted. 34 …”

Whole Transcriptome Profiling: An RNA‐Seq Primer and Implications for Pharmacogenomics Research

“…Additionally, the application of RNA‐Seq in HTN mouse models for transcriptome profiling revealed novel potential mechanisms involved in the pathophysiology of HTN and its complications. Cowley et al . identified genes and biological pathways associated with a protective effect on Dahl salt‐sensitive rats.…”

“…Additionally, the application of RNA-Seq in HTN mouse models for transcriptome profiling revealed novel potential mechanisms involved in the pathophysiology of HTN and its complications. Cowley et al 63 identified genes and biological pathways associated with a protective effect on Dahl saltsensitive rats. Tain et al 64 identified genes of importance for programmed HTN, through transcriptome characterization of the offspring of pregnant mouse models under suboptimal conditions (high fructose and dexamethasone administration).…”