Epistatic Genetic Determinants of Blood Pressure and Mortality in a Salt-Sensitive Hypertension Model

Abstract-Using congenic strains of the Dahl salt-sensitive (S) rat introgressed with genomic segments from the normotensive Lewis rat, a blood pressure quantitative trait locus was previously mapped within 104 kb on chromosome 10. The goal of the current study was to conduct extensive phenotypic studies and to further fine-map this locus. At 14 weeks of age, the blood pressure of the congenic rats fed a low-salt diet was significantly higher by 47 mm Hg (PϽ0.001) compared with that of the S rat. A time-course study showed that the blood pressure effect was significant from very young ages of 50 to 52 days (13 mm Hg; PϽ0.01). The congenic strain implanted with electrocardiography transmitters demonstrated shorter-QT intervals and increased heart rate compared with S rats (PϽ0.01). The average survival of the congenic strain was shorter (134 days) compared with the S rat (175 days; PϽ0.0007). The critical region was narrowed to Ͻ42.5 kb containing 171 variants and a single gene, rififylin. Both the mRNA and protein levels of rififylin were significantly higher in the hearts of the congenic strain. Overexpression of rififylin is known to delay endocytic recycling. Endocytic recycling of fluorescently labeled holotransferrin from cardiomyocytes of the congenic strain was slower than that of S rats (PϽ0.01). Frequency of cardiomyocyte beats in the congenic strain (62Ϯ9 bpm) was significantly higher than that of the S rat (24Ϯ6 bpm; PϽ0.001). Taken together, our study provides evidence to suggest that early perturbations in endocytic recycling caused by the overexpression of Rffl is a novel physiological mechanism potentially underlying the development of hypertension.

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“…Left ventricular (LV) function of S and congenic rats were evaluated by echocardiography as described previously [4, 5]. …”

Section: Methodsmentioning

confidence: 99%

Augmented Rififylin Is a Risk Factor Linked to Aberrant Cardiomyocyte Function, Short-QT Interval and Hypertension

et al. 2011

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“…Evidence for epistasis has previously been demonstrated for BP QTL located on different genetic regions of the same chromosome 8,32 and among loci located on different chromosomes. 4,6,7,[9][10][11] The identification of such interactions can be used to infer genetic networks affecting complex traits and greatly assist in the detection of the underlying biological mechanisms. 33,34 The combined effects of introgressing RNO2 and RNO3 genetic intervals essentially normalizes SBP, DBP, and PP parameters in the bicongenic strain.…”

Section: Discussionmentioning

confidence: 99%

“…In particular, there is growing evidence for epistasis among BP quantitative trait loci (QTL) in inbred rat models of hypertension. [4][5][6][7][8][9][10][11] We have previously identified BP QTL on rat chromosomes (RNO) 2 and RNO3 in a linkage analysis of an F2 cross between stroke-prone spontaneously hypertensive (SHRSP) and Wistar Kyoto (WKY) rats. 12 We subsequently confirmed the RNO2 loci with the production of congenic strains and identified candidate genes for baseline BP and response to salt loading.…”

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confidence: 99%

Interaction Between Chromosome 2 and 3 Regulates Pulse Pressure in the Stroke-Prone Spontaneously Hypertensive Rat

Koh-Tan

McBride²,

McClure³

et al. 2013

Hypertension

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H uman essential hypertension is a complex, multifactorial, quantitative trait under polygenic control, with inherited factors contributing ≤30% of the variation in blood pressure (BP). 1 The search for the specific genetic variations contributing to this heritability remains challenging. Recent genome-wide association studies collectively explain only a very small proportion of the total variation in systolic BP (SBP) or diastolic BP (DBP; ≈2.2%), 2,3 which suggests the existence of many more undiscovered BP-related variants.Genetic detection of complex polygenic diseases is complicated by potential gene-gene, gene-environment interactions, and nonsequence epigenetic modifications. In particular, there is growing evidence for epistasis among BP quantitative trait loci (QTL) in inbred rat models of hypertension. 4-11We have previously identified BP QTL on rat chromosomes (RNO) 2 and RNO3 in a linkage analysis of an F2 cross between stroke-prone spontaneously hypertensive (SHRSP) and Wistar Kyoto (WKY) rats. 12 We subsequently confirmed the RNO2 loci with the production of congenic strains and identified candidate genes for baseline BP and response to salt loading. [13][14][15] The aims of this study were to confirm the RNO3 QTL and to investigate interaction between the loci on RNO2 and RNO3 through the generation and phenotypic assessment of single and bicongenic strains. Methods Animal StrainsInbred colonies of SHRSP and WKY have been developed and maintained at the University of Glasgow since 1991, as described previously.12 All animals were housed under controlled environmental conditions, fed standard rat chow (rat and mouse no No. 1 maintenance diet, Special Diet Services) and water provided ad libitum. At 18 weeks of age, rats were given a salt challenge (1% NaCl in drinking water) for 3 weeks. All animal procedures performed were approved Abstract-In an F2 cross between stroke-prone spontaneously hypertensive (SHRSP) and Wistar Kyoto (WKY) rats, we previously identified blood pressure quantitative trait loci (QTL) on rat chromosome (RNO) 2 and a pulse pressure QTL on RNO3. The aims of this study were to confirm the QTL on RNO3 and to investigate interaction between RNO2 and RNO3 loci through the generation and phenotypic assessment of single RNO3 congenic (SP.WKY Gla 3a) and bicongenic (SP.WKY Gla 2a/3a) strains. Hemodynamic profiling, vascular function, and renal histology were examined in these newly generated strains along with the previously reported RNO2 congenic strain (SP.WKY Gla 2a). Our results demonstrate significant equivalent reduction in systolic, diastolic, and pulse pressure phenotypes in SP.WKY Gla 3a and SP.WKY Gla 2a rats, whereas greater reductions were observed with the SP.WKY Gla 2a/3a bicongenic strain achieving blood pressure levels similar to normotensive WKY rats. Epistasis was observed between pulse pressure QTL on RNO2 and 3 at baseline and during 1% salt challenge. Vascular function and renal pathology studies indicate that QTL on RNO3 are responsible for salt-induced kidney p...

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“…Left ventricular function and geometry of Dahl S rats, S.LEW congenic rats and 19bp targeted knock-in rescue model were evaluated by echocardiography, as described previously [ 45 , 46 ]. The specific details on the age of the rat and type of diet used in each study are provided in S1 and S2 Tables.…”

Section: Methodsmentioning

confidence: 99%

Positional cloning of quantitative trait nucleotides for blood pressure and cardiac QT-interval by targeted CRISPR/Cas9 editing of a novel long non-coding RNA

et al. 2017

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Multiple GWAS studies have reported strong association of cardiac QT-interval to a region on HSA17. Interestingly, a rat locus homologous to this region is also linked to QT-intervals. The high resolution positional mapping study located the rat QT-interval locus to a <42.5kb region on RNO10. This region contained no variants in protein-coding sequences, but a prominent contiguous 19bp indel polymorphism was noted within a novel predicted long non-coding RNA (lncRNA), which we named as Rffl-lnc1. To assess the candidacy of this novel lncRNA on QT-interval, targeted CRISPR/Cas9 based genome-engineering approaches were applied on the rat strains used to map this locus. Targeted disruption of the rat Rffl-lnc1 locus caused aberrant, short QT-intervals and elevated blood pressure. Further, to specifically examine the significance of the 19bp polymorphism within the Rffl-lnc1 locus, a CRISPR/Cas9 based targeted knock-in rescue model was constructed by inserting the 19bp into the strain which contained the deletion polymorphism. The knock-in alleles successfully rescued the aberrant QT-interval and blood pressure phenotypes. Further studies revealed that the 19bp polymorphism was necessary and sufficient to recapitulate the phenotypic effect of the previously mapped <42.5kb rat locus. To our knowledge, this study is the first demonstration of a combination of both CRISPR/Cas9 based targeted disruption as well as CRISPR/Cas9 based targeted knock-in rescue approaches applied for a mammalian positional cloning study, which defines the quantitative trait nucleotides (QTNs) within a rat long non-coding RNA as being important for the pleiotropic regulation of both cardiac QT-intervals and blood pressure.

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Epistatic Genetic Determinants of Blood Pressure and Mortality in a Salt-Sensitive Hypertension Model

Cited by 17 publications

References 35 publications

Augmented Rififylin Is a Risk Factor Linked to Aberrant Cardiomyocyte Function, Short-QT Interval and Hypertension

Augmented Rififylin Is a Risk Factor Linked to Aberrant Cardiomyocyte Function, Short-QT Interval and Hypertension

Interaction Between Chromosome 2 and 3 Regulates Pulse Pressure in the Stroke-Prone Spontaneously Hypertensive Rat

Positional cloning of quantitative trait nucleotides for blood pressure and cardiac QT-interval by targeted CRISPR/Cas9 editing of a novel long non-coding RNA

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