ABSTRACT: DEFINING A RAT BLOOD PRESSURE QUANTITATIVE TRAIT LOCUS TO A <81.8KB CONGENIC SEGMENT: COMPREHENSIVE SEQUENCING AND RENAL TRANSCRIPTOME ANALYSIS.
Project description:Evidence from multiple linkage and genome-wide association studies suggest that human chromosome 2 (HSA2) contains alleles that influence blood pressure (BP). Homologous to a large segment of HSA2 is rat chromosome 9 (RNO9), to which a BP quantitative trait locus (QTL) was previously mapped. The objective of the current study was to further resolve this BP QTL. Eleven congenic strains with introgressed segments spanning <81.8kb to <1.33Mb were developed by introgressing genomic segments of RNO9 from the Dahl salt-resistant (R) rat onto the genome of the Dahl salt-sensitive (S) rat and tested for BP. The congenic strain with the shortest introgressed segment spanning <81.8kb significantly lowered BP of the hypertensive S rat by 25 mm Hg and significantly increased its mean survival by 45 days. In contrast, two other congenic strains had increased BP compared with the S. We focused on the <81.8kb congenic strain which represents the shortest genomic segment to which a BP QTL has been definitively mapped to date in any species. Sequencing of this entire region in both S and R rats detected 563 variants. The region did not contain any known or predicted rat protein coding genes. Further, a whole genome renal transcriptome analysis between S and the <81.8kb S.R congenic strain revealed alterations in several critical genes implicated in renal homeostasis. Taken together, our results provide the basis for future studies to examine the relationship between the candidate variants within the QTL region and the renal differentially expressed genes as potential causal mechanisms for BP regulation.
Project description:Kidney samples from three Dahl Salt-sensitive S rats were compared with kidney samples from three S.R(9)x3A congenic rats. Keywords = Blood Pressure Keywords = Quantitative trait locus Keywords = QTL Keywords = hypertension Keywords = rat Keywords = congenic Keywords: parallel sample
Project description:Evidence from multiple linkage and genome-wide association studies suggest that human chromosome 2 (HSA2) contains alleles that influence blood pressure (BP). Homologous to a large segment of HSA2 is rat chromosome 9 (RNO9), to which a BP quantitative trait locus (QTL) was previously mapped. The objective of the current study was to further resolve this BP QTL. Eleven congenic strains with introgressed segments spanning <81.8kb to <1.33Mb were developed by introgressing genomic segments of RNO9 from the Dahl salt-resistant (R) rat onto the genome of the Dahl salt-sensitive (S) rat and tested for BP. The congenic strain with the shortest introgressed segment spanning <81.8kb significantly lowered BP of the hypertensive S rat by 25 mm Hg and significantly increased its mean survival by 45 days. In contrast, two other congenic strains had increased BP compared with the S. We focused on the <81.8kb congenic strain which represents the shortest genomic segment to which a BP QTL has been definitively mapped to date in any species. Sequencing of this entire region in both S and R rats detected 563 variants. The region did not contain any known or predicted rat protein coding genes. Further, a whole genome renal transcriptome analysis between S and the <81.8kb S.R congenic strain revealed alterations in several critical genes implicated in renal homeostasis. Taken together, our results provide the basis for future studies to examine the relationship between the candidate variants within the QTL region and the renal differentially expressed genes as potential causal mechanisms for BP regulation. Six male S control and 6 male congenic S.R(9)x3x2Bx1x8 rats born on the same day were selected, weaned at 30 days of age, and caged with 1 congenic and 1 S rat per cage. They were raised on a High-salt (2%) diet (Harlan Teklad diet TD 7034; Harlan–Sprague-Dawley) and sacrificed at 53 days of age and total RNAs were isolated from the kidney. The isolated RNA from two animals were pooled together and considered as one biological sample. Three such RNA samples from S and congenic rats were used for the cRNA preparation. cRNA was prepared and fragmented as suggested by Affymetrix technical manual, and simultaneously hybridized (15 µg adjusted cRNA for each chip) to Rat Expression Array 230 2.0 (3' IVT Expression Analysis). Statistical analyses of the microarray data were performed using R statistical package (version 2.8.1).
Project description:The overlap of congenic regions in an earlier substitution mapping study suggested the location of two blood pressure quantitative trait loci (QTL)-containing regions in the q-terminus of rat chromosome 3, QTL1 and the more distal, QTL2. Male SS/jr rats and two congenic substrain rats S.R(D3Mco36-D3Mco46) and S.R(D3Mco36-D3Got166) were maintained on a low salt (0.4% NaCl Harlan Teklad diet TD7034) diet until 39-41 days of age and then fed an intermediate (2% NaCl Harlan Teklad diet TD94217) salt diet for 28 days. These 3 rat strains will be hereafter referred to as S, S.R(ET3x1), and S.R(ET3x2), respectively. Both congenic substrains carry SR/jr (R)-rat alleles for QTL2 on an S-rat genetic background, while S.R(ET3x2) also carries R-rat alleles for QTL1. Renal gene expression analysis was used to identify differentially expressed genes or genes with altered activity within the S.R(ET3x2) congenic region. Keywords: strain differences in response to dietary changes
Project description:The overlap of congenic regions in an earlier substitution mapping study suggested the location of two blood pressure quantitative trait loci (QTL)-containing regions in the q-terminus of rat chromosome 3, QTL1 and the more distal, QTL2. Male SS/jr rats and two congenic substrain rats S.R(D3Mco36-D3Mco46) and S.R(D3Mco36-D3Got166) were maintained on a low salt (0.4% NaCl Harlan Teklad diet TD7034) diet until 39-41 days of age. These 3 rat strains will be hereafter referred to as S, S.R(ET3x1), and S.R(ET3x2), respectively. At 39-41 days of age, half of the rats from each strain were fed a high (4% NaCl Harlan Teklad diet TD83033) salt diet and water ad libitum for 24 hours. Both congenic substrains carry SR/jr (R)-rat alleles for QTL2 on an S-rat genetic background, while S.R(ET3x2) also carries R-rat alleles for QTL1. Renal gene expression analysis was used to identify differentially expressed genes or genes with altered activity within the S.R(ET3x2) congenic region. Keywords: strain differences in response to dietary changes
Project description:The spontaneously hypertensive rat (SHR) is the most widely used model of essential hypertension and is predisposed to left ventricular hypertrophy, myocardial fibrosis, and metabolic disturbances. Recently, a quantitative trait locus (QTL) influencing blood pressure, left ventricular mass and heart interstitial fibrosis was genetically isolated within 788 kb on chromosome 8 segment of SHR-PD5 congenic strain that contains only 7 genes, including mutant Plzf (promyelocytic leukemia zinc finger) gene. To identify Plzf as a quantitative trait gene, we targeted Plzf in the SHR using the TALEN technique and obtained SHR line harboring mutant Plzf gene with a premature stop codon at position of amino acid 58. The Plzf mutant allele is semi-lethal since approximately 95% of newborn homozygous animals die perinatally due to multiple developmental abnormalities. Heterozygous rats were grossly normal and were used for metabolic and hemodynamic analyses. SHR-Plzf+/- heterozygotes versus SHR wild type controls exhibited reduced body weight and relative weight of epididymal fat, lower serum and liver triglycerides and cholesterol and better glucose tolerance. In addition, SHR-Plzf+/- rats exhibited significantly increased sensitivity of adipose and muscle tissue to insulin action when compared to wild type controls. Blood pressure was comparable in SHR versus SHR-Plzf+/-, however, there was significant amelioration of cardiomyocyte hypertrophy and cardiac fibrosis in SHR-Plzf+/- rats. Gene expression profiles in the liver and expression of selected genes in the heart revealed differentially expressed genes playing a role in metabolic pathways, PPAR signaling, and cell cycle regulation. These results provide evidence for an important role of Plzf in regulation of metabolic and cardiac traits in the rat and suggest a cross-talk between cell cycle regulators, metabolism, cardiac hypertrophy and fibrosis.
Project description:Severe forms of hypertension are characterized by high blood pressure combined with end-organ damage. Through the development and refinement of a transgenic rat model of malignant hypertension (MH) incorporating the mouse renin gene, we previously identified a quantitative trait locus (QTL) on chromosome 10, which affects malignant hypertension severity and morbidity. We next generated an inducible MH model where the timing, severity and duration of hypertension was placed under the control of the researcher, allowing development of and recovery from end-organ damage to be investigated. We have now generated novel consomic Lewis (L) and Fischer (F) rat strains with inducible hypertension, and additional strains, which are reciprocally congenic for the refined chromosome 10 QTL – FL (Fischer with a Lewis congenic region and LF (Lewis with a Fischer congenic region). We have captured a modifier of end-organ damage within the QTL and, using a range of bioinformatic, biochemical and molecular biological techniques, have identified Angiotensin converting enzyme (Ace) as the modifier of tissue microvascular injury. This SuperSeries is composed of the SubSeries listed below.
Project description:Spontaneously hypertensive rat (SHR; Rat Genome Database (RGD) ID: 631848) is probably the most commonly used rodent model for essential hypertension. Its minimal congenic subline PD5 ( SHR.PD-(D8Rat42-D8Arb23)/Cub; (RGD ID: 1641851)) which differs by a short segment of chromosome 8 (encompassing only 7 genes) displays lower levels of blood pressure and amelioration of cardiac fibrosis compared to SHR. We used microarray aproach to unravel gene expression differences between SHR and PD5 responsible for the different phenotypes in our rat strains.
Project description:Despite recent advances in genomics, the identification of genes underlying complex diseases remains challenging. Inbred rat strains offer well-established experimental models to support the identification of susceptibility genes for diseases such as kidney damage associated with elevated blood pressure or hypertension. Here, we combined quantitative trait locus (QTL) mapping in two contrasting inbred rat strains with targeted next generation sequencing (NGS), compartment-specific transcriptome sequencing (RNA-Seq), and phenotype directed follow-up translational analysis.
Project description:Genetic dissection of the S rat genome has provided strong evidence for the presence of two interacting blood pressure (BP) quantitative trait loci (QTLs), termed QTL1 and QTL2, on rat chromosome 5. However, the identities of the underlying interacting genetic factors remain unknown. Further experiments targeted to identify the interacting genetic factors by the substitution mapping approach alone are difficult because of the interdependency of natural recombinations to occur at the two QTLs. We hypothesized that the interacting genetic factors underlying these two QTLs may interact at the level of gene transcription and thereby represent expression QTLs (eQTLs). To detect these interacting eQTLs, a custom QTL chip containing the annotated genes within QTL1 and QTL2 was developed and used to conduct a transcriptional profiling study of S and two congenic strains that retain either one or both the QTLs. The results uncovered an interaction between two transcription factors, DMRTA2 and NFIA. Further, the ‘biological signature’ elicited by these two transcription factors was differential between the congenic strain that retained LEW alleles at both QTL1 and 2 compared to the congenic strain that retained LEW alleles at QTL1 alone. A network of transcription factors potentially affecting BP could be traced, lending support to our hypothesis. Keywords: rat, hypertension, genetics, polygenic trait, microarray, gene expression