Three microsatellites defining four alleles for the rat SA gene.
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Alleles↗
Biomedical subjects
H Dene
Publications and source records attributed to H Dene.
Genetic mapping of two new blood pressure quantitative trait loci in the rat by genotyping endothelin system genes.
The endothelin system, consisting of a series of potent vasoconstrictor peptides and their receptors, is potentially important in the control of blood pressure. We found that the gene coding for endothelin-2 (ET2), also known as vasoctive intestine peptide, cosegregated strongly with systolic blood pressure in a F2 population [F2(S x LEW)] derived from a cross of the Dahl salt-sensitive (S) rat and the Lewis (LEW/NCrlBR) (LEW) rat. The ET2 locus was assigned to rat chromosome 5. The testis-specific histone (HITH) locus also strongly cosegregated with blood pressure in the F2(S x LEW) population and was assigned to rat chromosome 17. Genetic maps of the regions containing the quantitative trait loci (QTL) for blood pressure on chromosomes 5 and 17 were constructed and the QTL were localized using the MAPMAKER/QTL program. The rat genes for endothelin-1, endothelin-3, and endothelin receptor A did not cosegregate with blood pressure in several F2 populations tested and were assigned to rat chromosomes 17, 3, and 19, respectively. Endothelin receptor B cosegregated weakly with blood pressure and was provisionally assigned to rat chromosome 15. We conclude that, in the rat, one new blood pressure QTL is located on chromosome 5 marked by the ET2 locus and another new QTL is located on chromosome 17 near the HITH locus.
Animals↗
Mapping of a quantitative trait locus for blood pressure on rat chromosome 2.
A genetic map for rat chromosome 2 that includes five candidate genes for blood pressure regulation was constructed in a region containing a quantitative trait locus (QTL) for blood pressure. Two F2 populations of male rats raised on high salt (8% NaCI) diet from weaning were studied: F2(WKY x S), derived from a cross of Dahl salt-sensitive rats (S) and Wistar-Kyoto rats (WKY); and F2(MNS x S), derived from a cross of S rats and Milan normotensive strain (MNS). In both populations a blood pressure QTL was localized between Na+,K(+)-ATPase alpha 1 isoform and calmodulin-dependent protein kinase II-delta loci. The LOD score for existence of this blood pressure QTL based on the combined populations (n = 330) was 5.66 and accounted for 9.2% of the total variance and 26% of the genetic variance.
Animals↗
Seven renin alleles in rats and their effects on blood pressure.
OBJECTIVE: To survey inbred rat strains for renin alleles and to test those alleles for effects on blood pressure. DESIGN: Rat strains with renin alleles different from the s allele carried by inbred Dahl salt-sensitive (SS/Jr) rats were crossed with SS/Jr rats and subsequently intercrossed to produce F2 populations. Thus, in each F2 population segregation of the s renin allele and a contrasting renin allele occurred. F2 rats were raised on a high-salt diet and their blood pressures were determined. The cosegregation of renin alleles with blood pressure was evaluated in each F2 population. METHODS: Renin alleles were recognized by the variable number of tandem repeats in the first intron of the renin gene and by a variable HindIII site in the fifth intron. Genotyping was by restriction fragment length polymorphism analysis. RESULTS: Seven renin alleles were found, but breeding stock for only six of these alleles was available. From these stocks it was possible to construct five F2 populations in which the s renin allele segregated with a contrasting renin allele. In all five F2 populations the rats homozygous for the s allele had higher blood pressure than those homozygous for the contrasting renin allele, but statistical significance was most easily established in the F2 intercrossed offspring of an SS/Jr x inbred Dahl salt-resistant (SR/Jr) rat cross. This result was duplicated. CONCLUSIONS: There are at least seven alleles in rats at the renin locus, allowing many pairwise allelic comparisons to be made. Of the five alleles compared with the s renin allele, the r allele of SR/Jr rats was unique in providing strong evidence for cosegregation with blood pressure. The naive expectation that all crosses should yield the same cosegregation result with blood pressure for a candidate locus is not consistent with either theory or the present experimental results.
Alleles↗
Genetic analysis of alpha 2-adrenergic receptors and blood pressure using Dahl salt-sensitive rats.
OBJECTIVE: To evaluate the role of alpha 2-adrenergic receptors in genetic hypertension by cosegregation analysis using Dahl rats. DESIGN: Inbred Dahl salt-sensitive (SS/Jr) rats were crossed with inbred Dahl salt-resistant (SR/Jr) rats; also, SS/Jr rats were crossed with several control strains, and large F2 populations were subsequently produced from each cross. All F2 populations were raised on a high-salt diet. The rats were genotyped, where possible, at the loci for three different subtypes of alpha 2-adrenergic receptors designated as classes I, II and III. The blood pressures of the rats classified by genotype at each alpha 2-adrenergic receptor subtype locus were compared using analysis of variance. METHODS: Genomic clones of three classes of alpha 2-adrenergic receptors were isolated from genomic lambda-phage libraries of SS/Jr or SR/Jr rat strains, or both, by screening with complementary DNA for human alpha 2-adrenergic receptors. Fragments of the rat genomic clones obtained were used for genotyping by restriction fragment length polymorphism. Also, cloned genomic DNA flanking the alpha 2-adrenergic receptors and containing microsatellites was sequenced; genotyping at informative microsatellite markers was performed using the polymerase chain reaction. Two of the three classes of rat alpha 2-adrenergic receptors were localized to rat chromosomes by linkage analysis or using a panel of mouse-rat hybrid somatic cell lines. RESULTS: Rat alpha 2-adrenergic receptor classes I and III genes were assigned to rat chromosomes 14 and 3, respectively. These correspond to alpha 2-adrenergic receptor genes on human chromosomes 4 and 2, respectively. Extensive cosegregation analysis, involving five alleles in six segregating populations for class I alpha 2-adrenergic receptors, yielded no evidence of an effect of these loci on blood pressure. Classes II and III alpha 2-adrenergic receptors could each be tested in only one population and there was no evidence for an effect of either receptor gene on genetic differences in blood pressure. The dopamine-1B receptor was closely linked to the class I alpha 2-adrenergic receptor on rat chromosome 14. Thus, the negative cosegregation of the class I receptor with blood pressure applies equally to the dopamine-1B receptor. CONCLUSIONS: Genetic analysis in segregating populations involving crosses of inbred Dahl salt-sensitive rats with five other strains provides no evidence for a genetic effect of class I alpha 2-adrenergic receptors, or of the dopamine-1B receptor, on blood pressure. Classes II and III alpha 2-adrenergic receptors also failed to cosegregate with blood pressure but, because only limited testing was possible with the classes II and III receptors, this negative result is not definitive.
Animals↗
SA gene and blood pressure cosegregation using Dahl salt-sensitive rats.
Based on the published cDNA base sequence for the (anonymous) SA gene, a polymerase-chain-reaction (PCR) product from the SA gene was obtained from a Dahl salt-sensitive rat kidney cDNA library. Compared to the published sequence, this product had a 102 base pair insert in the 3' end of the cDNA, probably as the result of alternate mRNA splicing. A StuI restriction fragment length polymorphism detected three alleles among various rat strains using this PCR SA gene probe. Alleles at the SA locus strongly cosegregated with blood pressure (P = .0012) in a salt-fed F2 population derived from crossing Dahl S and Lewis rats. In contrast, a cosegregation analysis of blood pressure and SA alleles in salt-fed F2 rats derived from a Dahl S x Wistar-Kyoto cross gave a negative cosegregation result. It is concluded that in certain genetic backgrounds the SA gene (or a closely linked gene) can contribute a significant component of genetic hypertension.
Animals↗
Renin gene nucleotide sequence of coding and regulatory regions in Dahl rats.
Renin alleles in the Dahl salt-hypertension sensitive (S) and Dahl salt-hypertension resistant (R) rats are known to strongly cosegregate with blood pressure. The purpose of this work was to look for structural differences in the S and R renin alleles that could account for the cosegregation result. The nucleotide sequences determined for the coding region and the 5'-flanking regulatory region for the renin gene of S and R rats were identical. There were some minor nucleotide changes in selected regions of the 1st and 8th introns that were sequenced, but these were unlikely to be of functional importance. The remaining possible reasons for the cosegregation of blood pressure with renin alleles in Dahl rats are differences in renin regulatory elements out of the immediate 5'-flanking area, or differences in alleles at an unknown closely linked locus.
Alleles↗
Effect of genetic background on cosegregation of renin alleles and blood pressure in Dahl rats.
The cosegregation of renin alleles and blood pressure was evaluated in segregating populations derived from inbred Dahl salt hypertension sensitive (S) and inbred Dahl salt hypertension resistant (R) rats. The populations were raised on high salt diet (8% NaCl). In F2 and F1 X S populations, there was a significant positive gene-dosage relationship between the S-rat renin allele and blood pressure. In contrast, no such relationship was seen in the F1 X R population. Since in the F1 X R population the genetic background is strongly influenced by genes from the R rat (75% R, 25% S), the result is interpreted to mean that genes at other (unidentified) loci modify the blood pressure effect of the S-rat renin allele.
Alleles↗
Failure of alleles at the Na+, K(+)-ATPase alpha 1 locus to cosegregate with blood pressure in Dahl rats.
A previously described Pst I restriction fragment length polymorphism in Dahl rats at the Na+, K(+)-adenosine 5'-triphosphatase (ATPase) alpha 1 isoform locus was tested for cosegregation with blood pressure in segregating populations. Inbred Dahl salt-sensitive (S) and inbred Dahl salt-resistant (R) rats were crossed to produce F1 rats, and three segregating populations, F1 x R, F2 and F1 x S, were produced and raised on a high-salt diet for variable periods to attain the maximal blood pressure response in each population. In no segregating population was there a significant difference in blood pressure among genotypes at the Na+, K(+)-ATPase alpha 1 locus. Power calculations suggest that single-allele dosage effects of less than 7.5 mmHg were unlikely to be detected. It is concluded that either the S and R alleles at the Na+, K(+)-ATPase alpha 1 locus do not influence blood pressure under the conditions of these experiments (high dietary salt, Dahl rat genetic background) or, if they do, their effect is small.
Alleles↗
A genetic polymorphism in the renin gene of Dahl rats cosegregates with blood pressure.
Blood pressure is influenced by multiple genetic loci whose identities are largely unknown. A restriction fragment length polymorphism (RFLP) in the renin gene was found between Dahl salt-hypertension-sensitive (S) and Dahl salt-hypertension-resistant (R) rats. In an F2 population derived from crossing S and R rats, the renin RFLP cosegregated with blood pressure. One dose of the S-rat renin allele was associated with an increment in blood pressure of approximately 10 mmHg, and two doses of this allele increased blood pressure approximately 20 mmHg. From this it can be definitively concluded that in the rat the renin gene is, or is closely linked to, one of the genes regulating blood pressure.
Alleles↗
Regulation of adrenal renin messenger ribonucleic acid by dietary sodium chloride.
Zona glomerulosa (ZG) and zona fasciculata (ZF/M) poly(A)+ RNA were isolated from the adrenals of bilaterally nephrectomized female Sprague-Dawley rats and hybridized to a full-length 32P-labeled 1423-base pair (bp) renin cDNA as well as a 698-bp renin cDNA KpnI segment (corresponding to amino acids 92-325) by the dot blot procedure using Bio-Rad Zeta Probe membranes. Extensive hybridization was observed with ZG mRNA, and only slight binding was seen with ZF/M mRNA. These results extend earlier reports from this laboratory indicating that the enzymic activity for renin is predominantly localized in ZG cells. Hence, high message levels account for the high enzymic activity. Adrenal ZG poly(A)+ RNA was also isolated from rats maintained on normal and sodium-deplete diets for 15 days and was hybridized to the radiolabeled 698-bp renin probe. Essentially twice the amount of probe was bound to the message from salt-deplete ZG tissue compared to message from normal ZG per microgram mRNA. Hybridization was proportional to the amount of poly(A)+ RNA employed over the range of 0-1 microgram, suggesting the applicability of this procedure for approximate quantitation purposes. The membranes were freed from the 32P-labeled renin cDNA and subsequently rehybridized with a 32P-radiolabeled 1200-bp beta-actin cDNA probe. It was observed that ZF/M poly(A)+ RNA contained more beta-actin message than ZG poly(A)+ RNA, indicating a greater transcription rate for beta-actin in ZF/M tissue in contrast to transcription of the renin gene.
Adrenal Glands↗
Quantitation of renal renin and renin mRNA in Dahl rats in response to provocative stimuli.
It is known that inbred Dahl salt-sensitive (S) rats carry a different renin allele than inbred Dahl salt-resistant (R) rats. The levels of, and responses of, renal renin and renal renin mRNA to sodium deficient diet and to sodium deficient diet plus Captopril treatment were compared in S and R rats. S rats had lower renal renin and lower renal renin mRNA than R rats on control (1% NaCl) diet. Sodium deficient diet caused a modest increase, and sodium deficient diet plus Captopril caused a very large increase in both renal renin and renal renin mRNA in both strains. In general, both S and R strains appeared to regulate renin similarly in response to provocative stimuli.
Animals↗
Restriction fragment length polymorphisms for the renin gene in Dahl rats.
Genomic DNAs from inbred Dahl salt-hypertension sensitive (S) and inbred Dahl salt-hypertension resistant (R) rats were examined for restriction fragment length polymorphisms (RFLPs) using a rat renin cDNA probe. Eight of the 28 restriction enzymes used yielded polymorphic fragments between S and R strains. This suggests a major structural difference in or near the renin gene of Dahl rats. Some, but not all, of the polymorphisms are compatible with an insertion/deletion mutation of about 1.1 kb in size. The ratio of renin gene copy numbers for S to R was found to be 1, showing that the RFLPs are not likely to be due to gene duplication.
Animals↗
Recruitment of the left ventricle for production of atrial natriuretic factor in Dahl salt-hypertension sensitive rats.
Dahl salt-sensitive (S) rats on normal salt intake develop a chronic form of hypertension with aging whereas Dahl salt-resistant (R) rats do not. In old hypertensive S rats the left ventricle is recruited for the production of ANF as evidenced by a seven- to ten-fold increase in atrial natriuretic factor (ANF) mRNA and increased ANF in ventricular tissue. Plasma ANF is also markedly increased in hypertensive S rats but there is no direct proof that ventricular production of ANF contributes to high plasma ANF. Atrial ANF is higher in S than R rats but this strain difference is not associated with strain differences in ANF mRNA in atria and atrial ANF mRNA does not increase dramatically in hypertensive S rats as does ventricular mRNA. Recruitment of the ventricle to produce ANF is clearly a secondary consequence of hypertension, but its functional significance is not established.
Animals↗
Partial characterization of atrial natriuretic factor in the hearts of Dahl salt-sensitive and salt-resistant rats.
Atria of adult Dahl salt-sensitive rats contain more atrial natriuretic factor (ANF) than those of Dahl salt-resistant rats, as measured by RIA. This strain difference was not seen at 15 days of age, but was observed at and after 30 days of age. Neither a sodium-deficient diet nor an 8% NaCl diet started as early as 2 weeks of age altered this strain difference, although high dietary NaCl was associated with reduced atrial ANF concentration. In addition, no qualitative differences were found in the S and R ANF precursor, as assessed by 1) in vitro translation of atrial mRNA followed by immunoprecipitation of the ANF precursor and polyacrylamide gel electrophoresis, and 2) fractionation of S and R atrial extracts by reverse phase HPLC. These findings support the view that the S vs. R strain difference in atrial ANF concentration is more likely to arise from genetic control of regulatory phenomena than from alterations in the structural part of the ANF gene.
Age Factors↗
Quantification of messenger ribonucleic acid for atrial natriuretic factor in atria and ventricles of Dahl salt-sensitive and salt-resistant rats.
The levels of atrial natriuretic factor (ANF) and the mRNA for ANF were measured in the left ventricles of Dahl salt-sensitive (S) and salt-resistant (R) rats. ANF and ANF mRNA were both much higher in ventricular tissue of newborn rats of both strains compared to young adults, which represents the normal developmental pattern. There was no strain difference between S and R when the rats were young (1.5 months of age), but in older animals (8.5 months of age), when S rats were markedly hypertensive, there was a 5- to 10-fold increase in both left ventricular ANF and left ventricular ANF mRNA in S, but not R, rats. Atrial ANF mRNA was not similarly increased in hypertensive S rats. The ANF levels present in ventricles could not be accounted for by contamination with plasma ANF. Moreover, HPLC analysis of the forms of ANF in ventricles of newborn and hypertensive S rats showed that immunoreactive ANF in ventricles was present mainly in the same precursor form found in atria and not the shorter peptide form found in plasma. Northern blot analysis showed that ANF mRNA for atria and ventricles were the same size. It is concluded that in the S rat the heart left ventricle responds to hypertension by increasing production and storage of ANF.
Aging↗
Atrial natriuretic factor in inbred Dahl salt-sensitive and salt-resistant rats.
The atria of adult Dahl salt-sensitive (S) rats contain more atrial natriuretic factor (ANF) than the atria of adult Dahl salt-resistant (R) rats by both radio-immunoassay and bioassay. This strain difference is not present between 1 and 15 days of age but is present at 30 days of age and persists throughout adulthood. The precursors of ANF immunoprecipitated from in vitro translations of atrial messenger RNA (mRNA) had the same molecular weight in S and R strains. Hypothalamic levels of ANF were similar in S and R. Kidneys of weanling S rats were hyporesponsive to ANF compared with R, but as the S rats became hypertensive with age the situation was reversed, with S rats being hyperresponsive to ANF. Aortic vascular responses to ANF were identical in S and R rats. Plasma ANF was similar in S and R rats on low-salt diet, but increased markedly in S, but not R, on high-salt diet. It is concluded that any genetic defect in the ANF system in Dahl S rats is most likely to involve the kidney response to ANF, and that high plasma ANF in salt-fed rats may be a consequence of volume expansion and hypertension.
Animals↗
Lack of effects of maternal salt intake on blood pressure of offspring in Dahl salt-sensitive rats.
Inbred Dahl salt sensitive (S/JR) and salt resistant (R/JR) rats were used to look for effects of varying maternal intake of salt (NaCl) on the blood pressure of the offspring. Neither the blood pressure at weaning nor the blood pressure response to postweaning high salt diet of S/JR or R/JR rat pups was affected whether their mothers had eaten high salt (8% NaCl) or low salt (0.15% NaCl) diet during gestation. Similarly, maternal salt intake during lactation had no effect on the blood pressure of the offspring at weaning or the blood pressure response to salt feeding after weaning. Na+ was higher and K+ was lower in milk of S/JR compared to R/JR mothers during the last half of the lactation period, but dietary salt intake did not influence milk Na+ or K+. Previous cross-fostering experiments show that this strain difference in milk electrolytes does not influence S pups blood pressure. It is concluded that neither maternal salt intake nor the existing changes in milk Na+ have any influence on the blood pressure of Dahl salt sensitive rat pups in contrast to the marked effects of salt intake in these rats after weaning.
Age Factors↗