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J P Rapp

Publications and source records attributed to J P Rapp.

At least 37 records · Page 2Linked to original sources
PubMed1998

Short tandem repeat polymorphic markers for the rat genome from marker-selected libraries.

In an effort to generate a genome-wide set of high-quality polymorphic markers for the rat, we used the marker-selection method, which has already been proven useful for the development of markers, especially for the human genome. Small-insert (300-900 bp) rat genomic libraries were constructed with an estimated complexity of three genome equivalents and enriched for short tandem repeat sequences (STRs). The enriched libraries were found to contain 45% (CA)n and 27% (GATA)n, representing at least a 50-fold enrichment over unselected small insert genomic libraries. A subset of 2160 STR-containing clones, primarily of the (GATA)n class of repeats, were sequenced. PCR primers flanking the repeats were synthesized from some of the sequences from the (CA)n and (GATA)n classes of STRs and tested for polymorphism in a panel of eight inbred rat strains. This strategy yielded 147 polymorphic markers, which mapped with high odds to all chromosomes by linkage in three F2 populations. The integration of these STR markers with other rat genetic markers and mapping reagents will facilitate the mapping of disease genes in the rat and the identification of loci associated with complex mammalian phenotypes.

Animals↗
PubMed1998

Genome scan and congenic strains for blood pressure QTL using Dahl salt-sensitive rats.

An F2 population (n = 151) derived from Dahl salt-sensitive (S) and Lewis rats was raised on a 8% NaCl diet for 9 weeks and analyzed for blood pressure quantitative trait loci (QTL) by use of a whole genome scan. Chromosomes 5 and 10 yielded lod scores for linkage to blood pressure that were significant; chromosomes 1, 2, 3, 8, 16, 17, and 18 gave lod scores suggestive for linkage. Chromosome 7 gave a significant signal for heart weight with a lesser effect on blood pressure. Congenic strains were constructed by introgressing Lewis low-blood-pressure QTL alleles for chromosomes 1, 5, 10, and 17 into the S genetic background. Congenic strains for chromosomes 1, 5, and 10 had significantly lower blood pressure than S, proving the existence of QTL on these chromosomes, but the chromosome 17 congenic strain failed to trap a contrasting QTL allele. The QTL allele increasing blood pressure originated from S rats for all QTL except those on chromosomes 2 and 7 in which the Lewis allele increased blood pressure. Interactions between each QTL and every other locus in the genome scan yielded significant interactions between chromosomes 10 and 4, and between chromosomes 2 and 3.

Animals↗
PubMed1998

Practicable approaches to targeted comparative mapping of rat chromosome regions: linkage mapping of five genes on rat chromosome 13.

We demonstrate feasible approaches to comparative mapping between the region near the renin locus on rat chromosome 13 and human chromosome 1q by assigning five additional genes as anchor loci. Base-substitution polymorphisms were sought in the 3'- and/or 5'-untranslated regions for subsequent development of PCR-amplified markers, which, in turn, could be used for either restriction fragment analysis or allele-specific PCR.

Animals↗
PubMed1998

Candidate genes in the regulation of Na+ transport by inner medullary collecting duct cells from Dahl rats.

Recently, we reported that primary cultures of inner medullary collecting duct cells from Dahl salt-sensitive (S) rats absorb more Na+ than do cells cultured from Dahl salt-resistant (R) rats. To begin to evaluate the molecular basis for this difference, we selected four candidate gene products that on the basis of their physiology and genetics could participate in regulation of Na+ transport by these cells. During 24-hour exposure, inhibitors of the cytochrome P450 enzymes had no effect on Na+ transport by either S or R monolayers. Twenty-four-hour exposure to NG-monomethyl-L-arginine (0.5 mmol/L), a nonspecific inhibitor of NO synthase, also had no effect on Na+ transport by either S or R monolayers. Neither atrial natriuretic peptide 1-28 (100 nmol/L) nor 8-Br-cyclic GMP (100 micromol/L) had any short-term effect on Na+ transport by either S or R monolayers. 18-Hydroxy-11-deoxycorticosterone (100 nmol/L), an adrenocorticoid hormone that is produced in greater amounts in S rats, stimulated Na+ transport by both S and R monolayers via the mineralocorticoid receptor; however, its effect was less potent than aldosterone. Congenic rats in which the R isoform of the 11beta-hydroxylase gene was bred onto the S background had monolayers that transported Na+ at a rate similar to the S rats. These results demonstrate that neither cytochrome P450 genes, NO synthase genes, the atrial natriuretic peptide receptor gene, nor the 11beta-hydroxylase gene is a likely candidate to explain the difference in Na+ transport between S and R inner medullary collecting duct monolayers in primary culture.

18-Hydroxydesoxycorticosterone↗
PubMed1997

Linkage map and congenic strains to localize blood pressure QTL on rat chromosome 10.

Our purposes were to develop a linkage map for rat Chromosome (Chr) 10, using chromosome-sorted DNA, and to construct congenic strains to localize blood pressure quantitative trait loci (QTL) on Chr 10 with the map. The linkage mapping panel consisted of three F2 populations totaling 418 rats. Thirty-two new and 29 known microsatellite markers were placed on the map, which spanned 88.9 centiMorgans (cM). The average distance between markers was 1.46 cM. No markers were separated by more than 6.8 cM. Four congenic strains were constructed by introgressing various segments of Chr 10 from the Milan normotensive strain (MNS) onto the background of the Dahl salt-sensitive (S) strain. A blood pressure QTL with a strong effect on blood pressure (35-42 mm Hg) when expressed on the S background was localized to a 31-cM region between D10Mco6 and D10Mcol. The region does not include the locus for inducible nitric oxide synthase (Nos2), which had been considered to be a candidate locus for the QTL.

Animals↗
PubMed1997

Mapping of rat chromosome 5 markers generated from chromosome-sorted DNA.

Nineteen markers for rat Chromosome 5 (Chr) were generated by screening chromosome-sorted DNA libraries and were subsequently mapped by linkage to known markers by use of five F2 rat populations. Along with existing markers, these newly produced markers are potentially useful for fine mapping of certain quantitative trait loci for blood pressure and for obesity.

Animals↗
PubMed1997

Interval mapping and congenic strains for a blood pressure QTL on rat chromosome 13.

The renin locus (Ren) on rat Chromosome (Chr) 13 had previously been shown to cosegregate with blood pressure in crosses involving Dahl salt-sensitive (S) and Dahl salt-resistant (R) rats. In the present work, interval mapping of blood pressure on Chr 13 with a large F2 (S x R), n = 233, population yielded a maximum LOD = 4.2 for linkage to blood pressure, but the quantitative trait locus (QTL) was only poorly localized to a large 35-centiMorgan (cM) segment of Chr 13. In the linkage analysis, the S-rat QTL allele (S) was associated with higher, and the R-rat QTL allele (R) with lower blood pressure, the difference between homozygotes being about 20 mm Hg. A congenic strain was made by introgressing the R-rat Ren allele into the recipient S strain. This congenic strain showed a 24 mm Hg reduction (P = 0.004) in blood pressure compared with S rats for rats fed 2% NaCl diet for 24 days; this difference was confirmed by two other independent tests. Two congenic substrains were derived from the first congenic strain with shorter R Chr 13 segments on the S background. Comparisons among these congenic strains showed that a blood pressure QTL was in the 24-cM chromosomal segment between Syt2 and D13M1Mit108. This segment does not include the renin locus, which is thus excluded from being the gene on rat Chr 13 responsible for genetic differences in blood pressure detected by linkage analysis.

Animals↗
PubMed1997

Mapping of rat chromosome 2 markers generated from chromosome-sorted DNA.

A quantitative trait locus (QTL) for blood pressure has recently been mapped to a region of roughly 30 cM on rat Chromosome (Chr) 2 by linkage and by the use of congenic strains. For further fine mapping of the QTL, however, closely linked chromosome markers residing in this 30-cM region are required. In the current work, 36 new markers were generated by screening rat Chr 2-sorted DNA libraries and subsequently mapped using five F2 populations. Combining new and existing markers, the marker density for the 30-cM region approaches, on average, one marker per 1.1 cM.

Animals↗
PubMed1997

Blood pressure and survival of a chromosome 7 congenic strain bred from Dahl rats.

11 beta-hydroxylase (Cyp11b1) mutations were previously linked to altered steroid biosynthesis and blood pressure in Dahl salt-resistant (R) and Dahl salt-sensitive (S) rats. In the present work, interval mapping identified a putative blood pressure quantitative trait locus (QTL) near Cyp11b1 in an F1(SxR)xS population (LOD = 2.0). Congenic rats (Designated S.R-Cyp11b) were constructed by introgressing the R-rat Cyp11b1 allele into the S strain. S.R-Cyp11b rats had significantly lower blood pressure and heart weight compared with S rats, proving the existence of a blood pressure QTL on Chromosome (Chr) 7 despite the fact that QTL linkage analysis of blood pressure never achieved stringent statistical criteria for significance. To test the effects of the introgressed region on blood pressure and survival, S.R.-Cyp11b and S rats were maintained on a 4% NaCl diet until they died or became moribund. Analysis of variance (ANOVA) indicated significant strain differences in blood pressure and days survived (P < 0.0001 for both) as well as gender differences in days survived (P = 0.0003). Kaplan-Meier survival analysis also found significant strain (P < 0.0001) and gender (P = 0.007) differences in days survived. However, when the effects of blood pressure were removed, significant strain differences in survival essentially disappeared. This suggests that the increased survival of S.R-Cyp11b rats was largely due to their decreased blood pressure and thus strongly corroborates the existence of a blood pressure QTL on Chr 7 near or at Cyp11b1.

Adrenal Hyperplasia, Congenital↗
PubMed1997

Evaluation of the renin-angiotensin system in a congenic renin Dahl salt-sensitive rat.

When an approximately 30 centiMorgan (cM) region of chromosome 13 containing the renin gene from the Dahl salt-resistant rat (R) was introgressed into the Dahl salt-sensitive rat (S), the resulting congenic rat (designated S.R-Ren) had a systolic blood pressure on a 2% (w/w) salt diet that was 24 mmHg lower than that of its S counterpart. Due to the large size of the transferred segment (over 30 million bp), the question remained as to whether or not the renin gene was the cause of the blood-pressure difference between the strains. We evaluated the role of the renin-angiotensin system in S.R-Ren and S rats fed a 0.05% salt diet by examining differences between strains in (1) expression of renin in three tissue types, (2) the blood-pressure response to blockade of both angiotensin-converting enzyme and angiotensin II receptors, and (3) pressure natriuresis. No differences were found in renin levels in plasma, kidney or adrenal gland between strains. The blood-pressure responses to the angiotensin-converting-enzyme inhibitor captopril and to the angiotensin II-receptor blocker saralasin in conscious S and S.R-Ren rats were similar. Furthermore, renal function, evaluated by a pressure-natriuresis index that took into account both the time and the arterial pressure needed to excrete an acute salt load, did not differ between strains. Our findings therefore fail to demonstrate a role for the renin gene in conferring lower blood pressure in the congenic rat and suggest that there is an unknown arterial-pressure-regulating locus in this 30 cM region of chromosome 13.

Adrenal Glands↗
PubMed1997

A linkage map of the rat genome derived from three F2 crosses.

We report the construction of a dense linkage map of the rat genome integrating 767 simple sequence length polymorphism markers, combined over three crosses with high rates of polymorphism. F2 populations from WKY x S (n = 159), BN x S (n = 91), and BN x GK (n = 139) were selected and genotyped for combinations of microsatellite markers. The loci define 21 linkage groups corresponding to the 20 rat autosomal chromosomes and the X chromosome. The map spans a genetic length of 1998 cM. This combined linkage map should facilitate the advancement of genetic studies for a wide variety of rat models characterized for complex phenotypes.

Animals↗
PubMed1997

Absence of linkage for "endothelial" nitric oxide synthase locus to blood pressure in Dahl rats.

Nitric oxide is thought to be involved in blood pressure regulation. Nitric oxide synthase (NOS) genes are logical candidates for genetic hypertension. Of the three known forms of NOS, the "neuronal" and "inducible" Nos genes have been tested as candidate genes for causing inherited hypertension in Dahl salt-sensitive rats. In the present work, we analyzed the endothelial Nos gene, designated Nos3, directly and indirectly for cosegregation with blood pressure in six F2 populations independently generated from crosses of Dahl salt-sensitive rats with rats of various other strains. The Nos3 alleles did not cosegregate with blood pressure in these populations. Therefore, Nos3 is an improbable, if not impossible, candidate gene for causing hypertension in the Dahl salt-sensitive rat.

Animals↗
PubMed1997

Congenic strains for the blood pressure quantitative trait locus on rat chromosome 2.

A quantitative trait locus (QTL) for blood pressure was previously detected by linkage analysis in a region of rat chromosome 2 using segregating populations derived from crosses of the Dahl salt-sensitive (Dahl S) rat with rats of the Wistar-Kyoto (WKY) strain or Milan normotensive strain (MNS). Two congenic strains, S.WKY-D2N35/Nep and S.MNS-Adh/D2Mit5, have been constructed by replacing a region of chromosome 2 of the Dahl S rat with the homologous region (ie, low blood pressure QTL allele) of either the WKY or MNS rat, respectively. Systolic pressures of congenic strains S.WKY-D2N35/Nep and S.MNS-Adh/D2Mit5 fed a 2% NaCl diet for 24 days were 44+/-4.6 and 29+/-4.5 mm Hg lower, respectively, than that of the comparably treated Dahl S rats. The differences between congenic and Dahl S rats in blood pressure were highly significant (P<.001) and were corroborated by significantly (P<.001) lower ratio of heart weight to body weight in the congenic strains compared with Dahl S rats. The data from two congenic strains combined unequivocally establish the existence of a blood pressure QTL on rat chromosome 2.

Alleles↗
PubMed1997

[Preparation of new microsatellite markers of rat chromosome 10 in the region, containing genes regulating blood pressure level].

Primer walking is a simple and efficient technique to find new microsatellites in the regions adjacent to known sequences. The method was applied to obtaining new microsatellite markers for rat chromosome 10 in the region of a blood pressure quantitative trait locus. Eight microsatellites were found, five of them were polymorphic in at least one population used for mapping. Improved genetic maps of this region for F2(SxMNS) and F2(SxLEW) populatons were constructed.

Animals↗
PubMed1997

Mapping of selective rat chromosome regions using mouse microsatellite markers.

Four hundred eighty mouse microsatellite markers distributed in discrete regions on five mouse chromosomes were screened for producing PCR products in the rat. Ninety-eight of these markers or 20% give distinctive PCR products. Among these ninety-eight markers, twenty-three are polymorphic between the inbred hypertensive Dahl salt-sensitive (S) rat strain and several normotensive rat strains of interest. Fourteen of these polymorphic markers have been mapped to the homologous chromosome regions of the rat, and have further been utilized to localize quantitative trait loci (QTL) for blood pressure in the S rat.

Animals↗
PubMed1996

Genetic mapping of two blood pressure quantitative trait loci on rat chromosome 1.

A genetic map for rat chromosome 1 was constructed using 66 microsatellite markers typed on either or both of two populations derived from inbred Dahl salt-sensitive (S) rats: F2(LEW x S) n = 151, and F2(WKY x S) n = 159. These populations had been raised on a high salt (8% NaCl) diet. Systolic blood pressure and heart weight were found to be genetically linked to two separate regions on rat chromosome 1 in the F2(LEW x S) population. One region was centered around the anonymous SA locus and accounted for 24 mmHg of blood pressure. The other region was 55 cM from the SA locus centered around a cluster of cytochromes P450 loci, and accounted for 30 mmHg of blood pressure. Since blood pressure and heart weight were highly correlated these same regions were also linked to heart weight. These results were cross-specific as linkage of these chromosome 1 regions to blood pressure and heart weight was not observed in several other F2 populations derived by crossing S and other normotensive control strains. This is presumably due to different alleles and/or different genetic backgrounds in the various populations. The SA region of chromosome 1 was found to influence body weight in F2(LEW x S) rats. Combining the present data with our previously published data on the F2(LEW x S) population showed that four separate quantitative trait loci with additive effects accounted for 106 mmHg and 38% of the total variance of blood pressure and for 506 mg and 34% of the total variance of heart wt.

Animals↗