Genetic determinants of pulmonary hypertension in fawn-hooded rats.
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Animals↗
Biomedical subjects
H J Jacob
Publications and source records attributed to H J Jacob.
Genetic mapping and chromosome localization of the rat mitochondrial glycerol-3-phosphate dehydrogenase gene, a candidate for non-insulin-dependent diabetes mellitus.
The mitochondrial FAD-dependent glycerol-3-phosphate dehydrogenase (mtGPD) plays an important role in the regulation of insulin secretion and has been postulated as a candidate responsible for the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) in humans as well as in rodent models of NIDDM. Recent molecular genetic studies of the Goto-Kakizaki (GK) rat model of NIDDM have identified loci linked to NIDDM. To elucidate whether rat mtGPD might play a role in the pathogenesis of NIDDM, the rat mtGPD gene (Gpd2) was cloned, and a genetic marker for Gpd2 was developed. The gene mapped to the region of rat chromosome 3 that contains a region linked to NIDDM in the GK rat. Fluorescence in situ hybridization was also carried out to verify the map position.
Animals↗
Use of AFLP markers for gene mapping and QTL detection in the rat.
The AFLP technique is a new DNA marker technology based on the selective amplification of restriction fragments. Multiple polymorphic markers are simultaneously produced and can be tested in one PCR. No prior information on genomic DNA sequences is needed. In the current study, we contribute 18 AFLP markers to the linkage map of the rat. Seven AFLP markers were assigned to specific chromosomes by analysis of a (BN x ACI)F1 x ACI backcross progeny. Another 11 AFLP markers were mapped by using a panel of the H x B/B x H recombinant inbred (RI) strains. Genotypes of these AFLP markers were also tested for correlations with some blood pressure phenotypes in the RI strains. Suggestive correlation was found between the mean arterial pressure and two closely linked AFLP markers located on chromosome 20. The current study illustrates the value of AFLP markers for the construction of linkage maps and the detection of quantitative trait loci.
Animals↗
Novel missense mutation in the cyclic nucleotide-binding domain of HERG causes long QT syndrome.
Autosomal-dominant long QT syndrome (LQT) is an inherited disorder, predisposing affected individuals to sudden death from tachyarrhythmias. To identify the gene(s) responsible for LQT, we identified and characterized an LQT family consisting of 48 individuals. DNA was screened with 150 microsatellite polymorphic markers encompassing approximately 70% of the genome. We found evidence for linkage of the LQT phenotype to chromosome 7(q35-36). Marker D7S636 yielded a maximum lod score of 6.93 at a recombination fraction (theta) of 0.00. Haplotype analysis further localized the LQT gene within a 6.2-cM interval. HERG encodes a potassium channel which has been mapped to this region. Single-strand conformational polymorphism analyses demonstrated aberrant bands that were unique to all affected individuals. DNA sequencing of the aberrant bands demonstrated a G to A substitution in all affected patients; this point mutation results in the substitution of a highly conserved valine residue with a methionine (V822M) in the cyclic nucleotide-binding domain of this potassium channel. The cosegregation of this distinct mutation with LQT demonstrates that HERG is the LQT gene in this pedigree. Furthermore, the location and character of this mutation suggests that the cyclic nucleotide-binding domain of the potassium channel encoded by HERG plays an important role in normal cardiac repolarization and may decrease susceptibility to ventricular tachyarrhythmias.
Adult↗
Effects of renin gene transfer on blood pressure and renin gene expression in a congenic strain of Dahl salt-resistant rats.
To investigate whether a BP-regulatory locus exists in the vicinity of the renin locus on rat chromosome 13, we transferred this chromosome segment from the Dahl salt-sensitive (S) rat onto the genetic background of the Dahl salt-resistant (R) rat. In congenic Dahl R rats carrying the S renin gene and fed an 8% salt diet, systolic BP was significantly lower than in progenitor Dahl R rats: 127 +/- 1 mmHg versus 138 +/- 4 mmHg, respectively (P < 0.05). Moreover, the decreased BP in the congenic Dahl R strain was associated with decreased kidney renin mRNA and decreased plasma renin concentration. These findings demonstrate that the Dahl S strain carries alleles in or near the renin locus that confer lower plasma renin concentration and lower BP than the corresponding alleles in the Dahl R strain, at least when studied on the genetic background of the Dahl R rat and in the environment of a high salt diet. The occurrence of coincident reductions in kidney renin mRNA, plasma renin concentration, and BP after interstrain transfer of naturally occurring renin gene variants strongly suggests that genetically determined variation in renin gene expression can affect BP.
Alleles↗
Lack of association of trinucleotide repeat polymorphisms in very-low-density lipoprotein receptor gene with Alzheimer's disease.
Inheritance of the apolipoprotein E epsilon 4 allele is a risk factor for Alzheimer's disease (AD). A recent report studying Japanese patients suggested that a polymorphism of a trinucleotide repeat in the 5' untranslated region of an apolipoprotein E receptor, the very-low-density lipoprotein receptor, is genetically associated with AD, with overrepresentation of the allele containing five copies of the repeat. We determined the allele frequencies of the very-low-density lipoprotein receptor in 3 white populations totaling 469 individuals. In contrast to the previous report, we found no differences in allele frequencies between case patients and control subjects. The discrepancy could be due to differences in Japanese and white populations. Nonetheless, these data weaken the likelihood that this polymorphism in the very-low-density lipoprotein receptor gene is strongly associated with AD.
Alleles↗
Chromosomal mapping of the rat Slc4a family of anion exchanger genes, Ae1, Ae2, and Ae3.
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Animals↗
Genetic analysis of non-insulin dependent diabetes mellitus in the GK rat.
Non-insulin dependent diabetes mellitus (NIDDM) is a major public health problem, but its aetiology remains poorly understood. We have performed a comprehensive study of the genetic basis of diabetes in the Goto-Kakizaki (GK) rat, the most widely used animal model of non-obese NIDDM. The genetic dissection of NIDDM using this model has allowed us to map three independent loci involved in the disease. In addition, we identify a major factor affecting body weight, but not glucose tolerance, on chromosome 7 and map a further 10 regions that are suggestive for linkage. We conclude that NIDDM is polygenic and fasting hyperglycaemia and postprandial hyperglycaemia clearly have distinct genetic bases.
Animals↗
Renal disease susceptibility and hypertension are under independent genetic control in the fawn-hooded rat.
Hypertension, diabetes and hyperlipidemia are risk factors for life-threatening complications such as end-stage renal disease, coronary artery disease and stroke. Why some patients develop complications is unclear, but only susceptibility genes may be involved. To test this notion, we studied crosses involving the fawn-hooded rat, an animal model of hypertension that develops chronic renal failure. Here, we report the localization of two genes, Rf-1 and Rf-2, responsible for about half of the genetic variation in key indices of renal impairment. In addition, we localize a gene, Bpfh-1, responsible for about 26% of the genetic variation in blood pressure. Rf-1 strongly affects the risk of renal impairment, but has no significant effect on blood pressure. Our results show that susceptibility to a complication of hypertension is under at least partially independent genetic control from susceptibility to hypertension itself.
Animals↗
A landmark for orphan genomes?
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Animals↗
Renal cytochrome P4504A activity and salt sensitivity in spontaneously hypertensive rats.
Differences in the renal metabolism of arachidonic acid by cytochrome P450 have been reported in the spontaneously hypertensive rat (SHR) and Wistar-Kyoto rats, but the contribution of this system to the development of hypertension is unclear. The present study compared renal P450 activity and blood pressure in SHR and Brown-Norway rats (BN) under control conditions and in response to an elevation in sodium intake; genetic linkage analysis was performed in an F2 population (n=219) derived from these strains. Basal renal P4504A enzyme activity measured by conversion of [C(14)]arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE) was significantly greater in the kidneys of adult SHR (n=7) than of BN (n=8) (82 +/- 7 versus 60 +/- 5 pmol/min per milligram protein). Renal 20-HETE production fell 45 percent in SHR and 22 percent in BN in which salt intake was elevated by drinking of saline instead of water for 2 weeks. Mean arterial pressure averaged 157 +/- 3mm Hg in SHR (n = 9) and 100 +/- 2 mm Hg in BN fed a normal salt diet, and it rose to 170 +/- 7 mm Hg (P<.05) in SHR and fell to 90 +/- 3 mm Hg (P<.05) in BN (n=8) after sodium intake was elevated. A polymorphic marker, D5Rjr1, that spanned a repeated element in the P4504A gene on chromosome 5, where all three P4504A isoforms are located, was used for genotyping of the F2 population. The P4504A genotype did not cosegregate with baseline mean arterial pressure in the F2 population; however, significant linkage was observed with the change in mean arterial pressure after sodium intake of the rats was elevated. The degree of linkage differed in male and female rats, and the highest LOD score (3.6) was observed in male F2 rats with a BN grandfather. These findings suggest that the difference in renal P450 activity in SHR and BN does not contribute to the development of hypertension in this F2 population, but it may play some role in determining the blood pressure response to an elevation in salt intake.
Animals↗
Chronic inhalation of nitric oxide inhibits neointimal formation after balloon-induced arterial injury.
Systemic and local intravascular NO administration inhibits neointimal formation after vascular injury in animal models. NO appears to attenuate smooth muscle proliferation both directly and indirectly by preventing the release of growth factors. Inhalation of low concentrations of NO dilates pulmonary vascular smooth muscle but does not cause systemic vasodilatation. Recently, NO inhalation was found to inhibit platelet function in vivo. We studied the effects of NO inhalation on neointimal formation after balloon-induced injury of the adult rat carotid artery. Beginning 60 minutes before carotid injury, rats breathed either air with 0 or 80 ppm NO for 14 days. Rats were killed, carotid arteries were fixed and paraffin-embedded, and neointimal formation was measured by analyzing the ratio of intimal to medial areas (I/M ratio) in carotid artery cross sections. Intimal hyperplasia was evident in both groups of animals, but I/M ratios were 43% less in animals breathing 80 ppm NO for 2 weeks than in animals breathing air alone (0.78 +/- 0.12 and 1.37 +/- 0.11 [mean +/- SE], respectively; P < .02). Similarly, 1 week after carotid injury, neointimal formation was less in rats breathing 80 ppm NO than in rats breathing air alone (I/M ratio, 0.39 +/- 0.11 versus 0.76 +/- 0.06; P < .02). Breathing 20 ppm NO for 2 weeks or 80 ppm NO for 1 week followed by air alone for 1 week did not attenuate neointimal formation measured at 14 days. In anesthetized rats breathing 80 ppm NO or air alone for 1 hour, neither systemic blood pressure nor bleeding time differed. These observations demonstrate that inhaling 80 ppm NO inhibits neointimal formation after balloon-induced carotid artery injury in rats. NO inhalation may represent a safe and novel method of preventing restenosis after percutaneous angioplasty.
Administration, Inhalation↗
A reference cross DNA panel for zebrafish (Danio rerio) anchored with simple sequence length polymorphisms.
The ultimate informativeness of the zebrafish mutations described in this issue will rest in part on the ability to clone these genes. However, the genetic infrastructure required for the positional cloning in zebrafish is still in its infancy. Here we report a reference cross panel of DNA, consisting of 520 F2 progeny (1040 meioses) that has been anchored to a zebrafish genetic linkage map by 102 simple sequence length polymorphisms. This reference cross DNA provides: (1) a panel of DNA from the cross that was used to construct the genetic linkage map, upon which polymorphic gene(s) and genetic markers can be mapped; (2) a fine order mapping tool, with a maximum resolution of 0.1 cM; and (3) a foundation for the development of a physical map (an ordered array of clones each containing a known portion of the genome). This reference cross DNA will serve as a resource enabling investigators to relate genes or genetic markers directly to a single genetic linkage map and avoid the problem of integrating different maps with different genetic markers, as must be currently done when using randomly amplified polymorphic DNA markers, or as has occurred with human genetic linkage maps.
Alleles↗
Extensions to quantitative trait locus mapping in experimental organisms.
Quantitative trait locus (QTL) mapping studies involving inbred model organisms have become important and often-used investigative tools in contemporary genetics research. As a result, a number of statistical methods and study designs have been developed that have made it relatively easy for researchers to determine the rough locations of a number of QTLs that influence traits of all types, including a great many of relevance to hypertension and blood pressure regulation. However, as a whole, these methods and designs are limited in that they are not flexible enough to accommodate many of the complexities associated with quantitative trait expression. In this review, we describe a number of extensions to QTL mapping designs that should make QTL mapping experiments more insightful and compelling. These extensions include multiple QTL modeling with an emphasis on epistatic locus interaction and additive locus effects, the use of multiple phenotypic end points, the design of pharmacogenetic studies, the use of whole-genome parameters in quantitative trait investigations, and issues in mapping QTLs that influence traits that exhibit developmental trends. We use studies investigating the genetic basis of blood pressure regulation to exemplify relevant issues.
Animals↗
Three members of the nitric oxide synthase II gene family (NOS2A, NOS2B, and NOS2C) colocalize to human chromosome 17.
Nitric oxide synthases (NOSs) are a family of enzymes responsible for the synthesis of nitric oxide from L-arginine and molecular oxygen. Three human NOS enzymes (I, II, and III) with differing cellular distribution and regulatory mechanisms have been identified. To determine whether additional NOSs are encoded in the human genome, a bovine NOS II-related cDNA was used to screen two human genomic libraries. Clones containing three independent genes were isolated. One clone encoded the previously identified NOS II gene (NOS2A). The two other genes specified amino acids homologous, but not identical, to human NOS II (NOS2B and NOS2C). Southern blot hybridization demonstrated that all three genes are present in the human genome. DNA from human-mouse somatic cell hybrids were used to determine the chromosomal location of the NOS II-related genes. All three NOS II-related genes colocalized to human chromosome 17 between bands p13.1 and q25. These observations suggest that there is more than one NOS II-related gene in the human genome. This finding may have important implications for the design of NOS isoform-specific inhibitors.
Amino Acid Sequence↗
Cytosolic phospholipase A2 gene in human and rat: chromosomal localization and polymorphic markers.
We report the chromosomal localization and a simple sequence repeat (SSR) in the cytosolic phospholipase A2 (cPLA2) gene in both human and rat. A (CA)18 repeat in the promoter of the rat gene was determined to exhibit length polymorphism when analyzed using the polymerase chain reaction (PCR) in 19 different inbred rat strains. Genotyping for this marker in 234 F2 progeny of a SHR x BN intercross mapped the gene to rat chromosome 13. Using a PCR strategy, a fragment of the promoter for the human gene was isolated, and a (CA)18 repeat was identified. Since this marker displayed a low heterozygosity index, we also identified a mononucleotide repeat in the promoter for cPLA2 that displayed a polymorphism information content value of 0.76. The human gene was mapped using fluorescence in situ hybridization (FISH) to chromosome 1q25. Of interest, the gene encoding the enzyme prostaglandin-endoperoxide synthase 2 (cyclooxygenase-2), which acts on the arachidonic acid product of cPLA2, was previously localized to this same chromosomal region, raising the possibility of coordinate regulation. Identification of intragenic markers may facilitate studies of polymorphic variants of these genes as candidates for disorders in which perturbations of the eicosanoid cascade may play a role.
Animals↗
Genetic map of rat chromosome 5 including the fatty (fa) locus.
Thirteen loci, including the obesity gene fatty (fa), were incorporated into a linkage map of rat Chromosome (Chr) 5. These loci were mapped in obese (fa/fa) progeny of a cross between BN x 13M-fal+F1 animals. Obese rats were scored for BN and 13M alleles at four loci (Ifna, D1S85h, C8b, and Lck1) by restriction fragment length polymorphisms and at eight additional loci (Glut1, Sv4j2, R251, R735, R980, R252, R371, and R1138) by simple sequence length polymorphisms (SSLP). The resulting map spans 67.3 cM of Chr5, presenting nine previously unmapped loci and one locus (Lck1) previously assigned to Chr 5 by use of somatic cell hybrid lines. Seven of the eight SSLP loci are newly identified; the SSLP linkage group alone spans 56.8 cM. The order of the loci is Sv4j2-R251-R735-R980-R1138-Ifna-fa-+ ++D1S85h-C8b-(Glut1-R252-R371)-Lck1. One locus, D1S85h, was found to lie only 0.4 cM from fa, close enough to serve as a reliable marker for the prediction of phenotype from genotype, and will be useful also for studies on the development of obesity in the fatty rat.
Alleles↗
Use of simple sequence length polymorphisms for genetic characterization of rat inbred strains.
Genetic monitoring is an essential component of colony management and for the rat has been accomplished primarily by using immunological and biochemical markers. Here, we report that simple sequence length polymorphisms (SSLPs) are a faster and more economical way of monitoring inbred strains of rats. We characterized 61 inbred strains of rats, using primer pairs for 37 SSLPs. Each of these loci appeared to be highly polymorphic, with the number of alleles per locus ranging between 3 and 14 and, as a result, all the 61 inbred strains tested in this study could be provided with a unique strain profile. These strain profiles are also used for estimating the degree of similarity between strains. This information may provide the rationale in selecting strains for genetic crosses or for other specific purposes.
Animals↗