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ABSTRACT: Renin was the first blood pressure (BP) quantitative trait locus mapped by linkage analysis in the rat. Subsequent BP linkage and congenic studies capturing different portions of the renin region have returned conflicting results, suggesting that multiple interdependent BP loci may be residing in the chromosome 13 BP quantitative trait locus that includes Renin. We used SS-13BN congenic strains to map 2 BP loci in the Renin region (chr13: 45.2-49.0 Mb). We identified a 1.1-Mb protective Brown Norway region around Renin (chr13: 46.1-47.2 Mb) that significantly decreased BP by 32 mm Hg. The Renin protective BP locus was offset by an adjacent hypertensive locus (chr13: 47.2-49.0 Mb) that significantly increased BP by 29 mm Hg. Sequence analysis of the protective and hypertensive BP loci revealed 1433 and 2063 variants between Dahl salt-sensitive/Mcwi and Brown Norway rats, respectively. To further reduce the list of candidate variants, we regenotyped an overlapping SS-13SR congenic strain (S/renrr) with a previously reported BP phenotype. Sequence comparison among Dahl salt-sensitive, Dahl R, and Brown Norway reduced the number of candidate variants in the 2 BP loci by 42% for further study. Combined with previous studies, these data suggest that at least 4 BP loci reside within the 30-cM chromosome 13 BP quantitative trait locus that includes Renin.
Hypertension 03/2013; · 6.21 Impact Factor
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ABSTRACT: We previously reported that the fawn-hooded hypertensive (FHH) rat is a natural Rab38 knockout, supported by a congenic animal (FHH.BN-Rab38) having less proteinuria than FHH animals. Because these congenic animals contain Brown Norway (BN) alleles for five other named genes; however, a causal role for Rab38 in the FHH phenotype remains uncertain. Here, we used transgenic and knockout models to validate Rab38 and to exclude other genes within the 1.5 Mb congenic region from involvement in causing the FHH phenotype. Transgenic rats homozygous for the wild-type Rab38 BN allele on the FHH background exhibited phenotypic rescue, having 43% lower proteinuria and 75% lower albuminuria than nontransgenic FHH littermates. Conversely, knockout of the Rab38 gene on the FHH.BN-Rab38 congenic line recapitulated a proteinuric phenotype indistinguishable from the FHH strain. In addition, in cultured proximal tubule LLC-PK1 cells, knockdown of Rab38 mRNA significantly decreased endocytosis of colloidal gold-coupled albumin, supporting the hypothesis that Rab38 modulates proteinuria through effects on tubular re-uptake and not by altering glomerular permeability. Taken together, these findings validate Rab38 as a gene having a causal role in determining the phenotype of the FHH rat, which models hypertension-associated renal disease. Furthermore, our data suggest that Rab38 affects urinary protein excretion via effects in the proximal tubule.
Journal of the American Society of Nephrology 01/2013; · 9.66 Impact Factor
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Katharina Katter,
Aron M Geurts,
Orsolya Hoffmann,
Lajos Mátés,
Vladimir Landa,
László Hiripi, Carol Moreno,
Jozef Lazar,
Sanum Bashir,
Vaclav Zidek, [......],
Molly Corbett,
Artur Rangel Filho,
Matthew R Hodges,
Michael Bader,
Zoltán Ivics,
Howard J Jacob,
Michal Pravenec,
Zsuzsanna Bosze,
Thomas Rülicke,
Zsuzsanna Izsvák
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ABSTRACT: Germline transgenesis is an important procedure for functional investigation of biological pathways, as well as for animal biotechnology. We have established a simple, nonviral protocol in three important biomedical model organisms frequently used in physiological studies. The protocol is based on the hyperactive Sleeping Beauty transposon system, SB100X, which reproducibly promoted generation of transgenic founders at frequencies of 50-64, 14-72, and 15% in mice, rats, and rabbits, respectively. The SB100X-mediated transgene integrations are less prone to genetic mosaicism and gene silencing as compared to either the classical pronuclear injection or to lentivirus-mediated transgenesis. The method was successfully applied to a variety of transgenes and animal models, and can be used to generate founders with single-copy integrations. The transposon vector also allows the generation of transgenic lines with tissue-specific expression patterns specified by promoter elements of choice, exemplified by a rat reporter strain useful for tracking serotonergic neurons. As a proof of principle, we rescued an inborn genetic defect in the fawn-hooded hypertensive rat by SB100X transgenesis. A side-by-side comparison of the SB100X- and piggyBac-based protocols revealed that the two systems are complementary, offering new opportunities in genome manipulation.-Katter, K., Geurts, A. M., Hoffmann, O., Mátés, L., Landa,V., Hiripi, L., Moreno, C., Lazar, J., Bashir, S., Zidek, V., Popova, E., Jerchow, B., Becker, K., Devaraj, A., Walter, I., Grzybowksi, M., Corbett, M., Rangel Filho, A., Hodges, M. R., Bader, M., Ivics, Z., Jacob, H. J., Pravenec, M., Bősze, Z., Rülicke, T., Izsvák, Z. Transposon-mediated transgenesis, transgenic rescue, and tissue-specific gene expression in rodents and rabbits.
The FASEB Journal 11/2012; · 5.71 Impact Factor
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Chun Yang,
Francesco C Stingo,
Kwang Woo Ahn,
Pengyuan Liu,
Marina Vannucci,
Purushottam W Laud,
Meredith Skelton,
Paul O'Connor,
Terry Kurth,
Robert P Ryan, Carol Moreno,
Shirng-Wern Tsaih,
Giannino Patone,
Oliver Hummel,
Howard J Jacob,
Mingyu Liang,
Allen W Cowley
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ABSTRACT: Studies of transcriptome profiles have provided new insights into mechanisms underlying the development of hypertension. Cell type heterogeneity in tissue samples, however, has been a significant hindrance in these studies. We performed a transcriptome analysis in medullary thick ascending limbs of the loop of Henle isolated from Dahl salt-sensitive rats. Genes differentially expressed between Dahl salt-sensitive rats and salt-insensitive consomic SS.13(bn) rats on either 0.4% or 7 days of 8.0% NaCl diet (n=4) were highly enriched for genes located on chromosome 13, the chromosome substituted in the SS.13(bn) rat. A pathway involving cell proliferation and cell cycle regulation was identified as one of the most highly ranked pathways based on differentially expressed genes and by a Bayesian model analysis. Immunofluorescent analysis indicated that just 1 week of a high-salt diet resulted in a severalfold increase in proliferative medullary thick ascending limb cells in both rat strains, and that Dahl salt-sensitive rats exhibited a significantly greater proportion of medullary thick ascending limb cells in a proliferative state than in SS.13(bn) rats (15.0±1.4% versus 10.1±0.6%; n=7-9; P<0.05). The total number of cells per medullary thick ascending limb section analyzed was not different between the 2 strains. The study revealed alterations in regulatory pathways in Dahl salt-sensitive rats in tissues highly enriched for a single cell type, leading to the unexpected finding of a greater increase in the number of proliferative medullary thick ascending limb cells in Dahl salt-sensitive rats on a high-salt diet.
Hypertension 11/2012; · 6.21 Impact Factor
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ABSTRACT: Previous studies have identified multiple blood pressure and renal disease quantitative trait loci located on rat chromosome 12. In the present study, we narrowed blood pressure loci using a series of overlapping Dahl salt-sensitive/Mcwi (SS)-12 Brown Norway (BN) congenic lines. We found that transferring 6.1 Mb of SS chromosome 12 (13.4-19.5 Mb) onto the consomic SS-12(BN) background significantly elevated blood pressure on 1% NaCl (146 ± 6 versus 127 ± 1 mm Hg; P<0.001) and 8% NaCl diets (178 ± 7 versus 144 ± 2 mm Hg; P<0.001). Compared with the SS-12(BN) consomic, these animals also had significantly elevated albumin (218 ± 31 versus 104 ± 8 mg/d; P<0.001) and protein excretion (347 ± 41 versus 195 ± 12 mg/d; P<0.001) on a 1% NaCl diet. Elevated blood pressure, albuminuria, and proteinuria coincided with greater renal and cardiac damage, demonstrating that SS allele(s) within the 6.1 Mb congenic interval are associated with strong cardiovascular disease phenotypes. Sequence analysis of the 6.1 Mb congenic region revealed 12 673 single nucleotide polymorphisms between SS and BN rats. Of these polymorphisms, 293 lie within coding regions, and 18 resulted in nonsynonymous changes in conserved genes, of which 5 were predicted to be potentially damaging to protein function. Syntenic regions in human chromosome 7 have also been identified in multiple linkage and association studies of cardiovascular disease, suggesting that genetic variants underlying cardiovascular phenotypes in this congenic strain can likely be translated to a better understanding of human hypertension.
Hypertension 08/2012; 60(4):942-8. · 6.21 Impact Factor
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ABSTRACT: Human data and animal models of autosomal recessive polycystic kidney disease (ARPKD) suggest that genetic factors modulate the onset and severity of the disease. We report here for the first time that ARPKD susceptibility is attenuated by introgressing the mutated Pkhd1 disease allele from the polycystic kidney (PCK) rat onto the FHH (Fawn-Hooded Hypertensive) genetic background. Compared with PCK, the FHH.Pkhd1 strain had significantly decreased renal cyst formation that coincided with a threefold reduction in mean kidney weights. Further analysis revealed that the FHH. Pkhd1 is protected from increased blood pressure as well as elevated plasma creatinine and blood urea nitrogen levels. On the other hand, liver weight and biliary cystogenesis revealed no differences between PCK and FHH.Pkdh1, indicating that genes within the FHH genetic background prevent the development of renal, but not hepatic, manifestations of ARPKD. Microarray expression analysis of kidneys from 30-day-old PCK rats revealed increased expression of genes previously identified in PKD renal expression profiles, such as inflammatory response, extracellular matrix synthesis, and cell proliferation genes among others, whereas the FHH.Pkhd1 did not show activation of these common markers of disease. This newly developed strain can serve as a tool to map modifier genes for renal disease in ARPKD and provides further insight into disease variability and pathophysiology.
Physiological Genomics 06/2012; 44(15):741-53. · 2.73 Impact Factor
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ABSTRACT: In recent years, the PG group has begun to increase its scientific activities specifically at the Experimental Biology meetings as exemplified by this report on the activities of the Physiological Genomics (PG) Interest group of the American Physiological Society (APS) at the Experimental Biology meeting 2012 held in San Diego, CA, which coincided with the 125(th) anniversary of the APS. The wide-range of scientific activities and presentations sponsored by the group included a cross-sectional workshop, PG group specific symposium, featured topic session and a trainee-highlight session. The prestigious Henry Bowditch Award was also bagged by one of the members of the PG group, Dr. Mingyu Liang. Finally, this year's meeting was also testimony to the PG group's commitment and support to our trainees, whose research presentations were recognized with awards made possible through generous support from corporate organizations.
Physiological Genomics 05/2012; 44(14):699-701. · 2.73 Impact Factor
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Caitlin C O'Meara,
Michelle M Lutz,
Allison B Sarkis,
Haiyan Xu,
Rajendra K Kothinti,
Matthew Hoffman, Carol Moreno,
Niloofar M Tabatabai,
Jozef Lazar,
Richard J Roman,
Howard J Jacob
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ABSTRACT: The combined transfer of two renal function quantitative trait loci (QTLs), Rf-1 (rat chromosome 1) and Rf-4 (rat chromosome 14), from the Fawn-hooded hypertensive rat onto the August Copenhagen Irish genetic background significantly increases proteinuria and demonstrates an interaction between these QTLs. Because the original Rf-4 congenic region is 61.9 Mbp, it is necessary to reduce this interval to feasibly search for variants responsible for renal susceptibility in this region. Here, we generated a minimal congenic line (Rf-1a+4_a) to identify a 4.1-Mb region of the Rf-4 QTL that significantly contributes to the severity of proteinuria in the Fawn-hooded hypertensive rat. Rf-1a+4_a animals have an increased glomerular permeability to albumin without significant changes in BP, indicating that at least one genetic element in this refined region directly affects renal function. Sequence analysis revealed no variants predicted to damage protein function, implying that regulatory elements are responsible for the Rf-4 phenotype. Multiple human studies, including recent genome-wide association studies, link the homologous human region with susceptibility to renal disease, suggesting that this congenic line is an important model for studying pathways that contribute to the progression of kidney disease.
Journal of the American Society of Nephrology 02/2012; 23(5):825-33. · 9.66 Impact Factor
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ABSTRACT: A pharmacogenomic approach was used to further localize the genetic region responsible for previously observed enhanced cardiovascular sensitivity to propofol in Dahl Salt Sensitive (SS) versus control Brown Norway (BN) rats.
Propofol infusion levels that decreased blood pressure by 50% were measured in BN.13(SS) rats (substitution of SS chromosome 13 into BN) and in five congenic (partial substitution) strains of SS.13(BN). The effect of superfused 2,6 diisopropylphenol on small mesenteric arterial vascular smooth muscle transmembrane potential was measured in congenic strains before and during superfusion with Rp-adenosine-3',5'-cyclic monophosphorothioate and 2.5 μM (Rp)-8-(para-chlorophenylthio)guanosine-3',5'-cyclic monophosphorothioate, inhibitors of protein kinase A and G, respectively. The genetic locus and potential role of the renin gene in mediating vascular smooth muscle sensitivity to propofol were determined in three selected subcongenic SS.BN¹³ strains.
A 30-32% smaller propofol infusion rate reduced blood pressure by 50% in BN.13(SS) compared with BN and the SS.13(BN) congenic containing an 80 BN gene substitution. Compared with the 80 BN gene-containing SS.13(BN) congenic, SS exhibited greater protein kinase A dependent vascular smooth muscle hyperpolarization in response to propofol. Using subcongenics, the increased propofol-induced cardiovascular sensitivity and hyperpolarization was further localized to an eight-gene region (containing the BN renin gene). Blockade of angiotensin receptors with losartan in this subcongenic increased propofol-induced hyperpolarization by threefold to that observed in SS.
Enhanced cardiovascular sensitivity to propofol in SS (compared with BN) is caused by an altered renin gene. Through modified second messenger function, this differentially regulates vascular smooth muscle contractile state and reduces vascular tone, thereby exacerbating cardiovascular depression by propofol.
Anesthesiology 12/2011; 115(6):1192-200. · 5.36 Impact Factor
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ABSTRACT: Impaired regulation of renin in Dahl salt-sensitive rats (SS/JRHsdMcwi, SS) contributes to attenuated angiogenesis in this strain. This study examined angiogenic function and genomic structure of regions surrounding the renin gene using subcongenic strains of the SS and BN/NHsdMcwi (BN) rat to identify important genomic variations between SS and BN involved in angiogenesis. Three candidate regions on Chr 13 were studied: two congenic strains containing 0.89 and 2.62 Mb portions of BN Chr 13 that excluded the BN renin allele and a third strain that contained a 2.02 Mb overlapping region that included the BN renin allele. Angiogenesis induced by electrical stimulation of the tibialis anterior muscle was attenuated in the SS compared with the BN. Congenics carrying the SS renin allele had impaired angiogenesis, while strains carrying the BN renin allele had angiogenesis restored. The exception was a congenic including a region of BN genome 0.4 Mb distal to renin that restored both renin regulation and angiogenesis. This suggests that there is a distant regulatory element in the BN capable of restoring normal regulation of the SS renin allele. The importance of ANG II in the restored angiogenic response was demonstrated by blocking with losartan. Sequencing of the 4.05 Mb candidate region in SS and BN revealed a total of 8,850 SNPs and other sequence variants. An analysis of the genes and their variants in the region suggested a number of pathways that may explain the impaired regulation of renin and angiogenesis in the SS rat.
Physiological Genomics 04/2011; 43(13):808-17. · 2.73 Impact Factor
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ABSTRACT: The renin-angiotensin system plays an important role in the control of blood pressure (BP) and renal function. To illuminate the importance of renin in the context of a disease background in vivo, we used zinc-finger nucleases (ZFNs) designed to target the renin gene and create a renin knockout in the SS/JrHsdMcwi (SS) rat. ZFN against renin caused a 10-bp deletion in exon 5, resulting in a frameshift mutation. Plasma renin activity was undetectable in the Ren-/- rat, and renin protein was absent from the juxtaglomerular cells in the kidney. Body weight was lower in the Ren-/- rats (than in the Ren+/- or wild-type littermates), and conscious BP on low-salt diet (0.4% NaCl) was 58 ± 2 mm Hg in the Ren-/- male rats versus 117 mm Hg in the Ren+/- littermates, a reduction of almost 50 mm Hg. Blood urea nitrogen (BUN) and plasma creatinine levels were elevated in the Ren-/- strain (BUN 112 ± 7 versus 23 ± 2 mg/dL and creatinine 0.53 ± 0.02 versus 0.26 ± 0.02 mg/dL), and kidney morphology was abnormal with a rudimentary inner renal medulla, cortical interstitial fibrosis, thickening of arterial walls, and abnormally shaped glomeruli. The development of the first rat knockout in the renin-angiotensin system demonstrates the efficacy of the ZFN technology for creating knockout rats for cardiovascular disease on any genetic background and emphasizes the role of renin in BP regulation and kidney function even in the low-renin SS rat.
Hypertension 03/2011; 57(3):614-9. · 6.21 Impact Factor
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ABSTRACT: Transfer of chromosome 13 from the Brown Norway (BN) rat onto the Dahl salt-sensitive (SS) genetic background attenuates the development of hypertension, but the genes involved remain to be identified. The purpose of the present study was to confirm by telemetry that a congenic strain [SS.BN-(D13Hmgc37-D13Got22)/Mcwi, line 5], carrying a 13.4-Mb segment of BN chromosome 13 from position 32.4 to 45.8 Mb, is protected from the development of hypertension and then to narrow the region of interest by creating and phenotyping 11 additional subcongenic strains. Mean arterial pressure (MAP) rose from 118 ± 1 to 186 ± 5 mmHg in SS rats fed a high-salt diet (8.0% NaCl) for 3 wk. Protein excretion increased from 56 ± 11 to 365 ± 37 mg/day. In contrast, MAP only increased to 152 ± 9 mmHg in the line 5 congenic strain. Six subcongenic strains carrying segments of BN chromosome 13 from 32.4 and 38.2 Mb and from 39.9 to 45.8 Mb were not protected from the development of hypertension. In contrast, MAP was reduced by ∼30 mmHg in five strains, carrying a 1.9-Mb common segment of BN chromosome 13 from 38.5 to 40.4 Mb. Proteinuria was reduced by ∼50% in these strains. Sequencing studies did not identify any nonsynonymous single nucleotide polymorphisms in the coding region of the genes in this region. RT-PCR studies indicated that 4 of the 13 genes in this region were differentially expressed in the kidney of two subcongenic strains that were partially protected from hypertension vs. those that were not. These results narrow the region of interest on chromosome 13 from 13.4 Mb (159 genes) to a 1.9-Mb segment containing only 13 genes, of which 4 are differentially expressed in strains partially protected from the development of hypertension.
AJP Heart and Circulatory Physiology 01/2011; 300(4):H1530-5. · 3.71 Impact Factor
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ABSTRACT: This study evaluated endothelium-dependent vascular relaxation in response to acetylcholine (ACh) in isolated middle cerebral arteries (MCA) from Dahl salt-sensitive (Dahl SS) rats and three different congenic strains that contain a portion of Brown Norway (BN) chromosome 13 introgressed onto the Dahl SS genetic background through marker-assisted breeding. Two of the congenic strains carry a 3.5-Mbp portion and a 2.6-Mbp portion of chromosome 13 that lie on opposite sides of the renin locus, while the third contains a 2.0-Mbp overlapping region that includes the BN renin allele. While maintained on a normal salt (0.4% NaCl) diet, MCAs from Dahl SS rats and the congenic strains retaining the Dahl SS renin allele failed to dilate in response to ACh, whereas MCAs from the congenic strain carrying the BN renin allele exhibited normal vascular relaxation. In congenic rats receiving the BN renin allele, vasodilator responses to ACh were eliminated by nitric oxide synthase inhibition with N(G)-nitro-l-arginine methyl ester, angiotensin-converting enzyme inhibition with captopril, and AT(1) receptor blockade with losartan. N(G)-nitro-l-arginine methyl ester-sensitive vasodilation in response to ACh was restored in MCAs of Dahl SS rats that received either a 3-day infusion of a subpressor dose of angiotensin II (3 ng·kg(-1)·min(-1) iv), or chronic treatment with the superoxide dismutase mimetic tempol (15 mg·kg(-1)·day(-1)). These findings indicate that the presence of the Dahl SS renin allele plays a crucial role in endothelial dysfunction present in the cerebral circulation of the Dahl SS rat, even in the absence of elevated dietary salt intake, and that introgression of the BN renin allele rescues endothelium-dependent vasodilator responses by restoring normal activation of the renin-angiotensin system.
AJP Heart and Circulatory Physiology 12/2010; 299(6):H1865-74. · 3.71 Impact Factor
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ABSTRACT: The rat has long been a model favored by physiologists, pharmacologists and neuroscientists. However, over the past two decades, many investigators in these fields have turned to the mouse because of its gene modification technologies and extensive genomic resources. Although the genomic resources of the rat have nearly caught up, gene targeting has lagged far behind, limiting the value of the rat for many investigators. In the past two years, advances in transposon- and zinc finger nuclease (ZFN)-mediated gene knockout as well as the establishment and culturing of embryonic and inducible pluripotent stem cells have created new opportunities for rat genetic research. Here, we provide a high-level description and the potential uses of these new technologies for investigators using the rat for biomedical research.
Trends in Genetics 12/2010; 26(12):510-8. · 10.06 Impact Factor
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ABSTRACT: Rf-3, a quantitative trait locus (QTL) on rat chromosome 3, affects the development of CKD in Fawn-Hooded Hypertensive (FHH) rats. This QTL spans 110 Mb and approximately 1400 genes; therefore, narrowing the position of this locus is necessary to elucidate potential candidate genes. Here, we used congenic models and comparative genomics to refine the Rf-3 candidate region. We generated congenic lines carrying smaller intervals (subcongenics) of the Rf-3 region and used these lines to reduce the Rf-3 candidate region by 94% (to 7.1 Mb). We used comparative genomics to identify QTL for both nephropathy and albuminuria in the syntenic region of this interval for both human and mouse. We also used the overlapping homologous regions to reduce the number of likely positional candidate genes to 13 known or predicted genes. By combining congenic models and cross-species studies, we narrowed the list of candidate genes to a level that we could sequence the whole interval to further identify the causative gene in future studies.
Journal of the American Society of Nephrology 12/2010; 22(3):518-25. · 9.66 Impact Factor
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ABSTRACT: We here report the genetic basis for susceptibility and resistance to carcinogen-mediated [7,12-dimethylbenz[a]anthracene (DMBA)] mammary tumorigenesis using the full panel of SS/BN consomic rat strains, in which substitutions of individual chromosomes from the resistant BN strain onto the genomic background of the susceptible SS strain were made. Analysis of 252 consomic females identified rat mammary Quantitative Trait Loci (QTLs) affecting tumor incidence on chromosomes 3 and 5, latency on chromosomes 3, 9, 14, and 19, and multiplicity on chromosomes 13, 16, and 19. In addition, we unexpectedly identified a novel QTL on chromosome 6 controlling a lethal toxic phenotype in response to DMBA. Upon further investigation with chromosomes 6 and 13 congenic lines, in which an additional 114 rats were investigated, we mapped (1) a novel mammary tumor QTL to a region of 27.1 Mbp in the distal part of RNO6, a region that is entirely separated from the toxicity phenotype, and (2) a novel and powerful mammary tumor susceptibility locus of 4.5 Mbp that mapped to the proximal q-arm of RNO13. Comparison of genetic strain differences using existing rat genome databases enabled us to further construct priority lists containing single breast cancer candidate genes within the defined QTLs, serving as potential functional variants for future testing.
Genes Chromosomes and Cancer 11/2010; 49(11):1035-45. · 3.31 Impact Factor
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ABSTRACT: The importance of genetic laboratory models, such as mice and rats, becomes evident when there is a poor understanding of the nature of human disease. Many rat models for human disease, created over the years by phenotype-driven strategies, now provide a foundation for the identification of their genetic determinants. These models are especially valuable with the emerging need for validation of genes found in genome-wide association studies for complex diseases. The manipulation of the rat genome using engineered zinc-finger nucleases now introduces a key technology for manipulating the rat genome, which is broadly applicable. The ability to generate knockout rat models using zinc-finger nuclease technology will now enable its full emergence as an exceptional physiological and genetic research model.
Clinical Science 10/2010; 119(8):303-11. · 4.61 Impact Factor
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ABSTRACT: Congenic strains continue to be a fundamental resource for dissecting the genetic basis of complex traits. Traditionally, genetic variants (QTLs) that account for phenotypic variation in a panel of congenic strains are sought first by comparing phenotypes for each strain to the host (reference) strain, and then by examining the results to identify a common chromosome segment that provides the best match between genotype and phenotype across the panel. However, this "common-segment" method has significant limitations, including the subjective nature of the genetic model and an inability to deal formally with strain phenotypes that do not fit the model. We propose an alternative that we call "sequential" analysis and that is based on a unique principle of QTL analysis where each strain, corresponding to a single genotype, is tested individually for QTL effects rather than testing the congenic panel collectively for common effects across heterogeneous backgrounds. A minimum spanning tree, based on principles of graph theory, is used to determine the optimal sequence of strain comparisons. For two traits in two panels of congenic strains in mice, we compared results for the sequential method with the common-segment method as well as with two standard methods of QTL analysis, namely, interval mapping and multiple linear regression. The general utility of the sequential method was demonstrated with analysis of five additional traits in congenic panels from mice and rats. Sequential analysis rigorously resolved phenotypic heterogeneity among strains in the congenic panels and found QTLs that other methods failed to detect.
Mammalian Genome 06/2010; 21(5-6):276-86. · 2.89 Impact Factor
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Limin Lu,
Peigang Li,
Chun Yang,
Terry Kurth,
Michael Misale,
Meredith Skelton, Carol Moreno,
Richard J Roman,
Andrew S Greene,
Howard J Jacob,
Jozef Lazar,
Mingyu Liang,
Allen W Cowley
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ABSTRACT: Chromosome 13 consomic and congenic rat strains were analyzed to investigate the pattern of genomic pathway utilization involved in protection against salt-sensitive hypertension and renal injury. Introgression of the entire Brown-Norway chromosome 13 (consomic SS-13(BN)) or nonoverlapping segments of this chromosome (congenic strains, 16 Mbp in D13Rat151-D13Rat197 or 14 Mbp in D13Rat111-D13Got22) into the genome of the Dahl salt-sensitive rat attenuated salt-induced hypertension and proteinuria. mRNA abundance profiles in the renal cortex and the renal medulla from rats receiving 0.4% or 8% NaCl diets revealed two important features of pathway recruitment in these rat strains. First, the two congenic strains shared alterations in several pathways compared with Dahl salt-sensitive rats, despite the fact that the genomic segments introgressed in the two congenic strains did not overlap. Second, even though the genomic segment introgressed in each congenic strain was a part of the chromosome introgressed in the consomic strain, pathways altered in each congenic strain were not simply a subset of those altered in the consomic. Supporting the relevance of the mRNA data, differential expression of oxidative stress-related genes among the four strains of rats was associated with differences in urinary excretion of lipid peroxidation products. The findings suggest that different genetic alterations might converge to influence shared pathways in protection from hypertension, and that, depending on the genomic context, the same genetic alteration might diverge to affect different pathways.
Physiological Genomics 12/2009; 41(1):63-70. · 2.73 Impact Factor
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ABSTRACT: Cardiovascular sensitivity to general anesthetics is highly variable among individuals in both human and animal models, but little is known about the genetic determinants of drug response to anesthetics. Recently, we reported that propofol (2,6-diisopropylphenol) causes circulatory instability in Dahl salt-sensitive SS/JRHsdMcwi (SS) rats but not in Brown Norway BN/NHsdMcwi (BN) rats and that these effects are related to genes on chromosome 13. Based on the hypothesis that propofol does target mesenteric circulation, we investigated propofol modulation of mesenteric arterial smooth muscle cells (MASMC) in SS and BN rats. The role of chromosome 13 was tested using SS-13(BN)/Mcwi and BN-13(SS)/Mcwi consomic strains with chromosome 13 substitution. Propofol (5 microM) produced a greater in situ hyperpolarization of MASMC membrane potential in SS than BN rats, and this effect was abrogated by iberiotoxin, a voltage-activated potassium (BK) channel blocker. In inside-out patches, the BK channel number, P(o), and apparent Ca(2+) sensitivity, and propofol sensitivity all were significantly greater in MASMC of SS rats. The density of whole-cell BK current was increased by propofol more in SS than BN myocytes. Immunolabeling confirmed higher expression of BK alpha subunit in MASMC of SS rats. Furthermore, the hyperpolarization produced by propofol, the BK channel properties, and propofol sensitivity were modified in MASMC of SS-13(BN)/Mcwi and BN-13(SS)/Mcwi strains toward the values observed in the background SS and BN strains. We conclude that differential function and expression of BK channels, resulting from genetic variation within chromosome 13, contribute to the enhanced propofol sensitivity in SS and BN-13(SS)/Mcwi versus BN and SS-13(BN)/Mcwi strains.
Journal of Pharmacology and Experimental Therapeutics 07/2009; 330(3):727-35. · 3.83 Impact Factor
