Human chromosome 17 in essential hypertension

Long non-coding RNA and mRNA analysis of Ang II-induced neuronal dysfunction

The sustained activation of Angiotensin II (Ang II) induces the remodelling of neurovascular units, inflammation and oxidative stress reactions in the brain. Long non-coding RNAs (lncRNAs) play a crucial regulatory role in the pathogenesis of hypertensive neuronal damage. The present study aimed to substantially extend the list of potential candidate genes involved in Ang II-related neuronal damage. This study assessed apoptosis and energy metabolism with Annexin V/PI staining and a Seahorse assay after Ang II exposure in SH-SY5Y cells. The expression of mRNA and lncRNA was investigated by transcriptome sequencing. The integrated analysis of mRNA and lncRNAs and the molecular mechanism of Ang II on neuronal injury was analysed by bioinformatics. Ang II increased the apoptosis rate and reduced the energy metabolism of SH-SY5Y cells. The data showed that 702 mRNAs and 821 lncRNAs were differentially expressed in response to Ang II exposure (244 mRNAs and 432 lncRNAs were upregulated, 458 mRNAs and 389 lncRNAs were downregulated) (fold change ≥ 1.5, P < 0.05). GO and KEGG analyses showed that both DE mRNA and DE lncRNA were enriched in the metabolism, differentiation, apoptosis and repair of nerve cells. This is the first report of the lncRNA-mRNA integrated profile of SH-SY5Y cells induced by Ang II. The novel targets revealed that the metabolism of the vitamin B group, the synthesis of unsaturated fatty acids and glycosphingolipids are involved in the Ang II-related cognitive impairment. Sphingolipid metabolism, the Hedgehog signalling pathway and vasopressin-regulated water reabsorption play important roles in nerve damage.

Conditioning adaptive combination of P-values method to analyze case-parent trios with or without population controls

Detection of rare causal variants can help uncover the etiology of complex diseases. Recruiting case-parent trios is a popular study design in family-based studies. If researchers can obtain data from population controls, utilizing them in trio analyses can improve the power of methods. The transmission disequilibrium test (TDT) is a well-known method to analyze case-parent trio data. It has been extended to rare-variant association testing (abbreviated as "rvTDT"), with the flexibility to incorporate population controls. The rvTDT method is robust to population stratification. However, power loss may occur in the conditioning process. Here we propose a "conditioning adaptive combination of P-values method" (abbreviated as "conADA"), to analyze trios with/without unrelated controls. By first truncating the variants with larger P-values, we decrease the vulnerability of conADA to the inclusion of neutral variants. Moreover, because the test statistic is developed by conditioning on parental genotypes, conADA generates valid statistical inference in the presence of population stratification. With regard to statistical methods for next-generation sequencing data analyses, validity may be hampered by population stratification, whereas power may be affected by the inclusion of neutral variants. We recommend conADA for its robustness to these two factors (population stratification and the inclusion of neutral variants).

MicroRNA network changes in the brain stem underlie the development of hypertension

Hypertension is a major chronic disease whose molecular mechanisms remain poorly understood. We compared neuroanatomical patterns of microRNAs in the brain stem of the spontaneous hypertensive rat (SHR) to the Wistar Kyoto rat (WKY, control). We quantified 419 well-annotated microRNAs in the nucleus of the solitary tract (NTS) and rostral ventrolateral medulla (RVLM), from SHR and WKY rats, during three main stages of hypertension development. Changes in microRNA expression were stage- and region-dependent, with a majority of SHR vs. WKY differential expression occurring at the hypertension onset stage in NTS versus at the prehypertension stage in RVLM. Our analysis identified 24 microRNAs showing time-dependent differential expression in SHR compared with WKY in at least one brain region. We predicted potential gene regulatory targets corresponding to catecholaminergic processes, neuroinflammation, and neuromodulation using the miRWALK and RNA22 databases, and we tested those bioinformatics predictions using high-throughput quantitative PCR to evaluate correlations of differential expression between the microRNAs and their predicted gene targets. We found a novel regulatory network motif consisting of microRNAs likely downregulating a negative regulator of prohypertensive processes such as angiotensin II signaling and leukotriene-based inflammation. Our results provide new evidence on the dynamics of microRNA expression in the development of hypertension and predictions of microRNA-mediated regulatory networks playing a region-dependent role in potentially altering brain-stem cardiovascular control circuit function leading to the development of hypertension.

A haplotype of the GOSR2 gene is associated with essential hypertension in Japanese men

OBJECTIVES

The Golgi SNAP receptor complex member 2 (GOSR2) gene is a Golgi-associated soluble factor attachment receptor (SNARE) protein involved in intra-Golgi protein trafficking on chromosome 17q21, which is the hypertension linkage peak on the human chromosome. The aim of the present study was to assess the association between the human GOSR2 gene and essential hypertension (EH) using a haplotype-based case-control study.

METHODS

A total of 320 EH patients and 205 age-matched controls were genotyped for the five single-nucleotide polymorphisms (SNPs) used as genetic markers for the human GOSR2 gene (rs197932, rs3785889, rs197922, rs17608766, and rs16941382). Data were analyzed for three separate groups: the total subjects, men, and women.

RESULTS

The overall distribution of the haplotypes in men was significantly different between the EH patients and the control subjects (P=0.002). Additionally, the frequency of the T-A-G haplotype (rs197932-rs3785889-rs197922) for men was significantly higher in the EH patients than in the control subjects (P=0.049). After adjustment for the major risk factors, multiple logistic regression analysis also revealed that the frequency of men with the T-A-G haplotype (homozygous and heterozygous diplotypes) was significantly higher than that in men without the haplotype (OR=1.756, P=0.039).

CONCLUSIONS

The results of this study indicate that the T-A-G haplotype may be a useful genetic marker for EH in Japanese men.

Phenylethanolamine N-methyltransferase gene promoter haplotypes and risk of essential hypertension

BACKGROUND

Phenylethanolamine N-methyltransferase gene (PNMT) catalyzes the synthesis of epinephrine and plays an important role in regulating cardiovascular function. Genetic variation in the PNMT promoter is reportedly associated with the risk of essential hypertension in certain population.

METHODS

In the present study, we explored the association of two common PNMT promoter single-nucleotide polymorphisms (SNPs) G-367A (rs3764351) and G-161A (rs876493) and their haplotypes with the risk of essential hypertension in a Han Chinese population, using 316 pairs of age-, sex-, and geographically matched essential hypertension patients and normotensive controls.

RESULTS

No significant difference in allele and genotype frequencies at either G-367A (rs3764351) or G-161A (rs876493) was observed between essential hypertension patients and normotensive controls. However, the 2-SNP AA haplotype was found significantly more common in normotensive controls than in essential hypertensive patients (P = 0.01; adjusted odds ratios, 0.17; 95% confidence interval, 0.05-0.58).

CONCLUSIONS

The 2-SNP AA haplotype in the PNMT promoter is associated with decreased risk of essential hypertension in Han Chinese. This is the first evidence of an association between a PNMT promoter haplotype and the risk of essential hypertension.

Microarray analysis of differential gene expression profile in peripheral blood cells of patients with human essential hypertension

The polygenic nature of essential hypertension and its dependence on environmental factors pose a challenge for biomedical research. We hypothesized that the analysis of gene expression profiles from peripheral blood cells would distinguish patients with hypertension from normotensives. In order to test this, total RNA from peripheral blood cells was isolated. RNA was reversed-transcribed and labeled and gene expression analyzed using significance Analysis Microarrays (Stanford University, CA, USA). Briefly, Significance Analysis Microarrays (SAM) thresholding identified 31 up-regulated and 18 down-regulated genes with fold changes of ≥2 or ≤0.5 and q-value≤5% in expression. Statistically significantly gene ontology (GO) function and biological process differentially expressed in essential hypertension were MHC class II receptor activity and immune response respectively. Biological pathway analysis identified several related pathways which are associated with immune/inflammatory responses. Quantitative Real-Time RT-PCR results were consistent with the microarray results. The levels of C-reactive protein were higher in hypertensive patients than normotensives and inflammation-related genes were increased as well. In conclusion, genes enriched for "immune/inflammatory responses" may be associated with essential hypertension. In addition, there is a correlation between systemic inflammation and hypertension. It is anticipated that these findings may provide accurate and efficient strategies for prevention, diagnosis and control of this disorder.

Xylosyltransferase gene variants and their role in essential hypertension

BACKGROUND

An accumulation of extracellular matrix molecules, such as proteoglycans, is observed in the vascular wall of hypertensive patients. Xylosyltransferases I and II (XT-I and XT-II), the chain-initiating enzymes in the biosynthesis of proteoglycans, catalyze the transfer of D-xylose from UDP-D-xylose to specific serine residues of the core protein. Because associations between XYLT polymorphisms and an altered blood pressure have been observed, genetic variations in the XYLT genes might predispose to essential hypertension. The localization of the XYLT2 gene on chromosome 17q increases its attractiveness as this region has been reported to be a potential candidate locus for essential hypertension.

METHODS

Genotyping of four polymorphisms in the genes XYLT1 and XYLT2 was performed in 150 unrelated essential hypertension patients and 150 age- and sex-matched normotensive controls using restriction fragment length polymorphism analysis.

RESULTS

The allele and genotype frequencies of the XYLT variants investigated did not show any significant differences between patients and controls, among allele-carriers and nonallele-carriers and among recessive and nonrecessive allele-carriers comparing patients and controls. Systolic and diastolic blood pressures did not differ significantly between the genotypes concerning all XYLT variants analyzed. Two XYLT2 variants deviated from Hardy-Weinberg equilibrium (HWE) in the hypertensive group.

CONCLUSIONS

No statistically significant association was found between four XYLT variants and hypertension or blood pressure, suggesting that they do not play a significant role in the development of essential hypertension. The deviation from HWE of two XYLT2 variants might be due to gene-phenotype associations which remain to be explored, as well as the possibility of gene-gene interactions.

GOSR2 Lys67Arg is associated with hypertension in whites

BACKGROUND

Hypertension is a risk factor for coronary heart disease (CHD), but the causes of hypertension remain largely unknown. Genetic variation is thought to contribute to the etiology of hypertension. We tested a single-nucleotide polymorphism (SNP) (Lys67Arg, rs197922) in the Golgi SNAP Receptor Complex Member 2 (GOSR2) gene for association with hypertension and blood pressure (BP). We chose this SNP because it was nominally associated with CHD in earlier studies. Further, GOSR2 is located in a linkage region for hypertension and BP in human and animal studies.

METHODS

We used logistic and linear regression to test associations of the GOSR2 SNP with hypertension and BP among 3,528 blacks and 9,861 whites from the Atherosclerosis Risk in Communities (ARIC) study. Race-specific regression models of hypertension were adjusted for age and gender. Regression models of BP were further adjusted for antihypertensive medication use.

RESULTS

The GOSR2 Lys67 allele was associated with hypertension in whites (odds ratio (OR) = 1.09, P = 0.01) but not blacks (OR = 0.96, P = 0.47). The Lys67 allele was associated with increased systolic BP (SBP) in both races (0.87 mm Hg, P < 0.001 among whites and 1.05 mm Hg, P = 0.05 among blacks). A similar association in whites was observed for the GOSR2 SNP and SBP in the Women's Genome Health Study (WGHS) (OR = 1.03, P = 0.04). The OR remained unchanged after adjustment for antihypertensive medication use (OR = 1.03, P = 0.11), though it was no longer statistically significant.

CONCLUSIONS

We found evidence that a SNP in GOSR2 is modestly associated with hypertension in whites from the ARIC study and the WGHS.

Submegabase resolution of epistatically interacting quantitative trait loci for blood pressure applicable for essential hypertension

OBJECTIVE

Although genetic mapping of quantitative trait loci for blood pressure to large chromosome segments is readily achievable, their final identification confronts formidable hurdles. Restriction of the genes lodging in one quantitative trait locus interval to experimental limitation can facilitate their positional cloning. We previously delineated several quantitative trait loci for blood pressure on chromosome 10 of Dahl salt-sensitive rats, but their chromosome delimitations were either large or not definitive.

METHODS

In this study, we systematically and comprehensively constructed congenic strains with submegabase (Mb) genome resolution and analyzed their blood pressure by telemetry.

RESULTS

Three quantitative trait loci have been conclusively delimited by three congenic strains, each independently lowering the blood pressure. Their intervals are demarcated by genomic regions between 350 and 910 kilobases (kb) in size. Two of the three quantitative trait loci share an epistatic relationship and are separated from one another by less than 170 kb. Two additional quantitative trait loci for blood pressure were also tentatively delineated and their intervals range from 520 kb to 1.75 Mb. Possible genes dwelling in each quantitative trait locus-interval number between 11 and 17. None of these genes is known to exert a functional impact on blood pressure. Work is underway to find candidate genes with mutations that could be responsible for the blood pressure effect.

CONCLUSION

Novel diagnostic, prognostic, preventive and/or therapeutic targets for essential hypertension and hypertension-associated diseases are likely to emerge from the identification of these quantitative trait loci. Potential applications of these quantitative trait loci to humans are suggested from the positive results from several association studies, demonstrating the existence of quantitative trait loci in the broad homologous regions.

Resequencing PNMT in European hypertensive and normotensive individuals: no common susceptibilily variants for hypertension and purifying selection on intron 1

BACKGROUND

Human linkage and animal QTL studies have indicated the contribution of genes on Chr17 into blood pressure regulation. One candidate gene is PNMT, coding for phenylethanolamine-N-methyltransferase, catalyzing the synthesis of epinephrine from norepinephrine.

METHODS

Fine-scale variation of PNMT was screened by resequencing hypertensive (n = 50) and normotensive (n = 50) individuals from two European populations (Estonians and Czechs). The resulting polymorphism data were analyzed by statistical genetics methods using Genepop 3.4, PHASE 2.1 and DnaSP 4.0 software programs. In silico prediction of transcription factor binding sites for intron 1 was performed with MatInspector 2.2 software.

RESULTS

PNMT was characterized by minimum variation and excess of rare SNPs in both normo- and hypertensive individuals. None of the SNPs showed significant differences in allelic frequencies among population samples, as well as between screened hypertensives and normotensives. In the joint case-control analysis of the Estonian and the Czech samples, hypertension patients had a significant excess of heterozygotes for two promoter region polymorphisms (SNP-184; SNP-390). The identified variation pattern of PNMT reflects the effect of purifying selection consistent with an important role of PNMT-synthesized epinephrine in the regulation of cardiovascular and metabolic functions, and as a CNS neurotransmitter. A striking feature is the lack of intronic variation. In silico analysis of PNMT intron 1 confirmed the presence of a human-specific putative Glucocorticoid Responsive Element (GRE), inserted by Alu-mediated transfer. Further analysis of intron 1 supported the possible existence of a full Glucocorticoid Responsive Unit (GRU) predicted to consist of multiple gene regulatory elements known to cooperate with GRE in driving transcription. The role of these elements in regulating PNMT expression patterns and thus determining the dynamics of the synthesis of epinephrine is still to be studied.

CONCLUSION

We suggest that the differences in PNMT expression between normotensives and hypertensives are not determined by the polymorphisms in this gene, but rather by the interplay of gene expression regulators, which may vary among individuals. Understanding the determinants of PNMT expression may assist in developing PNMT inhibitors as potential novel therapeutics.

The genetic dissection of essential hypertension

QTL mapping in humans and rats has identified hundreds of blood-pressure-related phenotypes and genomic regions; the next daunting task is gene identification and validation. The development of novel rat model systems that mimic many elements of the human disease, coupled with advances in the genomic and informatic infrastructure for rats, promise to revolutionize the hunt for genes that determine susceptibility to hypertension. Furthermore, methods are evolving that should enable the identification of candidate genes in human populations. Together with the computational reconstruction of regulatory networks, these methods provide opportunities to significantly advance our understanding of the underlying aetiology of hypertension.

Genome-Wide Linkage Study of Retinal Vessel Diameters in the Beaver Dam Eye Study

Retinal vessels can be observed noninvasively and provide a window to microvascular systems elsewhere in the body. Generalized retinal arteriolar narrowing can represent structural changes resulting from persistent high blood pressure. However, data from recent studies also suggest that generalized retinal arteriolar narrowing might precede hypertension and contribute to its pathogenesis. To determine whether vessel diameters in the eye are genetically determined, we conducted a genome-wide linkage scan on retinal vessel diameters (central retinal artery equivalent and central retinal vein equivalent) using data from the Beaver Dam Eye Study. There were 7 regions on 5 chromosomes (3q28, 5q35, 7q21, 7q32, 11q14, 11q24, and 17q11) showing linkage signals at the nominal multipoint significance level of 0.01 for either covariate-unadjusted or -adjusted central retinal artery equivalent; there were 7 regions on 6 chromosomes (1p36, 6p25, 6q14, 8q21, 11p15, 13q34, and 14q21) showing linkage signals at the nominal multipoint significance level of 0.01 for either covariate-unadjusted or -adjusted central retinal vein equivalent. The linkage results for retinal vessel diameters indicate genetic contributions that remain significant even after adjusting for hypertension and other covariates. In summary, we provide evidence demonstrating that genetic factors independent of hypertension affect retinal vessel diameters.

Association of hypertension with single nucleotide polymorphisms in the quantitative trait locus for abdominal obesity-metabolic syndrome on chromosome 17

Genome scan in Chinese revealed an association of blood pressure with the microsatellite marker D17S1303, which lies in a quantitative trait locus for the abdominal obesity-metabolic syndrome (AOMS2) at 17p12 on chromosome 17. We previously reported that D17S1303 was associated with hypertension and obesity. Therefore, we studied 10 single nucleotide polymorphisms (SNP) within 3 kb of D17S1303. One hundred and eighty hypertensive subjects (91 men, 89 women, age 53+/-12 years) and 180 normotensive matched controls (91 men, 89 women, age 52+/-11) were genotyped using the Sequenom genotyping platform. Allelic frequencies in these Chinese subjects differed from those reported for Caucasians. Three SNPs (rs11656507, rs1357926, rs852319) were homozygous in our subjects. The genotype frequencies of rs852320, rs852321 and rs852322 did not differ between hypertensive and normotensive subjects. However, there were significant differences for rs1525402 (P=0.048), rs2692343 (P=0.022), rs2692344 (P=0.017) and rs2321313 (P=0.028). A four-locus haplotype comprising G at rs1525402, C at rs2692343, C at rs2692344 and G at rs2321313 was associated with lower systolic blood pressure (P=0.023) and normotension (P=0.048). Our results provide further evidence that there is a gene, as yet unidentified, influencing blood pressure in the vicinity of D17S1303 in a quantitative trait locus for abdominal obesity-metabolic syndrome at 17p12.

Epistasis, Not Numbers, Regulates Functions of Clustered Dahl Rat Quantitative Trait Loci Applicable to Human Hypertension

Quantitative trait loci (QTLs) for blood pressure (BP) were found on chromosome 10 of Dahl salt-sensitive rats and are potentially important to human essential hypertension. But their identities and how they influence BP together were not known. Presently, we first fine mapped existing QTLs, C10QTL1, C10QTL2, and C10QTL3, by constructing congenic strains. In the process, a new QTL, C10QTL4, was identified. Because the intervals harboring C10QTL1 and C10QTL4 contain a maximum of 16 and 10 possible genes, respectively, a limited number of specific gene targets has been identified to be QTLs residing in human homologous regions on chromosome 17. Moreover, because none of these candidates encodes a gene known to influence BP, the 2 QTLs will represent novel genes for BP regulations. Second, we used congenic strains with QTL combinations to analyze the interactions between the QTLs. Consequently, a double combination of C10QTL4 and C10QTL1 possessed the same BP as each of the 2 QTLs alone. BP of a triple combination of C10QTL4, C10QTL1, and C10QTL3 was not different from BP of the C10QTL4 and C10QTL1 double combination. These results demonstrate that C10QTL4, C10QTL1, and C10QTL3 are epistatic to one another in their BP effects. In contrast, when adding C10QTL2 into the triple formation of the 3 QTLs above to create a quadruple QTL combination, BP increased proportionately, indicating that C10QTL2 acts independently of C10QTL4, C10QTL1, and C10QTL3. The epistatic and additive interactions uncovered in the animal model will help elucidate similar interactions playing a role in human essential hypertension.

Two major QTLs and several others relate to factors of metabolic syndrome in the family blood pressure program

Genome-wide variance components linkage analysis was performed on 4 latent factors underlying metabolic syndrome derived from 10 risk factors. The latent factors represent obesity and insulin, blood pressure, lipids and insulin, and central obesity. The metabolic syndrome factor scores were derived in 4 ethnic groups recruited in 3 Networks of the Family Blood Pressure Program: GENOA (blacks, Hispanics, and whites), HyperGEN (blacks and whites), SAPPHIRe (Asians). Heritabilities of metabolic syndrome factors ranged from 66% for obesity and insulin to 11% for blood pressure factor. We observed higher heritabilities for obesity and insulin, and lipids and insulin, whereas those for blood pressure and central obesity were smaller. Linkage analysis detected two major quantitative trait loci. One of them linked to the obesity and insulin factor with a lod score of 3.94 (P=0.00001, marker GATA11A06, D18S53, 41.24 cM) at marker positions linkage (lod 4.71, at 46.84 cM at 1-cM-apart distances linkage), located on chromosome 18p11.21 in GENOA black. The other linked to the blood pressure factor with a lod score of 3.22 (P=0.000059, marker GATA49C09, D17S1290, 82 cM) at marker positions linkage (lod 3.56, at 84.63 cM for 1 cM apart distances linkage) located on chromosome 17q23.1 in Hispanics. These quantitative trait loci, together with 4 additional ones with lod scores >2.5, and 30 additional ones with lod score >1.7, offer hope for dissecting the genetic architecture of metabolic syndrome with beneficial implications for molecular diagnosis, prognosis, and in potential medical intervention.

Association of essential hypertension with a microsatellite marker on chromosome 17

Hypertension is related to sodium intake, and many patients with essential hypertension are overweight and have the metabolic syndrome. We therefore studied microsatellite markers close to the thiazide-sensitive Na-Cl cotransporter on chromosome 16 and a quantitative trait locus for abdominal obesity-metabolic syndrome (AOMS2) on chromosome 17, which have been found to be linked to hypertension in a previous genome scan in Chinese. There were 84 hypertensive subjects (44 men, 40 women, age 53+/-13 years) and 88 normotensive controls (40 men, 48 women, age 54+/-13 years) recruited. Specific oligonucleotide primers were used to amplify genomic DNA spanning the microsatellite markers D16S3396 and D17S1303 that consist of ATA and GATA repeats, respectively. We did not find any association between D16S3396 and blood pressure. In contrast, the distribution of D17S1303 genotypes differed between hypertensive subjects and normal controls (P = 0.014). The number of GATA repeats correlated inversely with diastolic blood pressure (r = -0.18, P = 0.02) and body mass index (r = -0.12, P = 0.01). Nine GATA repeats in D17S1303 were associated with hypertension (OR 2.19, 95% CI 1.08-4.44, P = 0.027), while 14 GATA repeats were associated with normotension (OR 0.26, 95% CI 0.10-0.66, P = 0.002). The diastolic blood pressure in those with or without the (GATA)9 allele was 85.9+/-13.6 and 79.2+/-13.6 mmHg respectively (P = 0.01), and in those with or without the (GATA)14 allele it was 73.8+/-11.0 and 81.8+/-14.0 mmHg respectively (P = 0.003). Our results provide further evidence that a gene predisposing to hypertension in Chinese is in the vicinity of the microsatellite D17S1303.

Angiotensin-converting enzyme (ACE) haplotypes and cyclosporine A (CsA) response: a model of the complex relationship between ACE quantitative trait locus and pathological phenotypes

It is highly controversial to define the role of angiotensin-converting enzyme (ACE) polymorphisms in essential hypertension. We studied a group of patients in whom hypertension was the major side effect of treatment by cyclosporine A (CsA). This study group comprised 227 Italian patients with nephrotic syndrome, 103 of which were treated with CsA and had different outcome. Forty-nine patients developed serious hypertension that was reversed after withdrawal of drug. ACE haplotypes were determined by a combination of molecular and statistical methods after verifying genotypes of six intragenic single nucleotide polymorphisms in 304 Italian blood donors and assembling them in clades (A, B, C) that include 95% of observed haplotypes. The association between ACE clade combinations and serum enzymatic levels confirmed the previous results about a role of an unidentified genetic variant at the 5' of the intragenic recombination site located near intron 7. ACE clades were then determined in patients, and regression methods were used to analyze variables associated with CsA responsivity and progression to renal failure. ACE genotype and responsiveness to CsA were strictly associated, because homozygosis for ACE B clade was able to influence CsA sensitivity. This highlights the role of 5' variants, which differentiate clades B and C. Other genetic markers were tested to search for possible additive effects. We found that PAI-1 4G allele was associated with progression to renal failure in the group of CsA-treated patients. Our results are in agreement with the hypothesis, raised after experimental results obtained in mouse models, that the effect of ACE polymorphisms on blood pressure is detectable once environmental factors, like CsA treatment in our case, overcome physiological homeostatic mechanisms.

Genetic variations related to hypertension: a review

Hypertension is a complex multifactorial disorder with genetic, environmental and demographic factors contributing to its prevalence. The genetic element contribution to blood pressure variation ranges from 30 to 50%. Therefore, identifying hypertension susceptibility genes will help understanding the pathophysiology of the disease. In addition to the potential impact of genomic information in selecting antihypertensive drug therapy, it may also help in recognizing those at risk of developing the disease, which may lead to new preventive approaches. Several strategies and methods have been used to identify hypertension susceptibility genes. Currently, genetic analysis of such data produced complex results, which makes it difficult to draw final conclusion on the use of genomic data in management of hypertension. This review attempts to summarize present known genetic variations that may be implicated in the pathogenesis of hypertension and to discuss various research strategies used to identify them. It also highlights some of the opportunities and challenges, which may be encountered in interpreting the value of these genetic variations to improve management of hypertension.

Genetic susceptibility loci for essential hypertension and blood pressure on chromosome 17 in 147 Chinese pedigrees

OBJECTIVES

We scanned human chromosome 17 to verify previous studies on the chromosome as well as to explore possible new loci of essential hypertension in a Chinese Han population.

METHODS

A genomic scan of chromosome 17 with 15 microsatellite markers was conducted in a total of 757 individuals from 147 Chinese hypertension pedigrees. We used three softwares to analyse hypertension as a qualitative trait and blood pressure as quantitative phenotypes linkage analyses in the North group (406 individuals from 78 northern families), the South group (351 individuals from 69 southern families) and the combined group of the Chinese population separately.

RESULTS

For qualitative trait, a 7-cM (centiMorgan) interval flanked by D17S831 (7 cM) and D17S938 (15 cM) showed suggestive linkage results (P < 0.00074) in the southern population by SAGE/SIBPAL2. For blood pressure (BP) quantitative phenotypes, the regions with lowest P values in SAGE and highest logarithm of odds (LOD) scores in SOLAR just overlapped this 7-cM interval in the South group for both systolic blood pressure (SBP) and diastolic blood pressure (DBP), though these peaks did not yet reach to the suggestive linkage criteria (P = 0.00074, LOD score = 2.2). In the northern population, in a region around 75.0 cM (D17S787) a peak was found with non-parametric-linkage (NPL) score 1.82 for qualitative trait using GENEHUNTER.

CONCLUSIONS

In the southern population of China, our results demonstrate that a 7-cM interval region flanked by D17S831 (7 cM) and D17S938 (15 cM) is suggestively linked with hypertension.

WNK4 Intron 10 Polymorphism Is Not Associated With Hypertension

A polymorphism in intron 10 of the serine-threonine kinase with no lysine (K) 4 gene WNK4 (G-->A, base 1156666 on chromosome 17) has recently been associated with essential hypertension in a white American population. We have attempted to replicate this finding in a well characterized cohort of 184 unrelated hypertensive Australians of British extraction in which biological power was enhanced by them each having 2 hypertensive parents. Controls were 219 normotensive ethnically matched subjects whose parents were both normotensive. Genotyping was performed using the homogeneous MassEXTEND Assay. This showed a frequency of 0.10 for the minor allele in each group (P=0.88). Moreover, blood pressure, body mass index, sex, and plasma lipid levels were similar across genotypes. In conclusion, our study provides no support for an association of the intron 10 variant of WNK4 with essential hypertension in the Anglo-Australian population studied.