Association and linkage analysis of the alpha-adducin gene and blood pressure

Variation in genes that regulate blood pressure are associated with glomerular filtration rate in Chinese

Chronic kidney disease (CKD) can be a consequence of diabetes, hypertension, immunologic disorders, and other exposures, as well as genetic factors that are still largely unknown. Glomerular filtration rate (GFR), which is widely used to measure kidney function, has a heritability ranging from 25% to 75%, but only 1.5% of this heritability is explained by genetic loci that have been identified to date. In this study we tested for associations between GFR and 234 SNPs in 26 genes from pathways of blood pressure regulation in 3,025 rural Chinese participants of the "Genetic Epidemiology Network of Salt Sensitivity" (GenSalt) study. We estimated GFR (eGFR) using baseline serum creatinine measurements obtained prior to dietary intervention. We identified significant associations between eGFR and 12 SNPs in 6 genes (ACE, ADD1, AGT, GRK4, HSD11B1, and SCNN1G). The cumulative effect of the protective alleles was an increase in mean eGFR of 4 mL/min per 1.73 m2, while the cumulative effect of the risk alleles was a decrease in mean eGFR of 3 mL/min per 1.73 m2. In addition, we identified a significant interaction between SNPs in CYP11B1 and ADRB2. We have identified common variants in genes from pathways that regulate blood pressure and influence kidney function as measured by eGFR, providing new insights into the genetic determinants of kidney function. Complex genetic effects on kidney function likely involve interactions among genes as we observed for CYP11B1 and ADRB2.

The Gly460Trp polymorphism of alpha-adducin gene as a predictor of renal function decline over 4 years of follow-up in an apparently healthy Chinese population

There were conflict data between alpha-adducin Gly460Trp genetic variant and changes of renal function. We conducted a prospective study to investigate the influence of alph-adducin Gly460Trp polymorphism on the quantitative changes of renal function. Of 1500 people screened, 112 non-diabetic normotensive elderly Chinese were recruited and received biochemistry examination at the baseline, at the second and fourth year follow-up. Serum creatinine and calculated renal parameter, using Modification of Diet in Renal Disease (MDRD) Study, were used to evaluate renal function and their progression. Genotyping was performed by polymerase chain reaction-restriction fragment length polymorphism. Age was 71.9 ± 3.7 years (range 60-81). Serum creatinine and MDRD glomerular filtration rate (GFR) were significantly worsened at the 2 and 4-year follow-up (all P < 0.001). The magnitude of 4-year decline of MDRD GFR was significantly higher in subjects carrying the a-adducin Gly460Trp G-allele than TT genotype (P = 0.045). The multivariate analyses showed that a-adducin Gly460Trp (P = 0.034), baseline MDRD GFR (P < 0.001), diastolic blood pressure (P = 0.021) and body weight (P = 0.022) could independently predict 4-year change of MDRD GFR. This longitudinal study showed that the aging process was associated with decline of renal function in the healthy elderly. The alpha-adducin Gly460Trp gene polymorphism might modulate these changes in the Chinese. This provides further knowledge essential in the assessment of renal disease and determination of renal function in the older subjects.

Renin-angiotensin system and alpha-adducin gene polymorphisms and their relation to responses to antihypertensive drugs: results from the GENRES study

BACKGROUND

Polymorphisms in genes coding for components of the renin-angiotensin system (RAS) and alpha-adducin (ADD1) have been reported to be associated with blood pressure (BP) responses to antihypertensive agents. The results, however, have not been consistent and most of the earlier studies have been small and lacked placebo-control. Therefore, the association of common polymorphisms in these genes with BP responses to four different antihypertensive drugs was analyzed in a controlled study.

METHODS

The study included 208 hypertensive Finnish men from the GENRES study. All of them used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide (HCT) 25 mg, and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, study. The treatment periods were separated by 4-week placebo periods. Both 24-h ambulatory (ABP) and office BP (OBP) measurements were carried out. The polymorphisms analyzed were ADD1 Gly460Trp, angiotensinogen (AGT) Met235Thr, angiotensin converting enzyme (ACE) insertion/deletion (I/D), and angiotensin II type 1 receptor (AGTR1) 1166A/C.

RESULTS

The presence of 460Trp allele of ADD1, previously suggested to be a marker of thiazide responsiveness, did not predict a better response to HCT. There was no significant association of AGT Met235Thr, ACE I/D, and AGTR1 1166A/C polymorphisms with BP responses to the study drugs. ADD1 460Trp and AGT 235Thr alleles were associated with higher systolic white coat effect (WCE) during the placebo periods (P values 0.03 and 0.01, respectively).

CONCLUSIONS

Common polymorphisms of ADD1, AGT, ACE, and AGTR1 do not markedly predict BP responses to amlodipine, bisoprolol, HCT, and losartan, at least in white hypertensive men.

Definition of phenotype

Definition of the phenotype is crucial in designing any genetic study, especially an association study, intended to detect the disease predisposing genes. In this chapter, we review the different types of phenotypes such as discrete or continuous and discuss the issues impacting on the phenotype definition related to study design, specifically, the impact of diagnostic error (misclassification) in case-control studies and measurement error in continuous traits. We show that the power of a study depends heavily on the phenotype measured and that misclassification or measurement error can dramatically reduce the power. We also suggest some possible responses to these challenges.

Relevance of Genetics and Genomics for Prevention and Treatment of Cardiovascular Disease

Atherosclerotic cardiovascular disease (CVD) is a major health problem in the United States and around the world. Evidence accumulated over decades convincingly demonstrates that family history in a parent or a sibling is associated with atherosclerotic CVD, manifested as coronary heart disease, stroke, and/or peripheral arterial disease. Although there are several mendelian disorders that contribute to CVD, most common forms of CVD are believed to be multifactorial and to result from many genes, each with a relatively small effect working alone or in combination with modifier genes and/or environmental factors. The identification and the characterization of these genes and their modifiers would enhance prediction of CVD risk and improve prevention, treatment, and quality of care. This scientific statement describes the approaches researchers are using to advance understanding of the genetic basis of CVD and details the current state of knowledge regarding the genetics of myocardial infarction, atherosclerotic CVD, hypercholesterolemia, and hypertension. Current areas of interest and investigation--including gene-environment interaction, pharmacogenetics, and genetic counseling--are also discussed. The statement concludes with a list of specific recommendations intended to help incorporate usable knowledge into current clinical and public health practice, foster and guide future research, and prepare both researchers and practitioners for the changes likely to occur as molecular genetics moves from the laboratory to clinic.

Pharmacogenomics and Pharmacogenetics of Hypertension: Update and Perspectives—The Adducin Paradigm: Figure 1

There is a growing literature on the potential prospective use of genome information to enhance success in finding new medicines. An example of a prospective efficacy of pharmacogenetic and pharmacogenomics is the detection and impact of adducin polymorphism on hypertension. Adducin is a heterodimeric cytoskeleton protein, the three subunits of which are encoded by genes (ADD1, ADD2, and ADD3) that map to three different chromosomes. A long series of parallel studies in the Milan hypertensive rat strain model of hypertension and humans indicated that an altered adducin function might cause hypertension through an enhanced constitutive tubular sodium reabsorption. In particular, six linkage studies, 18 of 20 association studies, and four of five follow-up studies that measured organ damage in hypertensive patients support the clinical impact of adducing polymorphism. As many modulatory genes and environment affect the adducin activity, the context must be taken into account to measure the clinical effect size of adducins. Pharmacogenomics is giving an important contribution to this end. In particular, the selective advantages of diuretics in preventing myocardial infarction and stroke over other antihypertensive therapies that produce a similar BP reduction in carriers of the mutated adducin may support new strategies that aim to optimize the use of antihypertensive agents for the prevention of hypertension-associated organ damage.

Genetic variations of tubular sodium reabsorption leading to “primary” hypertension: from gene polymorphism to clinical symptoms

The definition of the most appropriate strategy to demonstrate causation of a given genetic-molecular mechanism in a complex multifactorial polygenic disease like hypertension is hampered by the underestimation of the complexity arising from the genetic and environmental interactions. To disentangle this complexity, we developed a strategy based on six steps: 1) isolation of a rodent model of hypertension (Milan hypertensive strain and Milan normotensive strain) that shares some pathophysiological abnormalities with human primary hypertension; 2) definition in the model of the sequence of events linking these abnormalities to a genetic molecular mechanism; 3) determination of the polymorphism of the three adducin genes discovered in the model both in rats and in humans; 4) comparison at biochemical and physiological levels between the rodent models and the hypertensive carriers of the “mutated” gene variants; 5) evaluation of the impact of the adducin genes in hypertension and its organ complications with association and linkage studies in humans, also considering the genetic and environmental interactions; and 6) development of a pharmacogenomic approach aimed at establishing the therapeutic benefit of a drug interfering with the sequence of events triggered by adducin and their effect's size. The bulk of data obtained demonstrates the importance of a multidisciplinary approach considering a variety of genetic and environmental interactions. Adducin functions within the cells as a heterodimer composed of a combination of three subunits. Each of these subunits is coded by genes mapping to different chromosomes. Therefore, the interaction among these genes, taken together with the interactions with other modulatory genes or with the environment, is indispensable to establish the adducin clinical impact. The hypothesis that adducin polymorphism favors the development of hypertension via an increased tubular sodium reabsorption is well supported by a series of consistent experimental and clinical data. Many mechanistic aspects, underlying the link between these genes and clinical symptoms, need to be clarified. The clinical effect size of adducin must be established also with the contribution of pharmacogenomics with a drug that selectively interferes with the sequence of events triggered by the mutated adducin.

Model-fitting and linkage analysis of sodium–lithium countertransport

Increased sodium-lithium countertransport activity (SLC) associates with hypertension and is highly heritable, yet the underlying genes remain unknown. SLC, measured on 1113 and remeasured 2-3 years later on 675 adult members of 48 Utah pedigrees, was tested for candidate gene association, major locus inheritance, and linkage to genome scan markers using a bivariate model with genotype-specific effects of age, body mass index (BMI), and triglycerides level (TG). No effect of the alpha-adducin Gly460Trp polymorphism on SLC was found. In contrast, SLC increased with age in carriers of apolipoproteinE varepsilon2 (85 individuals; 8.7% of the sample) and decreased in noncarriers. Model-fitting analyses inferred two additional loci with genotype-specific responses to BMI and TG. Using the inferred model, lod scores >2 were obtained for D3S3038, D11S4464, and D10S677 for the BMI-responsive locus, and for D8S1048 for the TG-responsive locus.

Role of alpha-adducin DNA polymorphisms in the genetic predisposition to diabetic nephropathy

BACKGROUND

There is substantial evidence for genetic susceptibility to diabetic nephropathy. In particular, genes that predispose to hypertension in the general population may confer susceptibility to nephropathy in patients with diabetes. A Gly460Trp variant in the alpha-adducin gene has been associated with essential hypertension. Our aim was to screen the alpha-adducin gene for polymorphisms and to determine if any variants predisposed patients with diabetes to nephropathy. A secondary objective was to assess for association between the Gly460Trp variant and hypertension.

METHODS

The exons of the alpha-adducin gene were resequenced in 30 individuals. Selected variants were then genotyped in 155 patients with type 1 diabetes and nephropathy (cases) and 216 persons with type 1 diabetes but no evidence of nephropathy (controls) from Northern Ireland and in 95 cases and 118 controls from the Irish Republic.

RESULTS

Eleven polymorphisms were detected, of which six were novel and three caused amino-acid substitutions. The Gly460Trp and a novel Ser617Cys polymorphism were in strong linkage disequilibrium (D' = 0.98). Neither the genotype nor allele frequencies for the Gly460Trp polymorphism (P = 0.89 and 0.93 respectively) or the Ser617Cys polymorphism (P = 0.46 and 0.76) were significantly different between cases and controls when the Northern Ireland and Irish Republic sample groups were combined. Carriage of the 460Trp allele was not significantly associated with systolic or diastolic blood pressure in either the cases (P = 0.48 and 0.06, respectively) or in the controls (P = 0.50 and 0.94, respectively).

CONCLUSIONS

Variation in the alpha-adducin gene does not play a major role in the development of nephropathy in persons with type 1 diabetes in the Irish population. Furthermore, the Gly460Trp variant was not associated with hypertension in this population.

Influence of the alpha-adducin and ACE gene polymorphism on the progression of autosomal-dominant polycystic kidney disease

BACKGROUND

A significant phenotypical variability is observed in autosomal dominant polycystic kidney disease (ADPKD). The variability can not be fully explained by the genetic heterogeneity of the disease. We examined the influence of the ACE I/D polymorphism, adducin Trp460Gly polymorphism and the association of both polymorphisms on the progression of ADPKD towards end-stage renal failure (ESRF).

METHODS

320 ADPKD patients (pts) were analyzed, 220 pts (113 males, 107 females) with ESRF before 63 years of age, with a subgroup (rapid progressors) of 20 pts (12 males, 8 females) with ESRF before 40 years of age, 52 pts (23 males, 29 females) with ESRF later than 63 years of age (slow progressors), 48 ADPKD pts (18 males, 30 females) with mean age +/-50 years with serum creatinine <110 micromol/l (slow progressors) and 200 genetically unrelated healthy Czech subjects. DNA samples from collected blood were genotyped for the ACE I/D polymorphism and the Trp460Gly of alpha-adducin gene polymorphism.

RESULTS

The alpha-adducin genotypes showed no differences among the groups of slow progressors (74% Gly/Gly, 22.9% Gly/Trp and 3.1% Trp/Trp), pts with ESRF before 63 years of age (67.7% Gly/Gly, 30.5% Gly/Trp and 1.8% Trp/Trp) and rapid progressors (75% Gly/Gly, 25% Gly/Trp). The ACE genotypes did not differ among the groups of slow progressors (27.1% I/I, 44.8% I/D and 28.1% D/D), pts with ESRF before 63 years of age (23.6% I/I, 51.4% I/D and 25% D/D) and rapid progressors (20% I/I, 55% I/D and 25% D/D). The distribution did not differ from the control group. The ages of ESRF according to different genotypes did not significantly differ. We observed a significant tendency to better prognosis in Trp allele carriers for I/I genotype in comparison with Gly/Gly homozygous subjects.

CONCLUSION

The ACE and alpha-adducin polymorphisms do not play a significant role in the progression of ADPKD to ESRF.

Seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure

The National High Blood Pressure Education Program presents the complete Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Like its predecessors, the purpose is to provide an evidence-based approach to the prevention and management of hypertension. The key messages of this report are these: in those older than age 50, systolic blood pressure (BP) of greater than 140 mm Hg is a more important cardiovascular disease (CVD) risk factor than diastolic BP; beginning at 115/75 mm Hg, CVD risk doubles for each increment of 20/10 mm Hg; those who are normotensive at 55 years of age will have a 90% lifetime risk of developing hypertension; prehypertensive individuals (systolic BP 120-139 mm Hg or diastolic BP 80-89 mm Hg) require health-promoting lifestyle modifications to prevent the progressive rise in blood pressure and CVD; for uncomplicated hypertension, thiazide diuretic should be used in drug treatment for most, either alone or combined with drugs from other classes; this report delineates specific high-risk conditions that are compelling indications for the use of other antihypertensive drug classes (angiotensin-converting enzyme inhibitors, angiotensin-receptor blockers, beta-blockers, calcium channel blockers); two or more antihypertensive medications will be required to achieve goal BP (<140/90 mm Hg, or <130/80 mm Hg) for patients with diabetes and chronic kidney disease; for patients whose BP is more than 20 mm Hg above the systolic BP goal or more than 10 mm Hg above the diastolic BP goal, initiation of therapy using two agents, one of which usually will be a thiazide diuretic, should be considered; regardless of therapy or care, hypertension will be controlled only if patients are motivated to stay on their treatment plan. Positive experiences, trust in the clinician, and empathy improve patient motivation and satisfaction. This report serves as a guide, and the committee continues to recognize that the responsible physician's judgment remains paramount.

Problems of reporting genetic associations with complex outcomes

Inability to replicate many results has led to increasing scepticism about the value of simple association study designs for detection of genetic variants contributing to common complex traits. Much attention has been drawn to the problems that might, in theory, bedevil this approach, including confounding from population structure, misclassification of outcome, and allelic heterogeneity. Other researchers have argued that absence of replication may indicate true heterogeneity in gene-disease associations. We suggest that the most important factors underlying inability to replicate these associations are publication bias, failure to attribute results to chance, and inadequate sample sizes, problems that are all rectifiable. Without changes to present practice, we risk wastage of scientific effort and rejection of a potentially useful research strategy.

Angiotensin converting enzyme DD genotype is associated with hypertensive crisis

OBJECTIVE

The genetic background of hypertensive crisis is unknown. We examined the association of polymorphisms in genes involved in the renin-angiotensin-aldosterone-system with hypertensive crisis.

DESIGN

Population-based case-control study.

SETTING

Emergency department at a tertiary care university hospital.

PATIENTS

A total of 182 patients with essential hypertension who were admitted to an emergency department for treatment of hypertensive crisis and 182 age- and sex-matched healthy individuals.

INTERVENTIONS

None.

MEASUREMENTS

Analysis of polymorphisms in genes coding for angiotensinogen (AJT 704T-->C), angiotensin II receptor 1 (AGTR1 1166A-->C), renin (REN 2646G-->A), renin-binding protein (RENBP 61T-->C), alpha-adducin (ADD1 1378G-->T), beta-2-adrenergic receptor (ADRB2 46A-->G, 79C-->G), and angiotensin I converting enzyme (ACE I/D) was performed by polymerase chain reaction and restriction fragment length polymorphism analysis. MAIN RESULTS Among patients, the ACE I/D polymorphism showed a deviation from Hardy-Weinberg equilibrium (p =.01). In controls, all polymorphisms were in the Hardy-Weinberg equilibrium. The frequency of the DD genotype was increased in patients (n = 70, 38.5%) vs. controls (n = 51; 28.0%;p =.03; odds ratio, 1.61; 95% confidence interval, 1.03-2.50), which was due to the DD genotype in 40 male patients (44%) vs. 23 in male controls (25.3%;p =.004; odds ratio, 3.48; 95% confidence interval, 1.47-8.30). There were no differences in genotype distributions among other polymorphisms.

CONCLUSION

We demonstrate a possible association of the DD genotype with hypertensive crisis in men.

alpha-Adducin Gly460Trp polymorphism is associated with low renin hypertension in younger subjects in the Ohasama study

BACKGROUND

The Gly460Trp polymorphism of the alpha-adducin gene (ADD-1 ) has been examined as a candidate gene for essential hypertension with salt sensitivity in the Caucasian population. However, we failed to detect a positive association between the Gly460Trp polymorphism of ADD-1 and hypertension in a small series of Japanese subjects.

OBJECTIVE

To examine the precise association between the Gly460Trp polymorphism of ADD-1 and blood pressure (BP), we carried out an association study using a Japanese population: the Ohasama Study.

DESIGN

Subjects (n = 1490) were recruited from participants in the Ohasama Study, which is a cohort in a rural community of northern Japan.

METHODS

DNA was extracted from the buffy coat of the participants who gave informed consent for genetic analysis, and the Gly460Trp polymorphism of ADD-1 was determined by the TaqMan polymerase chain reaction method. Various BP values (casual BP, ambulatory BP and home BP) were measured in the Ohasama study. We used the mean values of these BP measurements for analysis.

RESULTS

The frequencies of genotypes in the Ohasama population were 23% Gly/Gly, 49% Gly/Trp, and 28% Trp/Trp. In the baseline characteristics, age, sex, body mass index, frequency of diabetes and hyperlipidemia were significantly different between hypertensive or normotensive subjects. In total subjects, all BP values were not different among genotypes. In the younger subjects ( 60 years old) with low plasma renin activity (< 1.0 ng/ml per h), however, ambulatory BP and home BP were significantly higher in the subjects with the Gly/Trp or Trp/Trp genotypes of ADD-1 polymorphism than in those with the Gly/Gly genotype. In the same population, the frequency of the Gly/Trp or Trp/Trp genotypes of was significantly higher in hypertensives than in normotensives (83 versus 72%, chi1(2) = 4.04, P<0.05; odds ratio, 2.12; 95% confidence interval, 1.02-4.68).

CONCLUSIONS

These findings suggest the possibility that the Gly460Trp polymorphism of ADD-1 is associated with low renin hypertension.

Role of the alpha-adducin genotype on renal disease progression

BACKGROUND

A genetic susceptibility to hypertension may predispose to the development of end-stage renal disease (ESRD) and promote a more rapid loss of renal function in patients with renal diseases. The alpha-adducin (ADD) gene, alone or in combination with the angiotensinogen (AGT) and the angiotensin-converting enzyme (ACE), is a candidate for abnormal blood pressure regulation and thus for increased susceptibility or faster progression to ESRD.

METHODS

Genotyping for the G460W-ADD, M235T-AGT and the insertion/deletion (I/D)-ACE gene polymorphisms was performed in 260 control subjects and 260 ESRD patients using polymerase chain reaction, gel analysis and appropriate restriction digest.

RESULTS

The frequencies of the ADD, AGT and ACE genotypes in ESRD patients did not differ from observed frequencies in control subjects. The average (+/-SE) time from diagnosis to the onset of ESRD tended to be shorter in the presence of the ADD-460WW (5.1 +/- 1.1 years, N = 10) than with the GW (9.9 +/- 0.7 years, N = 81) and GG (11.3 +/- 1.0 years, N = 164) genotypes (F-ratio=2.71, P = 0.068; WW vs. GW P < 0.06 and vs. GG <0.03). In the 167 patients homozygous for the ADD-G allele, a more rapid progression with the ACE-DD genotype as compared to ACE-DI and II was found (P < 0.02).

CONCLUSIONS

The ADD genotype is predictive of the course of renal function loss in an unselected renal population and influences the effect of the ACE genotype to modulate the rate of progression to ESRD. Thus, the ADD genotype may play a role for the understanding of interindividual differences in the course of renal diseases.

Lack of association between Gly460Trp polymorphism of alpha-adducin gene and salt sensitivity of blood pressure in Polish hypertensives

BACKGROUND

Previous studies have suggested that alpha-adducin (alpha-ADD) polymorphism may identify patients with a salt-sensitive form of hypertension.

AIM

To investigate the association between Gly460Trp polymorphism of alpha-ADD and the pattern of blood pressure response to subacute (1 week) salt loading and depletion in young adult thin Polish hypertensives.

METHODS

The study group consisted of 44 subjects with salt-sensitive hypertension (SS) and 24 subjects with non-salt-sensitive hypertension (SR). Genomic DNA isolated from peripheral blood leukocytes was amplified by PCR method with primers flanking the polymorphic region. The mismatch near to 3'-end of the upstream primer was introduced to create a Nla III restriction site in Trp 460 allele. In addition, excreted fraction of filtered sodium (FENa), plasma renin activity (PRA) and plasma concentrations of aldosterone (ALDO) were determined on normal, low and high salt diets.

RESULTS

FENa on normal or high salt diets were significantly lower in the SS hypertensives as compared with the SR patients. PRA in SS group was also significantly lower as compared with results in SR group, but only on high salt diet. No significant difference was detected in frequencies of genotypes and alleles of alpha-ADD gene between SS and SR subjects. An additional analysis with regard to genotype (Gly/Gly vs. Gly/Trp+Trp/Trp) showed no significant difference in changes of blood pressure as well as in results of laboratory investigations.

CONCLUSION

Our results suggest lack of association between Gly460Trp polymorphism of alpha-adducin gene and salt sensitivity of blood pressure in Polish hypertensives.

Multi-center genetic study of hypertension: The Family Blood Pressure Program (FBPP)

The Family Blood Pressure Program (FBPP) consists of 4 independently established multicenter networks of investigators who have complementary approaches to the genetics of blood pressure levels and hypertension. The program has recruited participants from the African American, Mexican American, Asian, and non-Hispanic white populations. Each network utilized study designs, laboratory measurements, and analytic methods that made efficient use of the unique characteristics of their populations and the investigators' expertise. The individual networks subsequently unified core study components into a single cohesive program. The unified FBPP includes (1) standardized clinic and laboratory protocols for core variables to facilitate direct comparison of results among networks, (2) coordination among laboratories to avoid unnecessary duplication of effort, (3) utilization of a single laboratory for genome-wide marker typing, and (4) a pooled data set containing phenotype and genotype information from >11 000 individuals.

Molecular genetics of essential hypertension: recent results and emerging strategies

Efforts to identify hypertension-predisposition genetic loci have focused largely on candidate gene strategies, in which specific candidates have been tested for linkage and association with blood pressure or the diagnosis of hypertension. A variety of candidate genes have been investigated, including loci involving the renin-angiotensin-aldosterone system, sodium epithelial channel, catecholaminergic/adrenergic function, renal kallikrein system, alpha-adducin, and others involving lipoprotein metabolism, hormone receptors, and growth factors. These studies, and more recently, several genome-wide scans, have yielded highly promising results suggesting a number of potential candidate genes and genomic regions that may contribute to blood pressure variation. The results also point to the need for more robust phenotypes that are intermediate in the pathogenetic development of high blood pressure. Additional methods and strategies for improving genetic studies of human hypertension include comparative genomics, in which results from animal studies are used to target potential blood pressure loci, the use of newly developed quantitative tests of linkage and association, comprehensive single-nucleotide polymorphism discovery in candidate loci, and the use of single-nucleotide polymorphisms in cladistic/haplotype analyses and genome-wide searches.