Blood pressure and human genetic variation in the general population

A statistical boosting framework for polygenic risk scores based on large-scale genotype data

Polygenic risk scores (PRS) evaluate the individual genetic liability to a certain trait and are expected to play an increasingly important role in clinical risk stratification. Most often, PRS are estimated based on summary statistics of univariate effects derived from genome-wide association studies. To improve the predictive performance of PRS, it is desirable to fit multivariable models directly on the genetic data. Due to the large and high-dimensional data, a direct application of existing methods is often not feasible and new efficient algorithms are required to overcome the computational burden regarding efficiency and memory demands. We develop an adapted component-wise L 2-boosting algorithm to fit genotype data from large cohort studies to continuous outcomes using linear base-learners for the genetic variants. Similar to the snpnet approach implementing lasso regression, the proposed snpboost approach iteratively works on smaller batches of variants. By restricting the set of possible base-learners in each boosting step to variants most correlated with the residuals from previous iterations, the computational efficiency can be substantially increased without losing prediction accuracy. Furthermore, for large-scale data based on various traits from the UK Biobank we show that our method yields competitive prediction accuracy and computational efficiency compared to the snpnet approach and further commonly used methods. Due to the modular structure of boosting, our framework can be further extended to construct PRS for different outcome data and effect types-we illustrate this for the prediction of binary traits.

Can I Buy My Health? A Genetically Informed Study of Socioeconomic Status and Health

BACKGROUND

A large literature demonstrates associations between socioeconomic status (SES) and health, including physiological health and well-being. Moreover, gender differences are often observed among measures of both SES and health. However, relationships between SES and health are sometimes questioned given the lack of true experiments, and the potential biological and SES mechanisms explaining gender differences in health are rarely examined simultaneously.

PURPOSE

To use a national sample of twins to investigate lifetime socioeconomic adversity and a measure of physiological dysregulation separately by sex.

METHODS

Using the twin sample in the second wave of the Midlife in the United States survey (MIDUS II), biometric regression analysis was conducted to determine whether the established SES-physiological health association is observed among twins both before and after adjusting for potential familial-level confounds (additive genetic and shared environmental influences that may underly the SES-health link), and whether this association differs among men and women.

RESULTS

Although individuals with less socioeconomic adversity over the lifespan exhibited less physiological dysregulation among this sample of twins, this association only persisted among male twins after adjusting for familial influences.

CONCLUSIONS

Findings from the present study suggest that, particularly for men, links between socioeconomic adversity and health are not spurious or better explained by additive genetic or early shared environmental influences. Furthermore, gender-specific role demands may create differential associations between SES and health.

Perceived neighborhood social cohesion and cardiometabolic risk: a gene × environment study

People living in socially cohesive neighborhoods generally have better health. We extend this research by evaluating the hypothesis that perceived neighborhood cohesion may influence health by attenuating genetic liability for cardiometabolic risk factors. Using data from the Health and Retirement Study (n = 6615; mean age 69.7), we conducted a gene × environment interaction study hypothesizing that perceived neighborhood cohesion would attenuate the link between polygenic scores for waist-to-hip ratio (WHR) and body mass index and a measure of multisystem cardiometabolic risk (systolic and diastolic blood pressure, heart rate, A1c, C-reactive protein, and total and high-density lipoprotein cholesterol). In support of the hypothesis, results indicated that among people perceiving low neighborhood cohesion, higher WHR polygenic scores were associated with greater cardiometabolic risk. In contrast, the genetic-cardiometabolic risk link was much attenuated among those living in neighborhoods perceived as socially cohesive. Our results support community-level interventions to enhance the social cohesiveness of individuals' neighborhoods which may provide health benefits by reducing the risks associated with known genetic risk factors.

The influence of angiotensin I-converting enzyme (ACE) I/D gene polymorphism on cardiovascular and muscular adaptations following 8 weeks of isometric handgrip training (IHG) in untrained normotensive males

We examined the association between the angiotensin I-converting enzyme (ACE) I/D gene polymorphism and isometric handgrip (IHG) training on cardiovascular and muscular responses among normotensive males. Thirty (II = 10, ID = 10, and DD = 10) normotensive untrained males underwent IHG training at 30% of their maximal voluntary contraction 3 days per week for 8 weeks. Cardiovascular and muscular variables were measured before IHG, after a session of IHG and after 8 weeks of IHG. No significant interaction effect was found between ACE I/D genotype and IHG training session on all dependent variables (all p > 0.05). There was a significant main effect of IHG training session on systolic blood pressure (SBP) (p = 0.002), mean arterial pressure (MAP) (p = 0.015) and handgrip strength (HGS) (p = 0.001) scores, while no difference in diastolic blood pressure (DBP), pulse pressure, or heart rate scores was found. A greater improvement in cardiovascular parameters following 8 weeks of IHG training was observed in participants with the D allele than the I allele (SBP reduction: ID+DD genotype group (-5.53 ± 6.2 mmHg) vs. II genotype group (-1.52 ± 5.3 mmHg)); MAP reduction: ID + DD genotype group (-2.80 ± 4.5 mmHg) vs. II genotype group (-1.45 ± 3.5 mmHg). Eight weeks of IHG training improved cardiovascular and muscular performances of normotensive men. Reduction in SBP and MAP scores in D allele carriers compared to I allele carriers indicates that the ACE I/D polymorphism may have an influence on IHG training adaptation in a normotensive population.

Sibling Similarity in Metabolic Syndrome: The Portuguese Sibling Study on Growth, Fitness, Lifestyle and Health

This study aims to estimate sibling resemblance in metabolic syndrome (MS) markers, and to investigate the associations of biological and behavioral characteristics with MS. The sample comprises 679 biological siblings (363 females; 316 males) aged 9-20 years. MS markers included waist circumference (WC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TRI), fasting glucose (GLU) and systolic blood pressure (SBP). Body mass index (BMI), biological maturation, muscular, and cardiorespiratory fitness were also assessed. Behavioral characteristics, including dietary intake and physical activity, were self-reported by questionnaire. Multilevel models were used, and sibling resemblance was estimated using the intraclass correlation (ρ). In general, same-sex siblings showed higher resemblance in MS markers than opposite-sex siblings. However, variability in sibling resemblance in MS markers was evident with the inclusion of covariates. Biological characteristics including age, BMI and maturity offset influenced all MS markers except for TRI. Importantly, behavioral characteristics diversely influenced MS markers: fruit and vegetables only influenced SBP, whereas physical activity affected HDL-C. Additionally, muscular fitness impacted significantly on MS Z-score, WC, SBP and GLU, whilst cardiorespiratory fitness only affected WC. In conclusion, biological and behavioral characteristics influenced the expression of MS markers. These results confirmed the importance of considering individual characteristics when designing individualized programs for diminishing the adverse effects of specific MS markers.

Association between ATP2B1 and CACNB2 polymorphisms and high blood pressure in a population of Lithuanian children and adolescents: a cross-sectional study

OBJECTIVES

Recently, genome-wide associated studies have identified several genetic loci that are associated with elevated blood pressure and could play a critical role in intracellular calcium homeostasis. The aim of this study was to assess the associations of ATP2B1 rs2681472 and CACNB2 rs12258967 gene polymorphisms with high blood pressure (HBP) among Lithuanian children and adolescents aged 12-15 years.

STUDY DESIGN AND PARTICIPANTS

This was a cross-sectional study of a randomly selected sample of 646 12-15-year-old adolescents who participated in the survey 'The Prevalence and Risk Factors of HBP in 12-15 Year-Old Lithuanian Children and Adolescents (from November 2010 to April 2012)'. Anthropometric parameters and BP were measured. The participants with HBP were screened on two separate occasions. Subjects were genotyped ATP2B1 rs2681472 and CACNB2 rs12258967 gene polymorphisms using real-time PCR method.

RESULTS

The prevalence of HBP was 36.7%, significantly higher for boys than for girls. In the multivariate analysis, after adjustment for body mass index and waist circumference, boys with CACNB2 CG genotype, CACNB2 GG genotype and CACNB2 CG +GG genotype had higher odds of having HBP in codominant (adjusted OR (aOR)=1.92; 95% CI 1.16 to 3.18, p=0.011; and aOR=2.64; 95% CI 1.19 to 5.90, p=0.018) and in dominant (aOR=2.05; 95% CI 1.27 to 3.30, p=0.003) inheritance models. Girls carrying CACNB2 CG genotype and CACNB2 CG +GG genotype had increased odds of HBP in codominant (aOR=1.82; 95% CI 1.02 to 3.24, p=0.044) and in dominant (aOR=1.89; 95% CI 1.09 to 3.28, p=0.023) inheritance models. Furthermore, significant associations were found in additive models separately for boys (aOR=1.72; 95% CI 1.20 to 2.46, p=0.003) and girls (aOR=1.52; 95% CI 1.05 to 2.20, p=0.027). No significant association was found between ATP2B1 gene polymorphism and the odds of HBP.

CONCLUSIONS

Our results indicate that CACNB2 gene polymorphism was significantly associated with higher odds of HBP in Lithuanian adolescents aged 12-15 years.

Perceived neighborhood social cohesion and cardiometabolic risk: a gene × environment study

People living in socially cohesive neighborhoods generally have better health. We extend this research by evaluating the hypothesis that perceived neighborhood cohesion may influence health by attenuating genetic liability for cardiometabolic risk factors. Using data from the Health and Retirement Study (n = 6,615; mean age 69.7), we conducted a gene × environment interaction study hypothesizing that perceived neighborhood cohesion would attenuate the link between polygenic scores for waist-to-hip ratio (WHR) and body mass index and a measure of multisystem cardiometabolic risk (systolic blood pressure [SBP] and diastolic blood pressure [DBP], heart rate, A1c, C-reactive protein, and total and high-density lipoprotein cholesterol). In support of the hypothesis, results indicated that among people perceiving low neighborhood cohesion, higher WHR polygenic scores were associated with greater cardiometabolic risk. In contrast, the genetic-cardiometabolic risk link was much attenuated among those living in neighborhoods perceived as socially cohesive. Our results support community-level interventions to enhance the social cohesiveness of individuals' neighborhoods which may provide health benefits by reducing the risks associated with known genetic risk factors.

Genetic mechanisms of human hypertension and their implications for blood pressure physiology

Hypertension, or elevated blood pressure, constitutes a major public health burden that affects more than 1 billion people worldwide and contributes to ~9 million deaths annually. Hereditary factors are thought to contribute to up to 50% of interindividual blood pressure variability. Blood pressure in the general population approximately shows a normal distribution and is thought to be a polygenic trait. In rare cases, early-onset hypertension or hypotension are inherited as Mendelian traits. The identification of the underlying Mendelian genes and variants has contributed to our understanding of the physiology of blood pressure regulation, emphasizing renal salt handling and the renin angiotensin aldosterone system as players in the determination of blood pressure. Genome-wide association studies (GWAS) have revealed more than 100 variants that are associated with blood pressure, typically with small effect sizes, which cumulatively explain ~3.5% of blood pressure trait variability. Several GWAS associations point to a role of the vasculature in the pathogenesis of hypertension. Despite these advances, the majority of the genetic contributors to blood pressure regulation are currently unknown; whether large-scale exome or genome sequencing studies will unravel these factors remains to be determined.

B-Type Natriuretic Peptide Deletion Leads to Progressive Hypertension, Associated Organ Damage, and Reduced Survival: Novel Model for Human Hypertension

Altered myocardial structure and function, secondary to chronically elevated blood pressure, are leading causes of heart failure and death. B-type natriuretic peptide (BNP), a guanylyl cyclase A agonist, is a cardiac hormone integral to cardiovascular regulation. Studies have demonstrated a causal relationship between reduced production or impaired BNP release and the development of human hypertension. However, the consequences of BNP insufficiency on blood pressure and hypertension-associated complications remain poorly understood. Therefore, the goal of this study was to create and characterize a novel model of BNP deficiency to investigate the effects of BNP absence on cardiac and renal structure, function, and survival. Genetic BNP deletion was generated in Dahl salt-sensitive rats. Compared with age-matched controls, BNP knockout rats demonstrated adult-onset hypertension. Increased left ventricular mass with hypertrophy and substantially augmented hypertrophy signaling pathway genes, developed in young adult knockout rats, which preceded hypertension. Prolonged hypertension led to increased cardiac stiffness, cardiac fibrosis, and thrombi formation. Significant elongation of the QT interval was detected at 9 months in knockout rats. Progressive nephropathy was also noted with proteinuria, fibrosis, and glomerular alterations in BNP knockout rats. End-organ damage contributed to a significant decline in overall survival. Systemic BNP overexpression reversed the phenotype of genetic BNP deletion. Our results demonstrate the critical role of BNP defect in the development of systemic hypertension and associated end-organ damage in adulthood.

Probing genetic overlap in the regulation of systolic and diastolic blood pressure in Danish and Chinese twins

Although the phenotypic correlation between systolic blood pressure (SBP) and diastolic blood pressure (DBP) is well known, the genetic basis for the correlation has rarely been investigated. The aim of this paper is to examine the genetic overlap between SBP and DBP by fitting bivariate models to Danish and Chinese twins and comparing ethnic differences between the two samples. Our estimates revealed a high proportion of additive genetic components shared by both SBP and DBP in Danish (0.71, 95% confidence interval (CI): 0.65-0.75) and Chinese (0.62, 95% CI: 0.50-0.71) twins with no statistically significant ethnic differences. The estimated genetic component in phenotypic correlation could serve to guide molecular genetic studies searching for genetic variants that affect both SBP and DBP. The bivariate model also estimated genetic and environmental contributions to SBP and DBP separately, with an overall pattern of higher genetic regulation or heritability in Danish (0.72, 95% CI: 0.67-0.76 for SBP; 0.70, 95% CI: 0.65-0.75 for DBP) than in Chinese (0.54, 95% CI: 0.44-0.63 for SBP; 0.57, 95% CI: 0.47-0.65 for DBP) twins and a higher contribution from unique environmental factors in Chinese compared with Danish twins. The estimated contribution from unique environmental factors suggests that promoting healthy lifestyles may provide an efficient way of controlling high blood pressure, particularly in the Chinese population.

Vascular disease and dementias: paradigm shifts to drive research in new directions

Vascular disease was once considered the principal cause of aging-related dementia. More recently, however, research emphasis has shifted to studies of progressive neurodegenerative disease processes, such as those giving rise to neuritic plaques, neurofibrillary tangles, and Lewy bodies. Although these studies have led to critical insights and potential therapeutic strategies, interest in the role of systemic and cerebrovascular disease mechanisms waned and has received relatively less attention and research support. Recent studies suggest that vascular disease mechanisms play an important role in the risk for aging-related cognitive decline and disorders. Vascular disease frequently coexists with cognitive decline in aging individuals, shares many risk factors with dementias considered to be of the "Alzheimer type," and is observed more frequently than expected in postmortem material from individuals manifesting "specific" disease stigmata, such as abundant plaques and tangles. Considerable difficulties have emerged in attempting to classify dementias as being related to vascular versus neurodegenerative causes, and several systems of criteria have been used. Despite multiple attempts, a lack of consensus remains regarding the optimal means of incorporating vascular disease into clinical diagnostic, neurocognitive, or neuropathologic classification schemes for dementias. We propose here an integrative, rather than a strictly taxonomic, approach to the study and elucidation of how vascular disease mechanisms contribute to the development of dementias. We argue that, instead of discriminating between, for example, "Alzheimer's disease," "vascular dementia," and other diseases, there is a greater need to focus clinical and research efforts on elucidating specific pathophysiologic mechanisms that contribute to dementia phenotypes and neuropathologic outcomes. We outline a multitiered strategy, beginning with clinical and public health interventions that can be implemented immediately, enhancements to ongoing longitudinal studies to increase their informative value, and new initiatives to capitalize on recent advances in systems biology and network medicine. This strategy will require funding from multiple public and private sources to support collaborative and interdisciplinary research efforts to take full advantage of these opportunities and realize their societal benefits.

Elements of 'missing heritability'

PURPOSE OF REVIEW

To discuss the basis of 'missing heritability', which has emerged as an enigma in the post-genome-wide association studies (GWAS) era.

RECENT FINDINGS

Alleles identified through GWAS account for a relatively small fraction of heritability of the complex phenotypes. Accordingly, a significant part of heritability of the complex traits remains unaccounted for ('missing heritability'). Recent findings offer several explanations, including overestimation of heritability of the complex traits and underestimation of the effects of alleles identified through GWAS. In addition, yet-to-be identified common as well as rare alleles might in part explain the 'missing heritability'. Moreover, gene-gene (epistasis) and gene-environmental interactions might explain another fraction of heritability of complex traits. Moreover, transgenerational epigenetic changes, regulated in part by microRNAs, might also contribute to the 'missing heritability'.

SUMMARY

The new findings suggest a multifarious nature of the 'missing heritability'. The findings de-emphasize the focus on delineating the basis of 'missing heritability' and shift the focus to elucidation of the molecular mechanisms by which genomic and genetic factors govern the pathogenesis of the complex phenotypes.

Fibrillin-1 genotype and risk of prevalent hypertension: a study in two independent populations

OBJECTIVE

Mutations in the fibrillin-1 gene are the cause of Marfan syndrome. We wanted to investigate the relationship between a mutation in this gene and risk of prevalent hypertension.

METHODS

In a cross-sectional study, the effect of a G-A substitution in intron 27 in the fibrillin-1 gene (rs11856553) on risk of prevalent hypertension was studied in two large population-based studies: the Health 2006 study, consisting of 3193 women and men, age 18-69 years, and the MONICA10 study, consisting of 2408 women and men, age 41-72 years. In 1646 MONICA10 participants, blood pressure (BP) was also measured by 24-h ambulatory recordings.

RESULTS

Among the 3193 Health 2006 participants 23 had the G-A variant, and among the 2408 MONICA10 participants 18 had the G-A variant. In Health 2006, the odds ratio estimate (95% confidence intervals) for the G-A variant for risk of hypertension, defined as systolic (S) BP ≥ 140 mmHg or diastolic (D) BP ≥ 90 mmHg or on antihypertensive medicine, was 2.67 (1.14-6.18), p = 0.022. The corresponding figure for moderate to severe hypertension, defined as SBP ≥ 160 mmHg or DBP ≥ 100 mmHg, was 9.68 (4.24-22.12), p < 0.0001. In MONICA10, the odds ratio estimate (95% confidence intervals) for the G-A variant for risk of moderate to severe ambulatory hypertension, defined as 24-h mean SBP ≥ 150 mmHg or 24-h mean DBP ≥ 90 mmHg, was 5.73 (1.96-16.7), p = 0.0014.

CONCLUSION

The G-A substitution in the fibrillin-1 gene (rs11856553) is a rare genetic variant that is associated with an increased risk of prevalent hypertension, particularly of moderate to severe prevalent hypertension.

Molecular genetic studies of complex phenotypes

The approach to molecular genetic studies of complex phenotypes evolved considerably during the recent years. The candidate gene approach, which is restricted to an analysis of a few single-nucleotide polymorphisms (SNPs) in a modest number of cases and controls, has been supplanted by the unbiased approach of genome-wide association studies (GWAS), wherein a large number of tagger SNPs are typed in many individuals. GWAS, which are designed on the common disease-common variant hypothesis (CD-CV), identified several SNPs and loci for complex phenotypes. However, the alleles identified through GWAS are typically not causative but rather in linkage disequilibrium (LD) with the true causal variants. The common alleles, which may not capture the uncommon and rare variants, account only for a fraction of heritability of the complex traits. Hence, the focus is being shifted to rare variants-common disease (RV-CD) hypothesis, surmising that rare variants exert large effect sizes on the phenotype. In conjunctional with this conceptual shift, technologic advances in DNA sequencing techniques have dramatically enhanced whole genome or whole exome sequencing capacity. The sequencing approach affords identification of not only the rare but also the common variants. The approach-whether used in complementation with GWAS or as a stand-alone approach-could define the genetic architecture of the complex phenotypes. Robust phenotyping and large-scale sequencing studies are essential to extract the information content of the vast number of DNA sequence variants (DSVs) in the genome. To garner meaningful clinical information and link the genotype to a phenotype, the identification and characterization of a large number of causal fields beyond the information content of DNA sequence variants would be necessary. This review provides an update on the current progress and limitations in identifying DSVs that are associated with phenotypic effects.

Genetic variants and blood pressure in a population-based cohort: the Cardiovascular Risk in Young Finns study

Clinical relevance of a genetic predisposition to elevated blood pressure was quantified during the transition from childhood to adulthood in a population-based Finnish cohort (N=2357). Blood pressure was measured at baseline in 1980 (age 3-18 years) and in follow-ups in 1983, 1986, 2001, and 2007. Thirteen single nucleotide polymorphisms associated with blood pressure were genotyped, and 3 genetic risk scores associated with systolic and diastolic blood pressures and their combination were derived for all of the participants. Effects of the genetic risk score were 0.47 mm Hg for systolic and 0.53 mm Hg for diastolic blood pressures (both P<0.01). The combination genetic risk score was associated with diastolic blood pressure from age 9 years onward (β=0.68 mm Hg; P=0.015). Replications in 1194 participants of the Bogalusa Heart Study showed essentially similar results. The participants in the highest quintile of the combination genetic risk score had a 1.82-fold risk of hypertension in adulthood (P<0.0001) compared with the lowest quintile, independent of a family history of premature hypertension. These findings show that genetic variants are associated with preclinical blood pressure traits in childhood; individuals with several susceptibility alleles have, on average, a 0.5-mm Hg higher blood pressure, and this trajectory continues from childhood to adulthood.

Medical DNA sequencing

PURPOSE OF REVIEW

To discuss implications of information garnered through whole-genome and exome sequencing in the practice of cardiovascular medicine.

RECENT FINDINGS

Whole-genome and exome sequencing unveils medical information embedded in individual genomes and exomes, which could be incorporated into the practice of medicine for diagnostic and therapeutic gains. The human, however, has considerable genetic diversity, as each genome encompasses about 4 million DNA sequence variants (DSVs). The challenging task is to identify the variants that have clinical implications. DSVs exert a continuum of effect sizes on the phenotype that ranges from negligible to large. From a clinical perspective, selected categories, in order of their significance, are disease-causing, likely disease-causing, disease-associated, biologically functional but unknown clinical significance, and unknown functional and clinical significance variants. The frequency of DSVs in the genome also follows a gradient from rare for the disease-causing variants to common for variants with unknown clinical and biological significance. A subset of DSVs might have implications in accurate and preclinical diagnosis, prognostication and individualization of therapy. Clinical phenotypes, however, are too complex to be determined solely by a single DSV. Even in the case of disease-causing variants, the severity of the disease is determined by multiple additional genetic and nongenetic factors.

SUMMARY

Medical DNA sequencing is expected to retool clinicians with the information content of DSVs. DSVs with large effect sizes are likely to offer clinical utility in early and preclinical diagnosis, prognostication and individualization of therapy.

Rare mutations in SLC12A1 and SLC12A3 protect against hypertension by reducing the activity of renal salt cotransporters

OBJECTIVES

Screening for variants in SLC12A1 and SLC12A3 genes, encoding the renal Na:Cl (NCC) and Na:K:2Cl (NKCC2) cotransporters, respectively, in 3125 members of the Framingham Heart Study (FHS) revealed that carrying a rare mutation in one of these genes was associated with a significant reduction in blood pressure, in the risk of arterial hypertension, and of death due to cardiovascular disease. Because near 60% of the rare mutations identified have not been related to Bartter's or Gitelman's disease, the consequence of such mutations on cotransporter activity is unknown.

METHODS

We used the heterologous expression system of Xenopus laevis oocytes, microinjected with wild-type or mutant NCC or NKCC2 cRNAs, to examine the effect of these inferred NCC and NKCC2 mutations on the cotransporters' functional properties. Cotransporter activity was defined as the diuretic-sensitive radioactive tracer uptake and response to known modulators was assessed.

RESULTS

Basal NCC activity was significantly reduced in all NCC mutants and, excluding NCC-S186F, response to WNK3, WNK4, or intracellular chloride depletion was conserved. Similarly, basal activity was reduced in six out of nine NKCC2 mutants and response to WNK3 was maintained. No effect on protein expression was seen, except for NCC-S186F, which was significantly reduced.

CONCLUSIONS

The rare NCC or NKCC2 mutations found in the FHS significantly reduced the basal activity of the cotransporters. This observation supports that even a small, but chronic reduction of NCC or NKCC2 function results in a lower blood pressure and decreased risk of hypertension in otherwise healthy individuals in the general population.

Strategic approaches to unraveling genetic causes of cardiovascular diseases

DNA sequence variants are major components of the "causal field" for virtually all medical phenotypes, whether single gene familial disorders or complex traits without a clear familial aggregation. The causal variants in single gene disorders are necessary and sufficient to impart large effects. In contrast, complex traits are attributable to a much more complicated network of contributory components that in aggregate increase the probability of disease. The conventional approach to identification of the causal variants for single gene disorders is genetic linkage. However, it does not offer sufficient resolution to map the causal genes in small families or sporadic cases. The approach to genetic studies of complex traits entails candidate gene or genome-wide association studies. Genome-wide association studies provide an unbiased survey of the effects of common genetic variants (common disease-common variant hypothesis). Genome-wide association studies have led to identification of a large number of alleles for various cardiovascular diseases. However, common alleles account for a relatively small fraction of the total heritability of the traits. Accordingly, the focus has shifted toward identification of rare variants that might impart larger effect sizes (rare variant-common disease hypothesis). This shift is made feasible by recent advances in massively parallel DNA sequencing platforms, which afford the opportunity to identify virtually all common as well as rare alleles in individuals. In this review, we discuss various strategies that are used to delineate the genetic contribution to medically important cardiovascular phenotypes, emphasizing the utility of the new deep sequencing approaches.

[Acute lung injury and acute respiratory distress syndrome: a genomic perspective]

Genomics have allowed important advances in the knowledge of the etiology and pathogenesis of complex disease entities such as acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Genomic medicine aims to personalize and optimize diagnosis, prognosis and treatment by determining the influence of genetic polymorphisms in specific diseases. The scientific community must cope with the important challenge of securing rapid transfer of knowledge to clinical practice, in order to prevent patients from becoming exposed to unnecessary risks. In the present article we describe the main concepts of genomic medicine pertaining to ALI/ARDS, and its currently recognized clinical applications.