Human tyrosine hydroxylase natural genetic variation: delineation of functional transcriptional control motifs disrupted in the proximal promoter

The Autosomal Short Tandem Repeat Polymorphisms Are Potentially Associated with Cardiovascular Disease Predisposition in the Latin American Population: A Mini Review

According to the World Health Organization, cardiovascular diseases (CVDs) are the leading cause of death worldwide across nearly all ethnic groups. Inherited cardiac conditions comprise a wide spectrum of diseases that affect the heart, including abnormal structural features and functional impairments. In Latin America, CVDs are the leading cause of death within the region. Factors such as population aging, unhealthy diet, obesity, smoking, and a sedentary lifestyle have increased the risk of CVD. The Latin American population is characterized by its diverse ethnic composition with varying percentages of each ancestral component (African, European, and Native American ancestry). Short tandem repeats (STRs) are DNA sequences with 2-6 base pair repetitions and constitute ~3% of the human genome. Importantly, significant allele frequency variations exist between different populations. While studies have described that STRs are in noncoding regions of the DNA, increasing evidence suggests that simple sequence repeat variations may be critical for proper gene activity and regulation. Furthermore, several STRs have been identified as potential disease predisposition markers. The present review is aimed at comparing and describing the frequencies of autosomal STR polymorphisms potentially associated with cardiovascular disease predisposition in Latin America compared with other populations.

Association studies of dopamine synthesis and metabolism genes with multiple phenotypes of heroin dependence

BACKGROUND

Heroin dependence is a complex disease with multiple phenotypes. Classification of heroin users into more homogeneous subgroups on the basis of these phenotypes could help to identify the involved genetic factors and precise treatments. This study aimed to identify the association between genetic polymorphisms of DA synthesis and metabolism genes, including tyrosine hydroxylase (TH), DOPA decarboxylase (DDC), solute carrier family 6 member 3 (SLC6A3) and DA beta-hydroxylase (DBH), with six important phenotypes of heroin dependence.

METHODS

A total of 801 heroin dependent patients were recruited and fourteen potential functional single nucleotide polymorphisms (SNPs) were genotyped by SNaPshot. Associations between SNPs with six phenotypes were mainly assessed by binary logistic regression. Generalized multifactor dimensionality reduction was used to analyze the gene-by-gene and gene-by-environment interactions.

RESULTS

We found that DBH rs1611114 TT genotype had a protective effect on memory impairment after heroin dependence (P = 0.002, OR = 0.610). We also found that the income-rs12666409-rs129915-rs1611114 interaction yielded the highest testing balance accuracy and cross-validation consistency for memory change after heroin dependence.

CONCLUSIONS

Our results suggest that the memory change after heroin dependence was a result of a combination of genetics and environment. This finding could lead to a better understanding of heroin dependence and further improve personalized treatment.

Tyrosine Hydroxylase Gene Polymorphisms Contribute to Opioid Dependence and Addiction by Affecting Promoter Region Function

Mounting evidence shows that drug dependence involves the complex interplay between genetics and the environment. Tyrosine hydroxylase (TH) is the rate-limiting enzyme in dopamine (DA) synthesis, which plays an essential role in the development of drug addiction. Noradrenergic dysfunction due to abnormalities TH expression has been implicated in the pathogenesis of drug addiction. We profiled thirteen single-nucleotide polymorphisms (SNPs) and one VNTR (TCAT repeat, UniSTS:240,639) in 512 cases and 600 healthy Chinese subjects to evaluate the relationship between common variants within the TH gene and opioids dependence (OD) in the Chinese Han population. The single-marker analysis determined that rs10770141 (p < 0.001, OR 1.739, 95% CI 1.302 - 2.323) and rs10770140 (p = 0.002, OR 1.536, 95% CI 1.164 - 2.026) are risk variants for OD. The haplotype-association analyses determined that A-C-C-C was a risk factor (p = 0.006, OR 1.662, 95% CI 1.241 - 2.225) for OD. We also observed a significant association between (TACT)_9/9 and the duration of transition from the first time using opioids to the development of opioid dependence (DTFUD) (p = 0.002, OR 2.153, 95% CI 1.319 - 3.513). Taken together, this study suggests that TH gene polymorphisms may contribute to the risk of OD in the Chinese Han population.

Genetic variation in dopamine availability modulates the self-reported level of action control in a sex-dependent manner

Although procrastination is a widespread phenomenon with significant influence on our personal and professional life, its genetic foundation is somewhat unknown. An important factor that influences our ability to tackle specific goals directly instead of putting them off is our ability to initiate cognitive, motivational and emotional control mechanisms, so-called metacontrol. These metacontrol mechanisms have been frequently related to dopaminergic signaling. To gain deeper insight into the genetic components of procrastination, we examined whether genetically induced differences in the dopaminergic system are associated with interindividual differences in trait-like procrastination, measured as decision-related action control (AOD). Analyzing the data of 278 healthy adults, we found a sex-dependent effect of TH genotype on AOD. Interestingly, only in women, T-allele carriers showed lower AOD values and were therefore more likely to procrastinate. Additionally, we investigated whether differences in the morphology and functional connectivity of the amygdala that were previously associated with AOD happen to be related to differences in the TH genotype and thus to differences in the dopaminergic system. However, there was no significant amygdala volume or connectivity difference between the TH genotype groups. Therefore, this study is the first to suggest that genetic, anatomical and functional differences affect trait-like procrastination independently.

Linking Y-chromosomal short tandem repeat loci to human male impulsive aggression

INTRODUCTION

Men are more susceptible to impulsive behavior than women. Epidemiological studies revealed that the impulsive aggressive behavior is affected by genetic factors, and the male-specific Y chromosome plays an important role in this behavior. In this study, we investigated the association between the impulsive aggressive behavior and Y-chromosomal short tandem repeats (Y-STRs) loci.

METHODS

The collected biologic samples from 271 offenders with impulsive aggressive behavior and 492 healthy individuals without impulsive aggressive behavior were amplified by PowerPlex^RY23 PCR System and the resultant products were separated by electrophoresis and further genotyped. Then, comparisons in allele and haplotype frequencies of the selected 22 Y-STRs were made in the two groups.

RESULTS

Our results showed that there were significant differences in allele frequencies at DYS448 and DYS456 between offenders and controls (p < .05). Univariate analysis further revealed significant frequency differences for alleles 18 and 22 at DYS448 (0.18 vs 0.27, compared to the controls, p = .003, OR=0.57,95% CI=0.39-0.82; 0.03 vs 0.01, compared to the controls, p = .003, OR=7.45, 95% CI=1.57-35.35, respectively) and for allele 17 at DYS456 (0.07 vs 0.14, compared to the controls, p = .006, OR=0.48, 95% CI =0.28-0.82) between two groups. Interestingly, the frequency of haploid haplotype 22-15 on the DYS448-DYS456 (DYS448-DYS456-22-15) was significantly higher in offenders than in controls (0.033 vs 0.004, compared to the control, p = .001, OR = 8.42, 95%CI =1.81-39.24). Moreover, there were no significant differences in allele frequencies of other Y-STRs loci between two groups. Furthermore, the unconditional logistic regression analysis confirmed that alleles 18 and 22 at DYS448 and allele 17 at DYS456 are associated with male impulsive aggression. However, the DYS448-DYS456-22-15 is less related to impulsive aggression.

CONCLUSION

Our results suggest a link between Y-chromosomal allele types and male impulsive aggression.

Genetic Variations of Tyrosine Hydroxylase in the Pathogenesis of Hypertension

One of the major pathophysiological features of primary hypertension is an inappropriate activation of the sympathetic nervous system, which is mediated by excessive synthesis and secretion of catecholamine into the blood. Tyrosine hydroxylase (TH), a rate-limiting enzyme in the synthesis of catecholamine, has been highlighted because genetic variations of TH could alter the activity of the sympathetic nervous system activity and subsequently contribute to the pathogenesis of hypertension. Here, we discuss the role of TH as a regulator of sympathetic activity and review several studies that investigated the relationship between genetic variations of TH and hypertension.

Defensive coping and essential amino acid markers as possible predictors for structural vascular disease in an African and Caucasian male cohort: The SABPA study

Defensive coping (DefS), oxidative stress, inflammation, and related amino acids (phenylalanine [Phe] and tyrosine [Tyr]) have been implicated in cardiovascular disease. This study assessed whether inflammation, oxidative stress, changes in essential amino acids, and altered coping strategies are correlated with subclinical vascular changes in African (n = 82) and Caucasian (n = 100) men from the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study. The Coping Strategy Indicator questionnaire identified DefS participants. Ambulatory blood pressure (BP) was monitored for 24 h, whereas carotid intima media thickness (CIMT) and cross-sectional wall area (CSWA) were determined ultrasonically. Essential amino acids were analyzed with a liquid chromatography tandem mass spectrometry method. Oxidative-inflammatory markers were measured by spectrophotometry. African men had poorer health than Caucasian men, including higher alcohol abuse, elevated BP, abdominal obesity, physical inactivity, and elevated inflammation. Phe (p < .001) and Phe/Tyr ratio (p = .006) as well as CIMT (p = .032) were higher in African men. DefS African men had higher levels of Phe (p = .002) and Phe/Tyr (p = .009) compared to DefS Caucasian men; these differences were not observed in non-DefS men. Systolic BP and inflammation (C-reactive protein) were positively associated with left (L-) CSWA, while Phe/Tyr was negatively associated with L-CSWA in DefS African men. African males presented with elevated Phe and Phe/Tyr ratio, catecholamine precursors, worsening during DefS-possibly driven by inflammation and BP contributing to structural vascular abnormalities.

Roles of catecholamine related polymorphisms in hypertension

The objective of this review is to summarize current data obtained so far in catecholamine-essential hypertension (EH) relationships on a genetic basis. As the major elements driving the sympathetic system’s actions, catecholamines modulate a variety of physiological processes and mutations related to the system. This could generate serious disorders, such as severe mental illnesses, stress-induced disorders, or impaired control of blood pressure or motor pathways. EH is idiopathic, and the genetic basis of its causes and substantial interindividual discrepancies in response to different types of treatments are the focus of interest. Susceptibility to disease or efficacy of treatments are thought to reflect genomic variabilities among individuals. Therefore, outlining the available knowledge in functional genetic polymorphisms linked to EH will make the picture clearer and will help to establish future prospects in the field.

Biological factors underlying sex differences in neurological disorders

The prevalence, age of onset, pathophysiology, and symptomatology of many neurological and neuropsychiatric conditions differ significantly between males and females. Females suffer more from mood disorders such as depression and anxiety, whereas males are more susceptible to deficits in the dopamine system including Parkinson's disease (PD), attention-deficit hyperactivity disorder (ADHD), schizophrenia, and autism spectrum disorders (ASD). Until recently, these sex differences have been explained solely by the neuroprotective actions of sex hormones in females. Emerging evidence however indicates that the sex chromosome genes (i.e. X- and Y-linked genes) also contribute to brain sex differences. In particular, the Y-chromosome gene, SRY (Sex-determining Region on the Y chromosome) is an interesting candidate as it is expressed in dopamine-abundant brain regions, where it regulates dopamine biosynthesis and dopamine-mediated functions such as voluntary movement in males. Furthermore, SRY expression is dysregulated in a toxin-induced model of PD, suggesting a role for SRY in the pathogenesis of dopamine cells. Taken together, these studies highlight the importance of understanding the interplay between sex-specific hormones and sex-specific genes in healthy and diseased brain. In particular, better understanding of regulation and function of SRY in the male brain could provide entirely novel and important insights into genetic factors involved in the susceptibility of men to neurological disorders, as well as development of novel sex-specific therapies.

Functional polymorphism (C-824T) of the tyrosine hydroxylase gene affects IQ in schizophrenia

AIMS

Progressive cognitive decline has been an important issue in the treatment and care of patients with schizophrenia. Tyrosine hydroxylase (TH) is the rate-limiting enzyme for the biosynthesis of catecholamine, including dopamine and noradrenaline. In this report, we examined a possible association of a genetic variant in the TH promoter region.

METHODS

Association of a genetic variant in the TH promoter region, C-824T (rs10770141), with intellectual ability in 132 patients with schizophrenia and 282 healthy subjects was examined. The transcriptional activity of the plasmids harboring the TH promoter region with either C or T nucleotide at -824 was assayed using a luciferase gene as a reporter.

RESULTS

We found significant effects of the genotype on the full-scale IQ, verbal IQ, and performance IQ, in patients with schizophrenia. IQ was lower in individuals with the C/C genotype than those with T carriers. The plasmid with the T allele at -824 showed higher transcriptional activity than that with the C allele in a transient transfection experiment using a luciferase gene as a reporter, implying that the T carriers may have higher TH activities and retain higher levels of catecholamines in the brain.

CONCLUSIONS

The present data suggest that the biosynthesis of catecholamine by the action of TH should be deeply involved in decreased intellectual ability in patients with schizophrenia. This is the first report, as far as we know, showing a correlation between TH expression and IQ in humans.

Genetic variants in CCNB1 associated with differential gene transcription and risk of coronary in-stent restenosis

BACKGROUND

The development of diagnostic tools to assess restenosis risk after stent deployment may enable the intervention to be tailored to the individual patient, for example, by targeting the use of drug-eluting stent to high-risk patients, with the goal of improving safety and reducing costs. The CCNB1 gene (encoding cyclin B1) positively regulates cell proliferation, a key component of in-stent restenosis. Therefore, we hypothesized that single-nucleotide polymorphisms in CCNB1 may serve as useful tools in risk stratification for in-stent restenosis.

METHODS AND RESULTS

We identified 3 single-nucleotide polymorphisms in CCNB1 associated with increased restenosis risk in a cohort of 284 patients undergoing coronary angioplasty and stent placement (rs350099: TT versus CC+TC; odds ratio [OR], 1.82; 95% confidence interval [CI], 1.09-3.03; P=0.023; rs350104: CC versus CT+TT; OR, 1.82; 95% CI, 1.02-3.26; P=0.040; and rs164390: GG versus GT+TT; OR, 2.27; 95% CI, 1.33-3.85; P=0.002). These findings were replicated in another cohort study of 715 patients (rs350099: TT versus CC+TC; OR, 1.88; 95% CI, 0.92-3.81; P=0.080; rs350104: CC versus CT+TT; OR, 2.23; 95% CI, 1.18-4.25; P=0.016; and rs164390: GG versus GT+TT; OR, 1.87; 95% CI, 1.03-3.47; P=0.040). Moreover, the haplotype containing all 3 risk alleles is associated with higher CCNB1 mRNA expression in circulating lymphocytes and increased in-stent restenosis risk (OR, 1.43; 95% CI, 1.00-1.823; P=0.039). The risk variants of rs350099, rs350104, and rs164390 are associated with increased reporter gene expression through binding of transcription factors nuclear factor-Y, activator protein 1, and specificity protein 1, respectively.

CONCLUSIONS

Allele-dependent transcriptional regulation of CCNB1 associated with rs350099, rs350104, and rs164390 affects the risk of in-stent restenosis. These findings reveal these common genetic variations as attractive diagnostic tools in risk stratification for restenosis.

The contribution of the C-824T tyrosine hydroxylase polymorphism to the prevalence of hypertension in a South African cohort: the SABPA study

The C-824T single nucleotide polymorphism in the promoter region of the tyrosine hydroxylase gene has been associated with hypertension. It is well documented that African South Africans exhibit a higher prevalence of hypertension than Caucasians. However, the possible role of this mutation on 24-hour ambulatory blood pressure (AMBP) has not been investigated in African South Africans. Blood samples of 409 South Africans were screened for the mutation. Ambulatory blood pressure and lifestyle factors were also measured. Africans had higher incidence of hypertension and higher occurrence of the mutation. However, the contribution of the tyrosine hydroxylase C-824T single nucleotide polymorphism to hypertension could not be confirmed in our cohort.

Comparative SRY incorporation on the regulatory regions of pluripotency/differentiation genes in human embryonic carcinoma cells after retinoic acid induction

Members of the SOX (SRY box) family proteins play critical roles in multiple aspects of development. SRY, as a founder member of SOX family, has been long believed to be involved in the development of sexual gonads by triggering signaling cascades which lead to the formation of testis or ovary from bipotential gonads. However, less is known about other potential regulatory roles of SRY in the development and differentiation. In order to gain further insight into the possible roles of SRY during development, we looked into possible SRY-regulated genes and their levels of expression in a human embryonic carcinoma cell line, named NTera2, before and after induction of differentiation. For this respect, SRY incorporation on the regulatory regions of two groups of genes including OCT4, NANOG, and SOX2 as pluripotency marker genes, and NESTIN and PAX6 as differentiation marker genes were evaluated quantitatively. Chromatin immunoprecipitation using SRY antibody was performed on chromatin extract of a human embryonic carcinoma cell line, NT2/NTERA-2, before and after onset of differentiation. The results showed that incorporation of SRY in both groups of genes was increased after induction of differentiation. Besides, lower expression of OCT4, SOX2, and NANOG and higher expression of PAX6 and NESTIN genes in differentiated cells suggest that SRY may act as a transcription repressor for pluripotency-associated genes and as a transcription activator for differentiation-related genes.

The human testis-determining factor SRY localizes in midbrain dopamine neurons and regulates multiple components of catecholamine synthesis and metabolism

The male gender is determined by the sex-determining region on the Y chromosome (SRY) transcription factor. The unexpected action of SRY in the control of voluntary movement in male rodents suggests a role in the regulation of dopamine transmission and dopamine-related disorders with gender bias, such as Parkinson's disease. We investigated SRY expression in the human brain and function in vitro. SRY immunoreactivity was detected in the human male, but not female substantia nigra pars compacta, within a sub-population of tyrosine hydroxylase (TH) positive neurons. SRY protein also co-localized with TH positive neurons in the ventral tegmental area, and with GAD-positive neurons in the substantia nigra pars reticulata. Retinoic acid-induced differentiation of human precursor NT2 cells into dopaminergic cells increased expression of TH, NURR1, D2 R and SRY. In the human neuroblastoma cell line, M17, SRY knockdown resulted in a reduction in TH, DDC, DBH and MAO-A expression; enzymes which control dopamine synthesis and metabolism. Conversely, SRY over-expression increased TH, DDC, DBH, D2 R and MAO-A levels, accompanied by increased extracellular dopamine levels. A luciferase assay demonstrated that SRY activated a 4.6 kb 5' upstream regulatory region of the human TH promoter/nigral enhancer. Combined, these results suggest that SRY plays a role as a positive regulator of catecholamine synthesis and metabolism in the human male midbrain. This ancillary genetic mechanism might contribute to gender bias in fight-flight behaviours in men or their increased susceptibility to dopamine disorders, such as Parkinson's disease and schizophrenia.

Disorders of blood pressure regulation-role of catecholamine biosynthesis, release, and metabolism

Catecholamines (epinephrine and norepinephrine) are synthesised and produced by the adrenal medulla and postganglionic nerve fibres of the sympathetic nervous system. It is known that essential hypertension has a significant neurogenic component, with the rise in blood pressure mediated at least in part by overactivity of the sympathetic nervous system. Moreover, novel therapeutic strategies aimed at reducing sympathetic activity show promise in the treatment of hypertension. This article reviews recent advances within this rapidly changing field, particularly focusing on the role of genetic polymorphisms within key catecholamine biosynthetic enzymes, cofactors, and storage molecules. In addition, mechanisms linking the sympathetic nervous system and other adverse cardiovascular states (obesity, insulin resistance, dyslipidaemia) are discussed, along with speculation as to how recent scientific advances may lead to the emergence of novel antihypertensive treatments.

Large-scale gene-centric meta-analysis across 39 studies identifies type 2 diabetes loci

To identify genetic factors contributing to type 2 diabetes (T2D), we performed large-scale meta-analyses by using a custom ∼50,000 SNP genotyping array (the ITMAT-Broad-CARe array) with ∼2000 candidate genes in 39 multiethnic population-based studies, case-control studies, and clinical trials totaling 17,418 cases and 70,298 controls. First, meta-analysis of 25 studies comprising 14,073 cases and 57,489 controls of European descent confirmed eight established T2D loci at genome-wide significance. In silico follow-up analysis of putative association signals found in independent genome-wide association studies (including 8,130 cases and 38,987 controls) performed by the DIAGRAM consortium identified a T2D locus at genome-wide significance (GATAD2A/CILP2/PBX4; p = 5.7 × 10(-9)) and two loci exceeding study-wide significance (SREBF1, and TH/INS; p < 2.4 × 10(-6)). Second, meta-analyses of 1,986 cases and 7,695 controls from eight African-American studies identified study-wide-significant (p = 2.4 × 10(-7)) variants in HMGA2 and replicated variants in TCF7L2 (p = 5.1 × 10(-15)). Third, conditional analysis revealed multiple known and novel independent signals within five T2D-associated genes in samples of European ancestry and within HMGA2 in African-American samples. Fourth, a multiethnic meta-analysis of all 39 studies identified T2D-associated variants in BCL2 (p = 2.1 × 10(-8)). Finally, a composite genetic score of SNPs from new and established T2D signals was significantly associated with increased risk of diabetes in African-American, Hispanic, and Asian populations. In summary, large-scale meta-analysis involving a dense gene-centric approach has uncovered additional loci and variants that contribute to T2D risk and suggests substantial overlap of T2D association signals across multiple ethnic groups.

The SHR Y chromosome increases cardiovascular, endocrine, and behavioral responses to stress compared to the WKY Y chromosome

The SHR Y chromosome has loci which are involved with behavioral, endocrine and brain phenotypes and respond to acute stress to a different degree than that of the WKY Y chromosome. The objectives were to determine if WKY males with an SHR Y chromosome (SHR/y) when compared to males with a WKY Y chromosome would have: 1. a greater increase in systolic and diastolic blood pressures (BP), heart rate (HR), and locomotor activity when placed in an open field environment and during an acute stress procedure; 2. enhanced stress hormone responses; 3. greater voluntary running; and 4. increased brain Sry expression. The SHR/y strain showed a significant rise in BP (32%) and HR (10%) during the open field test and exhibited higher BP (46% change) during air jet stress. SHR/y had higher locomotor activity and less immobility and had increased stress induced plasma norepinephrine and adrenocorticotrophic hormone and 3-4× more voluntary running compared to WKY. Differential Sry expression between WKY and SHR/y in amygdala and hippocampus was altered at rest and during acute stress more than that of WKY. Evidence suggests that this animal model allows novel functions of Y chromosome loci to be revealed. In conclusion, a transcription factor on the SHR Y chromosome, Sry, may be responsible for the cardiovascular, endocrine and behavioral phenotype differences between SHR/y and WKY males.

Circulating microRNAs involved in multiple sclerosis

Multiple sclerosis (MS) is an immune-mediated, demyelinating and neurodegenerative disease of the central nervous system. After traumatic brain injury, it is the leading cause of neurology disability in young adults. Considerable advances have been made in identifying genes involved in MS but the genetic and phenotypic complexity associated with this disease significantly hinders any progress. A novel class of small RNA molecules, microRNAs (miRNAs) has acquired much attention because they regulate the expression of up to 30% of protein-coding genes and may play a pivotal role in the development of many, if not all, complex diseases. Seven published studies investigated miRNAs from peripheral blood mononuclear cells, CD4+, CD8+ T cell, B lymphocytes, peripheral blood leukocytes, whole blood and brain astrocytes with MS risk. The absence of MS studies investigating plasma miRNA prompted the current investigation of identifying a circulating miRNA signature in MS. We conducted a microarray analysis of over 900 known miRNA transcripts from plasma samples collected from four MS individuals and four sex-aged and ethnicity matched healthy controls. We identified six plasma miRNA (miR-614, miR-572, miR-648, miR-1826, miR-422a and miR-22) that were significantly up-regulated and one plasma miRNA (miR-1979) that was significantly down-regulated in MS individuals. Both miR-422a and miR-22 have previously been implicated in MS. The present study is the first to show a circulating miRNA signature involved in MS that could serve as a potential prognostic and diagnostic biomarker for MS.

The Sry3 Y chromosome locus elevates blood pressure and renin-angiotensin system indexes

BACKGROUND

Sex-determining region Y (Sry) is a transcription factor. Our research group has shown that there are multiple copies of Sry in Wistar-Kyoto (WKY) and spontaneous hypertensive (SHR) rats, and that they have novel functions separate from testes determination.

OBJECTIVE

We hypothesized that exogenously delivered Sry3 to the normotensive WKY male kidney would activate the renin-angiotensin system (RAS) and raise blood pressure (BP), based on previous in vitro studies.

METHODS

Sry3 or control vector was electroporated to the left kidney of male WKY rats and the following measurements were taken: BP by telemetry, renin-angiotensin measures by radioimmunoassay, plasma and tissue catecholamines by HPLC with electrochemical detection, sodium by flame photometry, and inulin by ELISA.

RESULTS

Sry3 increased BP 10 to 20 mm Hg compared with controls (P < 0.01) and produced a significant 40% decrease in urine sodium compared with controls (P < 0.05). Sry3 increased renal angiotensin II and plasma renin activity by >100% compared with controls (P < 0.01 and P < 0.05, respectively).

CONCLUSION

The findings presented here confirm and extend the argument for Sry3 as one of the genes responsible for the SHR hypertensive Y chromosome phenotype and are consistent with increased tissue RAS activity due to Sry3 and increased sodium reabsorption.

Sry, more than testis determination?

The Sry locus on the mammalian Y chromosome is the developmental switch responsible for testis determination. Inconsistent with this important function, the Sry locus is transcribed in adult males at times and in tissues not involved with testis determination. Sry is expressed in multiple tissues of the peripheral and central nervous system. Sry is derived from Sox3 and is similar to other SOXB family loci. The SOXB loci are responsible for nervous system development. Sry has been demonstrated to modulate the catecholamine pathway, so it should have functional consequences in the central and peripheral nervous system. The nervous system expression and potential function are consistent with Sry as a SOXB family member. In mammals, Sox3 is X-linked and undergoes dosage compensation in females. The expression of Sry in adult males allows for a type of sexual differentiation independent of circulating gonadal hormones. A quantitative difference in Sox3 plus Sry expression in males vs. females could drive changes in the transcriptome of these cells, differentiating male and female cells. Sry expression and its transcriptional effects should be considered when investigating sexual dimorphic phenotypes.

Contemporary approaches to genetic influences on hypertension

PURPOSE OF REVIEW

Essential hypertension has long been considered to be primarily 'genetic,' though recent studies have only revealed minor contributions to blood pressure. Technology has advanced tremendously in the recent years, with much focus on DNA studies utilizing both candidate gene and genome-wide association studies. However, many new areas that need continued investigation have arisen.

RECENT FINDINGS

In addition to DNA studies, genetic studies are actively pursuing previously unexplored areas of potential variation, such as that which occurs posttranscriptionally in RNA and posttranslationally in protein structure. Advances have also been made in animal models and systems biology for large-scale integrative approaches. However, many other areas need continued investigation in the genetics of hypertension, including improved phenotyping and trait definition, gene-by-gene interactions (epistasis), and gene-by-environment interactions. 'Next generation' sequencing will assist researchers in performing more extensive genetic studies even more quickly, especially on unusual (rare) genetic variants.

SUMMARY

Hypertension appears to have many genetic contributions from each regulatory area ranging from DNA to RNA to protein to postprotein to interactive influences of the environment on genes. New technologies have enabled such research to advance in the recent years. However, for this complex trait of hypertension, continued efforts must progress in all of these areas as well as in increased modeling and sequencing, so that the knowledge may be united for a comprehensive understanding of this common disease, such that diagnosis and treatment options in hypertensive patients and those at risk are facilitated.

Proteomic analysis yields an unexpected trans-acting point in control of the human sympathochromaffin phenotype

BACKGROUND

The secretory protein chromogranin A (CHGA) plays a necessary role in formation of catecholamine storage vesicles and gives rise to a catecholamine release-inhibitory fragment. Because genetic variation in the proximal human CHGA promoter predicts autonomic function and blood pressure, we explored how a common genetic variant alters transcription of the gene.

METHODS AND RESULTS

Bioinformatic analysis suggested that the common G-462A promoter variant (rs9658634) may disrupt as many as 3 transcriptional control motifs: LEF1, COUP-TF, and PPARγ-RXRα. During electrophoretic mobility shifts, chromaffin cell nuclear proteins bound specifically to the A (though not G) allele of CHGA promoter G-462A. On oligonucleotide affinity chromatography followed by electrospray ionization followed by 2-dimensional (tandem) mass spectrometry analysis of A allele eluates, the transcription factor LEF1 (lymphoid enhancer-binding factor-1) was identified. Interaction of LEF1 with the A allele at G-462A was confirmed by supershift. On cotransfection, LEF1 discriminated between the allelic variants, especially in chromaffin cells. Allele specificity of trans-activation by LEF1 was transferable to an isolated G-462A element fused to a heterologous (SV40) promoter. Because β-catenin (CTNNB1) can heterodimerize with LEF1, we tested the effect of cotransfection of this factor and again found A allele-specific perturbation of CHGA transcription.

CONCLUSIONS

Common genetic variation within the human CHGA promoter alters the interaction of specific factors in trans with the promoter, with LEF1 identified by proteomic analysis and confirmed by supershift. Coexpression experiments show functional effects of LEF1 and CTNNB1 on CHGA promoter. The findings document a novel role for components of the immune and WNT pathways in control of human sympathochromaffin phenotypes.

Naturally occurring genetic variants in human chromogranin A (CHGA) associated with hypertension as well as hypertensive renal disease

Chromogranin A (CHGA) plays a fundamental role in the biogenesis of catecholamine secretory granules. Changes in storage and release of CHGA in clinical and experimental hypertension prompted us to study whether genetic variation at the CHGA locus might contribute to alterations in autonomic function, and hence hypertension and its target organ consequences such as hypertensive renal disease (nephrosclerosis). Systematic polymorphism discovery across the human CHGA locus revealed both common and unusual variants in both the open reading frame and such regulatory regions as the proximal promoter and 30-UTR. In chromaffin cell-transfected CHGA 30-UTR and promoter/luciferase reporter plasmids, the functional consequences of the regulatory/non-coding allelic variants were documented. Variants in both the proximal promoter and the 30-UTR displayed statistical associations with hypertension. Genetic variation in the proximal CHGA promoter predicted glomerular filtration rate in healthy twins. However, for hypertensive renal damage, both end-stage renal disease and rate of progression of earlier disease were best predicted by variants in the 30-UTR. Finally, mechanistic studies were undertaken initiated by the clue that CHGA promoter variation predicted circulating endothelin-1. In cultured endothelial cells, CHGA triggered co-release of not only the vasoconstrictor and pro-fibrotic endothelin-1, but also the pro-coagulant von Willebrand Factor and the pro-angiogenic angiopoietin-2. These findings, coupled with stimulation of endothelin-1 release from glomerular capillary endothelial cells by CHGA, suggest a plausible mechanism whereby genetic variation at the CHGA locus eventuates in alterations in human renal function. These results document the consequences of genetic variation at the CHGA locus for cardiorenal disease and suggest mechanisms whereby such variation achieves functional effects.

Human dopamine β-hydroxylase promoter variant alters transcription in chromaffin cells, enzyme secretion, and blood pressure

BACKGROUND

Dopamine β-hydroxylase (DBH) plays an indispensable role in catecholamine synthesis by converting dopamine into norepinephrine. Here, we characterized a DBH promoter polymorphism (C-2073T; rs1989787; minor allele frequency ~16%) that influences not only gene transcription but also enzyme secretion and blood pressure (BP) in vivo.

METHODS

Plasma DBH activity was measured spectrophotometrically. DBH genetic effects on BP were tested in subjects with the most extreme BP values in a large primary care population. Functional effects of promoter variants were studied by site-directed mutagenesis in DBH promoter haplotype/luciferase reporter plasmids transfected into chromaffin cells. Sequence motifs were predicted from position weight matrices, and endogenous transcription factor binding was probed by Chromatin ImmunoPrecipitation (ChIP).

RESULTS

The T-allele of common promoter variant C-2073T was contained in a promoter haplotype that associated with plasma DBH activity, a trait also predicted by that variant itself. Promoter haplotypes including C-2073T predicted BP in the population, and the effect was also referable to C-2073T itself. Computationally, C-2073 disrupted a predicted match for transcription factor c-FOS. Site-directed mutagenesis at C-2073T altered not only basal promoter activity, but also transactivation by c-FOS, as well as the chromaffin cell secretory stimuli nicotine or pituitary adenylate cyclase-activating polypeptide (PACAP). Endogenous c-FOS bound to the motif in chromatin.

CONCLUSIONS

These results suggest that DBH promoter variant C-2073T is functional in vivo: this promoter variant seems to initiate a cascade of transcriptional and biochemical changes including augmented DBH secretion, eventuating in elevation of basal BP, and hence cardiovascular risk. The observations suggest new strategies for probing the pathophysiology, risk, and treatment of hypertension.

Tyrosine hydroxylase polymorphism (C-824T) and hypertension: a population-based study

BACKGROUND

Sympathetic nervous system (SNS) overactivity is present in a large proportion of the hypertensive population and precedes the development of established hypertension. Variations in the proximal promoter of the tyrosine hydroxylase (TH) gene have been shown to influence biochemical and physiological traits in the SNS as well as hypertension.

METHODS

We investigated the relationship between a common single-nucleotide polymorphism (SNP) in the proximal TH promoter (C-824T) and blood pressure (BP) in a large general population sample, characterized by 24-h ambulatory BP (ABP) monitoring and office BP measurement.

RESULTS

The study population consisted of 1,221 women and 1,182 men, ages 41-71 years, without major cardiovascular diseases. Regarding the C-824T SNP, 32.4% had the C/C genotype, 50.0% the C/T genotype, and 17.6% the T/T genotype. The T/T genotype conferred an ~45% increase in relative risk of hypertension, defined by conventional criteria, compared with the C/C genotype, and participants with the T/T genotype had significantly higher mean (95% confidence interval (CI)) systolic BP (SBP) (138 (136-140) mm Hg vs. 135 (133-136)), diastolic BP (DBP) (88 (86-89) mm Hg vs. 85 (84-86)), and heart rate (68 (67-69) beats/min vs. 66 (65-67)) than participants with the C/C genotype (P < 0.05). BP, heart rate, and prevalence of hypertension were intermediate in participants with the C/T genotype. These effects were the same in women and men and whether BP was measured in the office or by 24-h ambulatory monitoring.

CONCLUSION

The C-824T SNP in the proximal TH promoter influences BP and prevalence of hypertension in the general population.

Human tyrosine hydroxylase natural allelic variation: influence on autonomic function and hypertension

The catecholamine biosynthetic pathway consists of several enzymatic steps in series, beginning with the amino acids phenylalanine and tyrosine, and eventuating in the catecholamines norepinephrine (noradrenaline) and epinephrine (adrenaline). Since the enzyme tyrosine hydroxylase (TH; tyrosine 3-mono-oxygenase; EC 1.14.16.2; chromosome 11p15.5) is generally considered to be rate-limiting in this pathway, probed as to whether common genetic variation at the TH gene occurred, and whether such variants contributed to inter-individual alterations in autonomic function, either biochemical or physiological. We began with sequencing a tetranucleotide (TCAT) repeat in the first intron, and found that the two most common versions, (TCAT)₆ and (TCAT)_10i, predicted heritable autonomic traits in twin pairs. We then conducted systematic polymorphism discovery across the ~8 kbp locus, and discovered numerous variants, principally non-coding. The proximal promoter block contained four common variants, and its haplotypes and SNPs (especially C-824T, rs10770141) predicted catecholamine secretion, environmental stress-induced BP increments, and hypertension. Finally, we found that two of the common promoter variants, C-824T (rs10770141) and A-581G (rs10770140), were functional in that they differentially affected transcriptional activity of the isolated promoter, disrupted recognition motifs for specific transcription factor binding, altered the promoter responses to the co-transfected (exogenous) factors, and bound the endogenous factors in the chromatin fraction of the nucleus. We concluded that common variation in the proximal TH promoter is functional, giving rise to changes in autonomic function and consequently cardiovascular risk.