The noradrenergic system is involved in the etiology and progression of Alzheimer’s disease (AD) but its role is still unclear. Dopamine beta-hydroxylase (DBH) as a catecholamine-synthesizing enzyme plays a central role in noradrenaline (NA) synthesis and turnover. Plasma DBH (pDBH) activity shows wide inheritable interindividual variability that is under genetic control. The aim of this study was to determine pDBH activity, DBH (C-970T; rs1611115) and DBH (C1603T; rs6271) gene polymorphisms in 207 patients with AD and in 90 healthy age-matched controls. Plasma DBH activity was lower, particularly in the early stage of AD, compared to values in middle and late stages of the disease, as well as to control values. Two-way ANOVA revealed significant effect of both diagnosis and DBH (C-970T) or DBH (C1603T) genotypes on pDBH activity, but without significant diagnosis×genotype interaction. No association was found between AD and DBH C-970T (OR=1.08, 95% CI 1.13–4.37; p=0.779) and C1603T (OR=0.89; 95% CI 0.36–2.20; p=0.814) genotypes controlled for age, gender, and ApoE4 allele. The decrease in pDBH activity, found in early phase of AD suggests that alterations in DBH activity represent a compensatory mechanism for the loss of noradrenergic neurons, and that treatment with selective NA reuptake inhibitors may be indicated in early stages of AD to compensate for loss of noradrenergic activity in the locus coeruleus.
Alzheimer’s disease; Cognitive decline; DBH gene polymorphisms; Dopamine beta-hydroxylase; Plasma DBH activity
Dopamine beta-hydroxylase (DBH) plays an essential role in catecholamine synthesis by converting dopamine into norepinephrine. Here we systematically investigated DBH polymorphisms associated with enzymatic activity as well as autonomic and BP/disease phenotypes in vivo.
Methods and Results
70 genetic variants were discovered at the locus; across ethnicities, much of the promoter was spanned by a 5’ haplotype block, with a larger block spanning the promoter in whites than blacks. DBH secretion was predicted by genetic variants in the DBH promoter, rather than the amino acid coding region. The C allele of common promoter variant C-970T increased plasma DBH activity, epinephrine excretion, the heritable change in BP during environmental stress in twin pairs, and also predicted higher basal BP in three independent populations. Mutagenesis and expression studies with isolated/transfected DBH promoter/luciferase reporters in chromaffin cells indicated that variant C-970T was functional. C-970T partially disrupted consensus transcriptional motifs for n-MYC and MEF-2, and this variant affected not only basal expression, but also the response to exogenous/co-transfected n-MYC or MEF-2; during ChIP, these two endogenous factors interacted with the motif.
These results suggest that common DBH promoter variant C-970T plays a role in the pathogenesis of human essential hypertension: common genetic variation in the DBH promoter region seems to initiate a cascade of biochemical and physiological changes eventuating in alterations of basal BP. These observations suggest new molecular strategies for probing the pathophysiology, risk, and rational treatment of systemic hypertension.
Dopamine beta-hydroxylase; polymorphism; hypertension
Disulfiram has been an effective cocaine addiction pharmacotherapy, and one of its possible mechanisms of efficacy is through copper chelation and inhibition of an enzyme involved in catecholamine metabolism, dopamine β-hydroxylase (DβH), which converts dopamine to norepinephrine. A variant in the gene encoding DβH leads to reduced DβH activity and as such, disulfiram may not be an effective treatment of cocaine dependence for individuals with this variant. This study explored that potential matching.
Seventy-four cocaine and opioid co-dependent (DSM-V) subjects were stabilized on methadone for two weeks and subsequently randomized into disulfiram (250 mg/day, N =34) and placebo groups (N =40) for 10 weeks. We genotyped the DBH gene polymorphism, −1021C/T (rs1611115), that reduces DβH enzyme levels and evaluated its role for increasing cocaine free urines with disulfiram.
Using repeated measures analysis of variance, corrected for population structure, disulfiram pharmacotherapy reduced cocaine positive urines from 80% to 62% (p = .0001), and this disulfiram efficacy differed by DBH genotype group. Patients with the normal DβH level genotype dropped from 84% to 56% on disulfiram (p = .0001), while those with the low DBH level genotype showed no disulfiram effect.
This study indicates that a patient’s DBH genotype could be used to identify a subset of individuals for which disulfiram treatment may be an effective pharmacotherapy for cocaine dependence.
Genes; disulfiram; polymorphism; cocaine; treatment; dependence
The loss of noradrenergic neurones of the locus coeruleus is a major feature of Alzheimer's disease (AD). Dopamine β-hydroxylase (DBH) catalyses the conversion of dopamine to noradrenaline. Interactions have been reported between the low-activity -1021T allele (rs1611115) of DBH and polymorphisms of the pro-inflammatory cytokine genes, IL1A and IL6, contributing to the risk of AD. We therefore examined the associations with AD of the DBH -1021T allele and of the above interactions in the Epistasis Project, with 1757 cases of AD and 6294 elderly controls.
We genotyped eight single nucleotide polymorphisms (SNPs) in the three genes, DBH, IL1A and IL6. We used logistic regression models and synergy factor analysis to examine potential interactions and associations with AD.
We found that the presence of the -1021T allele was associated with AD: odds ratio = 1.2 (95% confidence interval: 1.06-1.4, p = 0.005). This association was nearly restricted to men < 75 years old: odds ratio = 2.2 (1.4-3.3, 0.0004). We also found an interaction between the presence of DBH -1021T and the -889TT genotype (rs1800587) of IL1A: synergy factor = 1.9 (1.2-3.1, 0.005). All these results were consistent between North Europe and North Spain.
Extensive, previous evidence (reviewed here) indicates an important role for noradrenaline in the control of inflammation in the brain. Thus, the -1021T allele with presumed low activity may be associated with misregulation of inflammation, which could contribute to the onset of AD. We suggest that such misregulation is the predominant mechanism of the association we report here.
The role of the endothelin-B receptor (ETB) in vascular homeostasis is controversial because the receptor has both pressor and depressor effects in vivo. Spotting lethal (sl) rats carry a naturally occurring deletion in the ETB gene that completely abrogates functional receptor expression. Rats homozygous for this mutation die shortly after birth due to congenital distal intestinal aganglionosis. Genetic rescue of ETBsl/sl rats from this developmental defect using a dopamine-—hydroxylase (DBH)-ETB transgene results in ETB-deficient adult rats. On a sodium-deficient diet, DBH-ETB;ETBsl/sl and DBH-ETB;ETB+/+ rats both exhibit a normal arterial blood pressure, but on a high-sodium diet, the former are severely hypertensive. We find no difference in plasma renin activity or plasma aldosterone concentration between salt-fed wild-type, DBH-ETB;ETB+/+ or DBH-ETB;ETBsl/sl rats, and acute responses to intravenous L-NAME and indomethacin are similar between DBH-ETB;ETBsl/sl and DBH-ETB;ETB+/+ rats. Irrespective of diet, DBH-ETB;ETBsl/sl rats exhibit increased circulating ET-1, and, on a high-sodium diet, they show increased but incomplete hypotensive responses to acute treatment an ETA-antagonist. Normal pressure is restored in salt-fed DBH-ETB;ETBsl/sl rats when the epithelial sodium channel is blocked with amiloride. We conclude that DBH-ETB;ETBsl/sl rats are a novel single-locus genetic model of severe salt-sensitive hypertension. Our results suggest that DBH-ETB;ETBsl/sl rats are hypertensive because they lack the normal tonic inhibition of the renal epithelial sodium channel.
We examined a pharmacogenetic association of the dopamine β-hydroxylase (DBH) gene with a response to an anti-cocaine vaccine that was tested in a recent clinical trial. This gene is associated with cocaine-induced paranoia, which has a slower onset than the euphoria from cocaine. The vaccine reduced euphoria by slowing the entry of cocaine into the brain, but it may not reduce aversive symptoms like paranoia. A 16-week Phase IIb randomized double-blind placebo-controlled trial of 114 cocaine and opioid dependent subjects who received five vaccinations over the first 12 weeks was examined. We genotyped 71 subjects for the rs1611115 (−1021C>T) variant of the DBH gene and compared vaccine to placebo subjects on cocaine-free urines. Using repeated measures analysis of variance, corrected for population structure, vaccine pharmacotherapy reduced cocaine positive urines significantly based on DBH genotype. Patients with the low DβH level genotype dropped from 77% to 51% on vaccine (p = 0.0001), while those with the normal DβH level genotype dropped from 83% to 72%. Placebo showed no effect on cocaine use overall or by genotype. This study indicates that a patient’s DBH genotype could be used to identify a subset of individuals for whom vaccine treatment may be an effective pharmacotherapy for cocaine dependence.
Gene; dopamine; polymorphism; cocaine; treatment; vaccine
Elevated sympathetic activity is associated with kidney dysfunction. Here we used twin pairs to probe heritability of GFR and its genetic covariance with other traits.
We evaluated renal and adrenergic phenotypes in twins. GFR was estimated by CKD-EPI algorithm. Heritability and genetic covariance of eGFR and associated risk traits were estimated by variance-components. Meta-analysis probed reproducibility of DBH genetic effects. Effect of DBH genetic variation on renal disease was tested in the NIDDK-AASK cohort.
Norepinephrine secretion rose across eGFR tertiles while eGFR fell (p<0.0001). eGFR was heritable, at h2 = 67.3±4.7% (p = 3.0E-18), as were secretion of norepinephrine (h2 = 66.5±5.0%, p = 3.2E-16) and dopamine (h2 = 56.5±5.6%, p = 1.8E-13), and eGFR displayed genetic co-determination (covariance) with norepinephrine (ρG = −0.557±0.088, p = 1.11E-08) as well as dopamine (ρG = −0.223±0.101, p = 2.3E-02). Since dopamine β-hydroxylase (DBH) catalyzes conversion of dopamine to norepinephrine, we studied functional variation at DBH; DBH promoter haplotypes predicted transcriptional activity (p<0.001), plasma DBH (p<0.0001) and norepinephrine (p = 0.0297) secretion; transcriptional activity was inversely (p<0.0001) associated with basal eGFR. Meta-analysis validated DBH haplotype effects on eGFR across 3 samples. In NIDDK-AASK, we established a role for DBH promoter variation in long-term renal decline rate (GFR slope, p = 0.003).
The heritable GFR trait shares genetic determination with catecholamines, suggesting new pathophysiologic, diagnostic and therapeutic approaches towards disorders of GFR as well as CKD. Adrenergic activity may play a role in progressive renal decline, and genetic variation at DBH may assist in profiling subjects for rational preventive treatment.
Computerized aiding systems can assist human decision makers in complex tasks but can impair performance when they provide incorrect advice that humans erroneously follow, a phenomenon known as “automation bias.” The extent to which people exhibit automation bias varies significantly and may reflect inter-individual variation in the capacity of working memory and the efficiency of executive function, both of which are highly heritable and under dopaminergic and noradrenergic control in prefrontal cortex. The dopamine beta hydroxylase (DBH) gene is thought to regulate the differential availability of dopamine and norepinephrine in prefrontal cortex. We therefore examined decision-making performance under imperfect computer aiding in 100 participants performing a simulated command and control task. Based on two single nucleotide polymorphism (SNPs) of the DBH gene, −1041 C/T (rs1611115) and 444 G/A (rs1108580), participants were divided into groups of low and high DBH enzyme activity, where low enzyme activity is associated with greater dopamine relative to norepinephrine levels in cortex. Compared to those in the high DBH enzyme activity group, individuals in the low DBH enzyme activity group were more accurate and speedier in their decisions when incorrect advice was given and verified automation recommendations more frequently. These results indicate that a gene that regulates relative prefrontal cortex dopamine availability, DBH, can identify those individuals who are less susceptible to bias in using computerized decision-aiding systems.
The midline and intralaminar thalamic nuclei (MITN), locus coeruleus (LC) and cingulate cortex contain nociceptive neurons. The MITN that project to cingulate cortex have a prominent innervation by norepinephrinergic axons primarily originating from the LC. The hypothesis explored in this study is that MITN neurons that project to cingulate cortex receive a disproportionately high LC input that may modulate nociceptive afferent flow into the forebrain. Ten cynomolgus monkeys were evaluated for dopamine-β hydroxylase (DBH) immunohistochemistry and, nuclei with moderate or high DBH activity were analyzed for intermediate neurofilament proteins, calbindin, and calretinin. Sections of all but DBH were thionin counterstained to assure precise localization in the mediodorsal and MITN and cytoarchitecture was analyzed with neuron-specific nuclear binding protein. Moderate-high levels of DBH-immunoreactive (ir) axons were generally associated with high densities of CB-ir and CR-ir neurons and low levels of neurofilament proteins. The paraventricular, superior centrolateral, limitans and central nuclei had relatively high and evenly distributed DBH, the magnocellular mediodorsal and paracentral nuclei had moderate DBH-ir, and other nuclei had an even and low level of activity. Some nuclei also have heterogeneities in DBH-ir that raised questions of functional segregation. The anterior multiformis part of the mediodorsal nucleus but not middle and caudal levels had high DBH activity. The posterior parafascicular nucleus (Pf) was heterogeneous with the lateral part having little DBH activity, while its medial division had most DBH-ir axons and its multiformis part had only a small number. These findings suggest that the LC may regulate nociceptive processing in the thalamus. The well established role of cingulate cortex in premotor functions and the projections of Pf and other MITN to the limbic striatum suggests a specific role in mediating motor outflow for the LC-innervated nuclei of the MITN.
dopamine-β hydroxylase; cingulate cortex; thalamus; locus coeruleus; stress; pain
A single nucleotide polymorphism in the promoter region of the dopamine β-hydroxylase gene (DBH -1021C>T; rs1611115) is reported to regulate plasma enzyme activity levels. This variant has also been the focus of two large association studies in Parkinson’s disease yielding conflicting results. We examined this association in four Caucasian patient-control series (n=2696). A modest protective association was observed in the Norwegian series (OR=0.81, p=0.03; n=1676), however the effect was in the opposite direction in the Polish series (OR=2.01, p=0.01; n=224). No association was observed for DBH -1021C>T with disease susceptibility in the US and Irish series, or combining all four series (OR=0.91, p=0.16, n=2696). We observed a modest association between DBH -1021C>T and AAO in the combined series (p=0.01). Taken together, these findings indicate that DBH -1021C>T does not play a major role in the pathogenesis of Parkinson’s disease.
Genetics; PD; DBH; promoter SNP
Experiments in vivo and in cell culture demonstrated that oestradiol induces dopamine β-hydroxylase (DBH) gene transcription. Here we examined oestrogen-responsive elements of the rat DBH gene promoter to characterize the mechanisms of oestradiol-induced DBH transcription. Various mutations and deletions of DBH promoter reporter constructs were tested for responsiveness to 17 β-oestradiol (E2). Mutation of the half palindromic oestrogen response element (ERE) at position −759 reduced the response to E2 in PC12 cells co-transfected with ERα indicating a functional role for this motif. In cells co-transfected with ERβ, mutations at the −759 site were unresponsive to E2. To characterize the additional E2 responsive elements, mediated by ERα, the DBH promoter was truncated to the proximal 249 or 200 nucleotides upstream of the transcription start site. Despite either truncation, 10 nM E2 still elicited about a two-fold induction of DBH promoter activity. Mutation of a possible ERE like sequence at −59 had no effect. The lack of a functional ERE in the proximal region of the rat DBH promoter despite E2-mediated DBH promoter activity, suggests regulation by a non-classical mechanism, such as a membrane-initiated signaling pathway. Moreover, the induction of DBH promoter activity and the rise in DBH mRNA levels were observed within hours. To determine whether membrane-initiated E2 signaling is involved in rat DBH gene transcription, a membrane impermeable E2 conjugate, E2BSA, was used. Incubation with E2BSA induced luciferase promoter activity and elicited a significant rise in DBH mRNA levels in the ERα transfected cells. The findings indicate two different mechanisms whereby DBH transcription is regulated by E2 in the presence of ERα. The results implicate both genomic and membrane-initiated mechanisms, mediated by ERα, in E2-induced DBH gene transcription.
The anti-alcoholism medication, disulfiram (Antabuse), decreases cocaine use in humans regardless of concurrent alcohol consumption and facilitates cocaine sensitization in rats, but the functional targets are unknown. Disulfiram inhibits dopamine β-hydroxylase (DBH), the enzyme that converts dopamine (DA) to norepinephrine (NE) in noradrenergic neurons. The goal of this study was to test the effects of chronic genetic or pharmacological DBH inhibition on behavioral responses to cocaine using DBH knockout (Dbh −/−) mice, disulfiram, and the selective DBH inhibitor, nepicastat. Locomotor activity was measured in control (Dbh +/−) and Dbh −/− mice during a 5 day regimen of saline+saline, disulfiram+saline, nepicastat+saline, saline+cocaine, disulfiram+cocaine, or nepicastat+cocaine. After a 10 day withdrawal period, all groups were administered cocaine, and locomotor activity and stereotypy were measured. Drug-naïve Dbh −/− mice were hypersensitive to cocaine-induced locomotion and resembled cocaine-sensitized Dbh +/− mice. Chronic disulfiram administration facilitated cocaine-induced locomotion in some mice and induced stereotypy in others during the development of sensitization, while cocaine-induced stereotypy was evident in all nepicastat-treated mice. Cocaine-induced stereotypy was profoundly increased in the disulfiram+cocaine, nepicastat+cocaine, and nepicastat+saline groups upon cocaine challenge after withdrawal in Dbh +/− mice. Disulfiram or nepicastat treatment had no effect on behavioral responses to cocaine in Dbh −/− mice. These results demonstrate that chronic DBH inhibition facilitates behavioral responses to cocaine, although different methods of inhibition (genetic vs. non-selective inhibitor vs. selective inhibitor) enhance qualitatively different cocaine-induced behaviors.
Tardive dyskinesia (TD) is a human hyperkinetic movement disorder as a result of potentially irreversible long-term chronic first-generation antipsychotic medications. Unfortunately, mechanisms involved in the development of TD have been poorly understood. Previous studies have indicated that some genetic polymorphisms of immune system and dopamine beta-hydroxylase (DBH) genes may be involved in the pathogenesis of TD. Rs1800872 and rs72393728 are located on the promoter of interleukin-10 (IL10) and DBH gene, respectively. The genetic association between the rs1800872 and TD is unclear. Previous studies have indicated that genetic variations of IL 10 and DBH are implicated in the positive and negative symptoms in schizophrenia. However, the interaction of two variations with severity of TD and symptoms of schizophrenic patients with TD has not been reported. The present study investigated whether these variations and their interaction were associated with clinical phenotypes of TD with schizophrenia in a genetically homogeneous northern Chinese Han population.
Rs1800872 and rs72393728 were genotyped in schizophrenic patients with TD (n = 372) and without TD (NTD; n = 412). The Abnormal Involuntary Movement Scale (AIMS) and Positive and Negative Syndrome Scale (PANSS) were applied to assess the severity of TD and psychopathology of schizophrenia, respectively.
The allele and genotype frequencies of rs1800872 and rs72393728 did not significantly differ between TD and NTD patients (p>0.05). No significant difference was found in the AIMS total score among the genotypes of two loci (p>0.05). Interestingly, the interaction of rs1800872 and rs72393728 showed a significant association with the PANSS general score (p = 0.011), and a trend toward to the PANSS total score (p = 0.055).
These findings suggest that the interaction of rs1800872 and rs72393728 variants may play a role in psychopathology of the general symptoms on PANSS in schizophrenic patients with TD in a northern Chinese Han population.
Rett syndrome is a neurodevelopmental disorder caused by Mecp2 gene mutations. In RTT patients and Mecp2-null (Mecp2−/Y) mice, norepinephrine (NE) content drops significantly, which may play a role in breathing arrhythmia, sleep disorders and sudden death in RTT. However, the underlying mechanisms for the NE defect are not fully understood. The NE defect may result from decreased NE biosynthesis, loss of catecholaminergic neurons or both. Although deficiency in tyrosine hydroxylase (TH) has been demonstrated, it is possible that dopamine β-hydroxylase (DBH), the critical enzyme converting dopamine to NE, is also affected. To test these possibilities, we studied DBH expressions at mRNA and protein levels in pontine catecholaminergic neurons of Mecp2−/Y mice identified with breathing abnormalities. In comparison to the WT, Mecp2−/Y mice at 2 months of age showed ~50% decrease in the expressions of DBH and TH, at both protein and mRNA levels in the locus coeruleus (LC) region. Consistently, DBH and TH immunoreactivity was markedly decreased in LC neurons of Mecp2−/Y mice. No evidence was found for selective deficiency in TH- or DBH-containing neurons in Mecp2−/Y mice, as almost all TH-positive cells expressed DBH. By counting TH-immunoreactive cells in the LC, we found that the Mecp2−/Y mice lost only ~5% of the catecholaminergic neurons as compared to wild-type, although their LC volume shrank by ~15%. These results strongly suggest that the NE defect in Mecp2−/Y mice is likely to result from deficient expression of not only TH but also DBH without significant loss of catecholaminergic neurons in the LC.
Rett syndrome; catercholaminergic neurons; norepinephrine; dopamine β-hydroxylase; tyrosine hydroxylase
Pharmacogenetics uses genetic variation to predict individual differences in response to medications and holds much promise to improve treatment of addictive disorders.
To review how genetic variation affects responses to cocaine, amphetamine, and methamphetamine and how this information may guide pharmacotherapy.
We performed a cross-referenced literature search on pharmacogenetics, cocaine, amphetamine, and methamphetamine.
We describe functional genetic variants for enzymes dopamine-beta-hydroxylase (DβH), catechol-O-methyltransferase (COMT), and dopamine transporter (DAT1), dopamine D4 receptor, and brain-derived neurotrophic factor (BDNF). A single nucleotide polymorphism (SNP; C-1021T) in the DβH gene is relevant to paranoia associated with disulfiram pharmacotherapy for cocaine addiction. Individuals with variable number tandem repeats (VNTR) of the SLC6A3 gene 3′-untranslated region polymorphism of DAT1 have altered responses to drugs. The 10/10 repeat respond poorly to methylphenidate pharmacotherapy and the 9/9 DAT1 variant show blunted euphoria and physiological response to amphetamine. COMT, D4 receptor, and BDNF polymorphisms are linked to methamphetamine abuse and psychosis.
Disulfiram and methylphenidate pharmacotherapies for cocaine addiction are optimized by considering polymorphisms affecting DβH and DAT1 respectively. Altered subjective effects for amphetamine in DAT1 VNTR variants suggest a ‘protected’ phenotype.
Pharmacogenetic-based treatments for psychostimulant addiction are critical for successful treatment.
Gene variants; pharmacotherapies; drug therapy; stimulants; individualized therapy; gene-based therapeutics; polymorphisms; genetic variation; subjective effects; drug dependence; addiction psychiatry
Norepinephrine (NE) plays a central role in post-traumatic stress disorder (PTSD). Dopamine β-hydroxylase (DβH) converts dopamine (DA) to NE and its activity varies widely across individuals. Mustapic et al. (2007) reported a PTSD-associated deficit in serum DβH activity (sDβH) in a genotype-controlled analysis of combat veterans. We tested whether such a deficit would occur in a sample of civilians.
The severity of current adult PTSD symptoms and current DSM-IV diagnosis of PTSD were determined by the PTSD Symptom Scale (PSS). Adulthood trauma exposure was assessed using the Traumatic Experience Inventory (TEI). sDβH was assayed by HPLC with electrochemical detection and genotypes were determined using the Taqman® platform.
Two hundred and twenty seven African American (AA) subjects were enrolled in this study, with a mean age (± SD) of 42.9 (±12.9) years. We found a strong association between rs1611115 genotype and sDβH (p<0.0001). After controlling for adulthood trauma exposure, there were no significant differences of sDβH between subjects who met a PTSD diagnosis and those who did not (p>0.05) in any genotype group. No significant correlations were found between sDβH and PTSD severity, but sDβH significantly associated with the status of comorbid depression based on the cutoff of HAMD (p=0.014) in subjects with PTSD.
We have replicated in this sample the prior finding that DBH rs1611115 genotype strongly associates with sDβH. No associations between sDβH and PTSD diagnosis or symptom severity in this civilian sample.
post-traumatic stress disorder; serum dopamine β-hydroxylase; genotype; depression; civilian trauma; association
Associations of polymorphisms from dopaminergic neurotransmitter
pathway genes have been reported in Caucasian ancestry schizophrenia (SZ)
samples. As studies investigating single SNPs with SZ have been
inconsistent, more detailed analyses utilizing multiple SNPs with the
diagnostic phenotype as well as cognitive function may be more informative.
The analyses were conducted in a north Indian sample.
Indian SZ case-parent trios (n = 601 families); unscreened controls
(n= 468) and an independent set of 118 trio families were analyzed.
Representative SNPs in the Dopamine D3 receptor (DRD3),
dopamine transporter (SLC6A3), vesicular monoamine
transporter 2 (SLC18A2), catechol-o-methyltransferase
(COMT) and dopamine beta hydroxylase
(DBH) were genotyped using SNaPshot/SNPlex assays (n=59
SNPs). The Trail Making Test (TMT) was administered to a subset of the
sample (n=260 cases and_n=302 parents).
Eight SNPs were nominally associated with SZ in either case-control
or family based analyses (p<0.05, rs7631540 and rs2046496 in
DRD3; rs363399 and rs10082463 in
SLC18A2; rs4680, rs4646315 and rs9332377 in
COMT). rs6271 at DBH was associated in
both analyses. Haplotypes of DRD3 SNPs incorporating
rs7631540-rs2134655-rs3773678-rs324030-rs6280-rs905568 showed suggestive
associations in both case-parent and trio samples. At
SLC18A2, rs10082463 was nominally associated with
psychomotor performance and rs363285 with executive functions using the TMT
but did not withstand multiple corrections.
Though suggestive associations with dopaminergic genes were detected
in this study, but convincing links between dopaminergic polymorphisms and
SZ or cognitive function were not observed.
Schizophrenia; Dopamine genes; SNPs; association; Haplotypes; cognition
Dopamine beta-hydroxylase (DβH) deficiency is a very rare form of primary autonomic failure characterized by a complete absence of noradrenaline and adrenaline in plasma together with increased dopamine plasma levels. The prevalence of DβH deficiency is unknown. Only a limited number of cases with this disease have been reported. DβH deficiency is mainly characterized by cardiovascular disorders and severe orthostatic hypotension. First symptoms often start during a complicated perinatal period with hypotension, muscle hypotonia, hypothermia and hypoglycemia. Children with DβH deficiency exhibit reduced ability to exercise because of blood pressure inadaptation with exertion and syncope. Symptoms usually worsen progressively during late adolescence and early adulthood with severe orthostatic hypotension, eyelid ptosis, nasal stuffiness and sexual disorders. Limitation in standing tolerance, limited ability to exercise and traumatic morbidity related to falls and syncope may represent later evolution. The syndrome is caused by heterogeneous molecular alterations of the DBH gene and is inherited in an autosomal recessive manner. Restoration of plasma noradrenaline to the normal range can be achieved by therapy with the synthetic precursor of noradrenaline, L-threo-dihydroxyphenylserine (DOPS). Oral administration of 100 to 500 mg DOPS, twice or three times daily, increases blood pressure and reverses the orthostatic intolerance.
Cigarette smoking is a major risk factor for COPD and COPD severity. Previous genome-wide association studies (GWAS) have identified numerous single nucleotide polymorphisms (SNPs) associated with the number of cigarettes smoked per day (CPD) and a Dopamine Beta-Hydroxylase (DBH) locus associated with smoking cessation in multiple populations.
To identify SNPs associated with lifetime average and current CPD, age at smoking initiation, and smoking cessation in COPD subjects.
GWAS were conducted in 4 independent cohorts encompassing 3,441 ever-smoking COPD subjects (GOLD stage II or higher). Untyped SNPs were imputed using HapMap (phase II) panel. Results from all cohorts were meta-analyzed.
Several SNPs near the HLA region on chromosome 6p21 and in an intergenic region on chromosome 2q21 showed associations with age at smoking initiation, both with the lowest p=2×10−7. No SNPs were associated with lifetime average CPD, current CPD or smoking cessation with p<10−6. Nominally significant associations with candidate SNPs within alpha-nicotinic acetylcholine receptors 3/5 (CHRNA3/CHRNA5; e.g. p=0.00011 for SNP rs1051730) and Cytochrome P450 2A6 (CYP2A6; e.g. p=2.78×10−5 for a nonsynonymous SNP rs1801272) regions were observed for lifetime average CPD, however only CYP2A6 showed evidence of significant association with current CPD. A candidate SNP (rs3025343) in the DBH was significantly (p=0.015) associated with smoking cessation.
We identified two candidate regions associated with age at smoking initiation in COPD subjects. Associations of CHRNA3/CHRNA5 and CYP2A6 loci with CPD and DBH with smoking cessation are also likely of importance in the smoking behaviors of COPD patients.
Chronic Obstructive Pulmonary Disease (COPD); Genome Wide Association study (GWAS); smoking behaviors; Single Nucleotide Polymorphism (SNP)
Dopamine-β-hydroxylase (DBH) is a neurotransmitter (catecholamine)-mediating enzyme, which catalyzes the formation of norepinephrine from dopamine. The levels of DBH activity, its coenzyme (ascorbic acid) and cofactor (Cu++) and other biochemical parameters were measured in the serum of 32 arsenicosis patients of Bangladesh at three different age groups, namely, group 1 (10–18 years, 9 patients), group 2 (19–40 years, 14 patients) and group 3 (41–70 years, 9 patients) of the locality of Stadium Para of Meherpur district of Bangladesh. The values were compared with the same number of age-matched normal healthy individuals of the respective group. DBH activity was markedly decreased in the patients of group 1 as compared to that of the normal healthy people. The activities of DBH were decreased to lesser extents for the other two age groups. The total protein contents in the serum of arsenicosis patients were also significantly low as compared to that in the age-matched control groups. The levels of ascorbic acid and copper were found to be decreased in the serum of arsenicosis patients. The serum glucose levels were elevated in arsenicosis patients, as compared to that of the respective healthy controls. Other parameters, such as zinc and vitamin A levels were also decreased in the serum of arsenicosis patients. It was evident from the results of drinking of the arsenic contaminated water of shallow tube wells that the levels of DBH activity decreased significantly as compared to the control healthy persons. The levels of proteins, ascorbic acid, copper, zinc and vitamin A were decreased in the serum of people drinking the arsenic contaminated tube wells water as compared to that in the control healthy people with the exception that the levels of glucose were elevated in the serum of these patients. The pathophysiological significance of the results could be correlated with the decreased in proteins and that in DBH activities as DBH deficiency is characterized by lack of sympathetic noradrenergic function.The general physiologic findings of autonomic function indicate that complete DBH deficiency include minimal or absent plasma norepinephrine and epinephrine.
Arsenicosis; Drinking-water; Dopamine-β-Hydroxylase; Norepinephrine; Serum
OBJECTIVE—Elevated plasma triglyceride concentration is a component of the insulin resistance syndrome and is commonly associated with type 2 diabetes, obesity, and coronary heart disease. The goal of our study was to perform a genome-wide linkage scan to identify genetic regions that influence variation in plasma triglyceride levels in families that are enriched with individuals with type 2 diabetes.
RESEARCH DESIGN AND METHODS—We used phenotypic and genotypic data from 1,026 individuals distributed across 294 Mexican-American families, who were ascertained for type 2 diabetes, from the Veterans Administration Genetic Epidemiology Study (VAGES). Plasma triglyceride values were transformed, and a variance-components technique was used to conduct multipoint linkage analysis.
RESULTS—After adjusting for the significant effects of sex and BMI, heritability for plasma triglycerides was estimated as 46 ± 7% (P < 0.0001). Multipoint linkage analysis yielded the strongest evidence for linkage of plasma triglycerides near marker D12S391 on chromosome 12p (logarithm of odds [LOD] = 2.4). Our linkage signal on chromosome 12p provides independent replication of a similar finding in another Mexican-American sample from the San Antonio Family Diabetes Study (SAFDS). Combined multipoint linkage analysis of the VAGES and SAFDS data yielded significant evidence for linkage of plasma triglycerides to a genetic location between markers GATA49D12 and D12S391 on 12p (LOD = 3.8, empirical P value = 2.0 × 10−5). This region on 12p harbors the gene-encoding adiponectin receptor 2 (AdipoR2), where we previously have shown that multiple single nucleotide polymorphisms are associated with plasma triglyceride concentrations in the SAFDS. In the present study, we provided suggestive evidence in favor of association for rs929434 with triglyceride concentrations in the VAGES.
CONCLUSIONS—Collectively, these results provide strong evidence for a major locus on chromosome 12p that influences plasma triglyceride levels in Mexican Americans.
Multiple linkage regions have been reported in schizophrenia, and some appear to harbor susceptibility genes that are differentially expressed in postmortem brain tissue derived from unrelated individuals. We combined traditional genome-wide linkage analysis in a multiplex family with lymphocytic genome-wide expression analysis. A genome scan suggested linkage to a chromosome 4q marker (D4S1530, LOD 2.17, θ=0) using a dominant model. Haplotype analysis using flanking microsatellite markers delineated a 14 Mb region that cosegregated with all those affected. Subsequent genome-wide scan with SNP genotypes supported the evidence of linkage to 4q33−35.1 (LOD=2.39) using a dominant model. Genome-wide microarray analysis of five affected and five unaffected family members identified two differentially expressed genes within the haplotype AGA and GALNT7 (aspartylglucosaminidase and UDP-N-acetyl-alpha-d-galactosamine: polypeptide N-acetylgalactosaminyltransferase 7) with nominal significance; however, these genes did not remain significant following analysis of covariance. We carried out genome-wide linkage analyses between the quantitative expression phenotype and genetic markers. AGA expression levels showed suggestive linkage to multiple markers in the haplotype (maximum LOD=2.37) but to no other genomic region. GALNT7 expression levels showed linkage to regulatory loci at 4q28.1 (maximum LOD=3.15) and in the haplotype region at 4q33−35.1 (maximum LOD=2.37). ADH1B (alcohol dehydrogenase IB) was linked to loci at 4q21–q23 (maximum LOD=3.08) and haplotype region at 4q33−35.1 (maximum LOD=2.27). Seven differentially expressed genes were validated with RT-PCR. Three genes in the 4q33−35.1 haplotype region were also differentially expressed in schizophrenia in postmortem dorsolateral prefrontal cortex: AGA, HMGB2, and SCRG1. These results indicate that combining differential gene expression with linkage analysis may help in identifying candidate genes and potential regulatory sites. Moreover, they also replicate recent findings of complex trans- and cis- regulation of genes.
Concentrations of monoamine metabolites in human cerebrospinal fluid (CSF) have been used extensively as indirect estimates of monoamine turnover in the brain. CSF monoamine metabolite concentrations are partly determined by genetic influences.
We investigated possible relationships between DNA polymorphisms in the serotonin 2C receptor (HTR2C), the serotonin 3A receptor (HTR3A), the dopamine D4 receptor (DRD4), and the dopamine β-hydroxylase (DBH) genes and CSF concentrations of 5-hydroxyindolacetic acid (5-HIAA), homovanillic acid (HVA), and 3-methoxy-4-hydroxyphenylglycol (MHPG) in healthy volunteers (n = 90).
The HTR3A 178 C/T variant was associated with 5-HIAA levels (p = 0.02). The DBH-1021 heterozygote genotype was associated with 5-HIAA (p = 0.0005) and HVA (p = 0.009) concentrations. Neither the HTR2C Cys23Ser variant, nor the DRD4 -521 C/T variant were significantly associated with any of the monoamine metabolites.
The present results suggest that the HTR3A and DBH genes may participate in the regulation of dopamine and serotonin turnover rates in the central nervous system.
Serotonin receptor 2C gene; serotonin receptor 3A gene; dopamine D4 receptor gene; dopamine β-hydroxylase gene; monoamine metabolites (HVA; 5-HIAA; MHPG); cerebrospinal fluid
F1 hybrid clones of Eucalyptus grandis and E. urophylla are widely grown for pulp and paper production in tropical and subtropical regions. Volume growth and wood quality are priority objectives in Eucalyptus tree improvement. The molecular basis of quantitative variation and trait expression in eucalypt hybrids, however, remains largely unknown. The recent availability of a draft genome sequence (http://www.phytozome.net) and genome-wide genotyping platforms, combined with high levels of genetic variation and high linkage disequilibrium in hybrid crosses, greatly facilitate the detection of quantitative trait loci (QTLs) as well as underlying candidate genes for growth and wood property traits. In this study, we used Diversity Arrays Technology markers to assess the genetic architecture of volume growth (diameter at breast height, DBH) and wood basic density in four-year-old progeny of an interspecific backcross pedigree of E. grandis and E. urophylla. In addition, we used Illumina RNA-Seq expression profiling in the E. urophylla backcross family to identify cis- and trans-acting polymorphisms (eQTLs) affecting transcript abundance of genes underlying QTLs for wood basic density.
A total of five QTLs for DBH and 12 for wood basic density were identified in the two backcross families. Individual QTLs for DBH and wood basic density explained 3.1 to 12.2% of phenotypic variation. Candidate genes underlying QTLs for wood basic density on linkage groups 8 and 9 were found to share trans-acting eQTLs located on linkage groups 4 and 10, which in turn coincided with QTLs for wood basic density suggesting that these QTLs represent segregating components of an underlying transcriptional network.
This is the first demonstration of the use of next-generation expression profiling to quantify transcript abundance in a segregating tree population and identify candidate genes potentially affecting wood property variation. The QTLs identified in this study provide a resource for identifying candidate genes and developing molecular markers for marker-assisted breeding of volume growth and wood basic density. Our results suggest that integrated analysis of transcript and trait variation in eucalypt hybrids can be used to dissect the molecular basis of quantitative variation in wood property traits.
The antialcoholism drug disulfiram has shown recent promise as a pharmacotherapy for treating cocaine dependence, probably via inhibition of dopamine β-hydroxylase (DBH), the enzyme that catalyzes the conversion of dopamine (DA) to norepinephrine (NE). We previously showed that DBH knockout (Dbh -/-) mice, which lack NE, are susceptible to seizures and are hypersensitive to the psychomotor, rewarding, and aversive effects of cocaine, suggesting that disulfiram might exacerbate cocaine-induced seizures (CIS) by inhibiting DBH. To test this, we examined CIS in wild-type and Dbh -/- mice following administration of disulfiram or the selective DBH inhibitor nepicastat. We found that Dbh genotype had no effect on CIS probability or frequency, whereas disulfiram, but not nepicastat, increased the probability of having CIS in both wild-type and Dbh -/- mice. Both disulfiram and nepicastat increased CIS frequency in wild-type but not Dbh -/- mice. There were no genotype or treatment effects on serum cocaine levels, except for an increase in disulfiram-treated Dbh -/- mice at the highest dose of cocaine. These results suggest that disulfiram enhances CIS via two distinct mechanisms: it both increases CIS frequency by inhibiting DBH and increases CIS frequency in a DBH-independent manner.
norepinephrine; dopamine beta-hydroxylase; disulfiram; nepicastat; seizure; cocaine