Dopamine Β-hydroxylase Activity Research Articles

Role of novel protein kinase C in neuroendocrine-immune regulatory network in haemocytes of Litopenaeus vannamei: An in vitro approach

Shrimp lack adaptive immune systems and mainly rely on the cellular and humoral defences, involving the haemocytes (functionally analogous to vertebrate leukocytes) in non-self matter recognition, elimination, and in downstream coagulation. Furthermore, the linkage between stress-induced catecholamine (CA), a class of biogenic amines (BAs), releasing and immunological responses has been detected in shrimp. Varied isotypes of protein kinase C (PKC) regulate multiple cellular processes following their specific location and distribution within the cells, and a novel PKC identified in Litopenaeus vannamei (termed as LvnPKC) is proposed to mediate signaling transduction of immunocompetence and BA biosynthesis. In the present study, we analyzed the effects of the LvnPKC-silenced haemocytes by co-incubating with its dsRNA on the immune responses specific to prophenoloxidase (proPO) and antioxidant systems as well as phagocytic activity. In addition, the capability of haemocytes to produce BAs was assessed. The results revealed that LvnPKC-silenced haemocytes can induce interference in phenoloxidase and superoxide dismutase activities, respiratory bursts, and phagocytic activity; meanwhile, the disturbed gene expressions of proPO activating enzyme, proPOII, lipopolysaccharide- and β-1,3-glucan-binding protein, and cytosolic manganese superoxide dismutase were detected. The same deviated pattern was observed in tyrosine, dopamine, and norepinephrine levels, and in dopamine β-hydroxylase (DBH) activity and gene expressions of tyrosine hydroxylase, DOPA decarboxylase, and DBH involving in BA biosynthesis. Taken together, these results suggest that the immunocompetence and BA biosynthesis of haemocytes can be mediated via LvPKC signaling transduction, which proved the presence of a neuroendocrine-immune regulatory network in haemocytes.

Novel protein kinase C participates catecholamine biosynthesis and immunocompetence modulation in haemocytes of Litopenaeus vannamei

The catecholamine biosynthesis is required for physiological and immunological responses against stress, and the neuroendocrine-immune regulatory network plays a crucial role in immunocompetence of shrimp. A novel protein kinase C of Litopenaeus vannamei (LvnPKC) is involved in immune defense and signaling transduction in haemocytes, and in the present study, the gene silence technique is conducted to identify the role of LvnPKC on catecholamine biosynthesis and immunocompetence modulation in haemocytes of L. vannamei. The results show that tyrosine significantly increases in haemocytes of LvnPKC-silenced shrimp, and in the meantime, the obvious decrease of L-3, 4-dihydroxyphenylalanine and increase of dopamine as well as the consistent norepinephrine levels are detected. Tyrosine hydroxylase and dopamine β-hydroxylase activities are significantly reduced in haemocytes of LvnPKC-silenced shrimp. Total haemocyte count, hyaline cells and granulocytes insignificantly differ among treatments, and the obvious increase of phenoloxidase activity, respiratory bursts, superoxide dismutase and glutathione peroxidase activities are observed in haemocytes of LvnPKC-silenced shrimp, and furthermore, the downregulated phagocytic activity was observed. It is therefore concluded that the LvnPKC mediates catecholamine biosynthesis and immunocompetence in haemocytes, and plays a crucial role in the neuroendocrine-immune regulatory network.

Which Dopamine Polymorphisms Are Functional? Systematic Review and Meta-analysis of COMT, DAT, DBH, DDC, DRD1–5, MAOA, MAOB, TH, VMAT1, and VMAT2

BackgroundMany polymorphisms in dopamine genes are reported to affect cognitive, imaging, or clinical phenotypes. It is often inferred or assumed that such associations are causal, mediated by a direct effect of the polymorphism on the gene product itself. However, the supporting evidence is not always clear. MethodsWe conducted systematic reviews and meta-analyses to assess the empirical evidence for functional polymorphisms in genes encoding dopaminergic enzymes (COMT, DBH, DDC, MAOA, MAOB, and TH), dopamine receptors (DRD1, DRD2, DRD3, DRD4, and DRD5), the dopamine transporter (DAT), and vesicular transporters (VMAT1 and VMAT2). We defined functionality as an effect of the polymorphism on the expression, abundance, activity, or affinity of the gene product. ResultsWe screened 22,728 articles and identified 255 eligible studies. We found robust and medium to large effects for polymorphisms in 4 genes. For catechol-O-methyltransferase (COMT), the Val158Met polymorphism (rs4680) markedly affected enzyme activity, protein abundance, and protein stability. Dopamine β-hydroxylase (DBH) activity was associated with rs1611115, rs2519152, and the DBH–STR polymorphism. Monoamine oxidase A (MAOA) activity was associated with a 5′ VNTR polymorphism. Dopamine D2 receptor (DRD2) binding was influenced by the Taq1A (rs1800497) polymorphism, and rs1076560 affected DRD2 splicing. ConclusionsSome widely studied dopaminergic polymorphisms clearly and substantially affect the abundance or activity of the encoded gene product. However, for other polymorphisms, evidence of such an association is negative, inconclusive, or lacking. These findings are relevant when selecting polymorphisms as “markers” of dopamine function, and for interpreting the biological plausibility of associations between these polymorphisms and aspects of brain function or dysfunction.

Acute salt loading induces sympathetic nervous system overdrive in mice lacking salt-inducible kinase 1 (SIK1).

Loss of salt-inducible kinase 1 (SIK1) triggers an increase in blood pressure (BP) upon a chronic high-salt intake in mice. Here, we further addressed the possible early mechanisms that may relate to the observed rise in BP in mice lacking SIK1. SIK1 knockout (sik1-/-) and wild-type (sik1+/+) littermate mice were challenged with either a high-salt (8% NaCl) or control (0.3% NaCl) diet for 7 days. Systolic BP was significantly increased in sik1-/- mice after 7 days of high-salt diet as compared with sik1+/+ mice and to sik1-/- counterparts on a control diet. The renin-angiotensin-aldosterone system and the sympathetic nervous system were assayed to investigate possible causes for the increase in BP in sik1-/- mice fed a 7-day high-salt diet. Although no differences in serum renin and angiotensin II levels were observed, a reduction in aldosterone serum levels was observed in mice fed a high-salt diet. Urinary L-DOPA and noradrenaline levels were significantly increased in sik1-/- mice fed a high-salt diet as compared with sik1-/- mice on a control diet. Similarly, the activity of dopamine β-hydroxylase (DβH), the enzyme that converts dopamine to noradrenaline, was significantly increased in the adrenal glands of sik1-/- mice on a high-salt intake compared with sik1+/+ and sik1-/- mice on a control diet. Treatment with etamicastat (50 mg/kg/day), a peripheral reversible DβH inhibitor, administered prior to high-salt diet, completely prevented the systolic BP increase in sik1-/- mice. In conclusion, SIK1 activity is necessary to prevent the development of salt-induced high blood pressure and associated SNS overactivity.

Associations between the DBH gene, plasma dopamine β-hydroxylase activity and cognitive measures in Han Chinese patients with schizophrenia

The dopamine (DA) and norepinephrine (NE) systems modulate cognitive function. Dopamine β-hydroxylase (DβH) converts DA to NE, and its activity is under strong genetic control. This study examines the association of plasma DβH (pDβH) activity, DBH gene polymorphisms (−1021C>T, rs1611115 and 444G>A, rs1108580) and cognitive deficits in Han Chinese patients with schizophrenia. We assessed pDβH activity and cognitive function using the Verbal Fluency Test (VFT), Trail Making Test (TMT) A-B, Stroop color-word test and Wisconsin Card Sorting Test (WCST) in 200 patients with schizophrenia before and after 8weeks of antipsychotic treatment (96 patients completed assessments at baseline and post-treatment). We found that rs1611115 was significantly associated with pDβH activity, and there was strong LD between rs1611115 and rs1108580 polymorphisms. Correlation analysis indicated that pDβH activity correlated nominally with improvement in VFT score after 8weeks antipsychotic treatment. Moreover, there was a significant genotype effect of the rs1108580 on VFT: the VFT score of patients with AA genotype was higher than that of patients with AG/GG genotype either at baseline or the end of 8 weeks after treatment. However, this difference was not observed for rs1611115. Our findings confirm a strong association between genotype at rs1611115 and pDβH activity in Chinese patients with schizophrenia. Our data also suggest the rs1108580 polymorphism may influence some aspects of cognitive function in schizophrenia.

Abstract MP13: Etamicastat Prevents Arterial Blood Pressure Increase in Mice Lacking Salt-inducible Kinase 1 (SIK1)

Loss of salt-inducible kinase 1 (SIK1) triggers an increase in blood pressure (BP) upon a chronic high-salt intake in mice (Circ Res 2015;116:642-52). Here, we address possible acute mechanisms that may relate to the observed high BP in mice lacking SIK1. SIK1 knockout ( sik1 -/- ) and wild-type ( sik1 +/+ ) littermate mice were challenged for seven days with a normal- (0.3% NaCl) or high-salt (8% NaCl) diet. Systolic BP (SBP) was significantly increased in sik1 -/- mice (137.0±17.2 mmHg) after seven days of high-salt intake, as compared to sik1 +/+ mice counterparts (120.6±4.5 mmHg). The renin-angiotensin system (RAS) and the sympathetic nervous system (SNS) were assayed in order to investigate the possible causes for the increase in SBP in sik1 -/- mice fed a high-salt diet. No differences in renin (normal-salt: 463.4±17.9, high-salt: 462.9±28.9 pg/ml) and angiotensin II (normal-salt: 45.8±10.0, high-salt: 39.0±8.5 pg/ml) serum levels were observed. The activity of dopamine β-hydroxylase (DβH), the enzyme that converts dopamine (DA) to norepinephrine (NE), was significantly increased in the adrenal glands of sik1 -/- mice fed a high-salt diet (356.7±32.8 nmol/mg protein) as compared to sik1 -/- mice on a normal-salt diet (184.4±14.4 nmol/mg protein). Similarly, urinary catecholamines (DA, NE, epinephrine) and L-DOPA were significantly increased (3- to 7-fold increase) in sik1 -/- mice fed a high-salt diet as compared to sik1 -/- mice on a normal-salt intake. Altogether, this data supports the view that sik1 -/- mice fed a high-salt diet develop SNS overactivity. Next, we addressed the question if reducing SNS activity in sik1 -/- mice fed a high-salt diet would ameliorate hypertension. For that purpose, the effect of etamicastat, a peripheral reversible DβH inhibitor, was evaluated on the development of high BP upon high-salt diet. Etamicastat treatment (50 mg/kg/day), started prior to high-salt feeding, completely prevented SBP increase in sik1 -/- mice fed a high-salt diet (116.8±4.7 mmHg). It is concluded that the SNS is involved in the development of salt-induced hypertension in sik1 -/- mice and that the DβH inhibitor etamicastat is able to reduce SNS overactivity and high BP in this mouse model of hypertension.

Standard values for the urine HVA/VMA ratio in neonates as a screen for Menkes disease

Menkes disease is a lethal disorder associated with copper metabolism. Although early treatment with copper-histidine injections can improve outcomes, early diagnosis is difficult because the clinical features of Menkes disease are subtle or do not manifest in affected neonates. Previous report stated that the low activity of dopamine β-hydroxylase, a copper-dependent enzyme, leads to increases in the urine homovanillic acid/vanillylmandelic acid (HVA/VMA) ratios in patients with Menkes disease, and indicated that a urine HVA/VMA ratio cut-off value of >4 is useful in screening for Menkes disease. We examined the standard values of the urine HVA/VMA ratio in unaffected neonates and assessed its use as a screening parameter for Menkes disease among neonates. In total, 112 neonates, aged between 1 and 6 days, were enrolled in the study and were classified into 2 groups based on their urine HVA/VMA ratios: high (>4) and low (⩽ 4). Multivariate logistic analysis revealed that mechanical ventilation was an independent risk factor for a high urine HVA/VMA ratio (odds ratio: 21.94; 95% confidence interval: 2.82-247.03; p=0.004). The mean urine HVA/VMA ratio was 2.47 ± 0.67 among 92 neonates who did not receive mechanical ventilation. This study established standard values for the urine HVA/VMA ratio in newborn babies that could be useful in screening for Menkes disease among neonates.

Psychotic major depression in older people: a systematic review.

This study aimed to systematically review available evidence relevant to the following issues: (1) whether psychotic major depression (PMD) in older people differs in overall severity from non-PMD, besides the presence of psychotic symptoms; (2) whether it constitutes a distinct clinical entity from non-PMD; and (3) whether it differs from PMD in younger adults. A computerized MEDLINE, PsycINFO and the entire Cochrane Library search has been performed in June 2013 for prospective controlled studies investigating PMD features in older people. Thirty-five relevant studies were identified. PMD in older people compared with non-PMD has been shown to present with overall more severe depressive symptomatology, more psychomotor disturbance, more guilt feelings, more depressive episodes with psychosis, worse prognosis, more severe executive dysfunction associated with frontal lobe atrophy, and lower serum dopamine β-hydroxylase activity. No differences in the efficacy of an antidepressant plus antipsychotic combination versus antidepressant monotherapy in the acute treatment as well as in the maintenance treatment were found. PMD in older patients is characterized by more somatic complaints and delusions of hypochondriacaland impending disaster content and by a lower comorbidity with anxiety disorders compared with PMD in younger adults. Psychotic major depression in older people is associated with higher severity in most clinically important key features than in non-PMD. However, available evidence is still insufficient for the conclusive elucidation of its nosological status. Finally, the differences between PMD in older and younger patients can be attributed to biological and psychosocial changes of old age.

Effect of copper and disulfiram combination therapy on the macular mouse, a model of Menkes disease

Menkes disease (MD) is a genetic neurodegenerative disorder characterized by copper deficiency due to a defect in ATP7A. Standard treatment involves parenteral copper–histidine administration. However, the treatment is ineffective if initiated after two months of age, because the administered copper accumulates in the blood–brain barrier and is not transported to neurons. To resolve this issue, we investigated the effects of a combination therapy comprising copper and disulfiram, a lipophilic chelator, in the macular mouse, an animal model of MD. Seven-day-old macular mice treated subcutaneously with 50μg of CuCl2 on postnatal day 4 were used. The mice were given a subcutaneous injection of CuCl2 (10μg) with oral administration of disulfiram (0.3mg/g body weight) twice a week until eight weeks of age, and then sacrificed. Copper concentrations in the cerebellum, liver, and serum of treated macular mice were significantly higher than those of control macular mice, which received only copper. Mice treated with the combination therapy exhibited higher cytochrome c oxidase activity in the brain. The ratios of noradrenaline and adrenaline to dopamine in the brain were also increased by the treatment, suggesting that dopamine β-hydroxylase activity was improved by the combination therapy. Liver and renal functions were almost normal, although renal copper concentration was higher in treated macular mice than in controls. These results suggest that disulfiram facilitates the passage of copper across the blood–brain barrier and that copper–disulfiram combination therapy may be an effective treatment for MD patients.

Effects of disulfiram treatment in patients with Menkes disease and occipital horn syndrome

The clinical and biochemical effects of disulfiram were evaluated in three boys with the disorders characterized by copper deficiency due to the defect of ATP7A. Two suffered from Menkes disease (MD) and one from occipital horn syndrome. Disulfiram was orally given, in addition to a parenteral administration of copper-histidine in the case of MD patients. Serum levels of copper and ceruloplasmin slightly increased in one MD patient, and he showed favorable emotional expression and behavior more often than before according to his caretakers. However, no obvious changes were observed in the other two patients. Serum ratios of noradrenaline to dopamine, and adrenaline to dopamine, which are thought to be the indicators of dopamine β-hydroxylase activity, one of the copper requiring enzymes, were unaltered after disulfiram treatment. No adverse effects were recognized during the treatment period in all patients. Although the major improvement was not observed clinically or biochemically by disulfiram treatment so far, the trial will be continued to see the possible effects in these disorders with copper transport defect.

Linkage analysis of plasma dopamine β-hydroxylase activity in families of patients with schizophrenia.

Dopamine β-hydroxylase (DβH) catalyzes the conversion of dopamine to norepinephrine. DβH enters the plasma after vesicular release from sympathetic neurons and the adrenal medulla. Plasma DβH activity (pDβH) varies widely among individuals, and genetic inheritance regulates that variation. Linkage studies suggested strong linkage of pDβH to ABO on 9q34, and positive evidence for linkage to the complement fixation locus on 19p13.2-13.3. Subsequent association studies strongly supported DBH, which maps adjacent to ABO, as the locus regulating a large proportion of the heritable variation in pDβH. Prior studies have suggested that variation in pDβH, or genetic variants at DβH, associate with differences in expression of psychotic symptoms in patients with schizophrenia and other idiopathic or drug-induced brain disorders, suggesting that DBH might be a genetic modifier of psychotic symptoms. As a first step toward investigating that hypothesis, we performed linkage analysis on pDβH in patients with schizophrenia and their relatives. The results strongly confirm linkage of markers at DBH to pDβH under several models (maximum multipoint LOD score, 6.33), but find no evidence to support linkage anywhere on chromosome 19. Accounting for the contributions to the linkage signal of three SNPs at DBH, rs1611115, rs1611122, and rs6271 reduced but did not eliminate the linkage peak, whereas accounting for all SNPs near DBH eliminated the signal entirely. Analysis of markers genome-wide uncovered positive evidence for linkage between markers at chromosome 20p12 (multi-point LOD=3.1 at 27.2cM). The present results provide the first direct evidence for linkage between DBH and pDβH, suggest that rs1611115, rs1611122, rs6271 and additional unidentified variants at or near DBH contribute to the genetic regulation of pDβH, and suggest that a locus near 20p12 also influences pDβH.

Genotype-controlled analysis of serum dopamine β-hydroxylase activity in civilian post-traumatic stress disorder

Background 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 in a genotype-controlled analysis of combat veterans. We tested whether such a deficit would occur in a sample of civilians. Methods 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). Serum DβH activity (sDβH) was assayed by HPLC with electrochemical detection and genotypes were determined using the Taqman® platform. Results 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. Conclusions 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 were found in this civilian sample.

Divergent effects of estradiol on gene expression of catecholamine biosynthetic enzymes

Within the catecholaminergic systems, there are contradictory findings regarding ability of estradiol to regulate expression of genes related to catecholamine biosynthesis. Several parameters important for effects of estradiol on the catecholamine (CA) related enzyme gene expression were examined in two CA regions. Ovariectomized (OVX) female rats were given prolonged estradiol treatments, either in a pulsatile fashion by injections or continuously by pellets. The mode affected the response of tyrosine hydroxylase (TH) and GTP cyclohydrolase I (GTPCH) mRNAs differentially in the nucleus of solitary tract (NTS) and the locus coeruleus (LC). In rostral–medial NTS, TH mRNA levels were increased with injections, but declined in rats administered estradiol by pellets. In LC, a significant change was only observed in GTPCH with injections. These differences may reflect activation of different estrogen receptors (ER). The response to estradiol in the presence of ERα and ER β was examined in PC12 cell culture. Estradiol directly regulated promoter activity of TH, GTPCH and dopamine β-hydroxylase (DBH) genes. With ERα, 17 β-estradiol elevated TH promoter activity, while there was a decline with ERβ. In contrast, both DBH and GTPCH promoters were enhanced by 17 β-estradiol over a wide range of concentrations with either ER subtype. Thus, mode of administration, location examined and ER subtype expressed are important considerations in the overall response of catecholamine related enzymes to estradiol.

Transcription Factor GATA-3 Regulates the Transcriptional Activity of Dopamine β-Hydroxylase by Interacting with Sp1 and AP4

GATA-3 is a zinc finger transcription factor that is expressed in T cell lineages as well as in the nervous system during development. In this study, we report that forced expression of GATA-3 resulted in an increased number of dopamine beta-hydroxylase (DBH)-expressing neurons in primary neural crest stem cell (NCSC) culture, suggesting that the DBH gene may be a downstream target gene of GATA-3. GATA-3 robustly transactivates the promoter function of the noradrenaline (NA)-synthesizing DBH gene, via two specific upstream promoter domains; one at -62 to -32 bp and the other at -891 to -853 bp. Surprisingly, none of these domains contain GATA-3 binding sites but encompass binding motifs for transcription factors Sp1 and AP4, respectively. Protein-protein interaction analyses both in vitro and in vivo and chromatin immunoprecipitation (ChIP) assays showed that GATA-3 effects its transcriptional regulatory function through physical interactions with these transcription factors.

Correlation of Plasma Dopamine β-hydroxylase Activity with Polymorphisms in DBH Gene: A Study on Eastern Indian Population

Plasma dopamine beta-hydroxylase activity (plDbetaH) is tightly regulated by the DBH gene and several genetic polymorphisms have been found to independently exert their influence. In the present investigation, association of four DBH polymorphisms, DBH-STR, rs1611115, rs1108580, and rs2519152 with plDbetaH was examined in blood samples from 100 unrelated individuals belonging to the state of West Bengal, Eastern India. Genotypes obtained after PCR amplification and restriction digestion were used for statistical analyses. plDbetaH was measured using a photometric assay and its correlation with the genetic polymorphisms was analyzed using analysis of variance and linear regression. Moderate linkage disequilibrium (LD) was observed between DBH-STR and rs1611115, while rs1108580 and rs2519152 were in strong LD. 'T' allele of rs1611115 showed strong negative correlation with plDbetaH, whereas DBH-STR, rs1108580 and rs2519152 had no major effect. Four haplotypes showed significant influence on plDbetaH. This is the first report on the effect of genetic polymorphisms on plDbetaH from the Indian sub-continent. rs1611115 was the only polymorphism that showed substantial control over plDbetaH. Other polymorphisms which did not show individual effects could possibly be part of larger haplotype blocks that carry the functional polymorphisms controlling plDbetaH.

Genotypic and haplotypic associations of the DBH gene with plasma dopamine β-hydroxylase activity in African Americans

Several variants at DBH are significantly associated with plasma DbetaH activity (pDbetaH). However, the overwhelming majority of data on this genotype-phenotype relationship has been gathered in samples from Europeans and European Americans (EAs). In this study, we examined the relationship between DBH polymorphisms and pDbetaH in samples from African-American (AA) subjects. Genotypes were determined at a 19-bp insertion/deletion polymorphism (ins/del) and four single-nucleotide polymorphisms (SNPs) at DBH in 109 samples. Analyses were performed using analyses of variance (ANOVAs) (for individual SNPs) and regression procedures (to assess the joint effects and the specific SNP-based haplotypes). We found: (1) single-variant analysis of all polymorphisms revealed apparent associations to pDbetaH, with rs1611115 accounting for the largest proportion of the variance in pDbetaH (28.7%) and ins/del the smallest (6.5%); (2) modest but significant linkage disequilibrium (LD) existed between ins/del and rs1611115; (3) LD between all other pairs of variants was not observed; (3) stepwise regression showed that a model containing rs1611115, rs2519152 and rs6271 accounted for 37.6% of the variance in pDbetaH, with rs6271 showing additional 7.6% above the effect of rs1611115, and rs2519152 showing additional 2% above rs1611115 and rs6271; (4) two common haplotypes, C-T-C and T-C-C at rs1611115-rs2519152-rs6271 were significantly associated with pDbetaH (P=0.0025 and 0.0036, respectively). The data support the validity of prior reported associations and underscore the importance of analyzing multiple SNPs across DBH in future association studies examining disease and biochemical phenotypes.

A Single Nucleotide Polymorphism at DBH, Possibly Associated with Attention-Deficit/Hyperactivity Disorder, Associates with Lower Plasma Dopamine β-Hydroxylase Activity and is in Linkage Disequilibrium with Two Putative Functional Single Nucleotide Polymorphisms

The DBH gene regulates plasma dopamine beta-hydroxylase activity (pDbetaH). Two single nucleotide polymorphisms (SNPs), -1021C-->T (rs1611115; SNP1) and +1603C-->T (rs6271; SNP3), independently influence pDbetaH. Another SNP, commonly known as DBH Taq1A (rs2519152; SNP2) is associated with attention-deficit/hyperactivity disorder (ADHD) in some (but not all) studies. We tested whether 1) SNP2 associates with pDbetaH; and 2) whether linkage disequilibrium (LD) between SNP2 and the other SNPs explains that association. Plasma dopamine beta-hydroxylase activity and genotypes at the SNPs were determined in Caucasian subjects (n = 418). Associations to pDbetaH were examined using analyses of variance (ANOVAs) and LD among the SNPs using estimation maximization. 1) Each polymorphism analyzed alone associated with pDbetaH; 2) SNP2 was in strong LD with SNP1 and SNP3, respectively, but there was no significant LD between SNP1 and SNP3; and 3) analyzed jointly, each SNP contributed significantly and uniquely to plasma DbetaH activity. 1) SNP2 associates with pDbetaH; 2) SNP2 shows LD with SNP1 and SNP3; 3) most of the association between SNP2 and pDbetaH simply reflects that LD; however, 4) SNP2 also appears to exert a small independent effect on pDbetaH, suggesting that SNP2, or another variant in LD with it, uniquely influences pDbetaH.

Screening for Menkes disease using the urine HVA/VMA ratio

Menkes disease is a disorder of copper transport that results in early death. Early therapy with parenteral copper-histidine has been shown to markedly improve outcomes. However, early diagnosis is difficult because patients are asymptomatic in early infancy. In Menkes disease, impaired activity of dopamine beta-hydroxylase, a copper-dependent enzyme, leads to increased urine ratios of homovanillic acid/vanillylmandelic acid (HVA/VMA). Urine HVA/VMA ratios ranged from 4.1 to 69.7 among 15 patients with Menkes disease, whereas only 0.18% of controls had ratios greater than 4.0. Thus, the urine HVA/VMA ratio is a useful screening method for Menkes disease.

The Structure of Linkage Disequilibrium at the DBH Locus Strongly Influences the Magnitude of Association between Diallelic Markers and Plasma Dopamine β-Hydroxylase Activity

There is currently a great deal of interest in using linkage disequilibrium (LD) mapping to locate both disease and quantitative-trait loci on a genomewide scale. Recent findings suggest that much of the human genome is organized in discrete "blocks" of low haplotype diversity, but the utility of such blocks in identifying genes influencing complex traits is not yet known and must ultimately be tested empirically through use of real data. We recently identified a putative functional polymorphism (-1021C-->T) in the 5' upstream region of the DBH gene that accounted for 35%-52% of the total phenotypic variance in plasma dopamine beta-hydroxylase (DBH) activity in samples from three distinct populations. In the present study, we genotyped 11 diallelic markers at the DBH locus surrounding -1021C-->T in 386 unrelated individuals of European origin. We identified a single 10-kb block containing -1021C-->T, in which four haplotypes comprised 93% of the observed chromosomes. Only markers within the block were highly associated with phenotype (P< or =2.2 x 10(-10)), with one exception. In general, association with phenotype was strongly correlated with the degree of LD between each marker and -1021C-->T. Of four LD measures assessed, d(2) was the best predictor of this relationship. Had one attempted to map quantitative-trait loci for plasma DBH activity on a genomewide basis without prior knowledge of candidate regions and not included (by chance) markers within this haplotype block, the DBH locus might have been missed entirely. These results provide a direct example of the potential value of constructing a haplotype map of the human genome prior to embarking on large-scale association studies.

Genotype-controlled analysis of plasma dopamine β-hydroxylase activity in psychotic unipolar major depression

Background: Plasma activity of dopamine β-hydroxylase (DβH), the enzyme that converts dopamine to norepinephrine, is reportedly lower in patients with unipolar major depression with psychotic features (UDPF) than in those with nonpsychotic unipolar major depression (UD). Plasma DβH is under genetic control by the structural locus encoding DβH protein, DBH. This study tested the hypothesis that diagnosis-specific allelic variation at DBH accounts for lower plasma DβH in UDPF. Methods: Plasma DβH activity was measured in samples from patients with UDPF ( n = 33) and UD ( n = 45). Genotypes were determined at several functional DBH polymorphisms, including C-1021T, a single nucleotide polymorphism (SNP) in the proximal 5′ region that associates with variation in plasma DβH activity. Results: Mean plasma DβH activity was significantly lower in UDPF than in UD. Genotyping at DBH did not reveal genetic associations distinguishing UDPF from UD. A two-way analysis of variance showed significant effects of genotype and diagnostic group but no significant interaction. Conclusions: Although the effects of the diagnosis of UDPF, and of DBH allele status, on plasma DβH activity were replicated, the lower plasma DβH in patients with UDPF was not accounted for by DBH genotype. Several explanations for this result are possible. First, other variants at DBH, or at other loci, could account for the findings. Second, nongenetic factors could account for the differences in plasma DβH. In this regard, we hypothesize that abnormal regulation of hypothalamic-pituitary-adrenal function in UDPF lowers expression of DβH protein, which could in turn alter the ratio of dopamine and norepinephrine in noradrenergic neurons, thereby promoting development of psychotic symptoms.