Norepinephrine transporter gene polymorphism is not associated with susceptibility to alcohol dependence

Fluorescent Probes for STED Optical Nanoscopy

Progress in developing fluorescent probes, such as fluorescent proteins, organic dyes, and fluorescent nanoparticles, is inseparable from the advancement in optical fluorescence microscopy. Super-resolution microscopy, or optical nanoscopy, overcame the far-field optical resolution limit, known as Abbe's diffraction limit, by taking advantage of the photophysical properties of fluorescent probes. Therefore, fluorescent probes for super-resolution microscopy should meet the new requirements in the probes' photophysical and photochemical properties. STED optical nanoscopy achieves super-resolution by depleting excited fluorophores at the periphery of an excitation laser beam using a depletion beam with a hollow core. An ideal fluorescent probe for STED nanoscopy must meet specific photophysical and photochemical properties, including high photostability, depletability at the depletion wavelength, low adverse excitability, and biocompatibility. This review introduces the requirements of fluorescent probes for STED nanoscopy and discusses the recent progress in the development of fluorescent probes, such as fluorescent proteins, organic dyes, and fluorescent nanoparticles, for the STED nanoscopy. The strengths and the limitations of the fluorescent probes are analyzed in detail.

Genetic Association of the Norepinephrine Transporter Gene G1287A Polymorphism with Risk of Schizophrenia: A Case-Control Study and Meta-Analysis

BACKGROUND

The G1287A polymorphism (rs5569) in exon 9 of the norepinephrine transporter (NET) gene has been associated with schizophrenia in several populations. However, the results are conflicting. Moreover, few studies have investigated the relationship between the G1287A polymorphism and schizophrenia among the Chinese Han population.

METHODS

A case-control study was designed to explore whether the G1287A genetic variant is related to schizophrenia in the Chinese Han population. The results from this study were then included in the performance of a meta-analysis to further analyze the association of the G1287A polymorphism with schizophrenia.

RESULTS

No significant differences in the genotype and allele distributions of G1287A were found between Chinese Han patients with schizophrenia and control participants. Similarly, in gender-specific analyses, no significant differences were found for G1287A genotype and allele distributions in either the male or the female case-control comparisons. Finally, the results of this meta-analysis also showed that the NET gene G1287A polymorphism was not associated with schizophrenia in the total population under allelic, recessive, dominant, or homozygous genetic models.

CONCLUSION

Our case-control study and meta-analysis suggest that the NET gene G1287A polymorphism may not be involved in the etiology of schizophrenia in the Chinese Han population.

Genetics of alcohol dependence: a review of clinical studies

BACKGROUND/AIMS

Alcohol dependence is a common severe psychiatric disorder with a multifactorial etiology. Since the completion of the human genome project and with the increased availability of high-throughput genotyping, multiple genetic risk factors for substance-related disorders, including alcohol dependence, have been identified, but not all results could be replicated.

METHODS

We systematically review the clinical literature on genetic risk factors for alcohol dependence and alcohol-related phenotypes, including candidate gene-based studies, linkage studies and genome-wide association studies (GWAS).

RESULTS

Irrespectively of the methodology employed, the most robust findings regarding genetic risk factors for alcohol dependence concern genetic variations that affect alcohol metabolism. GWAS confirm the importance of the alcohol dehydrogenase gene cluster on chromosome 4 in the genetic risk for alcohol dependence with multiple variants that exert a small, but cumulative influence. A single variant with strong influence on individual risk is the aldehyde dehydrogenase 2 ALDHD2*2 variant common in Asian populations. Other robust associations have been found with previously uncharacterized genes like KIAA0040, and such observations can lead to the identification of thus far unknown signaling pathways. Converging evidence also points to a role of glutamatergic, dopaminergic and serotonergic neurotransmitter signaling in the risk for alcohol dependence, but effects are small, and gene-environment interactions further increase the complexity.

CONCLUSION

With few exceptions like ALDH2*2, the contribution of individual genetic variants to the risk for alcohol-related disorders is small. However, the concentration of risk variants within neurotransmitter signaling pathways may help to deepen our understanding of the underlying pathophysiology and thereby contribute to develop novel therapeutic strategies.

Multiple polymorphisms in genes of the adrenergic stress system confer vulnerability to alcohol abuse

Environmental factors such as stress influence both the predisposition to and development of alcoholism, as well as have significant implications for alcoholism relapse. One predominant biological response to acute stress is the release of norepinephrine, which activates the peripheral stress response and also the hypothalamic-pituitary-adrenal axis. We aimed to examine the role of two genes of the adrenergic system (SLC6A2 and ADRA2A) in alcoholism by genotyping 21 SNPs in 785 adult alcohol-dependent patients and 1237 controls. Two single nucleotide polymorphisms (SNP) (rs36020 and rs36029) in SLC6A2 were significantly associated with alcoholism [false discovery rate corrected P-value (FDR) P = 0.007]. Two SNPs in ADRA2A (rs521674 and rs602618) were associated with a positive family history of alcoholism (FDR P ≤ 0.05). A combined SNP-set analysis was also carried out to determine the risk of harbouring multiple alcohol risk alleles across SLC6A2 and ADRA2A. Logistic regression analysis revealed that an increase in the number of alcohol risk alleles increased the risk for alcoholism (P = 0.000567, odds ratio = 1.75, 95% confidence interval 1.26-2.44). A three-SNP haplotype consisting of rs187715, rs36020 and rs40147 alleles, AGC, was also found, which was significantly over-represented in cases compared with controls (61% versus 56%). We therefore demonstrate an association of SLC6A2 and ADRA2A with adult alcoholism. These data confirm the relevance of the adrenergic stress system when considering genetic predisposition to alcohol dependence and suggest that SLC6A2 and ADRA2A should be studied in additional alcohol-dependent cohorts.

Psychopathological aspects of dopaminergic gene polymorphisms in adolescence and young adulthood

Dopamine hypotheses of several psychiatric disorders are based upon the clinical benefits of drugs affecting dopamine transporter or receptors, and have prompted intensive candidate gene research within the dopaminergic system during the last two decades. The aim of this review is to survey the most important findings concerning dopaminergic gene polymorphisms in attention deficit hyperactivity disorder (ADHD), Tourette syndrome (TS), obsessive compulsive disorder, and substance abuse. Also, genetic findings of related phenotypes, such as inattention, impulsivity, aggressive behavior, and novelty seeking personality trait are presented, because recent studies have applied quantitative trait measures using questionnaires, symptom scales, or other objective endophenotypes. Unfortunately, genetic variants with minor effects are problematic to detect in these complex inheritance disorders, often leading to contradictory results. The most consistent association findings relate to ADHD and the dopamine transporter and the dopamine D4 receptor genes. Meta-analyses also support the association between substance abuse and the D2 receptor gene. The dopamine catabolizing enzyme genes, such as monoamine oxidase (MAO) A and catechol-O-methyltransferase (COMT) genes, have been linked to aggressive behaviors.

Pharmacogenetics of antidepressants

Up to 60% of depressed patients do not respond completely to antidepressants (ADs) and up to 30% do not respond at all. Genetic factors contribute for about 50% of the AD response. During the recent years the possible influence of a set of candidate genes as genetic predictors of AD response efficacy was investigated by us and others. They include the cytochrome P450 superfamily, the P-glycoprotein (ABCB1), the tryptophan hydroxylase, the catechol-O-methyltransferase, the monoamine oxidase A, the serotonin transporter (5-HTTLPR), the norepinephrine transporter, the dopamine transporter, variants in the 5-hydroxytryptamine receptors (5-HT1A, 5-HT2A, 5-HT3A, 5-HT3B, and 5-HT6), adrenoreceptor beta-1 and alpha-2, the dopamine receptors (D2), the G protein beta 3 subunit, the corticotropin releasing hormone receptors (CRHR1 and CRHR2), the glucocorticoid receptors, the c-AMP response-element binding, and the brain-derived neurotrophic factor. Marginal associations were reported for angiotensin I converting enzyme, circadian locomotor output cycles kaput protein, glutamatergic system, nitric oxide synthase, and interleukin 1-beta gene. In conclusion, gene variants seem to influence human behavior, liability to disorders and treatment response. Nonetheless, gene × environment interactions have been hypothesized to modulate several of these effects.

Effect of genetic polymorphisms on smoking cessation: a trial of bupropion in Korean male smokers

BACKGROUND

Even though bupropion is first-line pharmacological agent for smoking cessation, not all the smokers successfully quit smoking by bupropion. It means other factors like genetic predisposition could contribute to the therapeutic outcome.

OBJECTIVES

The aim of this study is to elucidate the question of whether the abstinence rates by bupropion trial would be different depending on the genotypes.

METHODS

Six candidate genes, thought to be involved in the interaction of nicotine and bupropion (for example, the dopamine receptor type 2, dopamine transporter, norepinephrine transporter, serotonin transporter, catecholamine-O-methyltransferase), and the clinical outcomes of smoking behavior were investigated. The participants were 225 male smokers to whom 150 mg of bupropion SR was administered for 4 weeks. The abstinence rates of specific genotypes were also compared.

MAIN RESULTS

The results are as follows: (a) the frequencies of the A1/A2 genotype of the dopamine receptor type 2 TaqI A gene and SLC6A3-9 genotype of the dopamine transporter 1 gene were higher in the nonabstinence group than in the abstinence group (chi2=20.40, P<0.01 for A1/A2, chi2=7.76, P=0.01 for SLC6A3-9). The frequencies of the COMTH/COMTH and A/G genotypes of the norepinephrine transporter gene were higher in the abstinence group than in the nonabstinence group (chi2=8.12,P=0.02 for COMTH/COMTH, chi2=3.04, P<0.01 for A/G). (b) Participants having specific genotypes such as homozygotes (A1/A1 or A2/A2) of DRD2 TaqI A, COMTH/COMTH, AG of NET-8, and LL of 5-HTTLPR showed a higher abstinence rate than the other participants.

CONCLUSIONS

It can be concluded that genetic diversity might determine the effects of bupropion on smoking cessation.

Norepinephrine transporter polymorphisms T-182C and G1287A are not associated with alcohol dependence and its clinical subgroups

Several studies have suggested that the norepinephrine transporter (NET) may play an important role in the pathogenesis of alcohol dependence. Additional studies have shown that the polymorphisms of T-182C (rs2242446) and G1287A (rs5569) in NET gene (hSLC6A2) may affect the NET function. Therefore, in this study, we examined whether these hSLC6A2 gene polymorphisms are a susceptibility factor for alcohol dependence or its clinical subgroup(s). A total of 690 Han Chinese subjects (408 alcohol dependent patients and 282 controls) in Taiwan were recruited for this study. Individuals with alcohol dependence were classified into several clinical subgroups to reduce the clinical heterogeneity. All subjects were interviewed with identical methods, and the mental disorders were diagnosed according to DSM-IV criteria. The polymorphisms of T-182C and G1287A in hSLC6A2 gene were analyzed by using a standard method. No significant differences in genotype and allele frequencies of hSLC6A2 polymorphisms were found between controls and total alcohol dependence or between more homogeneous subgroups with alcohol dependence and controls. This study suggests that the polymorphisms of T-182C and G1287A in hSLC6A2 gene are not major risk factors in increasing susceptibility to either alcohol dependence or its clinical subtypes.

No association of the G1287A polymorphism in the norepinephrine transporter gene and susceptibility to major depressive disorder in a Japanese population

Norepinephrinergic neurotransmission in the central nervous system have a major impact on the symptomatology in major depressive disorder (MDD), and genetic polymorphisms of norepinephrine transporter (NET) have a possibility to be involved in susceptibility to MDD. We investigated the association of the G1287A (rs5569) polymorphism of the NET gene and susceptibility to MDD by comparing 145 major depressive patients with 164 healthy individuals first in a Japanese population. The genotype frequencies in depressed patients and health volunteers of the NET G1287A polymorphism were 52.4% (G/G), 39.3% (G/A) and 8.3% (A/A) in depressed patients, 61.6% (G/G), 29.9% (G/A allele) and 8.5% (A/A) in healthy volunteers, respectively. The allele frequencies in depressed patients and health volunteers of the NET G1287A polymorphism were 72.1% (G allele) and 27.9% (A allele) in depressed patients, 76.5% (G allele) and 23.5% (A allele) in healthy volunteers, respectively. The genotype distribution and allele frequencies were not significantly different between major depressive patients and healthy volunteers. NET G1287A polymorphism appears not to be an important factor in susceptibility to MDD in a Japanese population.

Treatment with risperidone for 4 weeks increased plasma 3-methoxy-4-hydroxypnenylglycol (MHPG) levels, but did not alter plasma brain-derived neurotrophic factor (BDNF) levels in schizophrenic patients

In the present study, we investigated the effects of risperidone treatment for 4 weeks on plasma levels of 3-methoxy-4-hydroxyphenylglycol (MHPG) and brain-derived neurotrophic factor (BDNF) in 89 schizophrenic patients. We also compared the plasma levels of BDNF and MHPG between the schizophrenic group and 103 sex-and age-matched normal controls. In addition, we investigated the effects of two SNPs of the noradrenaline transporter (NAT) gene on plasma levels of MHPG, BDNF, and clinical improvement. The mean dose of risperidone was 3.8+/-1.4 mg/day. We demonstrated that treatment with risperidone increased plasma MHPG levels, and this increase was associated with an improvement of the negative symptoms of schizophrenia. In contrast, plasma BDNF did not change after 4 weeks of risperidone treatment, and the two SNPs in NAT did not influence the response to risperidone treatment or plasma MHPG and BDNF levels. These results suggest that the enhancement of noradrenergic neurons by risperidone, which occurs independently of the two SNPs of NAT, plays a role in the clinical efficacy of the drug.

The functional impact of SLC6 transporter genetic variation

Solute carrier 6 (SLC6) is a gene family of ion-coupled plasma membrane cotransporters, including transporters of neurotransmitters, amino acids, and osmolytes that mediate the movement of their substrates into cells to facilitate or regulate synaptic transmission, neurotransmitter recycling, metabolic function, and fluid homeostasis. Polymorphisms in transporter genes may influence expression and activity of transporters and contribute to behavior, traits, and disease. Determining the relationship between the monoamine transporters and complex psychiatric disorders has been a particular challenge that is being met by evolving approaches. Elucidating the functional consequences of and interactions among polymorphic sites is advancing our understanding of this relationship. Examining the influence of environmental influences, especially early-life events, has helped bridge the gap between genotype and phenotype. Refining phenotypes, through assessment of endophenotypes, specific behavioral tasks, medication response, and brain network properties has also improved detection of the impact of genetic variation on complex behavior and disease.

Norepinephrine transporter gene (NET) polymorphism in patients with type 2 diabetes

BACKGROUND

Norepinephrine transporter (NET) is involved in the regulation of norepinephrine (NE) turnover and metabolism. Neuronal NE reuptake may be impaired in individuals with renal disease and/or hypertension due to dysfunction of the NE transporter. A silent G1287A nucleotide substitution in exon 9 of the NET gene was studied in human conditions involving hypertension. We investigated its effect in patients with type 2 diabetes.

METHODS

The study involved 215 type 2 diabetes patients with nephropathy, 95 patients with diabetes duration > or =10 years, free of nephropathy, and 360 healthy subjects. All individuals were genotyped for the NET-8 gene polymorphism with the PCR-RFLP method. Genotype and allele frequencies were compared between the groups. NE was measured by high-performance liquid chromatography and electrochemical detection.

RESULTS

We genotyped 310 patients and 360 controls for the NET gene polymorphism. Genotype distribution in both groups was in accordance with the Hardy-Weinberg equilibrium. There were no significant differences in the frequency of genotypes and alleles between patients and controls (p = 0.43). The frequencies were also similar for patients with nephropathy and those without. After dividing the patient group into hypertensive (n = 208) and normotensive (n = 102) subjects, there was a significant increase in the frequency of the AA genotype in patients with hypertension compared to normotensives (19 vs. 10%, p < 0.05).

CONCLUSION

No association was found between G1287A polymorphism in the NET gene and diabetes. Our results suggest that this polymorphism has a possible role in increased susceptibility to hypertension in patients with type 2 diabetes.

Positive association between T-182C polymorphism in the norepinephrine transporter gene and susceptibility to major depressive disorder in a japanese population

Norepinephrinergic neurotransmission in the central nervous system appears to have a major impact on the symptomatology in major depressive disorder and the human norepinephrine transporter (NET) gene is one of the key candidates for genetic studies in major depressive disorder. The authors established a new allele-specific PCR-based genotyping procedure and examined whether the NET T-182C polymorphism was associated with the susceptibility to major depressive disorder in a Japanese population. This study included 145 patients with major depressive disorder (according to DSM-IV) and 164 healthy volunteers. There was a significant difference in the genotype distribution between major depressive disorder patients and healthy volunteers (p = 0.02), and the C/C genotype was associated with lesser susceptibility to major depressive disorder. The NET T-182C polymorphism may be in part related to the pathophysiology of major depressive disorder in a Japanese population.

Haplotype architecture of the norepinephrine transporter gene SLC6A2 in four populations

The norepinephrine transporter (NET) regulates levels of monoamine neurotransmitters integral to a variety of behaviors and autonomic functions. Two SLC6A2 polymorphisms have been used in genetic association studies, generating intriguing but nondefinitive results on traits such as hypertension and mood. One of these SLC6A2 variants is functional but rare. The other is common but not informative over the entire 48 kb SLC6A2 region and is insufficient to capture the functional diversity potentially contained within any SLC6A2 region. To elucidate SLC6A2 haplotype structure and define markers sufficient to capture haplotype diversity within detected haplotype blocks, 26 single-nucleotide polymorphisms (SNPs) were genotyped in 384 individuals evenly divided across Finnish Caucasian, US Caucasian, Plains American Indian, and African American populations. Three conserved blocks, 13.6, 12.5, and 25 kb in size and showing little evidence for historical recombination were observed in all populations. Haplotype diversity in block 1 and numbers of common haplotypes were highest in African Americans, among whom 5-6 optimal markers were sufficient to maximize diversity of each block. For other populations, 2-3 markers/block sufficed, but the optimal markers differed across populations. The SLC6A2 haplotype map and 25-marker panel (excluding the monomorphic one) is a comprehensive tool for genetic linkage studies on phenotypes related to NET function.

Genetic polymorphisms in the expression and treatment of neuropsychiatric disorders

Recent advances in molecular genetics have greatly increased the understanding of the pathophysiology of certain neurobehavioral disorders and the core symptoms of these disorders. This paper reviews key concepts important in understanding the genetics of neuropsychiatric disorders, and gives an overview of several different types of genetic disorders, including trinucleotide repeat disorders, and functional polymorphisms of monoamine neurotransmitter systems.