Showing papers in "Molecular Psychiatry in 1998"

The A1 allele of the human D2 dopamine receptor gene predicts low D2 receptor availability in healthy volunteers.

Abstract: Positron emission tomography (PET) studies have revealed significant interindividual variation in dopamine D2 receptor density in vivo in human striatum. Low D2 receptor binding in vivo has been found to associate with alcohol/substance dependence. It has been suggested that the A1 allele of human D2 receptor gene might be associated to a specific type of alcoholism and possibly to a reduced D2 receptor density in vitro. We have determined D2 dopamine receptor-binding density (Bmax), affinity (Kd) and availability (Bmax/Kd) in 54 healthy Finnish volunteers using PET and [11C]raclopride in order to determine whether the A1 allele is associated with a 'baseline' difference in D2 receptor characteristics in vivo. A statistically significant reduction in D2 receptor availability reflecting an alteration in receptor density was observed in the A1/A2 genotype group compared to the A2/A2 group. There was no difference in apparent Kd between the two groups. In conclusion, the association between the A1 allele and low D2 receptor availability in healthy subjects indicates that the A1 allele of the TaqIA polymorphism might be in linkage disequilibrium with a mutation in the promoter/regulatory gene element that affects dopamine D2 receptor expression. This study provides an in vivo neurobiological correlate to the A1 allele in healthy volunteers.

Polymorphism within the promoter of the serotonin transporter gene and antidepressant efficacy of fluvoxamine.

Abstract: Depression with psychotic features has been shown to respond to selective serotonin reuptake inhibitors (SSRIs). The serotonin transporter (5-HTT) is a prime target for SSRIs. A functional polymorphism within the promoter region of the 5-HTT gene, leading to different transcriptional efficiency, was recently reported. We tested the hypothesis that allelic variation of the 5-HTT promoter could be related to the antidepressant response to fluvoxamine and/or augmentation with pindolol (a serotonin autoreceptors antagonist) which has been suggested as an augmentation therapy for nonresponders. One hundred and two inpatients with major depression with psychotic features were randomly assigned to treatment with a fixed dose of fluvoxamine and either placebo or pindolol for 6 weeks. Depression severity was assessed once a week using the Hamilton Depression Rating Scale. Allelic variation in each subject was determined using a PCR-based method. Data were analyzed with a three-way repeated measures analysis of variance. Both homozygotes for the long variant (l/l) of the 5-HTT promoter and heterozygotes (l/s) showed a better response to fluvoxamine than homozygotes for the short variant (s/s). In the group treated with fluvoxamine plus pindolol all the genotypes acted like l/l treated with fluvoxamine alone. Fluvoxamine efficacy in delusional depression seems to be related to allelic variation within the promoter of the 5-HTT gene. Even though other factors may be implicated, genotyping at 5-HTT promoter may represent a promising tool to individualize the pharmacological treatment of depression.

Association of the dopamine receptor D4 (DRD4) gene with a refined phenotype of attention deficit hyperactivity disorder (ADHD): a family-based approach.

Abstract: Previously in this journal, we reported an association of the dopamine D4 receptor gene (DRD4) and attention deficit hyperactivity disorder (ADHD) In a population-association (case-control) study of 39 children with a refined phenotype of ADHD and 39 ethnically matched controls, we observed an increased percentage of the 7 repeat allele (29% vs 12%) and the 7+ genotype (49% vs 21%) in the ADHD group compared to the control group In a replication and an extension of our initial study, we recruited another sample of ADHD subjects and found percentages of the 7 repeat allele (28%) and the 7+ genotype (48%) consistent with our previous findings We used a family-based approach to evaluate a predicted association of DRD4 and ADHD based on a test of allele transmission focused on the 7 repeat allele We identified 52 families based on the diagnosis of the refined phenotype of ADHD in the proband and the availability of DNA from both biological parents as well as the proband Haplotype relative risk (HRR) analysis was performed to test our a priori hypothesis and produced significant results (chi-square = 465, P < 0035) This provides additional evidence that the DRD4 gene is associated with a refined phenotype of ADHD

Neuroimaging abnormalities in the subgenual prefrontal cortex: implications for the pathophysiology of familial mood disorders

Abstract: The prefrontal cortex (PFC) ventral to the genu of the corpus callosum has been implicated in the modulation of visceral responses to stressful and emotionally provocative stimuli, based upon analysis of lesion effects involving this area in humans and experimental animals. In a recent magnetic resonance imaging (MRI) study of familial mood disorders, we demonstrated that the mean grey matter volume of this cortex is abnormally reduced in subjects with major depressive disorder (MDD) and bipolar disorder, irrespective of their treatment status or current mood state. Moreover, in preliminary histopathological assessments of subgenual PFC tissue taken post mortem from subjects with MDD and bipolar disorder we obtained results suggesting that this decrement in grey matter volume is associated with a reduction in glia without an equivalent loss of neurons. The potential functional significance of these neuroimaging and microscopic abnormalities is discussed with respect to evidence that subgenual PFC dysfunction may disturb stress-related autonomic and neuroendocrine responses and reward-related mesolimbic dopamine function. These data may thus hold important implications for the development of neural models of mood disorders that can account for the abnormal hedonic, motivational, neuroendocrine, and autonomic manifestations evident in these idiopathic conditions.

Antipsychotic drugs which elicit little or no Parkinsonism bind more loosely than dopamine to brain D2 receptors, yet occupy high levels of these receptors

Abstract: This review addresses two questions. First, why does clozapine apparently occupy low levels of dopamine D2 receptors in patients, in contrast to all other antipsychotic drugs which occupy 70-80% of brain dopamine D2 receptors? Second, what is the receptor basis of action of antipsychotic drugs which elicit low levels of Parkinsonism? Antipsychotic doses of clozapine occupy between 0% and 50% of D2 receptors, as measured in patients by a variety of radioligands. It has recently been found, however, that the percent occupancy of a receptor by a drug depends on the radioligand used to measure that receptor. Based on this new finding, this review concludes that clozapine clinically occupies high levels of D2 receptors in the absence of any radioligand. This occupancy is estimated to be of the order of 70-80% in the dopamine-rich region of the human striatum, and even higher in the limbic D2-containing regions which are low in endogenous synaptic dopamine. This conclusion arises from two different approaches. One approach is to relate the reported clozapine occupancies in the human striatum with the dissociation constants of the various radioligands at the D2 receptor. This relation extrapolates to approximately 70-80% occupancy by clozapine when clozapine competes with endogenous dopamine at the D2 receptor. The second approach is to calculate the D2 occupancy of each antipsychotic drug, using the average spinal fluid concentration and the correct dissociation constant of the antipsychotic, thereby revealing that all antipsychotic drugs, including clozapine, occupy approximately 70-80% of dopamine D2 receptors in the human striatum, and possibly higher in the limbic regions. As determined by the new dissociation constants, antipsychotic drugs which elicit Parkinsonism (trifluperazine, chlorpromazine, raclopride, haloperidol, fluphenazine, risperidone) bind more tightly than dopamine to D2, while those antipsychotic drugs which elicit little or no Parkinsonism (melperone, seroquel, perlapine, clozapine, remoxipride, molindone, sulpiride, olanzapine, sertindole) bind more loosely than dopamine to D2 receptors. Compared to the tightly bound antipsychotic drugs, the more loosely bound antipsychotics generally require higher clinical doses, require fewer days for clinical adjustment, but may dissociate from the D2 receptor more rapidly and could lead to clinical relapse somewhat earlier than that found with the traditional tightly bound antipsychotic drugs.

Anti-hyperactivity medication: methylphenidate and amphetamine

Abstract: How do 'stimulants' reduce hyperactivity in children and adults? How can drugs which raise extracellular dopamine result in psychomotor slowing of hyperactive children when dopamine is known to enhance motor activity, such as in Parkinson's disease? These apparent paradoxes are the focus of this brief review on the mechanism of action of stimulant medications used in the treatment of children, and of an increasing number of adults who meet diagnostic criteria for attention deficit hyperactivity disorder.

A family based association study of T102C polymorphism in 5HT2A and schizophrenia plus identification of new polymorphisms in the promoter

Abstract: Several studies have shown an association between schizophrenia and the C allele of a T-C polymorphism at nucleotide 102 and the 5HT2A receptor gene. In the present study we observed this association in a sample of 63 parent/offspring trios where the proband received a diagnosis of DSM-III-R schizophrenia using TDT analysis (chi2 = 6.26, P= 0.006, chi2 = 9.00, P=0.001 when one affected offspring was selected at random from each family, suggesting that the results are due to association rather than linkage). There was no significant difference between the transmission of C102 from heterozygous fathers and mothers, which fails to support a role for genomic imprinting in this effect. T102C does not result in an alteration of the amino acid sequence of the protein. We therefore screened the promoter of 5HT2A for polymorphisms using single-strand confirmation polymorphism analysis. An A-G polymorphism at -1438 that creates an HpaII restriction site was identified. This was found to be in complete linkage disequilibrium with T102C and is hence a candidate for the pathogenic variant in schizophrenia. Functional analysis of A-1438G using luciferase assay demonstrated significant basal promoter activity in 5HT2A expressing HeLa cells by both the A and G variants. However, comparison of the A and G variants showed no significant differences in basal activity nor when promoter activity was induced by cAMP and protein kinase C-dependent mechanisms.

Dopamine DRD4 receptor polymorphism and attention deficit hyperactivity disorder

Abstract: A polymorphism in the dopamine receptor 4 gene (DRD4) has been related to novelty seeking, Tourette's syndrome, and attention deficit hyperactivity disorder (ADHD). The variability is in a 48-bp repeat in exon 3 of the gene (a transmembrane region). This study examined the relation of the 7-repeat (i.e., high-risk) allele to questionnaire-based diagnoses of ADHD (both combined type and inattentive type). Several positive findings were obtained for ADHD-inattentive type. In an association test, the 7-repeat allele occurred more frequently in children with ADHD-inattentive type than in control children. In genetically discordant sibling pairs, the sibling with a greater number of 7-repeat alleles displayed more inattentive symptoms than his/her co-sibling with fewer 7-repeat alleles. For ADHD-combined type, the 7-repeat allele frequency was greater than that in the control sample. However, a quantitative transmission disequilibrium test yielded no significant linkage of the 7-repeat allele with hyperactive-impulsive symptoms. A categorical TDT yielded no significant findings, but the number of transmissions was small, especially for ADHD-inattentive type.

Evidence for association between polymorphisms in the promoter and coding regions of the 5-HT2A receptor gene and response to clozapine

Abstract: Clozapine is a potent atypical antipsychotic which binds to a variety of neurotransmitter receptors including serotonin (5-HT) receptors. However, the precise neurochemical site of clozapine's therapeutic action is unknown. We hypothesize that genetic variation in the neurotransmitter receptors to which the drug binds may influence clozapine response. To test this hypothesis we genotyped a novel -1438-G/A polymorphism detected in the promoter region, and a His452Tyr polymorphism described in the coding region of the 5-HT2A receptor gene in two independent samples of clozapine-treated patients including responders and non-responders. Although the strong association between these polymorphisms and clozapine response observed in the first sample (sample I) was not statistically significant in the second sample (sample II), the results in both samples were in the same direction. Homozygosity for the allele G-1438 was higher among non-responders (56% in sample I, 43% in sample II) than in responders (28% in sample I and 32% in sample II) in both samples. Similarly, the frequency of allele Tyr452 was higher in non-responders (11% in sample I, 16% in sample II) than in responders (6% in sample I and 10% in sample II). A combined analysis of both samples showed association between both polymorphisms and clozapine response. These results provide further evidence suggesting that genetic variation at 5-HT2A receptors may influence clozapine response and strengthen the candidacy of these receptors as important therapeutic targets.

Evidence that the dopamine D4 receptor is a susceptibility gene in attention deficit hyperactivity disorder.

Abstract: Evidence that the dopamine D4 receptor is a susceptibility gene in attention deficit hyperactivity disorder

Isolation of a novel potassium channel gene hSKCa3 containing a polymorphic CAG repeat: a candidate for schizophrenia and bipolar disorder?

Abstract: Many human hereditary neurodegenerative diseases are caused by expanded CAG repeats, and anonymous CAG expansions have also been described in schizophrenia and bipolar disorder We have isolated and sequenced a novel human cDNA encoding a neuronal, small conductance calcium-activated potassium channel (hSKCa3) that contains two arrays of CAG trinucleotide repeats The second CAG repeat in hSKCa3 is highly polymorphic in control individuals, with alleles ranging in size from 12 to 28 repeats The overall allele frequency distribution is significantly different in patients with schizophrenia compared to ethnically matched controls (Wilcoxon Rank Sum test, P = 0024), with CAG repeats longer than the modal value being over-represented in patients (Fisher Exact test, P = 00035) A similar, non-significant, trend is seen for patients with bipolar disorder These results provide evidence for a possible association between longer alleles in the hSKCa3 gene and both of these neuropsychiatric diseases, and emphasize the need for more extensive studies of this new gene Small conductance calcium-activated K+ channels play a critical role in determining the firing pattern of neurons These polyglutamine repeats may modulate hSKCa3 channel function and neuronal excitability, and thereby increase disease risk when combined with other genetic and environmental effects

Evidence for linkage disequilibrium between serotonin transporter protein gene (SLC6A4) and obsessive compulsive disorder

Abstract: Obsessive compulsive disorder (OCD) is characterized by recurrent and intrusive thoughts that are distressing (obsessions) and/or repetitive behaviors or mental acts that the person feels driven to perform (compulsions). OCD has a partly genetic basis. For treatment of OCD, potent serotonin reuptake inhibitor (SRI) drugs (clomipramine (Anafranil), fluvoxamine (Luvox), fluoxetine (Prozac), sertraline (Zoloft), and paroxetine (Paxil)), which act on the serotonin transporter protein, are uniquely efficacious. A polymorphism in the promoter region of the gene (SLC6A4) encoding this protein, was recently reported to affect protein expression and to be associated with measures of anxiety and depression and with autism (using a family-controlled transmission disequilibrium test (TDT) design). SLC6A4 therefore has strong a priori support for potentially influencing risk for OCD: the protein it encodes is a medication target; a polymorphism in the gene affects function; and that polymorphism has been shown to be associated with behavioral phenotypes. We used the TDT with a set of 34 European-American family trios, 30 unrelated and four drawn from an extended pedigree, to test for linkage disequilibrium between OCD and alleles at the SLC6A4 promoter polymorphic locus. Of 35 heterozygous parents, 24 transmitted the 'l' SLC6A4 allele and 11 transmitted the 's' allele (chi 2 TDT = 4.83; P < 0.03). Considering only the 13 SRI drug nonresponders, there were 13 heterozygous parents, of whom 10 transmitted the 'l' allele and three the 's' allele (chi 2 TDT = 3.77; P < 0.052). These data provide preliminary support for association and linkage disequilibrium between the SLC6A4 'l' allele and OCD.

Dopamine D4 receptor and serotonin transporter promoter in the determination of neonatal temperament.

Abstract: Genetic effects on behavior were evaluated at a time in early development when we hypothesized that environmental influences are minimal and least likely to confound associations between temperament and genes. The behavioral effects of two common polymorphisms linked respectively in some, but not all, studies to novelty seeking (dopamine D4 receptor-D4DR) and neuroticism and harm avoidance (serotonin transporter promoter region-STPR) were examined in a group of 81 two-week-old neonates. Neonate temperament was evaluated using the Brazelton neonatal assessment scale (NBAS). Multivariate tests of significance showed a significant association of D4DR across four behavioral clusters pertinent to temperament including orientation, motor organization, range of state and regulation of state. A significant multivariate interaction was also observed between D4DR and STPR. The effect of the homozygous short STPR genotype (s/s) was to lower the orientation score for the group of neonates lacking the long form (L) of D4DR. When adult subjects were grouped by the STPR polymorphism there is no significant effect of L-D4DR in those subjects homozygous for the STPR short form (s/s) whereas in the group without the homozygous genotype the effect of L-D4DR is significant and accounts for 13% of the variance in novelty seeking scores between groups.

Lack of an association between a dopamine-4 receptor polymorphism and attention-deficit/hyperactivity disorder: genetic and brain morphometric analyses.

Abstract: Although the etiology of attention-deficit/hyperactivity disorder (ADHD) is likely multifactorial, family,1 adoption,2 and twin studies3 suggest that genetic factors contribute significantly. Polymorphisms of the dopamine 4 receptor (DRD4) affect receptor binding,4 and one allele with seven tandem repeats in exon 3 (DRD4*7R) has been associated with ADHD.5,6 We examined this putative association in 41 children with severe ADHD and 56 healthy controls who were group matched for ethnicity and sex. The frequency of the DRD4*7R allele did not vary by diagnosis (0.220 vs 0.205 in patients and controls, respectively). Behavioral and brain anatomic MRI measures, previously found to discriminate patients from controls,7 did not differ significantly between subjects having and those lacking a DRD4*7R allele. These data do not support the reported association between DRD4*7R and the behavioral or brain morphometric phenotype associated with ADHD.

Low activity allele of catechol-O-methyltransferase gene associated with rapid cycling bipolar disorder

Abstract: Catechol-O-methyltransferase (COMT) plays a major role in the breakdown of catecholamines. An amino acid polymorphism (val-108-met) determines high and low activity of the enzyme. A recent study in a small sample of patients with velo-cardio-facial syndrome who had bipolar affective disorder suggested that the Met (low activity) COMT allele might be associated with rapid-cycling in this population. We therefore tested the hypothesis that the Met allele might be associated with rapid cycling bipolar disorder in the wider population. We studied a sample of British Caucasian DSM-IV bipolar patients, of whom 55 met criteria for rapid cycling at some time during the illness and 110 met stringent criteria for a definite non-rapid cycling course. The COMT genotype was determined using a PCR assay. The low activity allele was more frequent in the group of rapid cyclers: 0.55 vs 0.42 (one-tailed chi 2 = 5.12, d.f. = 1, P = 0.012), and bearers of low activity alleles showed a dose-dependent increased risk of lifetime occurrence of rapid cycling: chi 2 test of linear association = 4.84, d.f. = 1, P = 0.014. Our data support the hypothesis that variation in the COMT gene modifies the course of bipolar disorder.

Ultra-ultra rapid cycling bipolar disorder is associated with the low activity catecholamine-O- methyltransferase allele

Abstract: Bipolar spectrum disorders are recurrent illnesses characterized by episodes of depression, hypomania, mania or the appearance of mixed states. Great variability is evident in the frequency of episode recurrence and duration. In addition to regular circannual episodes, a spectrum of cycle frequencies has been observed, from the classical rapid cycling (RC) pattern of four or more episodes per year, to those with distinct shifts of mood and activity occurring within a 24-48 h period, described as ultra-ultra rapid cycling (UURC) or ultradian cycling. RC has a female preponderance, and occurs with greater frequency premenstrually, at the puerperium and at menopause. Tricyclic antidepressants and MAOIs, both of which increase functional monoamines norepinephrine, dopamine and serotonin, are known to precipitate mania or rapid-cycling in an estimated 20-30% of affectively ill patients. We have recently reported a strong association between velo-cardio-facial syndrome (VCFS) patients diagnosed with rapid-cycling bipolar disorder, and an allele encoding the low enzyme activity catechol-O-methyltransferase variant (COMT L). Between 85-90% of VCFS patients are hemizygous for COMT. Homozygosity for the low activity allele (COMT LL) is associated with a 3-4 fold reduction of COMT enzyme activity compared with homozygotes for the high activity variant (COMT HH). There is nearly an equal distribution of L and H alleles in Caucasians. Individuals with COMT LL would be expected to have higher levels of transynaptic catecholamines due to a reduced COMT degradation of norepinephrine and dopamine. We therefore hypothesized that the frequency of COMT L would be greater in RC BPD ascertained from the general population. Significantly, we found that the frequency of COMT L was higher in the UURC variant of BPD than among all other groups studied (P = 0.002). These findings indicate that COMT L could represent a modifying gene that predisposes to ultra-ultra or ultradian cycling in patients with bipolar disorder.

Role of serotonin transporter promoter repeat length polymorphism (5-HTTLPR) in seasonality and seasonal affective disorder.

Abstract: Role of serotonin transporter promoter repeat length polymorphism (5-HTTLPR) in seasonality and seasonal affective disorder

Serum leptin levels increase rapidly after initiation of clozapine therapy.

Abstract: Weight gain is a major side-effect of treatment with clozapine. In order to investigate the influence of the atypical neuroleptic clozapine on leptin secretion, serum leptin levels were measured in 12 patients at baseline and for a 10-week period after initiation of treatment. Serum clozapine levels and levels of its metabolites were simultaneously assessed. Alterations of body weight and body composition were determined. During the 10-week observation period leptin levels differed significantly from the levels determined at baseline (P < 0.0001). During the first 2 weeks of treatment serum leptin levels at least doubled in eight of the 12 patients. The maximal relative increase over baseline was 536%. Low doses of clozapine were sufficient to induce this effect. Within a 10-week period mean body weight, mean body mass index, mean fat mass and mean lean body mass all increased. Based on the results we suggest that in predisposed individuals clozapine induces an increased appetite; overeating and weight gain can ensue, which in turn underlie elevated leptin secretion.

Systematic mutation screening and association study of the A1 and A2a adenosine receptor genes in panic disorder suggest a contribution of the A2a gene to the development of disease.

Abstract: Several lines of evidence suggest a contribution of adenosinergic neurotransmission to the development of panic disorder. We therefore hypothesized that variation in the A1 and A2a adenosine receptor (AR) genes modifies genetic susceptibility to panic disorder. To test this hypothesis, we screened 38 patients with panic disorder for mutations in the coding sequence of the A1AR and A2aAR genes. An association study between the identified DNA sequence variants and panic disorder was performed in an extended sample of 89 patients and matched controls. One silent mutation (716T/G) in the A1AR gene and two silent mutations (432C/T and 1083C/T) in the A2aAR gene were detected. The association sample shows a significant association between the 1083T allele (P=0.01) and 1083T/T genotype (P=0.024) of the A2AR gene and panic disorder. Our findings thus lend further support to the hypothesis that the A2aAR gene, or a locus in linkage disequilibrium with it, confers susceptibility to panic disorder. Replication studies in independent samples with nuclear families applying the transmission disequilibrium test (TDT) are warranted.

A meta-analysis and transmission disequilibrium study of association between the dopamine D3 receptor gene and schizophrenia

Abstract: We performed a meta-analysis of over 30 case-control studies of association between schizophrenia and a bi-allelic, Bali polymorphism in exon 1 of the dopamine D3 receptor gene. We observed a significant excess of both forms of homozygote in patients (P = 0.0009, odds ratio (OR) = 1.21, 95% Confidence Interval (CI) = 1.07-1.35) in the combined sample of 5351 individuals. No significant heterogeneity was detected between samples and the effects did not appear to be the product of publishing bias. In addition we undertook an independent, family-based association study of this polymorphism in 57 parent/proband trios, taken from unrelated European multiplex families segregating schizophrenia. A transmission disequilibrium test (TDT) showed a significant excess of homozygotes in schizophrenic patients (P = 0.004, odds ratio (OR) = 2.7, 95% CI = 1.35-5.86). Although no significant allelic association was observed, a significant association was detected with the 1-1 genotype alone (P = 0.02, OR = 2.32, 95% CI = 1.13-4.99). In addition when the results of the family-based association study were included in the meta-analysis, the homozygosity effect increased in significance (P = 0.0002, OR = 1.23, 95% CI = 1.09-1.38). The results of the meta-analysis and family-based association study provide independent support for a relationship between schizophrenia and homozygosity at the Bali polymorphism of the D3 receptor gene, or between a locus in linkage disequilibrium with it.

D2 receptors binding potential is not affected by Taq1 polymorphism at the D2 receptor gene

Abstract: Alcoholism and substance abuse have been associated with a polymorphism in a noncoding region of the D2 receptor gene (the A1 allele of the Taq1 'A' system) in several, but not all studies. In addition, the presence of the A1 allele has been associated with lower density of D2 receptors in the caudate nucleus in one postmortem study. If the Taq1 'A1' allele is in linkage disequilibrium with a mutation that decreases the expression of the D2 receptor gene, it is conceivable that subjects with the A1 allele might be predisposed to behaviors which stimulate dopamine transmission, such as alcoholism or substance abuse. In this study, we attempted to confirm the association between the A1 allele and lower D2 receptor density, and explored a possible association between the B1 allele and D2 receptor expression. Genotypes at the Taq1 'A' and 'B' systems were determined in 70 subjects who underwent in vivo measurement of D2 receptors-binding potential with single photon emission computerized tomography (SPECT) and the selective dopamine D2 receptor radiotracer [123I]IBZM. [123I]IBZM-binding potential was identical in A1 carriers (i.e., subjects heterozygous or homozygous for that allele) (230 +/- 85 ml g-1, n = 27) and A1 noncarriers (231 +/- 70 ml g-1, n = 43). Similarly, we found no effect of the B1 allele on [123I]IBZM-binding potential. In conclusion, the results of this study failed to replicate the previously reported association between A1 allele and lower D2 receptor expression.

Alpha synuclein is present in Lewy bodies in sporadic Parkinson's disease

Abstract: A missense mutation in the human alpha synuclein gene was recently identified in some cases of familial Parkinson's disease (FPD). We have developed an antibody that recognizes the C-terminal 12 amino acids of the human alpha synuclein protein and have demonstrated that alpha synuclein is an abundant component of the Lewy bodies found within the degenerating neurons of patients with Parkinson's disease (PD). The presence of alpha synuclein in Lewy bodies of sporadic PD patients suggests a central role for alpha synuclein in the pathogenesis of PD.

Predisposition of Wolfram syndrome heterozygotes to psychiatric illness.

Abstract: Identification of specific genes that predispose to psychiatric illness will lead to more precise psychiatric diagnosis and more effective treatment. Heterozygous carriers of genes for many autosomal recessive syndromes may be 1% or more of the general population. Thus, if mutations at a specific locus produce psychiatric manifestations in homozygous affected individuals, it is important to determine whether mutations at such a locus also predispose heterozygous carriers to psychiatric disorders. The hypothesis that heterozygous carriers of the gene for the Wolfram syndrome (WS) are predisposed to psychiatric illness was supported previously by the finding of an excess of psychiatric hospitalizations and suicides in WS blood relatives compared to spouse controls. This hypothesis has now been tested further by comparing the number of psychiatrically hospitalized blood relatives with the specific marker haplotype associated with the Wolfram syndrome gene in their families to the number expected under the null hypothesis, calculated from Mendelian inheritance principles and the estimated haplotype frequency. The proportion of psychiatrically hospitalized relatives who were WS carriers (10/11) was much higher than expected (3.1/11), leading to the provisional estimate that WS gene carriers are 26-fold more likely to require psychiatric hospitalization than non-carriers.

An association study of a functional polymorphism of the serotonin transporter gene with personality and psychiatric symptoms

Abstract: A functional polymorphism in the regulatory region of the serotonin transporter gene has been reported to be associated with anxiety-related personality traits.1 We attempted to replicate this finding in an association study involving 759 Caucasians selected from the general Australian population. We found no associations with personality traits (including neuroticism, negative affect and behavioral inhibition), anxiety and depressive symptoms, or alcohol misuse.

A functional serotonin transporter (5-HTT) polymorphism is associated with psychosis in neuroleptic-free schizophrenics

Abstract: The neurotransmitter serotonin has been implicated in the pathophysiology of psychosis. The serotonin transporter (5-HTT) plays a critical role in regulation of serotonergic function. A recently identified polymorphism in the promoter region of the 5-HTT gene (5-HTTLPR) produces significant differences in 5-HTT expression and function and was found to be associated with anxiety-related traits in healthy volunteers. We investigated whether 5-HTTLPR is associated with psychosis in neuroleptic-free schizophrenic or schizoaffective patients. Fifty patients with schizophrenia or schizoaffective disorder by DSM-III-R criteria were genotyped at 5-HTTLPR and underwent double-blind Brief Psychiatric Rating Scale (BPRS) ratings while neuroleptic-free for approximately 4 weeks. Patients with the 5-HTTLPR II genotype (n = 19) had significantly higher BPRS ratings for psychosis than patients with the Is (n = 25) or ss (n = 6) genotypes. Examination of individual items revealed a specific significant increase in intensity of hallucinations in patients with the 5-HTTLPR II genotpe. These data provide preliminary evidence for a role of serotonin in the pathophysiology of hallucinations and may represent the identification of an allelic variant that modifies the complex clinical presentation of schizophrenia.

Polygenic inheritance and micro/minisatellites.

Abstract: While it has often been stated that the identification of the genes involved in complex polygenic traits may be extremely difficult, the principles learned in the past century about single gene-single disease inheritance may not be relevant to polygenic inheritance. A new paradigm specific to complex disorders may be needed. It is proposed that micro- and minisatellite polymorphisms play a role in the expression of many genes. As a result, these genes exist in the population with many functional alleleomorphic variants. While each variant has only a modest effect on a given phenotype, because the variants are common, and most quantitative traits are controlled by a number of genes, there is a reasonable probability that an individual will inherit a threshold number of functional variants beyond which there is an appreciable effect on the phenotype. Twelve different aspects of such a new model for complex inheritance, some corollary implications, and three examples of its immediate application, are presented with the hope that the model may allow an acceleration of the identification of the genes involved in complex polygenic disorders.

Evidence for a role of phospholipase C-gamma1 in the pathogenesis of bipolar disorder.

Abstract: Several studies have indicated that patients with bipolar disorder (BD) who respond well to lithium prophylaxis constitute a biologically distinct subgroup. Lithium is thought to stablize mood by acting at the phosphoinositide cycle. We have investigated a polymorphism located in the gene (PLCG1) that codes for a γ-1 isozyme of phospholipase (PLC), an enzyme that plays an important role in the phosphoinositide second messenger system. A population-based association study and a family-based linkage study were carried out on patients who were considered excellent responders to lithium prophylaxis. Response to lithium was evaluated prospectively with an average follow-up of 14.4 ± 6.8 years. The PLCG1 polymorphism was investigated in 136 excellent lithium responders and 163 controls. In addition, the segregation of this marker was studied in 32 families ascertained through lithium-responsive bipolar probands. The allele distributions between lithium-responsive bipolar patients and controls were different, with a higher frequency of one of the PLCG1 polymorphisms in patients (χ2 = 8.09; empirical P = 0.033). This polymorphism, however, confers only a small risk (OR = 1.88, CI 1.19–3.00). Linkage studies with the same marker yielded modest support for the involvement of this gene in the pathogenesis of BD when unilineal families were considered (Max LOD = 1.45; empirical P = 0.004), but not in the whole sample. Our results provide preliminary evidence that a PLC isozyme may confer susceptibility to bipolar disorder, probably accounting for a fraction of the total genetic variance. Whether this polymorphism is implicated in the pathogenesis of BD or in the mechanism of lithium response remains to be determined.

Leptin in relation to resumption of menses in women with anorexia nervosa

Abstract: Serum levels of leptin are decreased in underweight AN patients and increase with weight restoration. To assess the relationship of decreased leptin levels with other hormonal abnormalities in AN and to evaluate the possible role of increasing leptin levels, alone or in combination with other hormones, in the resumption of menses that accompanies weight gain, we studied cross-sectionally sixty-five consecutively enrolled AN patients. Subjects were divided in three groups: (I) underweight and amenorrheic; (II) weight-recovered but still amenorrheic; and (III) weight-recovered and eumenorrheic women. Patients in group I had decreased BMI, serum leptin, estradiol (E2), insulin-like growth factor 1 (IGF-1) and urinary growth hormone (GH) levels and increased sex hormone-binding globulin (SHBG) levels, compared to AN patients in groups II and III. Moreover, although no differences in leptin levels or BMI were observed between amenorrheic and eumenorrheic weight-recovered patients (groups II and III), free E2 and GH levels were higher (P<0.02) in weight-recovered, eumenorrheic women. Thus, it appears that leptin is a necessary, but not a sufficient, factor for the resumption of menses in AN patients.

Homozygosity at the dopamine D3 receptor gene is associated with opiate dependence.

Abstract: Anatomical, pharmacological and human post-mortem studies suggest the dopamine D3 receptor (DRD3) gene as a candidate for drug dependence. We thus performed an association study of the Bal I polymorphism at the DRD3 gene, including 54 opiate addicts and 70 controls. Opiate addicts had a higher sensation-seeking score (on the Zuckerman scale) than controls (P = 0.001), particularly a subgroup (70%) who had a distinctly higher score, exceeding 24. There were no marked differences in genotypes between patients as a whole and controls. However, patients with a sensation-seeking score above 24 were more frequently homozygotes for both alleles than patients with a sensation-seeking score under 24 (P = 0.038) or controls (P = 0.034). Although obtained in a sample of limited size, these results suggest that the DRD3 gene may have a role in drug dependence susceptibility in individuals with high sensation-seeking scores. This hypothesis is consistent with the role of DRD3 in mediating responses to drugs of abuse in animals and the association of homozygosity at the Bal I polymorphism with drug abuse in schizophrenic patients (see companion article by Krebs et al).

The dopamine D3 receptor (DRD3) Ser9Gly polymorphism and schizophrenia: A haplotype relative risk study and association with clozapine response

Abstract: Several lines of evidence suggest that the dopamine D3 receptor is involved in the pathophysiology of schizophrenia. The D3 receptor gene (DRD3) contains a polymorphism resulting in a serine-glycine substitution in the N-terminus of the receptor. Shaikh and colleagues have reported a significant association between the DRD3 Ser9 allele and the Ser9/Ser9 genotype with schizophrenia in 133 Caucasians. In a meta-analysis of previous studies, Ser9 and the Ser9/Ser9 genotype were found to be significantly associated with schizophrenia, although these investigators could not confirm reports of excess homozygosity at this locus in schizophrenia. These authors also report that, in an unblinded study, the Ser9/Ser9 genotype was more frequent in patients who did not respond to clozapine. These data represent the most comprehensive examination of DRD3 Ser9Gly in schizophrenia to date. We have therefore determined DRD3 Ser9Gly genotypes in 58 patients with schizophrenia and in their parents. Moreover, we have genotyped 68 schizophrenics participating in double-blind clozapine trials. We do not find that Ser9 is preferentially transmitted in schizophrenia, cannot confirm excess DRD3 homozygosity in schizophrenia, and do not replicate the association between DRD3 and clozapine response. These data suggest that allelic variation in DRD3 may not play a role in the pathophysiology of schizophrenia or in clozapine response.