A family‐based study of the Cys23Ser 5HT2C serotonin receptor polymorphism in schizophrenia

The 5HT2C receptor has a high affinity for clozapine, a nontypical neuroleptic, and has therefore been postulated to play a role in mediating negative symptoms and neuroleptic response in schizophrenia. In the current study, the Cys23Ser 5HT2C serotonin receptor polymorphism was examined for linkage to schizophrenia by genotyping 207 nuclear families consisting of both parents and schizophrenic child and using the transmission disequilibrium test to examine possible preferential transmission of these alleles from 68 heterozygous mothers to their ill child. No evidence was obtained for preferential transmission of the Cys23Ser 5HT2C alleles in schizophrenia in either of the two main ethnic groups examined (German and Palestinian Arab) or in the combined cohort (TDT chi‐square = 0.00, NS). © 2001 Wiley‐Liss, Inc.     

Distribution of the serotonin 2C (5HT2C) receptor gene -759C/T polymorphism in patients with schizophrenia and normal controls

BACKGROUND: In patients with schizophrenia, the percentage of patients with diabetes has been found to be twice that of the normal population. The risk factors for this higher rate are unknown, although dietary, lifestyle, and genetic factors have all been suggested. Recently, a polymorphism (-759C/T) in the serotonin 2C (5HT2C) receptor promoter region has been associated with the development of diabetes in a normal control population, with the frequency of the T allele being higher in subjects without diabetes. AIM: To determine whether the distribution of the -759C/T polymorphism of the 5HT2C receptor is different among patients with schizophrenia and normal controls. METHODS: DNA from 100 patients with schizophrenia and 81 normal controls were analyzed for the 5HT2C receptor -759C/T polymorphism to determine its allelic frequencies in these two groups. RESULTS: Using a chi-squared analysis, no statistical differences in the distribution of C alleles and T alleles were found between the two groups (P=0.2931). CONCLUSIONS: Patients with schizophrenia have a higher risk for developing diabetes than the general population. We did not find a higher distribution of the -759T allele of the 5HT2C receptor in normal controls compared with in patients with schizophrenia. This suggests the higher prevalence of diabetes in schizophrenia is not due to this polymorphism.     

Association analysis between a Cys23Ser substitution polymorphism of the human 5-HT2c receptor gene and neuronal hyperexcitability

Transgenic mice lacking a functional 5-HT2c receptor gene are extremely susceptible to audiogenic seizures, suggesting that 5-HT2c receptors mediate inhibition of neuronal network excitability. The present association study tested the hypothesis that a Cys23Ser substitution polymorphism within the human 5-HT2c receptor gene modulates neuronal excitability. Genotypes of the Cys23Ser polymorphism were assessed in 454 subjects of German descent, comprising: 1) 93 severely affected alcohol-dependent males with a history of alcohol withdrawal seizure or delirium, 2) 119 patients affected by an idiopathic generalized epilepsy, and 3) 242 controls. Both sexes were analyzed separately because of the X-chromosomal location of the 5-HT2c receptor gene. The allele frequencies of the Cys23Ser variants did not differ significantly between the controls and either the severely affected alcohol-dependent males (P = 0.34), or patients with idiopathic generalized epilepsy (P > 0.57). Our results suggest that the common Cys23Ser substitution polymorphism of the human 5-HT2c receptor gene does not confer susceptibility to neuronal hyperexcitability in either idiopathic generalized epilepsy or alcohol withdrawal seizure or delirium.     

Sex differences in allelic frequencies of the 5-HT2C Cys23Ser polymorphism in psychiatric patients and healthy volunteers: findings from an association study

Polymorphisms in the serotonergic system are believed to play a role in the etiology and treatment of different psychiatric illnesses. The 5-HT2C receptor gene is X-linked, with a frequent mutation at nucleotide 68 leading to a Ser-->Cys transition at amino acid 23. Recent studies have demonstrated an impaired function of 5-HT2C receptors and an increased production of the major noradrenergic metabolite 3-methoxy-4-hydroxyphenylethyleneglycol in the cerebrospinal fluid among the subjects carrying the Ser23 allele (Lappalainen et al., 1999). Biol. Psychiatry 46:821). We genotyped patients with alcohol dependence, panic disorder without agoraphobia, generalized anxiety disorder, narcolepsy and normal healthy volunteers for the 5-HT2C Cys23Ser polymorphism. 5-HT2C Cys23Ser allele frequencies and genotypes did not differ among patients with alcohol dependence, panic disorder, generalized anxiety disorder, narcolepsy and normal healthy volunteers. In an overall analysis, female subjects (n = 173) displayed a higher frequency of 5-HT2C Ser23 alleles as compared to males (n = 298, P = 0.0178). The potential mechanisms of the observed gender difference in allele frequencies, including transmission ratio distortion, are discussed.     

The Cys allele (the Ser311Cys polymorphism) of the dopamine d2 receptor is associated with schizophrenia and impairments to selective attention in patients

We report here our studies of the Ser311Cys polymorphism of the D2 dopamine receptor gene in 366 patients with schizophrenia and 387 control subjects. The incidence of the Cys allele was found to be greater (p < 0.009) among patients than controls (8.5% and 3.9%, respectively). Selective attention was also studied on the basis of assessment of parameters of the P300 wave of auditory evoked potentials in 66 patients with different genotypes – SerSer and SerCys (the CysCys genotype was not seen among the patients). This revealed a significant influence of genotype (p = 0.01) on the latent period (LP) of the P300 wave in the frontal, central and temporal leads. In carriers of the Cys allele, which is associated with the risk of developing schizophrenia, LP was longer than in subjects with other genotypes, which is evidence for slowing of mental processes associated with activation of attention resources in these subjects. Thus, the results obtained here support data obtained previously for other populations showing that the Cys allele is associated with schizophrenia, and we also observed an association between this allele and degradation of selective attention in patients.     

Clozapine-induced weight gain associated with the 5HT2C receptor -759C/T polymorphism.

Weight gain has been documented as a significant adverse effect associated with many of the atypical antipsychotic medications. Several recent reports have linked a -759C/T polymorphism of the 5HT2C receptor gene and obesity as well as chlorpromazine, risperidone, and clozapine induced to weight gain. This aim was to determine the association between changes in body mass index (BMI) during clozapine treatment and the -759C/T polymorphism of the 5HT2C receptor gene. This study included 41 patients with treatment-refractory schizophrenia (DSM-IV) who were followed prospectively during treatment with clozapine. Weight and height measurements were obtained prior to starting clozapine and after 6-months of treatment. Genomic DNA was isolated from a whole blood sample and analyzed for the -759C/T polymorphism of the 5HT2C receptor gene. A chi(2) analysis comparing whether or not the subjects carried a -759T allele in subjects grouped as having an increase of more or less than 7% of their baseline BMI during treatment with clozapine found that the presence of the -759T allele was significantly higher in subjects with less than or equal to a 7% increase in baseline BMI compared to those with a greater than 7% increase in BMI. A multiple linear regression analysis showed that both baseline BMI and the presence or absence of the -759T allele had significant effects on 6-month BMI. The T allele may have a protective function in preventing significant weight gain from clozapine. Subjects without the -759T variant allele were at a greater risk for weight gain from clozapine over 6-months compared to those with the -759T allele.     

A family-based association study of T1945C polymorphism in the proline dehydrogenase gene and schizophrenia in the Chinese population

Previous studies have reported genetic linkage evidence for a candidate gene of schizophrenia on chromosome 22q11 but no genes in this region have been really confirmed to be involved in the etiology of schizophrenia so far. Very recently, the proline dehydrogenase gene (PRODH), located in the most centromeric part of the 22q11 microdeletion region, has been reported to be strongly associated with schizophrenia from three sets of independent samples and the most significant evidence for association was derived from a single nucleotide polymorphism-PRODH*1945(T/C). We genotyped this polymorphism in 166 Chinese family trios with schizophrenia from East China. No evidence for preferential transmission of the PRODH*1945 alleles from parents to affected offsprings was found using either Transmission Disequilibrium Test (P=0.4) or Haplotype-based Haplotype Relative Risk analysis (P=0.35). Our results suggest that the 1945(T/C) polymorphism of the proline dehydrogenase gene is unlikely to play a major role in the susceptibility to schizophrenia in the Chinese population.     

Polymorphism of 5HT2A serotonin receptor gene is implicated in smoking addiction.

Smoking behavior is influenced by genetic factors. Polymorphisms affecting the dopaminergic system have been linked to smoking habits. The aim of this study was to investigate if the T102C polymorphism of the 5-HT(2A) receptor gene is related to tobacco use, since this receptor modulates the mesolimbic dopamine system and the C allele is associated with reduced receptor gene expression. A sample of 625 subjects were genotyped and classified according to their smoking behavior (never, former, or current smokers). We found differences in the distribution of the genotypes when the current smokers were compared with the never + former smokers, suggesting that T102C polymorphism is associated with maintenance, but not with initiation of the smoking habit. The CC genotype was more frequent in the current smokers than in the never + former smokers (chi(2) = 6.825, P = 0.03). The odds ratio of being a current smoker with a CC genotype was 1.63, 95% CI 1.06-2.51.     

Population-based and family-based association study of 5'UTR polymorphism of the reelin gene and schizophrenia.

Reelin is a glycoprotein involved in the migration and positioning of proliferating neurons and synaptic connectivity during neurodevelopment. It may also modulate neuronal plasticity throughout life. Therefore, the reelin gene is a candidate gene for schizophrenia. We examined the association of the CGG repeat polymorphism in the 5'-untranslated region of the reelin gene with schizophrenia in 266 unrelated French Caucasian patients, 156 of their parents, and 103 controls. We found no difference in the allele distribution between patients and controls although there was a significant higher prevalence of the genotype 8-8 in controls (CLUMP T3: chi(2) = 6.3, P = 0.035). There was no significant transmission disequilibrium in intrafamilial analysis. To refine our phenotypic characterization and in accordance with converging evidence suggesting that treatment resistance is associated with indices of abnormal neurodevelopment, we studied the association between reelin gene polymorphism and response to antipsychotics. Patients who responded to antipsychotics had a higher frequency of both the (CGG)(10) allele and (CGG)(10)-containing genotypes (P = 0.02; P = 0.006, respectively), with an odd ratio for genotypes of 4.2 (CI = [1.4;12.4]). Our results weakly support an association of reelin gene variants with schizophrenia as a whole, yet suggest that reelin could be associated with treatment-resistant schizophrenia.     

No association between the serotonin 1B receptor gene and schizophrenia in a case-control and family-based association study

Previous studies have demonstrated that polymorphisms in the putative promoter region of the human serotonin receptor 1B (HTR1B) gene affect gene expression [H.F. Sun, Y.T. Chang, C.S. Fann, C.J. Chang, Y.H. Chen, Y.P. Hsu, W.Y. Yu, A.T. Cheng, Association study of novel human serotonin 5-HT(1B) polymorphisms with alcohol dependence in Taiwanese Han, Biol. Psychiatry 51 (2002) 896-901; J. Duan, A.R. Sanders, J.E. Molen, L. Martinolich, B.J. Mowry, D.F. Levinson, R.R. Crowe, J.M. Silverman, P.V. Gejman, Polymorphisms in the 5'-untranslated region of the human serotonin receptor 1B (HTR1B) gene affect gene expression, Mol. Psychiatry 8 (2003) 901-910]. And the silent mutation G861C allele has been reported to be associated with several psychiatric disorders. Thus, we performed a case-control association study (456 cases and 557 controls) of the five variants in HTR1B gene (T-261G, -182INS/DEL-181, A-161T, C129T and G861C) with schizophrenia. The results showed that neither the allelic distribution nor the major haplotype distribution (except for a rare haplotype) of five SNPs in patients was significantly different from that in controls. A further family-based association study (229 family trios) of G861C allele suggested that HTR1B was not a susceptible gene with schizophrenia in our sample. In conclusion, these data do not support the idea that HTR1B gene plays a major role in the etiopathogenesis of schizophrenia in Chinese Han population.     

Weight gain associated with the -759C/T polymorphism of the 5HT2C receptor and olanzapine.

BACKGROUND: Weight gain from atypical antipsychotic use has become a significant problem. Recent reports have liked the -759 polymorphism of the 5HT2C receptor and obesity as well as weight gain from chlorpromazine, risperidone, and clozapine. AIM: To determine associations between weight gain during olanzapine treatment and the -759C/T polymorphism of the 5HT2C receptor gene. METHODS: This study included 42 acutely ill patients with schizophrenia (DSM-IV). Weekly assessments included Brief Psychiatric Rating Scale (BPRS), Scale for Assessment of Negative Symptoms (SANS), and weight measurements. Olanzapine was titrated to a fixed dose (7.5-20 mg/day) for 2-6 weeks. A 24 hr plasma level was obtained at the endpoint visit. Genomic DNA was isolated from a whole blood sample and analyzed for the -759C/T polymorphism of the 5HT2C receptor. RESULTS: A chi-square analysis was conducted comparing the distribution of T and C alleles in subjects grouped as gaining more or less than 5, 7, and 10% of their baseline weight during treatment with olanzapine. A threshold of 10% was found to be significant. The distribution of T alleles was higher in subjects not gaining 10% of more of their body weight compared who did gain significant weight (11/27 (40.7%) vs. 0/15 (100%), chi2 = 11.805, P = 0.0035). CONCLUSIONS: Subjects with a T allele of the 5HT2C receptor -759C/T polymorphism may have a lower incidence of weight gain from olanzapine over a 6 week period compared to those with the C allele. These results need to be replicated.     

Association of a serotonin receptor 2A gene polymorphism with cognitive functions in patients with schizophrenia.

The aim of this study was to investigate the association between the T102C polymorphism on the 5HT2A gene and cognitive function as well as clinical manifestations in patients with schizophrenia. Eighty-two outpatients with schizophrenia participated in this study. The Brief Psychiatric Rating Scale (BPRS) was used to assess the severity of each patient's symptoms. In order to evaluate their short-term attention capacity, a Digit Span Test was used. The Continuous Performance Test (CPT) was used to test the sustained attention span of each of the subjects. Cognitive flexibility was measured with the Wisconsin Card Sorting Test (WCST). The polymorphism of the 5-HT2A gene at codon 102 (T/C) was genotyped by sequence specific polymerase chain reaction. The T allele at codon 102 correlated with a lower hit rate and more commission errors in the CPT and patients with the heterogeneous genotype (TC) had more commission errors than those who were of homogeneous type (CC or TT). Patients with the TC genotype also had significantly fewer correct responses in the WCST compared to those who were type CC or TT. No relationship was found to exist between the C allele and cognitive variables. There was also no relationship established between the codon 102 polymorphism and clinical parameters. These findings suggest that the TC genotype might be related to certain cognitive impairments in patients with schizophrenia.     

Association of 5HT2A receptor gene polymorphism and alcohol abuse with behavior problems

This study investigated the association between T/C polymorphism, at position 102, of the 5-hydroxytryptamine 2A receptor gene and alcoholism with and without behavior problems. Eighty-five subjects (45 men, 40 women) with alcohol abuse, 75 subjects (51 men, 24 women) with alcohol dependence, and 70 normal control subjects (21 men, 49 women) participated in the study. The results show that the frequency of the homozygous T102 genotype was significantly lower in the group of male alcohol abuse with behavior problems than in the female group (chi(2) = 4.072, df = 1, P < 0.05) and the allele frequency of T102 was also lower in the male group than in the female group (chi(2) = 4.187, df = 1, P < 0.05). Of the male alcohol abuse subjects, the group with behavior problems was found to have lower frequencies of the T102 allele than the group without behavior problems (chi(2) = 4.328, df = 1, P < 0.05). In conclusion, this study demonstrates that alcoholism is heterogeneous and male alcohol abuse with behavioral problems was associated with T/C 102 polymorphism of the 5HT2A receptor gene. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:797-800, 2000.     

Transmission disequilibrium studies of the serotonin 5‐HT2A receptor gene (HTR2A) in autism

Hyperserotonemia in autism is one of the longest‐standing biochemical findings in a psychiatric disorder. This well‐replicated finding and subsequent studies of platelet serotonin receptors in autism indicate that the serotonin 2A receptor gene (HTR2A) on chromosome 13q is a primary candidate gene in autism. Converging data from recent genome screens also implicates the genomic region containing HTR2A. Based on these lines of evidence, the transmission/disequilibrium test (TDT) was used to assess transmission disequilibrium between autism and haplotypes of three polymorphisms, including the promoter ‐1438 G/A single nucleotide polymorphism (SNP) in perfect linkage disequilibrium with the 102 T/C SNP in previous studies, a newly identified SNP in intron 1 near exon 2, and the SNP responsible for the His452Tyr amino acid change in exon 3. Because expression studies have shown HTR2A to be polymorphically imprinted in the brain, secondary analyses were split into maternal and paternal transmissions. No evidence was found for unequal transmission of haplotypes; however, power analysis reveals low power to detect a parent‐of‐origin effect in this sample size. © 2002 Wiley‐Liss, Inc.     

The Cys allele of the DRD2 Ser311Cys polymorphism has a dominant effect on risk for schizophrenia: evidence from fixed- and random-effects meta-analyses.

Previously we derived independent estimates of the effect of the dopamine D2 receptor (DRD2) Ser311Cys polymorphism on risk for schizophrenia using fixed- and random-effects meta-analyses. Both analyses identified a significant association between the Cys allele and schizophrenia, but neither included all available data. Furthermore, genotype data were not evaluated in either analysis, thus precluding any determination of the mode of inheritance. The present study was conducted to resolve discrepancies between the existing meta-analyses, and provide more comprehensive and accurate estimates of the nature and magnitude of the influence of the Ser311Cys polymorphism on risk for schizophrenia. All discrepancies between the two sets of previously meta-analyzed studies were identified and resolved to the mutual satisfaction of the authors, and the final dataset was analyzed independently by fixed- and random-effects meta-analyses. A total of 27 samples, comprising 3,707 schizophrenia patients and 5,363 control subjects, were included in the analyses of allelic association, while smaller numbers of studies and subjects were included in each of the genotypic association analyses. A significant effect of the Cys allele was observed under both fixed-effects (odds ratio [OR] = 1.4; P = 0.002) and random-effects (OR = 1.4; P = 0.007) models. Cys/Ser heterozygotes were at elevated risk for schizophrenia when compared to Ser/Ser homozygotes (fixed- and random-effects OR = 1.4, p(s) or= 0.948). There was no evidence of heterogeneity, excessive influence of any single study, or publication bias in any of the analyses, suggesting that the effect of this DRD2 polymorphism on schizophrenia risk is reliable and uniform across populations, and our estimates of its magnitude are robust and accurate.     

Identification of a new polymorphism in the 3'-untranslated region of the human serotonin receptor 2C (5-HT2C) gene

We identified a polymorphism (2831T > G) in the 3'-untranslated region of 5-HT2C receptor gene, approximately 100 kb from a previously reported coding sequence polymorphism, 796G > C (C23S). Allele frequencies were 0.90 (T) and 0.10 (G) and cosegregation analysis of the alleles at the two loci demonstrated frequencies of 0.82 (GT), 0.08 (CT), 0.10 (GG), and 0 (CC). The increased informativity gained by analysis of both polymorphisms will prove useful for future studies of this gene in X-linked neuropsychiatric disorders.     

5-HT 102T/C多态性与Tourette综合征的病例对照及核心家系关联分析

目的 研究5－羟色胺受体102T／C多态性是否与Tourette综合征（TS）相关联,方法对157个核心家系样本采用病例－对照关联分析,传递不平衡检验方法,聚合酶链反应及RFLP等技术,根据TS与强迫症（obsessive compulsive disorder,OCD)的同病现象,将TS划分亚组进行与5－羟色胺受体102T／C多态性的关联分析。结果 合并OCD的TS与该位点的基因型102C／C（X2＝8．38,P＝0．004）及等位基因102C／（X2＝4．84,P＝0．028）存在关联,进一步采用传递不平衡分析,发现合并（美国精神疾病诊断和统计手册IV》论断标准的OCD的TS与该位点存在关联或连锁不平衡（X2＝5．12,,P＝0．02）,而在TS总体样本及单纯TS样本中未发现与该位点的关联,结论 5－羟色胺受体102T／C多态性与中国人群合并OCD的TS存在关联,合并OCD的TS可能是TS中相对独立的一个亚型。