Salvador Contreras

Cannabinoid Receptor 1 Gene (CNR1) and Susceptibility to a Quantitative Phenotype for Hebephrenic Schizophrenia

Functional alterations of components of the endogenous cannabinoid system, in particular of the cannabinoid receptor 1 protein (CB1), are hypothetical contributors to many of the symptoms seen in schizophrenia. Variants within the cannabinoid receptor 1 gene (CNR1) have been shown to be directly associated with the hebephrenic form of schizophrenia in a Japanese population. This finding, however, has yet to be replicated. In the present study we sought to study the same (AAT)n‐repeat microsatellite of the CNR1 gene which showed association to hebephrenic schizophrenia in Japan, and to investigate whether this microsatellite showed association to a hebephrenic type of schizophrenia in a family‐based association study in a population of the Central Valley of Costa Rica. The Lifetime Dimensions of Psychosis Scale and a best estimate consensus process were utilized to identify subjects with schizophrenia who had an elevated lifetime dimensional score for negative and disorganized symptoms, which we used as a proxy for “hebephrenia.” Using the Family Based Association Test we found association of these hebephrenic subjects and the (AAT)n‐repeat marker of the CNR1 (multi‐allelic P = 0.0368). Our hypothesis that an association with the (AAT)n‐repeat marker of CNR1 would not be found with the more general type of schizophrenia was also confirmed. Schizophrenic subjects with prominent lifetime scores for disorganization and negative symptoms (dimension for hebephrenia) are associated with the CNR1 gene and present a type of symptomatology that resembles chronic cannabinoid‐induced psychosis. The current finding points to the possibility of different genetic and pathophysiologic mechanisms underlying different types of schizophrenia.

Cerebrospinal fluid HVA, central brain atrophy, and clinical state in schizophrenia

In 16 patients with chronic schizophrenia, cerebrospinal fluid (CSF) concentrations of homovanillic acid (HVA) showed a significant negative correlation with computed tomographic measures of brain third ventricle size. Clinical state during a drug-free period was also significantly correlated with CSF HVA level, but not with third ventricle size when the effect of CSF HVA was partialed out. The authors propose that these findings may reflect an atrophic process involving structures around the third ventricle and a decrease in dopaminergic activity.

Fluoxetine and desipramine in major depressive disorder.

The efficacy and safety of fluoxetine and desipramine were compared in a 6-week double-blind, parallel group study of patients with major depression. Twenty-five were studied while hospitalized for treatment, and 33 were studied as outpatients. Improvement on the Hamilton Rating Scale for Depression was significant for both treatments from week 1 through the end of the study and did not differ between the two treatments at any week. Overall, 64% of fluoxetine-treated patients and 68% of desipramine-treated patients had at least a 50% reduction in Hamilton Depression score. We assessed whether improvement relatively early in treatment was predictive of categorical response at 6 weeks. Among fluoxetine-treated patients, but not desipramine-treated patients, the week 3 change in the Hamilton Depression mood item was significantly predictive of the response at 6 weeks. Patients treated with fluoxetine had significantly fewer side effects than those treated with desipramine. Desipramine, but not fluoxetine, caused a persistent increase in heart rate. The results suggest that early signs of response to fluoxetine are not dependent on achieving steady-state levels of the drug.

Evidence of genetic overlap of schizophrenia and bipolar disorder: Linkage disequilibrium analysis of chromosome 18 in the Costa Rican population

The long‐standing concept that schizophrenia (SC) and bipolar disorder (BP) represent two distinct illnesses has been recently challenged by findings of overlap of genetic susceptibility loci for these two diseases. We report here the results of a linkage disequilibrium (LD) analysis of chromosome 18 utilizing subjects with SC from the Central Valley of Costa Rica. Evidence of association (P < 0.05) was obtained in three chromosomal regions: 18p11.31 (D18S63), 18q12.3 (D18S474), and 18q22.3‐qter (D18S1161, D18S70), all of which overlap or are in close proximity with loci previously shown to be in LD with BP, type I in this population. Since both the SC and bipolar samples contained cases with a history of mania and almost all cases of SC and BP had a history of psychosis, we performed an alternative phenotyping strategy to determine whether presence or absence of mania, in the context of psychosis, would yield distinct linkage patterns along chromosome 18. To address this issue, a cohort of psychotic patients (including a range of DSMIV diagnoses) was divided into two groups based on the presence or absence of mania. Regions that showed association with SC showed segregation of association when the sample was stratified by history of mania. Our results are compared with previous genetic studies of susceptibility to SC or BP, in Costa Rica as well as in other populations. This study illustrates the importance of detailed phenotype analysis in the search for susceptibility genes influencing complex psychiatric disorders in isolated populations and suggests that subdivision of psychoses by presence or absence of past mania syndromes may be useful to define genetic subtypes of chronic psychotic illness.

Association analyses of the neuregulin 1 gene with schizophrenia and manic psychosis in a Hispanic population

Objective:  This study used the population of the Central Valley of Costa Rica (CVCR) and phenotyping strategies alternative to DSMIV classifications to investigate the association of neuregulin 1 with schizophrenia.

Malic enzyme 2 and susceptibility to psychosis and mania

Previous studies have identified a putative gene locus for both schizophrenia and bipolar disorder in the chromosome 18q21 region. To identify candidate genes associated with these disorders we completed fine mapping analyses (using microsatellite markers) in 152 families from the Central Valley of Costa Rica (CVCR) (376 total subjects, 151 with a history of psychosis, 97 with a history of mania). Microsatellite analyses showed evidence of association at two contiguous markers, both located at the same genetic distance and spanning approximately 11 known genes. In a corollary gene expression study, one of these genes, malic enzyme 2 (ME2), showed levels of gene expression 5.6-fold lower in anterior cingulate tissue from post-mortem bipolar brains. Subsequent analysis of individual SNPs in strong linkage disequilibrium with the ME2 gene revealed one SNP and one haplotype associated with the phenotype of psychosis in the CVCR sample. ME2 interacts directly with the malate shuttle system, which has been shown to be altered in schizophrenia and bipolar disorder, and has roles in neuronal synthesis of glutamate and gamma-amino butyric acid. The present study suggests that genetic variation in or near the ME2 gene is associated with both psychotic and manic disorders, including schizophrenia and bipolar disorder.

The Serotonin Transporter 5-HTTPR Polymorphism is associated with Current and Lifetime Depression in Persons with Chronic Psychotic Disorders

Objective:  Variation in the serotonin transporter gene (SLC6A4) promoter region has been shown to influence depression in persons who have been exposed to a number of stressful life events.

Anti-depressant prescribing patterns for prison inmates with depressive disorders

BACKGROUND Although prison inmates are reported to exhibit elevated rates of depressive disorders, little is known about anti-depressant prescribing patterns in correctional institutions. METHODS The study population consisted of 5305 Texas Department of Criminal Justice (TDCJ) inmates who were diagnosed with one of three depressive disorders: major depression, dysthymia, and bipolar disorder (excluding those with manic episodes only). Information on medical conditions, sociodemographic factors, and pharmacotherapy was obtained from an institution-wide medical information system. RESULTS In 1998, 78.2% of all inmates diagnosed with depressive disorders were treated with antidepressant medication. Of these, 47.3% were treated exclusively with tricyclic anti-depressants (TCA); 30.9% were treated with selective serotonin re-uptake inhibitors (SSRI); and 21.8% were not treated with any form of anti-depressant medication. Prescribing patterns varied substantially according to a number of sociodemographic factors under study. LIMITATIONS Because the present study relied on retrospective, clinical data, the investigators had limited ability to assess: specific symptomatology for each diagnosed depressive condition under study; socio-economic status, pre-incarceration access to health care; and the overall reliability and validity of the data. CONCLUSION The proportion of prison inmates with depressive disorders who receive appropriate medication management is substantially higher than that reported among similarly diagnosed nonincarcerated samples. It will be important, however, for future investigators to examine the sources of sociodemographic variation in treatment patterns found in the present study.

Suggestive evidence for association between L-type voltage-gated calcium channel (CACNA1C) gene haplotypes and bipolar disorder in Latinos: a family-based association study

OBJECTIVES   Through recent genome-wide association studies (GWASs), several groups have reported significant association between variants in the calcium channel, voltage-dependent, L-type, alpha 1C subunit (CACNA1C) and bipolar disorder (BP) in European and European-American cohorts. We performed a family-based association study to determine whether CACNA1C is associated with BP in the Latino population. METHODS   This study included 913 individuals from 215 Latino pedigrees recruited from the USA, Mexico, Guatemala, and Costa Rica. The Illumina GoldenGate Genotyping Assay was used to genotype 58 single-nucleotide polymorphisms (SNPs) that spanned a 602.9-kb region encompassing the CACNA1C gene including two SNPs (rs7297582 and rs1006737) previously shown to associate with BP. Individual SNP and haplotype association analyses were performed using Family-Based Association Test (version 2.0.3) and Haploview (version 4.2) software. RESULTS   An eight-locus haplotype block that included these two markers showed significant association with BP (global marker permuted p = 0.0018) in the Latino population. For individual SNPs, this sample had insufficient power (10%) to detect associations with SNPs with minor effect (odds ratio = 1.15). CONCLUSIONS   Although we were not able to replicate findings of association between individual CACNA1C SNPs rs7297582 and rs1006737 and BP, we were able to replicate the GWAS signal reported for CACNA1C through a haplotype analysis that encompassed these previously reported significant SNPs. These results provide additional evidence that CACNA1C is associated with BP and provides the first evidence that variations in this gene might play a role in the pathogenesis of this disorder in the Latino population.

TGFB-induced factor (TGIF): a candidate gene for psychosis on chromosome 18p.

Schizophrenia (SC) and bipolar disorder (BP) share many clinical features, among them psychosis. We previously identified a putative gene locus for psychosis on chromosome 18p in a sample from the Central Valley of Costa Rica (CVCR) population. The present study replicated the association to a specific allele of microsatellite marker D18S63 on 18p11.3, using a newly collected sample from the CVCR. A combined analysis of both samples, plus additional subjects, showed that this specific allele on D18S63, which lies within an intron on the TGFB-induced factor (TGIF) gene, is strongly associated (P-value=0.0005) with psychosis. Eleven additional SNP markers, spanning five genes in the region, were analyzed in the combined sample from the CVCR. Only the four SNPs within the TGIF gene were in strong linkage disequilibrium with D18S63 (D′=1.00). A specific haplotype for all five markers within the TGIF gene showed evidence of association (P-value=0.011) to psychosis. A second, distinct haplotype, containing a newly identified nonsynonymous polymorphism in exon 5 of the TGIF gene, showed a nonsignificant trend towards association to psychosis (P-value=0.077). TGIF is involved in neurodevelopment, neuron survival and controls the expression of dopamine receptors. Altogether, our results point to the possible involvement of TGIF in the pathophysiology of psychotic disorders in the CVCR population.