Lack of association between the G681C polimorphism in the 5-HT1Dbeta autoreceptor gene and schizophrenia

Cordeiro, Quirino; Vallada, Homero

doi:10.1590/S0004-282X2005000300002

Abstracts

A major role of the serotonergic system has been hypothesized in the pathogenesis of schizophrenia, mostly based on the evidence of action of atypical antipsychotics. Disturbances of serotonergic pathways have been implicated in the etiology of schizophrenia. The aim of this study was to investigate the association between schizophrenia and the G861C polymorphism in the 5-HT1Dbeta autoreceptor gene. There was conducted a case-control analysis in a sample of 196 schizophrenic patients and 143 gender, age and ethnic matched controls. No statistically differences were found in allelic or genotypic distributions between cases and controls. Thus, the results do not support an association of the G861C polymorphism in the 5-HT1Dbeta autoreceptor gene with schizophrenia in the studied sample.

schizophrenia; 5-HT1Dbeta; G861C polymorphism; genetic association

O sistema serotonérgico tem sido implicado na fisiopatologia da esquizofrenia, principalmente por conta dos mecanismos de ação dos antipsicóticos atípicos. Alterações nas vias cerebrais serotonérgicas têm sido relacionadas com a etiologia desse transtorno psiquiátrico. Assim, o objetivo do presente estudo foi investigar uma possível associação entre esquizofrenia e o polimorfismo G861C no gene do auto-receptor serotonérgico 5-HT1Dbeta. Para tanto, conduziu-se estudo do tipo caso-controle em amostra de 196 pacientes com esquizofrenia e 143 indivíduos pareados para sexo, idade e etnia. Não se evidenciaram diferenças estatísticas nas distribuições alélicas e genotípicas entre as populações de pacientes e controles. Desse modo, os resultados dessa investigação não correlacionaram o polimorfismo G861C no gene do auto-receptor serotonérgico 5-HT1Dbeta como fator de susceptibilidade genética para o desenvolvimento de esquizofrenia na amostra estudada.

esquizofrenia; 5-HT1Dbeta; polimorfismo G861C; associação genética

Lack of association between the G681C polimorphism in the 5-HT1Db autoreceptor gene and schizophrenia

Ausência de associação entre o polimorfismo G861C do gene do auto-receptor 5-HT1Db e esquizofrenia

Quirino Cordeiro; Homero Vallada

Department of Psychiatry, University of São Paulo Medical School (FMUSP), São Paulo SP, Brazil

^{Correspondence} Correspondence to Dr. Homero Vallada Instituto de Psiquiatria / FMUSP 05403-010 São Paulo SP-Brasil E-mail: hvallada@usp.br

ABSTRACT

A major role of the serotonergic system has been hypothesized in the pathogenesis of schizophrenia, mostly based on the evidence of action of atypical antipsychotics. Disturbances of serotonergic pathways have been implicated in the etiology of schizophrenia. The aim of this study was to investigate the association between schizophrenia and the G861C polymorphism in the 5-HT1Db autoreceptor gene. There was conducted a case-control analysis in a sample of 196 schizophrenic patients and 143 gender, age and ethnic matched controls. No statistically differences were found in allelic or genotypic distributions between cases and controls. Thus, the results do not support an association of the G861C polymorphism in the 5-HT1Db autoreceptor gene with schizophrenia in the studied sample.

Key words: schizophrenia, 5-HT1Db, G861C polymorphism, genetic association

RESUMO

O sistema serotonérgico tem sido implicado na fisiopatologia da esquizofrenia, principalmente por conta dos mecanismos de ação dos antipsicóticos atípicos. Alterações nas vias cerebrais serotonérgicas têm sido relacionadas com a etiologia desse transtorno psiquiátrico. Assim, o objetivo do presente estudo foi investigar uma possível associação entre esquizofrenia e o polimorfismo G861C no gene do auto-receptor serotonérgico 5-HT1Db. Para tanto, conduziu-se estudo do tipo caso-controle em amostra de 196 pacientes com esquizofrenia e 143 indivíduos pareados para sexo, idade e etnia. Não se evidenciaram diferenças estatísticas nas distribuições alélicas e genotípicas entre as populações de pacientes e controles. Desse modo, os resultados dessa investigação não correlacionaram o polimorfismo G861C no gene do auto-receptor serotonérgico 5-HT1Db como fator de susceptibilidade genética para o desenvolvimento de esquizofrenia na amostra estudada.

Palavras-chave: esquizofrenia, 5-HT1Db, polimorfismo G861C, associação genética.

Schizophrenia (SCZ) is a psychiatric disorder that affects some 1% of the general population, being associated with disturbances of thought, affect, sensoperception and behavior. Data from twin, adoption and family studies have demonstrated that genetics plays an important role in the etiology of this disorder, and heritability as high as 80% has been reported¹. The most common mode of inheritance of SCZ involves multiple susceptibility loci². Some evidences suggest that serotonergic dysfunctions may be related to the susceptibility for SCZ. The serotonin hypothesis emerged following observations of psychotic features related to LSD, a serotonergic drug. Later, reports showing that serotonergic-depleting drugs, such as reserpine could alleviate some symptoms of SCZ helped to build the theory that an increase in serotonin may be related to the disorder³. More evidences of the interest of serotonin in SCZ come from the finding of Joyce et al.⁴ that this neurotransmitter uptake sites and receptors are altered in the limbic system of patients with the disorder, and the observation that the new generation antipsychotics have potent serotonin-related activities⁵.

Serotonin is involved in a variety of sensory, motor and cortical functions, being particularly relevant in modulating the effects of dopamine, the first neurotransmitter supposed to be implicated in SCZ. Serotonin receptors are classified into seven main classes which can be further divided into different subclasses⁶. Among many serotonin receptors subtypes, 5-HT1D receptors are important for SCZ because their major function is to control serotonin release from serotonergic neuron terminals (autoreceptors) in the brain⁶. Cloning studies found two 5-HT1D receptors subtypes, termed 5-HT1Da and 5-HT1Db^7-9. The gene for 5-HT1D receptor has been localized to chromosome 6p13 and it is widely expressed in the human brain¹⁰, with the highest levels of receptor expression observed in limbic regions and basal ganglia⁹. Considering the important role of 5-HT1Db receptor in the control of serotonin release and its location of preferential expression⁶, mutations occurring in this serotonin autoreceptor gene may contribute to the susceptibility for SCZ by causing altered function of serotonergic neurons. Some studies have reported genetic linkage between SCZ and regions on chromosome 6^11-13. These linkage studies have been performed to localize major effect susceptibility genes for SCZ, although, since its genetic etiology may be multifactorial and polygenic, association study design is more appropriated. Any single susceptibility gene contributes only a small fraction to the overall risk for SCZ and can be directly evaluated as susceptibility factors using candidate gene association studies^14,15.

Serotonergic systems have been implicated in the pathophysiology of SCZ and the genetic association study is one of the most important approaches to detect genes for susceptibility to a complex disorder, such as SCZ. Thus in the present study, the silent polymorphism G681C, which is located in the coding region of 5-HT1Db autoreceptor gene, will be investigated as a possible risk factor for SCZ.

METHOD

Sample  All controls and SCZ patients provided written informed consent. The ethical approval for the study was obtained from the Ethics Committee at the Hospital das Clínicas, University of São Paulo Medical School (CAPPesq).

A) Patients sample: 196 patients were recruited from inpatient and outpatient services at the Institute of Psychiatry of the Hospital das Clínicas, University of São Paulo Medical School and diagnosed according to DSM-IV¹⁶ criteria for SCZ.

B) Controls sample: 143 sex, age and ethnic matched healthy controls were recruited from the Blood Donation Service at the Hospital das Clínicas, University of São Paulo Medical School.

Genotyping  We collected ten milli-liters of venous blood from each subject and genomic DNA was extracted using the phenol chloroform method. The G861C genotypes (GG, GC, CC) were determined by the polymerase chain reaction method¹⁷. Determination of genotypes was performed by raters blind to the clinical status of the individuals.

Statistical analysis  For comparisons between cases and controls regarding frequencies of alleles and genotypes, we utilized the chi-square test. Hardy-Weinberg equilibrium was calculated using the STATA Program¹⁸.

RESULTS

There were no significant deviations from the Hardy-Weinberg equilibrium in any of the samples for the polymorphism studied (SCZ: p=0.31; controls: p=0.49). Case-control analysis provided no difference in allelic (p=0.13, c²=2.22, OR=0.77 0.54<OR<1.10) and genotypic (p=0.18, c²=3.36, 2d.f.) distributions between patients and controls samples (Table).

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DISCUSSION

The results of the present study found no evidence for an association between the polymorphism and SCZ. These findings are in agreement with a linkage study in a Canadian population¹⁹, a case-control association study in a Portuguese population²⁰, and a trio-based (father, mother and proband) study also in a Portuguese sample²¹. However, these results do not support some linkage studies that found evidence of linkage in regions of chromosome 6 and SCZ. Such phenomenon may reflect the possibility that there might be other mutations in this gene that play a role in SCZ, or that there are other genes related to the susceptibility for SCZ in chromosome 6.

A possible limitation of the present investigation is related to the population stratification. Association studies using case-control approach can generate false association because it is difficult to precisely match patients and controls for ethnicity because physical characteristics are not always related to genetic background, especially in Brazil where the population is so mixed²². So differences in allele frequencies between populations could generate false results. Even trying to match the populations for ethnicity, as done in this work, this is an issue that has to be considered in case-control investigations.

In conclusion, the results of this work do not provide evidence of association between SCZ and alleles and genotypes of the G861C polymorphism in the 5-HT1Db autoreceptor gene with SCZ in the studied sample.

Received 13 September 2004, received in final form 29 November 2004. Accepted 26 January 2005.

1. McGuffin P, Owen MJ, O'Donovan MC, Thapar A, Gottesman I. Seminars in psychiatric genetics. London: Royal College of Psychiatrists, 1994.
2. Prasad S, Semwal P, Deshpande S, Bhatia T, Nimgaonkar VL, Telma BK. Molecular genetics of schizophrenia: past, present and future. J Biosci 2002;27:35-52.
3. Stahl SM, Wets K. Neurochemistry and neuropharmacology of schizophrenia. London: Elsevier, 1987.
4. Joyce JN, Shane A, Lexow N, Winokur A, Casanova MF, Kleinman JE. Serotonin uptake sites and serotonin receptors are altered in the limbic system of schizophenics. Neuropsychopharmacology 1993;8315-8336.
5. Kapur S, Remington G. Serotonin-dopamine interaction and its relevance to schizophrenia. Am J Psychiatry 1996;153:466-476.
6. Barnes NM, Sharp T. A review of central 5-HT receptors and their function. Neuropharmacology 1999;38:1083-1152.
7. Hamblin MW, Metcalf MA. Primary structure and functional characterization of a human 5T1D-type serotonin receptor. Mol Pharmacol 1991; 40:143-148.
8. Demchyshyn L, Sunahara R, Miller K, et al. A human serotonin 1D receptor variant (5HT1Db) encoded by an intronless gene on chromosome 6. Proc Natl Acad Sci USA 1992;89:5522-5526.
9. Weinshank RL, Zgombick JM, Maccihi MJ, Branchek TA, Harting PR. Human serotonin 1D receptor is encoded by a subfamily of two distinct genes: 5-HT1D alpha and 5-HT1D beta. Proc Natl Acad Sci USA 1992;89:3630-3634.
10. Jin H, Oksenberg D, Askhenazi A, et al. Characterization of human 5-hydroxytryptamine1B receptor. J Biol Chem 1992;267:5735-5738.
11. Martinez M, Goldi L, Cao Q, et al Follow-up study on a susceptibility locus for schizophrenia on chromosome 6q. Am J Med Genet 1999;83:337-343.
12. Hwu H-G, Lin M-W, Lee P-C, Lee F-C, Ou-Yang W-C, Liu C-M. Evaluation of linkage of markers on chromosome 6p with schizophrenia in Taiwanese families. Am J Med Genet 2000;96:74-78.
13. Baron M. Genetics of schizophrenia and the new millennium: progress and pitfalls. Am J Hum Genet 2001;68:299-312.
14. Lander ES. The new genomics: global views of biology. Science 1996; 274:1594-1595.
15. Collins FS, Guyer MS, Chakravarti A. Variations on the theme: cataloging human DNA sequence variation. Science 1997;278:1580-1581.
16. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed. Washington, DC: American Psychiatric Association, 1994.
17. Lappalainen J, Dean M, Charbonneau L, Virkkunen M, Linnoila M, Goldman D. Mapping of the serotonin 5-HT1Db autoreceptor gene on chromosome 6 and direct analysis for sequence variants. Am J Med Genet 1995;60:157-161.
18. Shan P. Statistics in human genetics. New York: Arnold, 1998.
19. Sidenberg DG, Basset AS, Demchyshyn L, et al. New polymorphism for human serotonin 1D receptor variant (5-HT1Db) not linked to schizophrenia in five canadian pedigrees. Hum Hered 1993;43:315-318.
20. Coelho I, Macedo A, Valente J, et al. Association study of serotonin receptors and schizophrenia in a portuguese population. Psiquiatria Clínica 1997;18:41-47.
21. Ambrósio AM, Kennedy JL, Macciardi F, et al. Lack of association or linkage disequilibrium between schizophrenia and polymorphisms in the 5-HT1DA and 5-HT1DB autoreceptor genes: family-based association study. Am J Med Genet 2004;128:1-5.
22. Parra FC, Amado RC, Lambertucci JR, Rocha J, Antunes CM, Pena SD.Color and genomic ancestry in Brazilians. Proc Natl Acad Sci U S A 2003;100:177-182.

Correspondence to

Dr. Homero Vallada

Instituto de Psiquiatria / FMUSP

05403-010 São Paulo SP-Brasil

E-mail:

hvallada@usp.br

Publication Dates

Publication in this collection
25 July 2005
Date of issue
June 2005

History

Accepted
26 Jan 2005
Reviewed
29 Nov 2004
Received
13 Sept 2004

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

[1] 1. McGuffin P, Owen MJ, O'Donovan MC, Thapar A, Gottesman I. Seminars in psychiatric genetics. London: Royal College of Psychiatrists, 1994.

[2] 2. Prasad S, Semwal P, Deshpande S, Bhatia T, Nimgaonkar VL, Telma BK. Molecular genetics of schizophrenia: past, present and future. J Biosci 2002;27:35-52.

[3] 3. Stahl SM, Wets K. Neurochemistry and neuropharmacology of schizophrenia. London: Elsevier, 1987.

[4] 4. Joyce JN, Shane A, Lexow N, Winokur A, Casanova MF, Kleinman JE. Serotonin uptake sites and serotonin receptors are altered in the limbic system of schizophenics. Neuropsychopharmacology 1993;8315-8336.

[5] 5. Kapur S, Remington G. Serotonin-dopamine interaction and its relevance to schizophrenia. Am J Psychiatry 1996;153:466-476.

[6] 6. Barnes NM, Sharp T. A review of central 5-HT receptors and their function. Neuropharmacology 1999;38:1083-1152.

[7] 7. Hamblin MW, Metcalf MA. Primary structure and functional characterization of a human 5T1D-type serotonin receptor. Mol Pharmacol 1991; 40:143-148.

[8] 8. Demchyshyn L, Sunahara R, Miller K, et al. A human serotonin 1D receptor variant (5HT1Db) encoded by an intronless gene on chromosome 6. Proc Natl Acad Sci USA 1992;89:5522-5526.

[9] 9. Weinshank RL, Zgombick JM, Maccihi MJ, Branchek TA, Harting PR. Human serotonin 1D receptor is encoded by a subfamily of two distinct genes: 5-HT1D alpha and 5-HT1D beta. Proc Natl Acad Sci USA 1992;89:3630-3634.

[10] 10. Jin H, Oksenberg D, Askhenazi A, et al. Characterization of human 5-hydroxytryptamine1B receptor. J Biol Chem 1992;267:5735-5738.

[11] 11. Martinez M, Goldi L, Cao Q, et al Follow-up study on a susceptibility locus for schizophrenia on chromosome 6q. Am J Med Genet 1999;83:337-343.

[12] 12. Hwu H-G, Lin M-W, Lee P-C, Lee F-C, Ou-Yang W-C, Liu C-M. Evaluation of linkage of markers on chromosome 6p with schizophrenia in Taiwanese families. Am J Med Genet 2000;96:74-78.

[13] 13. Baron M. Genetics of schizophrenia and the new millennium: progress and pitfalls. Am J Hum Genet 2001;68:299-312.

[14] 14. Lander ES. The new genomics: global views of biology. Science 1996; 274:1594-1595.

[15] 15. Collins FS, Guyer MS, Chakravarti A. Variations on the theme: cataloging human DNA sequence variation. Science 1997;278:1580-1581.

[16] 16. American Psychiatric Association. Diagnostic and statistical manual of mental disorders, 4th ed. Washington, DC: American Psychiatric Association, 1994.

[17] 17. Lappalainen J, Dean M, Charbonneau L, Virkkunen M, Linnoila M, Goldman D. Mapping of the serotonin 5-HT1Db autoreceptor gene on chromosome 6 and direct analysis for sequence variants. Am J Med Genet 1995;60:157-161.

[18] 18. Shan P. Statistics in human genetics. New York: Arnold, 1998.

[19] 19. Sidenberg DG, Basset AS, Demchyshyn L, et al. New polymorphism for human serotonin 1D receptor variant (5-HT1Db) not linked to schizophrenia in five canadian pedigrees. Hum Hered 1993;43:315-318.

[20] 20. Coelho I, Macedo A, Valente J, et al. Association study of serotonin receptors and schizophrenia in a portuguese population. Psiquiatria Clínica 1997;18:41-47.

[21] 21. Ambrósio AM, Kennedy JL, Macciardi F, et al. Lack of association or linkage disequilibrium between schizophrenia and polymorphisms in the 5-HT1DA and 5-HT1DB autoreceptor genes: family-based association study. Am J Med Genet 2004;128:1-5.

[22] 22. Parra FC, Amado RC, Lambertucci JR, Rocha J, Antunes CM, Pena SD.Color and genomic ancestry in Brazilians. Proc Natl Acad Sci U S A 2003;100:177-182.

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