Study Report

Reference	Cordeiro, Q.,2005 PMID: 15660667
Citation	Cordeiro, Q., M. E. Talkowski, et al. (2005). Association and linkage analysis of RGS4 polymorphisms with schizophrenia and bipolar disorder in Brazil. Genes Brain Behav 4(1): 45-50.
Disease Type	Bipolar Disorder & Schizophrenia
Study Design	case-control and family-based
Study Type	Candidate-region linkage study and candidate-gene association study
Sample Size	patients with SCZ (n=271),patients with BD1 (n=306) and 576 community-based controls.
SNP/Region/Marker Size	4 SNPs
Predominant Ethnicity
Population	Brazilian

Sample Diagnosis	DSM
Sample Status	1.Patients:Participants were recruited from inpatient and outpatient services at the Institute of Psychiatry of the Hospital das Clinicas,University of Sao Paulo Medical School. Individuals diagnosed with SCZ or BD participated in the study, but individuals with SZAD were not included.The SCZ sample comprised 271 individuals. Parents of 49 SCZ probands were also available; this group comprised the 'case-parent trios'. The BD sample consisted of 306 individuals, of whom 44 probands participated as case-parent trios.2.Parents of patients:When feasible, participation by parents of the probands was sought. Parents were not included if they had been diagnosed with a psychiatric illness. Parents were also submitted to clinical interviews with two independent psychiatrists. If a parent was diagnosed with a psychiatric disorder, for at least one psychiatrist,he/she was excluded from the study. From those parents who agreed to participate in the study andwere submitted to the clinical interviews, two mothers and one father (mothers: two unipolar depressions; father: BD) were excluded from the SCZ sample. In the BD, two mothers and one father (mothers: two unipolar depressions; father: unspecified psychosis) were also excluded due to a history of psychiatric disorder. The rest of the parents of our unitary patients were not able to be contacted. Both parents were available for 49 patients with SCZ and 44 patients with BD. 3.Controls:Adults participating in the Blood Donation Service at the Hospital das Clinicas, University of Sao Paulo School of Medicine, were asked to participate. Such individuals undergo a physical examination, but psychiatric evaluations were not completed (n=576). Ethnicity for cases and controls was determined by two independent raters and was based on skin pigmentation in the medial part of the arm, hair color and texture and the shape of the nose and lips. The participants were classified as Caucasian, Black, Mulatto, Asiatic,Brazilian Indian or Unknown.
Technique	genotyping
Statistical Method	We used PEDCHECK software (O'Connell & Weeks 1998) to test for Mendelian inconsistencies and the web-based GENEPOP program to test for Hardy-Weinberg equilibrium (http://wbiomed.curtin.edu.au/genepop). We used the SNPEM software,which utilizes the expectation maximization algorithm to estimate haplotype frequencies. Further, the software uses permutation-based methods to estimate the statistical significance of differences in haplotype frequencies among cases and controls (Fallin et al. 2001). We employed the TDT(GENEHUNTER software) to assess transmission distortions from parents to affected probands for single SNPs and haplotypes (Kruglyak et al. 1996). We also used TRANSMIT software for global tests of association involving multiple haplotypes(Clayton 1999; Clayton & Jones 1999). Linkage disequilibrium (LD) was evaluated for all pairwise SNP combinations using published software (Zhao et al. 2000). An a-level of 0.05 was used to assess statistical significance in all analyses.
Result Summary	In the SCZ samples, significant case-control differences were not observed for individual SNPs or haplotypes, though the TDT suggested transmission distortion similar to that observed in the initial report. For the BD sample, case-control comparisons revealed no significant differences for individual SNPs, but an omnibus test suggested differences in the overall distribution of haplotypes bearing all four SNPs (SNP-EM Omnibus likelihood ratio test; P=0.003). The TDT revealed over-transmission of allele A at SNP7 (P=0.016), as well as haplotypes incorporating this allele. However, global tests incorporating all haplotypes yielded only suggestive trends for association (P=0.19). In conclusion, association with SCZ was not detected in the present analyses. The failure to detect an association may be related to inadequate power or to confounds related to ethnic admixture. Suggestive associations with BD detected here require further investigation in a larger sample.