RESUMEN
Meta-analyses of bipolar disorder (BD) genome-wide association studies (GWAS) have identified several genome-wide significant signals in European-ancestry samples, but so far account for little of the inherited risk. We performed a meta-analysis of â¼750,000 high-quality genetic markers on a combined sample of â¼14,000 subjects of European and Asian-ancestry (phase I). The most significant findings were further tested in an extended sample of â¼17,700 cases and controls (phase II). The results suggest novel association findings near the genes TRANK1 (LBA1), LMAN2L and PTGFR. In phase I, the most significant single nucleotide polymorphism (SNP), rs9834970 near TRANK1, was significant at the P=2.4 × 10(-11) level, with no heterogeneity. Supportive evidence for prior association findings near ANK3 and a locus on chromosome 3p21.1 was also observed. The phase II results were similar, although the heterogeneity test became significant for several SNPs. On the basis of these results and other established risk loci, we used the method developed by Park et al. to estimate the number, and the effect size distribution, of BD risk loci that could still be found by GWAS methods. We estimate that >63,000 case-control samples would be needed to identify the â¼105 BD risk loci discoverable by GWAS, and that these will together explain <6% of the inherited risk. These results support previous GWAS findings and identify three new candidate genes for BD. Further studies are needed to replicate these findings and may potentially lead to identification of functional variants. Sample size will remain a limiting factor in the discovery of common alleles associated with BD.
Asunto(s)
Trastorno Bipolar/etnología , Trastorno Bipolar/genética , Predisposición Genética a la Enfermedad , Metaanálisis como Asunto , Polimorfismo de Nucleótido Simple , Ancirinas/genética , Ancirinas/metabolismo , Antidepresivos/farmacología , Pueblo Asiatico/genética , Línea Celular Transformada , Citocinas/genética , Relación Dosis-Respuesta a Droga , Femenino , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/genética , Frecuencia de los Genes , Estudio de Asociación del Genoma Completo , Humanos , Lectinas/genética , Lectinas/metabolismo , Cloruro de Litio/farmacología , Masculino , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/metabolismo , ARN Mensajero/metabolismo , Receptores de Prostaglandina/genética , Receptores de Prostaglandina/metabolismo , Factores de Tiempo , Ácido Valproico/farmacología , Población Blanca/genéticaRESUMEN
BACKGROUND: Linkage of bipolar disorder to a broad region on chromosome 13q has been supported in several studies including a meta-analysis on genome scans. Subsequent reports have shown that variations in the DAOA (G72) locus on 13q33 display association with bipolar disorder but these may not account for all of the linkage evidence in the region. OBJECTIVE: To identify additional susceptibility loci on 13q32-q33 by linkage disequilibrium mapping and explore the impact of phenotypic heterogeneity on association. METHODS: In the initial phase, 98 single nucleotide polymorphism (SNPs) located on 13q32-q33 were genotyped on 285 probands with bipolar disorder and their parents were drawn from families in the NIMH Genetics Initiative consortium for bipolar disorder (NIMH1-4) and two other series. Fine scale mapping using one family series (NIMH1-2) as the test sample was targeted on a gene that displayed the highest evidence of association. A secondary analysis of familial component phenotypes of bipolar disorder was conducted. RESULTS: Three of seven SNPs in DOCK9, a gene that encodes an activator of the Rho-GTPase Cdc42, showed significant excess allelic transmission (P=0.0477-0.00067). Fine scale mapping on DOCK9 yielded evidence of association at nine SNPs in the gene (P=0.02-0.006). Follow-up tests detected excess transmission of the same allele of rs1340 in two out of three other sets of families. The association signals were largely attributable to maternally transmitted alleles (rs1927568: P=0.000083; odds ratio=3.778). A secondary analysis of familial component phenotypes of bipolar disorder detected significant association across multiple DOCK9 markers for racing thoughts, psychosis, delusion during mania and course of illness indicators. CONCLUSION: These results suggest that DOCK9 contributes to both risk and increased illness severity in bipolar disorder. We found evidence for the effect of phenotypic heterogeneity on association. To our knowledge this is the first report to implicate DOCK9 or the Rho-GTPase pathway in the etiology of bipolar disorder.
Asunto(s)
Trastorno Bipolar/genética , Predisposición Genética a la Enfermedad , Variación Genética , Factores de Intercambio de Guanina Nucleótido/genética , Polimorfismo de Nucleótido Simple , Trastorno Bipolar/fisiopatología , Familia , Femenino , Humanos , Desequilibrio de Ligamiento , Masculino , Fenotipo , Índice de Severidad de la EnfermedadRESUMEN
BACKGROUND: We have reported genetic linkage between bipolar disorder and markers on chromosome 6q16.3-22.1 in the National Institute of Mental Health Genetics Initiative wave 3 pedigrees. Here we test for: 1) robustness of the linkage to differing analysis methods, genotyping error, and gender-specific maps; 2) parent-of-origin effects; and 3) interaction with markers within the schizophrenia linkage region on chromosome 6p. METHODS: Members of 245 families ascertained through a sibling pair affected with bipolar I or schizoaffective-bipolar disorder were genotyped with 18 markers spanning chromosome 6. Nonparametric linkage analysis was performed. RESULTS: Linkage to 6q is robust to analysis method, gender-specific map differences, and genotyping error. The locus confers a 1.4-fold increased risk. Affected siblings share the maternal more often than the paternal chromosome (p =.006), which could reflect a maternal parent-of-origin effect. There is a positive correlation between family-specific linkage scores on 6q and those on 6p22.2 (r =.26; p <.0001). Linkage analysis for each locus conditioned on evidence of linkage to the other increases the evidence for linkage at both loci (p <.0005). Logarithm of the odds (LOD) scores increased from 2.26 to 5.42 on 6q and from.35 to 2.26 on 6p22.2. CONCLUSIONS: These results support linkage of bipolar disorder to 6q, uncover a maternal parent-of-origin effect, and demonstrate an interaction of this locus with one on chromosome 6p22.2, previously linked only to schizophrenia.
Asunto(s)
Trastorno Bipolar/genética , Cromosomas Humanos Par 6 , Ligamiento Genético , Predisposición Genética a la Enfermedad , Trastorno Bipolar/epidemiología , Epistasis Genética , Femenino , Humanos , Escala de Lod , Masculino , National Institute of Mental Health (U.S.) , Linaje , Trastornos Psicóticos/genética , Esquizofrenia/genética , Estados Unidos/epidemiologíaRESUMEN
The major mood disorders, which include bipolar disorder and major depressive disorder (MDD), are considered heritable traits, although previous genetic association studies have had limited success in robustly identifying risk loci. We performed a meta-analysis of five case-control cohorts for major mood disorder, including over 13,600 individuals genotyped on high-density SNP arrays. We identified SNPs at 3p21.1 associated with major mood disorders (rs2251219, P = 3.63 x 10(-8); odds ratio = 0.87; 95% confidence interval, 0.83-0.92), with supportive evidence for association observed in two out of three independent replication cohorts. These results provide an example of a shared genetic susceptibility locus for bipolar disorder and MDD.