We report the first genome-wide association study in 1000 bipolar I patients and 1000 controls, with a replication of the top hits in another 409 cases and 1000 controls in the Han Chinese population. Four regions with most strongly associated single-nucleotide polymorphisms (SNPs) were detected, of which three were not found in previous GWA studies in the Caucasian populations. Among them, SNPs close to specificity protein 8 (SP8) and ST8 a-Nacetyl-neuraminide a-2,8-sialyltransferase (ST8SIA2) are associated with Bipolar I, with Pvalues of 4.87 Â 10 À7 (rs2709736) and 6.05 Â 10 À6 (rs8040009), respectively. We have also identified SNPs in potassium channel tetramerization domain containing 12 gene (KCTD12) (rs2073831, P = 9.74 Â 10 À6 ) and in CACNB2 (Calcium channel, voltage-dependent, b-2 subunit) gene (rs11013860, P = 5.15 Â 10 À5 ), One SNP nearby the rs1938526 SNP of ANK3 gene and another SNP nearby the SNP rs11720452 in chromosome 3 reported in previous GWA studies also showed suggestive association in this study (P = 6.55 Â 10 À5 and P = 1.48 Â 10 À5 , respectively). This may suggest that there are common and population-specific susceptibility genes for bipolar I disorder.

Our findings are in line with those of animal studies, and show that KCNK2 is related to the susceptibility to MDD, and involved in antidepressant treatment response. However, the finding of heterosis association of rs6686529 and MDD may be mechanistic, and further replication studies will be essential.

ObjectivesThe forced swim test (FST) is a commonly used model to predict antidepressant efficacy. Uncovering the genetic basis of the model may unravel the mechanism of antidepressant treatment.MethodsFVB/NJ (FVB) and C57BL/6J (B6) were first identified as the response and non-response strains to fluoxetine (a serotonin-specific reuptake inhibitor antidepressant) treatment in the mouse FST. Simple-interval (SIM) and composite-interval (CIM) mappings were applied to map the quantitative trait loci (QTLs) of the anti-immobility effect of fluoxetine in FST (FSTFLX) in 865 male B6×FVB-F2 mice. The brain mRNA expressions of the gene with the maximum QTL-linkage signal for FSTFLX after the FST were compared between B6 and FVB mice and also compared between fluoxetine and saline treatment. The association of the variants in the human homologue of the mouse FSTFLX-QTL gene with major depressive disorder (MDD) and antidepressant response were investigated in 1080 human subjects (MDD/control = 582/498).ResultsOne linkage signal for FSTFLX-QTL was detected at an intronic SNP (rs6215396) of the mouse Zfp326 gene (maximal CIM-LOD = 9.36). The Zfp326 mRNA expression in the FVB thalamus was significantly down-regulated by fluoxetine in the FST, and the higher FVB-to-B6 Zfp326 mRNA expressions in the frontal cortex, striatum and hypothalamus diminished after fluoxetine treatment. Two coding-synonymous SNPs (rs2816881 and rs10922744) in the human homologue of Zfp326, ZNF326, were significantly associated with the 8-week antidepressant treatment response in the MDD patients (Bonferroni-corrected p = 0.004–0.028).ConclusionsThe findings suggest the involvement of the Zfp326 and ZNF326 genes in antidepressant treatment response.

Genetic variations in the PAWR gene are related to susceptibility to MDD but not to SSRI treatment response.