Animal studies have strongly implicated a role of S100B in spatial ability and our recent study of humans found that S100B gene polymorphisms (rs9722, rs1051169, and rs2839357) were associated with schizophrenia patients' spatial ability (as assessed by a block design task and a mental rotation task). In this study, we explored the associations between these and three additional SNPs in S100B and prefrontal functions (working memory and executive control) among 434 schizophrenia patients and 412 healthy controls. Results showed that, for both schizophrenia patients and healthy controls, two SNPs were significantly associated with prefrontal functions in the spatial domain (P value threshold was set at 0.014 after correcting for multiple comparisons), with the AA genotype of rs9722 and the GG genotype of rs2839357 linked to poorer performance. No SNP was associated with prefontal functions in the verbal domain (all Ps >0.05). These results extend our previous study and further confirm the important roles of the S100B gene in spatial abilities.

CACNA1C gene polymorphism (rs1006737) is a susceptibility factor for both schizophrenia (SCZ) and bipolar disorder (BP). However, its role in working memory, a cognitive function that is impaired in both diseases, is not clear. Using three samples, including healthy controls, patients with SCZ, and patients currently in manic episodes of BP, this study tested the association between the SNP rs1006737 and spatial working memory as measured by an N-back task and a dot pattern expectancy (DPX) task. Among SCZ patients and healthy controls, the clinical risk allele was associated with impaired working memory, but the association was either in opposite direction or non-significant in patients with BP. These results indicated that rs1006737 may have differential effects on working memory in different disease populations and pointed to the necessity for more studies in different patient populations.

Rs9722 and rs1051169 have been reported as affecting the levels of S100B in the serum or the brain, and haplotypes containing these two SNPs have been associated with schizophrenia. The current study investigated the role of the S100B gene in an endophenotype of schizophrenia-spatial disability. 304 schizophrenia patients and 196 healthy controls were given a block design task and a mental rotation task. Results showed that the two aforementioned SNPs and related haplotypes were associated with the spatial disability of schizophrenia patients. Specifically, risk factors for the elevated S100B levels, including the A allele of rs9722, the G allele of rs1051169, and the AG haplotype, were associated with a poorer performance on both tests of spatial ability, especially the mental rotation task. These results implicate a role for S100B gene polymorphisms in the cognitive functions of schizophrenia patients and encourage further investigation into spatial disability as an endophenotype of schizophrenia.

ZNF804A gene polymorphism rs1344706 has been suggested as the most compelling case of a candidate gene for schizophrenia by a genome-wide association study and several replication studies. The current study of 570 schizophrenia patients and 448 controls again found significantly different genotype frequencies of rs1344706 between patients and controls. More important, we found that this association was modulated by IQ, with a stronger association among individuals with relatively high IQ, which replicated results of Walters et al, 2010. We further examined whether this IQ-modulated association also existed between the SNP and the intermediate phenotypes (working memory and executive functions) of schizophrenia. Data were available from an N-back task (366 patients and 414 controls) and the attention network task (361 patients and 416 controls). We found that the SNP and IQ had significant interaction effects on the intermediate phenotypes for patients, but not for controls. The disease risk allele was associated with poorer cognitive function in patients with high IQ, but better cognitive function in patients with low IQ. Together, these results indicated that IQ may modulate the role of rs1344706 in the etiology of both schizophrenia and its cognitive impairments, and pointed to the necessity of considering general cognitive function as indexed by IQ in the future studies of genetic bases of schizophrenia.