Linkage Analyses of Event-Related Potential Slow Wave Phenotypes Recorded in a Working Memory Task

Case control study of association between the ANK3 rs10761482 polymorphism and schizophrenia in persons of Uyghur nationality living in Xinjiang China

Background

The rs10761482 polymorphism of the ANK3 gene has been associated with the occurrence of schizophrenia.

Aim

Assess the relationship between the ANK3 gene and schizophrenia in individuals of Uyghurian descent.

Methods

A total of 630 patients with schizophrenia and 535 healthy controls of Uyghur descent were genotyped for the ANK3 gene rs10761482 locus using Taqman probe technology. SHEsis and SPSS17.0 software were used for data analysis.

Results

There were no significant differences in the genotype or allele frequencies between the case group and control group. Within the case group there was no relationship between gender or age of onset of schizophrenia and the genotype or allele frequencies. Separate analyses among men and among women also failed to identify significant differences in the allele and genotype frequencies between cases and controls or between patients with adolescent-onset schizophrenia and those with adult-onset schizophrenia

Conclusion

Our findings do not support previous reports about the relationship of the ANK3 gene and schizophrenia. In the Uyghur nationality group recruited for this study there was no significant association between the ANK3 gene rs10761482 polymorphism and schizophrenia. If these results are replicated in further studies, then the focus should change to understanding why this widely acknowledged association does not exist in this particular ethnic group.

Genetic modulation of working memory deficits by ankyrin 3 gene in schizophrenia

Neuropsychological endophenotype approach is an emerging strategy in schizophrenia research to understand and identify the functional importance of genetically transmitted, brain-based deficits present in this disorder. Accumulating evidence indicated that working memory deficit is a core neuropsychological dysfunction in schizophrenia and a primary endophenotype indexing the liability to develop schizophrenia. Genetic variation in ankyrin 3 gene (ANK3) is likely to have widespread cognitive effects. Our previous study has identified a significant association of ANK3 SNPs and schizophrenia. In this study, we aimed to examine whether the schizophrenia-risk SNPs within ANK3 may affect working memory deficits in schizophrenia patients. Herein, we assess the working memory performance in 163 patients with first-episode, antipsychotic-naïve schizophrenia and 42 sex, age-matched healthy subjects using N-back task. Two SNPs rs10761482 and rs10994336 were genotyped among the patients and 209 controls. Our results showed that schizophrenia patients showed significantly poorer performance than healthy controls on N-back task (ps<0.01). After adjusting for the scores of intelligence quotient, memory quotient and the demographic factors, there was a significant genotype effect of the rs10994336 on the accuracy rate and reaction time of 2-back item (p=0.048 and 0.024, respectively). Post-hoc analyses showed that patients with rs10994336T/T genotype had significantly lower accuracy rate and more reaction time at 2-back task than those with T/C and C/C genotypes. The association of SNP rs10994336 with schizophrenia was replicated in our sample (genotypic p=0.024 and allelic p=0.006). However, we did not find any significant association of rs10761482 with schizophrenia and parameters in N-back task. Our results indicated that genetic variation within ANK3 may exert gene-specific modulating effects on working memory deficits in schizophrenia.

Genetic overlap among intelligence and other candidate endophenotypes for schizophrenia

BACKGROUND

A strategy to improve genetic studies of schizophrenia involves the use of endophenotypes. Information on overlapping genetic contributions among endophenotypes may provide additional power, reveal biological pathways, and have practical implications for genetic research. Several cognitive endophenotypes, including intelligence, are likely to be modulated by overlapping genetic influences.

METHODS

We quantified potential genetic and environmental correlations among endophenotypes for schizophrenia, including sensorimotor gating, openness, verbal fluency, early visual perception, spatial working memory, and intelligence, using variance component models in 35 patients and 145 relatives from 25 multigenerational Dutch families multiply affected with schizophrenia.

RESULTS

Significant correlations were found between spatial working memory and intelligence (.45), verbal fluency and intelligence (.36), verbal fluency and spatial working memory (.20), and early visual perception and spatial working memory (.19). A strong genetic correlation (.75) accounted for 76% of the variance shared between spatial working memory and intelligence. Significant environmental correlations were found between verbal fluency and openness (.50) and between verbal fluency and spatial working memory (.58). Sensorimotor gating and openness showed few genetic or environmental correlations with other endophenotypes.

CONCLUSIONS

Our results suggest that intelligence strongly overlaps genetically with a known cognitive endophenotype for schizophrenia. Intelligence may thus be a promising endophenotype for genetic research in schizophrenia, even though the underlying genetic mechanism may still be complex. In contrast, sensorimotor gating and openness appear to represent separate genetic entities with simpler inheritance patterns and may therefore augment the detection of separate genetic pathways contributing to schizophrenia.

QTLs identified for P3 amplitude in a non-clinical sample: importance of neurodevelopmental and neurotransmitter genes

BACKGROUND

The P3(00) event-related potential is an index of processing capacity (P3 amplitude) and stimulus evaluation (P3 latency) as well as a phenotypic marker of various forms of psychopathology where P3 abnormalities have been reported.

METHODS

A genome-wide linkage scan of 400-761 autosomal markers, at an average spacing of 5-10 centimorgans (cM), was completed in 647 twins/siblings (306 families mostly comprising dizygotic twins), mean age 16.3, range 15.4-20.1 years, for whom P3 amplitude and latency data were available.

RESULTS

Significant linkage for P3 amplitude was observed on chromosome 7q for the central recording site (logarithm-of-odds [LOD] = 3.88, p = .00002) and in the same region for both frontal (LOD = 2.19, p = .0015) and parietal (LOD = 1.67, p = .0053) sites, with multivariate analysis also identifying linkage in this region (LOD = 2.14, p = .0017). Suggestive linkage was also identified on 6p (LOD(max) = 2.49) and 12q (LOD(max) = 2.24), with other promising regions identified on 9q (LOD(max) = 2.14) and 10p (LOD(max) = 2.18). Less striking were the results for P3 latency; LOD > 1.5 were found on chromosomes 1q, 9q, 10q, 12q, and 19p.

CONCLUSIONS

This is a first step in the identification of genes for normal variation in the P3. Loci identified here for P3 amplitude suggest the possible importance of neurodevelopmental genes in addition to those influencing neurotransmitters, fitting with the evidence that P3 amplitude is sensitive to diverse types of brain abnormalities.

Genetic covariation between event-related potential (ERP) and behavioral non-ERP measures of working-memory, processing speed, and IQ

The aim of this study was to identify genetic covariants for fundamental measures of brain function (event-related potentials (ERPs): P300 latency and slow wave amplitude recorded in a working-memory task) and more complex cognitive measures (behavioral non-ERP measures: working-memory performance, information processing speed, IQ). Data were collected from 252 monozygotic and 297 dizygotic twin pairs aged 16. Multivariate modeling identified two independent genetic factors associated with processing speed that also influenced working-memory performance (one reflected the duration of neural activity required to evaluate target information, the other reflected more general cognitive and speed-related abilities). However, the allocation of neural resources, as assessed by ERP slow wave amplitude measures, was not associated with the other cognitive measures investigated. Thus, of the ERP measures examined, P300 latency, but not slow wave amplitude, may be an informative measure to include (i.e., with working-memory performance) in future multivariate linkage and association analyses of cognitive function.