The standard and sex-specific AUDIT-Cs are effective screening tests for past-year hazardous drinking and/or active alcohol abuse or dependence in female patients in a VA study.
Context: Exploration of the genetic architecture of specific endophenotypes may be a powerful strategy for understanding the genetic basis of schizophrenia.Objective: To characterize the genetic architecture of some key endophenotypic measures selected for their reported heritabilities in schizophrenia.Design: Family-based heritability study.
Objective
We have used a custom 1,536-SNP array to interrogate 94 functionally relevant candidate genes for schizophrenia and identify associations with 12 heritable neurophysiological and neurocognitive endophenotypes collected as part of the Consortium on the Genetics of Schizophrenia (COGS).
Method
Variance-component association analyses of 534 genotyped subjects from 130 families were conducted using Merlin. A novel bootstrap Total Significance Test was also developed to overcome the limitations of existing genomic multiple testing methods and robustly demonstrate the presence of significant associations in the context of complex family data and possible population stratification effects.
Results
Associations were observed for 46 genes of potential functional significance with 3 SNPs at p<10−4, 27 SNPs at p<10−3, and 147 SNPs at p<0.01. The bootstrap analyses confirmed that the 47 SNP-endophenotype combinations with the strongest evidence of association significantly exceeded (p=0.001) that expected by chance alone with 93% of these findings expected to be true. Many of the genes interact on a molecular level, and eight genes displayed evidence for pleiotropy (e.g., NRG1 and ERBB4), revealing associations with four or more endophenotypes. Our results collectively support a strong role for genes related to glutamate signaling in mediating schizophrenia susceptibility.
Conclusions
This study supports the use of relevant endophenotypes and the bootstrap Total Significance Test for the identification of genetic variation underlying the etiology of schizophrenia. In addition, the observation of extensive pleiotropy for some genes and singular associations for others in our data suggests alternative, independent pathways mediating pathogenesis in the “group of schizophrenias”.
Successful multisite genetics collaborations must institute standardized methodological criteria for assessment and recruitment that are clearly defined, well communicated, and uniformly applied. In parallel, studies utilizing endophenotypes require strict adherence to criteria for cross-site data acquisition, equipment calibration and testing and software equivalence, and continuous quality assurance for many measures obtained across sites. This report describes methods and presents the structure of the COGS as a model of multisite endophenotype genetic studies. It also provides demographic information after the first 2 years of data collection on a sample for whom the behavioral data and genetics of endophenotype performance will be fully characterized in future articles. Some issues discussed in the reviews that follow reflect the challenges of evaluating endophenotypes in studies of the genetic architecture of endophenotypes in schizophrenia.
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