Three small schizophrenia GWAS (178-738 cases) have tested association to SNPs using individual genotyping, (61-63) and two others (69, 70) used pooled genotyping (not included in Table 3). No genomewide significant finding has emerged yet for schizophrenia alone, but when the 12 “best” SNPs from a GWAS of 479 cases and 2,937 WTCCC controls were genotyped in an additional 7,308 schizophrenia cases and 12,834 controls, and the 1,868 WTCCC bipolar disorder cases were added to the analysis, a genomewide significant p-value was seen for a SNP in a gene of unknown function (ZNF804A, zinc finger protein 804A). (63) This will require replication in these disorders both separately and combined. It illustrates the potential importance of cross-diagnosis analyses, although these will increase the problem of multiple testing and thus require very large samples for confirmation.
