Confirmation of the genetic association between the U2AF homology motif (UHM) kinase 1 (UHMK1) gene and schizophrenia on chromosome 1q23.3.

UHMK1 has previously been implicated as a susceptibility gene for schizophrenia in the 1q23.3 region by significant evidence of allelic and haplotypic association between schizophrenia and several genetic markers at UHMK1 in a London-based case-control sample. Further fine mapping of the UHMK1 gene locus in the University College London schizophrenia case-control sample was carried out with tagging SNPs. Two additional SNPs were found to be associated with schizophrenia (rs6604863 P = 0.02, rs10753578 P = 0.017). Tests of allelic and haplotypic association were then carried out in a second independent sample from Aberdeen consisting of 858 individuals with schizophrenia and 591 controls. Two of these SNPs also showed association in the Aberdeen sample (rs7513662 P = 0.0087, rs10753578 P = 0.022) and several haplotypes were associated (global permutation P = 0.0004). When the UCL and Aberdeen samples were combined three SNPs (rs7513662 P = 0.0007, rs6427680 P = 0.0252, rs6694863 P = 0.015) and several haplotypes showed association (eg HAP-A, HAP-B, HAP-C permutation P = 0.00005). The finding of allelic association with markers in the UHMK1 gene might help explain why it has not been possible, despite great effort, to satisfactorily confirm previously reported associations between schizophrenia and the genes RGS4 and NOS1AP/CAPON. These genes flank UHMK1 and all three loci are within a 700 kb region showing linkage to schizophrenia. The confirmation of association between UHMK1 and schizophrenia, rather than RGS4 and NOS1AP in the London sample, points to the possibility that previous efforts to accurately fine map a gene in the 1q23.3 region have lacked accuracy or may have suffered from methodological flaws.

Fine mapping by genetic association implicates the chromosome 1q23.3 gene UHMK1, encoding a serine/threonine protein kinase, as a novel schizophrenia susceptibility gene.

BACKGROUND: Linkage studies by us and others have confirmed that chromosome 1q23.3 is a susceptibility locus for schizophrenia. Based on this information, several research groups have published evidence that markers within both the RGS4 and CAPON genes, which are 700 kb apart, independently showed allelic association with schizophrenia. Tests of allelic association with both of these genes in our case control sample were negative. Therefore, we carried out further fine mapping between the RGS4 and CAPON genes. METHODS: Twenty-nine SNP and microsatellite markers in the 1q23.3 region were genotyped in the United Kingdom based sample of 450 cases and 450 supernormal control subjects. RESULTS: We detected positive allelic association after the eighth marker was genotyped and found that three microsatellite markers (p = .011, p = .014, p = .049) and two SNPs (p = .004, p = .043) localized in the 700 kb region between the RGS4 and CAPON genes, within the UHMK1 gene, were associated with schizophrenia. Tests of significance for marker rs10494370 remained significant following Bonferroni correction (alpha = .006) for multiple tests. Tests of haplotypic association were also significant for UHMK1 (p = .009) using empirical permutation tests, which make it unnecessary to further correct for both multiple alleles and multiple markers. CONCLUSIONS: These results provide preliminary evidence that the UHMK1 gene increases susceptibility to schizophrenia. Further confirmation in adequately powered samples is needed. UHMK1 is a serine threonine kinase nuclear protein and is highly expressed in regions of the brain implicated in schizophrenia.

Genetic association and brain morphology studies and the chromosome 8p22 pericentriolar material 1 (PCM1) gene in susceptibility to schizophrenia.

CONTEXT: There is evidence of linkage to a schizophrenia susceptibility locus on chromosome 8p21-22 found by several family linkage studies. OBJECTIVES: To fine map and identify a susceptibility gene for schizophrenia on chromosome 8p22 and to investigate the effect of this genetic susceptibility on an endophenotype of abnormal brain structure using magnetic resonance imaging. DESIGN: Fine mapping and identification of a chromosome 8p22 susceptibility gene was carried out by finding linkage disequilibrium between genetic markers and schizophrenia in multiply affected families, a case-control sample, and a trio sample. Variation in brain morphology associated with pericentriolar material 1 (PCM1) alleles was examined using voxel-based morphometry and statistical parametric mapping with magnetic resonance imaging. Setting and Patients A family sample of 13 large families multiply affected with schizophrenia, 2 schizophrenia case-control samples from the United Kingdom and Scotland, and a sample of schizophrenic trios from the United States containing parents and 1 affected child with schizophrenia. MAIN OUTCOME MEASURES: Tests of transmission disequilibrium between PCM1 locus polymorphisms and schizophrenia using a family sample and tests of allelic association in case-control and trio samples. Voxel-based morphometry using statistical parametric mapping. RESULTS: The family and trio samples both showed significant transmission disequilibrium between marker D85261 in the PCM1 gene locus and schizophrenia. The case-control sample from the United Kingdom also found significant allelic association between PCM1 gene markers and schizophrenia. Voxel-based morphometry of cases who had inherited a PCM1 genetic susceptibility showed a significant relative reduction in the volume of orbitofrontal cortex gray matter in comparison with patients with non-PCM1-associated schizophrenia, who, by contrast, showed gray matter volume reduction in the temporal pole, hippocampus, and inferior temporal cortex. CONCLUSIONS: The PCM1 gene is implicated in susceptibility to schizophrenia and is associated with orbitofrontal gray matter volumetric deficits.

Failure to confirm allelic association between markers at the CAPON gene locus and schizophrenia in a British sample.

BACKGROUND: Linkage studies have confirmed that chromosome 1q23.3 is a susceptibility locus for schizophrenia. It was then claimed that markers at the carboxyl-terminal PDZ ligand of neuronal nitric oxide synthase (CAPON) gene showed allelic association with schizophrenia in Canadian families. A second Chinese study found a base pair polymorphism at the CAPON gene also associated with schizophrenia. METHODS: We attempted replication using eight markers from the Canadian study in a UK based sample of 450 cases and 450 supernormal controls. RESULTS: We found no evidence for allelic or haplotypic association with schizophrenia for any of the markers found to be associated in the Canadian sample. CONCLUSIONS: The negative results might reflect genetic heterogeneity between the Canadian, Chinese and UK samples or be due to methodological problems. The present finding weakens the evidence that mutations or variation in the CAPON gene are causing genetic susceptibility to schizophrenia in European populations.

Case-case genome-wide association analysis shows markers differentially associated with schizophrenia and bipolar disorder and implicates calcium channel genes.

OBJECTIVE: There are theoretical reasons why comparing marker allele frequencies between cases of different diseases, rather than with controls, may offer benefits. The samples may be better matched, especially for background risk factors common to both diseases. Genetic loci may also be detected which influence which of the two diseases occurs if common risk factors are present. METHOD: We used samples of UK bipolar and schizophrenic cases that had earlier been subject to genome-wide association studies and compared marker allele frequencies between the two samples. When these differed for a marker, we compared the case sample allele frequencies with those of a control sample. RESULTS: Eight markers were significant at P value of less than 10(-5). Of these, the most interesting finding was for rs17645023, which was significant at P value of less than 10(-6) and which lies 36 kb from CACNG5. Control allele frequencies for this marker were intermediate between those for bipolar and schizophrenic cases. CONCLUSION: The application of this approach suggests that it does have some merits. The finding for CACNG5, taken together with the earlier implication of CACNA1C and CACNA1B, strongly suggests a key role for voltage-dependent calcium channel genes in the susceptibility to bipolar disorder and/or schizophrenia.

A genetic association study of chromosome 11q22-24 in two different samples implicates the FXYD6 gene, encoding phosphohippolin, in susceptibility to schizophrenia.

Previous linkage analyses of families with multiple cases of schizophrenia by us and others have confirmed the involvement of the chromosome 11q22-24 region in the etiology of schizophrenia, with LOD scores of 3.4 and 3.1. We now report fine mapping of a susceptibility gene in the 11q22-24 region, determined on the basis of a University College London (UCL) sample of 496 cases and 488 supernormal controls. Confirmation was then performed by the study of an Aberdeen sample consisting of 858 cases and 591 controls (for a total of 2,433 individuals: 1,354 with schizophrenia and 1,079 controls). Seven microsatellite or single-nucleotide polymorphism (SNP) markers localized within or near the FXYD6 gene showed empirically significant allelic associations with schizophrenia in the UCL sample (for D11S1998, P=.021; for rs3168238, P=.009; for TTTC20.2, P=.048; for rs1815774, P=.049; for rs4938445, P=.010; for rs4938446, P=.025; for rs497768, P=.023). Several haplotypes were also found to be associated with schizophrenia; for example, haplotype Hap-F21 comprising markers rs10790212-rs4938445-rs497768 was found to be associated with schizophrenia, by a global permutation test (P=.002). Positive markers in the UCL sample were then genotyped in the Aberdeen sample. Two of these SNPs were found to be associated with schizophrenia in the Scottish sample (for rs4938445, P=.044; for rs497768, P=.037). The Hap-F21 haplotype also showed significant association with schizophrenia in the Aberdeen sample, with the same alleles being associated (P=.013). The FXYD6 gene encodes a protein called "phosphohippolin" that is highly expressed in regions of the brain thought to be involved in schizophrenia. The protein functions by modulating the kinetic properties of Na,K-ATPase to the specific physiological requirements of the tissue. Etiological base-pair changes in FXYD6 or in associated promoter/control regions are likely to cause abnormal function or expression of phosphohippolin and to increase genetic susceptibility to schizophrenia.