Differential effects of chronic stress in young-adult and old female mice: cognitive-behavioral manifestations and neurobiological correlates.

Stress-related psychopathology is highly prevalent among elderly individuals and is associated with detrimental effects on mood, appetite and cognition. Conversely, under certain circumstances repeated mild-to-moderate stressors have been shown to enhance cognitive performance in rodents and exert stress-inoculating effects in humans. As most stress-related favorable outcomes have been reported in adolescence and young-adulthood, this apparent disparity could result from fundamental differences in how aging organisms respond to stress. Furthermore, given prominent age-related alterations in sex hormones, the effect of chronic stress in aging females remains a highly relevant yet little studied issue. In the present study, female C57BL/6 mice aged 3 (young-adult) and 20-23 (old) months were subjected to 8 weeks of chronic unpredictable stress (CUS). Behavioral outcomes were measured during the last 3 weeks of the CUS protocol, followed by brain dissection for histological and molecular end points. We found that in young-adult female mice, CUS resulted in decreased anxiety-like behavior and enhanced cognitive performance, whereas in old female mice it led to weight loss, dysregulated locomotion and memory impairment. These phenotypes were paralleled by differential changes in the expression of hypothalamic insulin and melanocortin-4 receptors and were consistent with an age-dependent reduction in the dynamic range of stress-related changes in the hippocampal transcriptome. Supported by an integrated microRNA (miRNA)-mRNA expression analysis, the present study proposes that, when confronted with ongoing stress, neuroprotective mechanisms involving the upregulation of neurogenesis, Wnt signaling and miR-375 can be harnessed more effectively during young-adulthood. Conversely, we suggest that aging alters the pattern of immune activation elicited by stress. Ultimately, interventions that modulate these processes could reduce the burden of stress-related psychopathology in late life.

Alterations in the expression of a neurodevelopmental gene exert long-lasting effects on cognitive-emotional phenotypes and functional brain networks: translational evidence from the stress-resilient Ahi1 knockout mouse.

Many psychiatric disorders are highly heritable and may represent the clinical outcome of early aberrations in the formation of neural networks. The placement of brain connectivity as an 'intermediate phenotype' renders it an attractive target for exploring its interaction with genomics and behavior. Given the complexity of genetic make up and phenotypic heterogeneity in humans, translational studies are indicated. Recently, we demonstrated that a mouse model with heterozygous knockout of the key neurodevelopmental gene Ahi1 displays a consistent stress-resilient phenotype. Extending these data, the current research describes our multi-faceted effort to link early variations in Ahi1 expression with long-term consequences for functional brain networks and cognitive-emotional phenotypes. By combining behavioral paradigms with graph-based analysis of whole-brain functional networks, and then cross-validating the data with robust neuroinformatic data sets, our research suggests that physiological variation in gene expression during neurodevelopment is eventually translated into a continuum of global network metrics that serve as intermediate phenotypes. Within this framework, we suggest that organization of functional brain networks may result, in part, from an adaptive trade-off between efficiency and resilience, ultimately culminating in a phenotypic diversity that encompasses dimensions such as emotional regulation and cognitive function.

Convergent lines of evidence support CAMKK2 as a schizophrenia susceptibility gene.

Genes that are differentially expressed between schizophrenia patients and healthy controls may have key roles in the pathogenesis of schizophrenia. We analyzed two large-scale genome-wide expression studies, which examined changes in gene expression in schizophrenia patients and their matched controls. We found calcium/calmodulin (CAM)-dependent protein kinase kinase 2 (CAMKK2) is significantly downregulated in individuals with schizophrenia in both studies. To seek the potential genetic variants that may regulate the expression of CAMKK2, we investigated the association between single-nucleotide polymorphisms (SNPs) within CAMKK2 and the expression level of CAMKK2. We found one SNP, rs1063843, which is located in intron 17 of CAMKK2, is strongly associated with the expression level of CAMKK2 in human brains (P=1.1 × 10(-6)) and lymphoblastoid cell lines (the lowest P=8.4 × 10(-6)). We further investigated the association between rs1063843 and schizophrenia in multiple independent populations (a total of 130 623 subjects) and found rs1063843 is significantly associated with schizophrenia (P=5.17 × 10(-5)). Interestingly, we found the T allele of rs1063843, which is associated with lower expression level of CAMKK2, has a higher frequency in individuals with schizophrenia in all of the tested samples, suggesting rs1063843 may be a causal variant. We also found that rs1063843 is associated with cognitive function and personality in humans. In addition, protein-protein interaction (PPI) analysis revealed that CAMKK2 participates in a highly interconnected PPI network formed by top schizophrenia genes, which further supports the potential role of CAMKK2 in the pathogenesis of schizophrenia. Taken together, these converging lines of evidence strongly suggest that CAMKK2 may have pivotal roles in schizophrenia susceptibility.

Neural mechanisms underlying stress resilience in Ahi1 knockout mice: relevance to neuropsychiatric disorders.

The Abelson helper integration site 1 (AHI1) gene has a pivotal role in brain development. Studies by our group and others have demonstrated association of AHI1 with schizophrenia and autism. To elucidate the mechanism whereby alteration in AHI1 expression may be implicated in the pathogenesis of neuropsychiatric disorders, we studied Ahi1 heterozygous knockout (Ahi1(+/-)) mice. Although their performance was not different from wild-type mice on tests that model classical schizophrenia-related endophenotypes, Ahi1(+/-) mice displayed an anxiolytic-like phenotype across different converging modalities. Using behavioral paradigms that involve exposure to environmental and social stress, significantly decreased anxiety was evident in the open field, elevated plus maze and dark-light box, as well as during social interaction in pairs. Assessment of core temperature and corticosterone secretion revealed a significantly blunted response of the autonomic nervous system and the hypothalamic-pituitary-adrenal axis in Ahi1(+/-) mice exposed to environmental and visceral stress. However, response to centrally acting anxiogenic compounds was intact. On resting-state functional MRI, connectivity of the amygdala with other brain regions involved in processing of anxiogenic stimuli and inhibitory avoidance learning, such as the lateral entorhinal cortex, ventral hippocampus and ventral tegmental area, was significantly reduced in the mutant mice. Taken together, our data link Ahi1 under-expression with a defect in the process of threat detection. Alternatively, the results could be interpreted as representing an anxiety-related endophenotype, possibly granting the Ahi1(+/-) mouse relative resilience to various types of stress. The current knockout model highlights the contribution of translational approaches to understanding the genetic basis of emotional regulation and its associated neurocircuitry, with possible relevance to neuropsychiatric disorders.

Support for association of HSPG2 with tardive dyskinesia in Caucasian populations.

Tardive dyskinesia (TD) is a severe adverse effect of chronic antipsychotic drug treatment. In addition to clinical risk factors, TD susceptibility is influenced by genetic predisposition. Recently, Syu et al. (2010) reported a genome-wide association screening of TD in Japanese schizophrenia patients. The best result was association of single-nucleotide polymorphism (SNP) rs2445142 in the HSPG2 (heparan sulfate proteoglycan 2) gene with TD. In the present study, we report a replication study of the five top Japanese TD-associated SNPs in two Caucasian TD samples. Applying logistic regression and controlling for relevant clinical risk factors, we were able to replicate the association of HSPG2 SNP rs2445142 with TD in a prospective study sample of 179 Americans of European origin by performing a secondary analysis of the CATIE (Clinical Antipsychotic Trials of Intervention Effectiveness) genome-wide association study data set, and using a perfect proxy surrogate marker (rs878949; P = 0.039). An association of the 'G' risk allele of HSPG2 SNP rs2445142 with TD was also shown in a sample of Jewish Israeli schizophrenia patients (retrospective, cross-sectional design; P = 0.03). Although the associations were only nominally significant, the findings provide further support for the possible involvement of HSPG2 in susceptibility to TD.

Effect of triiodothyronine on antidepressant screening tests in mice and on presynaptic 5-HT1A receptors: mediation by thyroid hormone α receptors.

Although triiodothyronine (T3) is widely used clinically, preclinical support for its antidepressant-like effects is limited, and the mechanisms are unknown. We evaluated 1) the antidepressant-like effects of T3 in the novelty suppressed feeding test (NSFT), tail suspension test (TST), and forced swim test (FST), 2) the role of presynaptic 5-HT(1A) receptors in the antidepressant-like mechanism of T3 by the hypothermic response to the 5-HT(1A) receptor agonist, 8-hydroxy-N,N-dipropyl-2-aminotetralin (8-OH-DPAT), 3) the thyroid hormone receptor type mediating the antidepressant-like effects by concurrent administration of the specific thyroid hormone α receptor (TRα) antagonist, dronedarone, and 4) the presence of these effects in both genders. Male and female BALB/c mice were administered 1) T3 (20, 50, 200, or 500 µg/kg per day) or vehicle or 2) T3 (50 µg/kg per day), dronedarone (100 µM/day), or the combination intraperitoneally for 21 days and then underwent a behavioral test battery. The NSFT showed a shortened latency to feed in males at the two lower T3 doses. The TST and FST showed decreased immobility in male mice at T3 doses >20 µg/kg per day and in females at all T3 doses. Concurrent dronedarone prevented T3 effects in males on the NSFT and in the TST and FST in both genders. Attenuation of 8-OH-DPAT-induced hypothermia was observed in males only and may be reduced by concurrent dronedarone. These findings support an antidepressant-like effect of T3. Attenuation of 8-OH-DPAT-induced hypothermia in males only suggests the need to evaluate a possible gender disparity in the role of presynaptic 5-HT(1A) receptors in T3 antidepressant mechanisms. Blockade by dronedarone of the antidepressant-like effects of T3 suggests that these effects are TRα receptor-mediated.

Why do young women smoke? VI. A controlled study of nicotine effects on attention: pharmacogenetic interactions.

In prior studies we found that young, female smokers manifest poorer performance than non-smokers on attention-related tasks and that these findings can be moderated by variation in nicotinic acetylcholine receptor (nAChR) genes. We predicted that under controlled conditions (1) nicotine would improve functioning on attentional tasks in smokers who previously manifested relatively poor performance, and that (2) smokers who carry genetic variations associated with poorer attention performance would derive greater benefit from nicotine. To test these hypotheses, 31 young female smokers, who participated in our previous study, performed the Matching Familiar Figures Test (MFFT), Tower of London Test and Continuous Performance Task (CPT) in a double-blind, within-between subject design, placebo or nicotine (4 mg as gum) serving as the within factor and genetic profile as the between factor. Repeated measures ANCOVA controlling for attention deficit symptomatology, substance abuse and nicotine dependence showed better performance under nicotine among participants with higher levels of attention deficit symptoms (MFFT errors: P=0.04; CPT commissions: P=0.01) and nicotine dependence (CPT stability of response: P=0.04) and greater consumption of caffeine (CPT stability of response: P=0.04). An interactive effect of genetic profile was demonstrated for SNP rs2337980 in CHRNA7. These findings suggest that nicotine may have stronger short-term facilitating effects on attention in women who have more attention deficit symptoms and consume more nicotine and caffeine. This effect may be modified by a specific genetic make-up. Such individuals may be at increased risk for nicotine addiction and for greater difficulties in smoking cessation.

Differential contribution of genetic variation in multiple brain nicotinic cholinergic receptors to nicotine dependence: recent progress and emerging open questions.

Nicotine dependence (ND), a major public health challenge, is a complex, multifactorial behavior, in which both genetic and environmental factors have a role. Brain nicotinic acetylcholine receptor (nAChR)-encoding genes are among the most prominent candidate genes studied in the context of ND, because of their biological relevance as binding sites for nicotine. Until recently, most research on the role of nAChRs in ND has focused on two of these genes (encoding the alpha4- and beta2-subunits) and not much attention has been paid to the possible contribution of the other nine brain nAChR subunit genes (alpha2-alpha3, alpha5-alpha7, alpha9-alpha10, beta3-beta4) to the pathophysiology and genetics of ND. This situation has changed dramatically in the last 2 years during which intensive research had addressed the issue, mainly from the genetics perspective, and has shown the importance of the CHRNA5-CHRNA3-CHRNB4 and CHRNA6-CHRNB3 loci in ND-related phenotypes. In this review, we highlight recent findings regarding the contribution of non-alpha4/beta2-subunit containing nAChRs to ND, based on several lines of evidence: (1) human genetics studies (including linkage analysis, candidate-gene association studies and whole-genome association studies) of several ND-related phenotypes; (2) differential pharmacological and biochemical properties of receptors containing these subunits; (3) evidence from genetically manipulated mice; and (4) the contribution of nAChR genes to ND-related personality traits and neurocognitive profiles. Combining neurobiological genetic and behavioral perspectives, we suggest that genetic susceptibility to ND is not linked to one or two specific nAChR subtype genes but to several. In particular, the alpha3, alpha5-6 and beta3-4 nAChR subunit-encoding genes may play a much more pivotal role in the neurobiology and genetics of ND than was appreciated earlier. At the functional level, variants in these subunit genes (most likely regulatory) may have independent as well as interactive contributions to the ND phenotype spectrum. We address methodological challenges in the field, highlight open questions and suggest possible pathways for future research.

Meta-analysis of 32 genome-wide linkage studies of schizophrenia.

A genome scan meta-analysis (GSMA) was carried out on 32 independent genome-wide linkage scan analyses that included 3255 pedigrees with 7413 genotyped cases affected with schizophrenia (SCZ) or related disorders. The primary GSMA divided the autosomes into 120 bins, rank-ordered the bins within each study according to the most positive linkage result in each bin, summed these ranks (weighted for study size) for each bin across studies and determined the empirical probability of a given summed rank (P(SR)) by simulation. Suggestive evidence for linkage was observed in two single bins, on chromosomes 5q (142-168 Mb) and 2q (103-134 Mb). Genome-wide evidence for linkage was detected on chromosome 2q (119-152 Mb) when bin boundaries were shifted to the middle of the previous bins. The primary analysis met empirical criteria for 'aggregate' genome-wide significance, indicating that some or all of 10 bins are likely to contain loci linked to SCZ, including regions of chromosomes 1, 2q, 3q, 4q, 5q, 8p and 10q. In a secondary analysis of 22 studies of European-ancestry samples, suggestive evidence for linkage was observed on chromosome 8p (16-33 Mb). Although the newer genome-wide association methodology has greater power to detect weak associations to single common DNA sequence variants, linkage analysis can detect diverse genetic effects that segregate in families, including multiple rare variants within one locus or several weakly associated loci in the same region. Therefore, the regions supported by this meta-analysis deserve close attention in future studies.

Evidence for an interaction of schizophrenia susceptibility loci on chromosome 6q23.3 and 10q24.33-q26.13 in Arab Israeli families.

A genome scan for schizophrenia related loci in Arab Israeli families by Lerer et al. [Lerer et al. (2003); Mol Psychiatry 8:488-498] detected significant evidence for linkage at chromosome 6q23. Subsequent fine mapping [Levi et al. (2005); Eur J Hum Genet 13:763-771], association [Amann-Zalcenstein et al. (2006); Eur J Hum Genet 14:1111-1119] and replication studies [Ingason et al. (2007); Eur J Hum Genet 15:988-991] identified AHI1 as a putative susceptibility gene. The same genome scan revealed suggestive evidence for a schizophrenia susceptibility locus in the 10q23-26 region. Genes at these two loci may act independently in the pathogenesis of the disease in our homogeneous sample of Arab Israeli families or may interact with each other and with other factors in a common biological pathway. The purpose of our current study was to test the hypothesis of genetic interaction between these two loci and to identify the type of interaction between them. The initial stage of our study focused on the 10q23-q26 region which has not been explored further in our sample. The second stage of the study included a test for possible genetic interaction between the 6q23.3 locus and the refined 10q24.33-q26.13 locus. A final candidate region of 19.9 Mb between markers D10S222 (105.3 Mb) and D10S587 (125.2 Mb) was found on chromosome 10 by non-parametric and parametric linkage analyses. These linkage findings are consistent with previous reports in the same chromosomal region. Two-locus multipoint linkage analysis under three complex disease inheritance models (heterogeneity, multiplicative, and additive models) yielded a best maximum LOD score of 7.45 under the multiplicative model suggesting overlapping function of the 6q23.3 and 10q24.33-q26.13 loci.

Further evidence for association of the RGS2 gene with antipsychotic-induced parkinsonism: protective role of a functional polymorphism in the 3'-untranslated region.

RGS2 (regulator of G-protein signaling 2) modulates dopamine receptor signal transduction. Functional variants in the gene may influence susceptibility to extrapyramidal symptoms (EPS) induced by antipsychotic drugs. To further investigate our previous report of association of the RGS2 gene with susceptibility to antipsychotic-induced EPS, we performed a replication study. EPS were rated in 184 US patients with schizophrenia (115 African Americans, 69 Caucasian) treated for at least a month with typical antipsychotic drugs (n=45), risperidone (n=46), olanzapine (n=50) or clozapine (n=43). Six single nucleotide polymorphisms (SNPs) within or flanking RGS2 were genotyped (rs1933695, rs2179652, rs2746073, rs4606, rs1819741 and rs1152746). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by logistic regression. Our results indicate association of SNP rs4606 with antipsychotic-induced parkinsonism (AIP), as measured by the Simpson Angus scale, in the overall sample and in the African-American subsample, the G (minor) allele having a protective effect. ORs for AIP among rs4606 G-allele carriers were 0.23 (95% CI 0.10-0.54, P=0.001) in the overall sample, and 0.20 (0.07-0.57, P=0.003) in the African-American subsample. In the previously studied Israeli sample the OR was 0.31 (0.11-0.84, P=0.02). We completely sequenced the RGS2 gene in nine patients with AIP and nine patients without, from the Israeli sample. No common coding polymorphisms or additional regulatory variants were revealed, suggesting that association of the rs4606 C/G polymorphism with AIP is biologically meaningful and not a consequence of linkage disequilibrium with another functional variant. Taken together, the findings of the current study support the association of RGS2 with AIP and focus on a possible protective effect of the minor G allele of SNP rs4606. This SNP is located in the 3'-regulatory region of the gene, and is known to influence RGS2 mRNA levels and protein expression.

Why do young women smoke? V. Role of direct and interactive effects of nicotinic cholinergic receptor gene variation on neurocognitive function.

Previous work suggests that young women who smoke cigarettes regularly, or did so in the past, manifest a neurocognitive profile that is characterized by small but significant impairments of response inhibition and attention. The present study sought to determine whether variation in nicotinic cholinergic receptor (nAchR) genes impacts upon cognitive function in these domains by overall or differential effects on the performance of current, former and non-smokers. The study sample consisted of 100 female college students, current or past smokers, and 144 who had never smoked. All performed a computerized neurocognitive test battery and were genotyped for 39 single nucleotide polymorphisms in 11 nAchR genes. The results, derived from linear or logistic regression, show significant direct and interactive relationships between single nucleotide polymorphisms and haplotypes in several nAchR genes and performance on the Matching Familiar Figures Test (MFFT) Stroop test, Continuous Performance Task (CPT) and Tower of London (TOL) test. Response inhibition (MFFT, Stroop, CPT Loading Phase, TOL) was associated with variants in CHRNA2, CHRNA4, CHRNA5, CHRNA7, CHRNA9, CHRNA10, CHRNB2 and CHRNB3. Selective attention (Stroop) was associated with CHRNA4, CHRNA5, CHRNA9 and CHRNB2. Sustained attention (CPT Boring Phase) was associated with CHRNA4, CHRNA5, CHRNA7, CHRNA10 and CHRNB3. Up to 37% of the variance among the smokers and up to 47% of the variance among the non-smokers on the test measures was explained. Differences between smokers and non-smokers in neurocognitive function, putatively implicated in susceptibility to nicotine dependence, may be modulated by variants in nAchR genes, with potential implications for prevention and treatment.

Allelic variation in ApoC3, ApoA5 and LPL genes and first and second generation antipsychotic effects on serum lipids in patients with schizophrenia.

Schizophrenic patients who are treated with antipsychotics, especially second generation antipsychotics, such as clozapine and olanzapine, manifest an increase in cholesterol and triglycerides as well as other changes associated with diabetes or the metabolic syndrome. Previous studies have shown that polymorphisms in several genes that regulate lipid metabolism can influence the levels of these lipids and response to drug treatment. We have investigated in an exploratory study whether polymorphisms in the apolipoprotein C-III (ApoC3), apolipoprotein A-V gene (ApoA5) and lipoprotein lipase genes influence differential lipid response to treatment with three second generation antipsychotics-olanzapine, clozapine and risperidone-or treatment with a first generation antipsychotic. A total of 189 patients with schizophrenia or schizoaffective disorder who were being treated with a single antipsychotic were studied in a cross-sectional study design in which fasting serum cholesterol and triglycerides and selected single-nucleotide polymorphosms (SNPs) in the three lipid metabolism genes were assessed. The treatment with antipsychotic monotherapy makes drug haplotype ascertainment less complex. Our analyses showed several nominally significant drug x gene and drug x haplotype interactions. The rarer C allele or the ApoA5_1131 (T/C) SNP was associated with higher cholesterol levels in patients treated with first generation antipsychotics and lower cholesterol levels in patients treated with olanzapine or clozapine. The rarer C allele of the ApoA5_SW19 (G/C) SNP was associated with higher cholesterol in risperidone-treated patients. An ApoA5 CG haplotype was associated with decreased cholesterol in olanzapine- or clozapine-treated patients and higher cholesterol in patients treated with first generation antipsychotics. The presence of the rarer T allele of the ApoC3_1100 (C/T) SNP or the presence of the ApoC3 TG haplotype was associated with decreased triglyceride levels in patients treated with olanzapine or clozapine and a nonsignificant trend for increased triglycerides in patients treated with first generation antipsychotics. The presence of the ApoC3 CC haplotype was associated with increased triglycerides in patients treated with olanzapine or clozapine. The overall magnitude of the effects was not large. These results provide a potential initial step toward a pharmacogenetic approach to selection of antipsychotic treatment which may help minimize the side effect of increases in serum lipids.

Genetic susceptibility to Tardive Dyskinesia in chronic schizophrenia subjects: V. Association of CYP1A2 1545 C>T polymorphism.

Tardive dyskinesia (TD) is an iatrogenic disorder observed in approximately 20-30% of schizophrenia patients on long-term treatment with typical antipsychotic drugs. CYP1A2 is involved in the metabolism of atypical antipsychotic drugs such as clozapine and olanzapine. It is not directly involved in the metabolism of typical antipsychotic drugs, but gains importance when the schizophrenia patients are under long-term chronic treatment, acting as a low-affinity high-capacity metabolizing enzyme. In this study, we have completely sequenced the coding region to ascertain the presence of common coding polymorphisms and their role if any in susceptibility to TD and schizophrenia. Four previously reported polymorphisms, CYP1A2*1F (intron A), rs2472304 & rs3743484 (intron D) and rs2470890 (CYP1A2 1545 C>T) in exon 7 were identified. We further investigated whether the CYP1A2 1545 C>T polymorphism has any role to play in susceptibility to TD and in schizophrenia per se. Association of this single nucleotide polymorphism with TD (P=0.03) and schizophrenia (P=0.04) was observed, but was rendered insignificant after corrections for multiple comparisons.

Evaluation of association of SNPs in the TNF alpha gene region with schizophrenia.

The association of the tumor necrosis factor alpha (TNFalpha) -G308A promoter polymorphism with schizophrenia has complemented clinical findings of increased levels of the TNFalpha cytokine in schizophrenic patients, with some support for a functional consequence of the variant. Our previous studies of genetic causes in schizophrenia supported findings of linkage to the major histocompatibility complex (MHC) region where the TNFalpha gene is located as well as association with the -G308A promoter polymorphism. While the common G-allele shows association in our sample, association with the A-allele has been reported by other groups. This suggests linkage disequilibrium (LD) rather than direct involvement in the disorder. In order to define LD of DNA variants with the disorder in this area, we analyzed 36 SNPs in a 165-kb region around this polymorphism. We detected nominally significant associations (P < 0.05) of three markers (including the -G308A promoter polymorphism) and multiple haplotypes with schizophrenia in our sample of 204 families (79 sib-pairs and 125 trios). The association is largely restricted to a 30 kb high LD region/block and should assist in the identification of a schizophrenia susceptibility gene within the block or elsewhere in the MHC.

Evidence for association of DNA sequence variants in the phosphatidylinositol-4-phosphate 5-kinase IIalpha gene (PIP5K2A) with schizophrenia.

Linkage studies in schizophrenia have identified a candidate region on chromosome 10p14-11 as reported for several independent samples. We investigated association of DNA sequence variants in a plausible candidate gene located in this region, the gene for phosphatidylinositol-4-phosphate 5-kinase IIalpha (PIP5K2A), in a sample of 65 sib-pair families for which linkage had been reported. Evidence for association was obtained for 15 polymorphisms spanning 73.6 kb in the genomic region of the gene between intron 4 and the 3' untranslated region, a region with high degree of linkage disequilibrium. Single nucleotide polymorphism (SNP) rs10828317 located in exon 7 and causing a non-synonymous amino-acid exchange (asparagine/serine) produced a P-value of 0.001 (experiment-wide significance level 0.00275) for over-transmission of the major allele coding for serine, analysed by transmission disequilibrium test using FAMHAP. Association of this SNP with schizophrenia has been also described in a sample of 273 Dutch schizophrenic patients and 580 controls (P=0.0004). PIP5K2A is involved in the biosynthesis of phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2), one of the key metabolic crossroads in phosphoinositide signalling. PI(4,5)P2 plays a role in membrane transduction of neurotransmitter signals as well as in intracellular signalling, pathways that may be impaired in schizophrenia.