Lymphoblast and brain expression of AHI1 and the novel primate-specific gene, C6orf217, in schizophrenia and bipolar disorder

Effect of chronic unpredictable stress on mice with developmental under-expression of the Ahi1 gene: behavioral manifestations and neurobiological correlates

The Abelson helper integration site 1 (Ahi1) gene plays a pivotal role in brain development and is associated with genetic susceptibility to schizophrenia, and other neuropsychiatric disorders. Translational research in genetically modified mice may reveal the neurobiological mechanisms of such associations. Previous studies of mice heterozygous for Ahi1 knockout (Ahi1+/-) revealed an attenuated anxiety response on various relevant paradigms, in the context of a normal glucocorticoid response to caffeine and pentylenetetrazole. Resting-state fMRI showed decreased amygdalar connectivity with various limbic brain regions and altered network topology. However, it was not clear from previous studies whether stress-hyporesponsiveness reflected resilience or, conversely, a cognitive-emotional deficit. The present studies were designed to investigate the response of Ahi1+/- mice to chronic unpredictable stress (CUS) applied over 9 weeks. Wild type (Ahi1+/+) mice were significantly affected by CUS, manifesting decreased sucrose preference (p < 0.05); reduced anxiety on the elevated plus maze and light dark box and decreased thigmotaxis in the open field (p < 0.01 0.05); decreased hyperthermic response to acute stress (p < 0.05); attenuated contextual fear conditioning (p < 0.01) and increased neurogenesis (p < 0.05). In contrast, Ahi1+/- mice were indifferent to the effects of CUS assessed with the same parameters. Our findings suggest that Ahi1 under-expression during neurodevelopment, as manifested by Ahi1+/- mice, renders these mice stress hyporesponsive. Ahi1 deficiency during development may attenuate the perception and/or integration of environmental stressors as a result of impaired corticolimbic connectivity or aberrant functional wiring. These neural mechanisms may provide initial clues as to the role Ahi1 in schizophrenia and other neuropsychiatric disorders.

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.

Primary Cilia as a Possible Link between Left-Right Asymmetry and Neurodevelopmental Diseases

Cilia have multiple functions in the development of the entire organism, and participate in the development and functioning of the central nervous system. In the last decade, studies have shown that they are implicated in the development of the visceral left-right asymmetry in different vertebrates. At the same time, some neuropsychiatric disorders, such as schizophrenia, autism, bipolar disorder, and dyslexia, are known to be associated with lateralization failure. In this review, we consider possible links in the mechanisms of determination of visceral asymmetry and brain lateralization, through cilia. We review the functions of seven genes associated with both cilia, and with neurodevelopmental diseases, keeping in mind their possible role in the establishment of the left-right brain asymmetry.

A cis-eQTL in AHI1 confers risk to schizophrenia in European populations

Schizophrenia is a devastating mental disorder, with heritability as high as 80%. Although genome-wide association studies have identified multiple promising risk variants of schizophrenia, they could only explain a small portion of the disease heritability, and other variants with low to moderate effect remain to be identified. Abelson helper integration site 1 (AHI1) is highly expressed in mammals throughout the developing brain, with lower expression continuing into adulthood. Besides, previous evidence suggested that AHI1 expression was changed in schizophrenia patients. Furthermore, association signal between AHI1 variants and schizophrenia has been reported in several European samples. In the present study, we first analyzed two expression quantitative trait loci (eQTL) datasets in healthy individuals and investigated the associations of eQTL of AHI1 with schizophrenia in independent European samples. We observed that a cis-eQTL of AHI1, rs11154801, showed significant association with AHI1 expression in both datasets (P<5E-05). Genetic evidence exhibited that rs11154801 was significantly associated with schizophrenia risk in both the discovery sample (9394 cases and 12462 controls, P=0.046, OR=0.958, 95% CI=0.918-0.999) and the replication sample (3240 cases and 14786 controls, P=0.024, OR=0.949, 95% CI=0.870-0.990). When the discovery and replication samples were pooled together, this association was further strengthened (P=0.004, OR=0.949, 95% CI=0.916-0.983). These results suggested that AHI1 is likely a risk gene for schizophrenia, at least in European populations.

The Influence of Microdeletions and Microduplications of 16p11.2 on Global Transcription Profiles

Copy number variants (CNVs) of a 600 kb region on 16p11.2 are associated with neurodevelopmental disorders and changes in brain volume. The authors hypothesize that abnormal brain development associated with this CNV can be attributed to changes in transcriptional regulation. The authors determined the effects of 16p11.2 dosage on gene expression by transcription profiling of lymphoblast cell lines derived from 6 microdeletion carriers, 15 microduplication carriers and 15 controls. Gene dosage had a significant influence on the transcript abundance of a majority (20/34) of genes within the CNV region. In addition, a limited number of genes were dysregulated in trans. Genes most strongly correlated with patient head circumference included SULT1A, KCTD13, and TMEM242. Given the modest effect of 16p11.2 copy number on global transcriptional regulation in lymphocytes, larger studies utilizing neuronal cell types may be needed in order to elucidate the signaling pathways that influence brain development in this genetic disorder.

The influence of AHI1 variants on the diagnosis and treatment outcome in schizophrenia

The present study aimed to explore whether four single nucleotide polymorphisms (SNPs) within the AHI1 gene could be associated with schizophrenia (SCZ) and whether they could predict the clinical outcomes in SCZ patients treated with antipsychotics. Four hundred twenty-six (426) in-patients with SCZ and 345 controls were genotyped for four AHI1 SNPs (rs11154801, rs7750586, rs9647635 and rs9321501). Baseline and clinical measures for SCZ patients were assessed through the Positive and Negative Syndrome Scale (PANSS). Allelic and genotypic frequencies in SCZ subjects were compared with those of controls using the χ² statistics. The repeated-measure ANOVA was used for the assessment of treatment outcomes measured by PANSS changes. The case-control analysis did not show any difference in the genotypic distribution of the SNPs, while in the allelic analysis, a weak association was found between the rs9647635 A allele and SCZ. Furthermore, in the haplotype analysis, three haplotypes resulted in being associated with SCZ. On the other hand, two SNPs (rs7750586 and rs9647635) were associated with clinical improvement of negative symptoms in the allelic analysis, although in the genotypic analysis, only trends of association were found for the same SNPs. Our findings suggest a possible influence of AHI1 variants on SCZ susceptibility and antipsychotic response, particularly concerning negative symptomatology. Subsequent well-designed studies would be mandatory to confirm our results due to the methodological shortcomings of the present study.

A primate-specific functional GTTT-repeat in the core promoter of CYTH4 is linked to bipolar disorder in human

Evidence of primate-specific genes and gene regulatory mechanisms linked to bipolar disorder (BD) lend support to evolutionary/adaptive processes in the pathogenesis of this disorder. Following a genome-scale analysis of the entire protein coding genes annotated in the GeneCards database, we have recently reported that cytohesin-4 (CYTH4) contains the longest tetra-nucleotide short tandem repeat (STR) identified in a human protein-coding gene core promoter, which may be of adaptive advantage to this species. In the current study, we analyzed the evolutionary trend of this STR across evolution. We also analyzed the functional implication and distribution of this STR in a group of patients with type 1 BD (n=233) and controls (n=262). We found that this STR is exceptionally expanded in primates (Fisher exact p<0.00003). Association was observed between type I BD and the 6-repeat allele of this STR, (GTTT)₆ (Yates corrected Χ(2)=12.68, p<0.0001, OR: 1.68). This allele is the shortest length of the GTTT-repeat identified in the human subjects studied. Consistent with that finding, excess homozygosity was observed for the shorter alleles, (GTTT)₆ and (GTTT)₇, vs. the longer alleles, (GTTT)₈ and (GTTT)₉ in the BD group (Yates corrected Χ(2)=5.18, p<0.01, 1 df, OR: 1.96). Using Dual Glo luciferase system in HEK-293 cells, a trend for gene expression repression was observed from the 6- to the 9-repeat allele (p<0.003), and the GTTT-repeat significantly down-regulated gene expression, per se (p<0.0006). This is the first evidence of a link between a primate-specific STR and a major psychiatric disorder in human. It may be speculated that the CYTH4 GTTT-repeat in primates may have conferred selective advantage to this order, reflected in neural function and neurophenotypes. The role of the CYTH4 gene in the pathogenesis of type I BD remains to be clarified in the future studies.

Genomic assortative mating in marriages in the United States

Assortative mating in phenotype in human marriages has been widely observed. Using genome-wide genotype data from the Framingham Heart study (FHS; number of married couples = 989) and Health Retirement Survey (HRS; number of married couples = 3,474), this study investigates genomic assortative mating in human marriages. Two types of genomic marital correlations are calculated. The first is a correlation specific to a single married couple "averaged" over all available autosomal single-nucleotide polymorphism (SNPs). In FHS, the average married-couple correlation is 0.0018 with p = 3 × 10(-5); in HRS, it is 0.0017 with p = 7.13 × 10(-13). The marital correlation among the positively assorting SNPs is 0.001 (p = .0043) in FHS and 0.015 (p = 1.66 × 10(-24)) in HRS. The sizes of these estimates in FHS and HRS are consistent with what are suggested by the distribution of the allelic combination. The study also estimated SNP-specific correlation "averaged" over all married couples. Suggestive evidence is reported. Future studies need to consider a more general form of genomic assortment, in which different allelic forms in homologous genes and non-homologous genes result in the same phenotype.

Neuroinformatic analyses of common and distinct genetic components associated with major neuropsychiatric disorders

Major neuropsychiatric disorders are highly heritable, with mounting evidence suggesting that these disorders share overlapping sets of molecular and cellular underpinnings. In the current article we systematically test the degree of genetic commonality across six major neuropsychiatric disorders-attention deficit hyperactivity disorder (ADHD), anxiety disorders (Anx), autistic spectrum disorders (ASD), bipolar disorder (BD), major depressive disorder (MDD), and schizophrenia (SCZ). We curated a well-vetted list of genes based on large-scale human genetic studies based on the NHGRI catalog of published genome-wide association studies (GWAS). A total of 180 genes were accepted into the analysis on the basis of low but liberal GWAS p-values (<10(-5)). 22% of genes overlapped two or more disorders. The most widely shared subset of genes-common to five of six disorders-included ANK3, AS3MT, CACNA1C, CACNB2, CNNM2, CSMD1, DPCR1, ITIH3, NT5C2, PPP1R11, SYNE1, TCF4, TENM4, TRIM26, and ZNRD1. Using a suite of neuroinformatic resources, we showed that many of the shared genes are implicated in the postsynaptic density (PSD), expressed in immune tissues and co-expressed in developing human brain. Using a translational cross-species approach, we detected two distinct genetic components that were both shared by each of the six disorders; the 1st component is involved in CNS development, neural projections and synaptic transmission, while the 2nd is implicated in various cytoplasmic organelles and cellular processes. Combined, these genetic components account for 20-30% of the genetic load. The remaining risk is conferred by distinct, disorder-specific variants. Our systematic comparative analysis of shared and unique genetic factors highlights key gene sets and molecular processes that may ultimately translate into improved diagnosis and treatment of these debilitating disorders.

Abelson helper integration site-1 gene variants on major depressive disorder and bipolar disorder

OBJECTIVE

The present study aimed to explore whether 4 single nucleotide polymorphisms (SNPs) within the AHI1 gene could be associated with major depressive disorder (MD) and bipolar disorder (BD), and whether they could predict clinical outcomes in mood disorders.

METHODS

One hundred and eighty-four (184) patients with MD, 170 patients with BD and 170 healthy controls were genotyped for 4 AHI1 SNPs (rs11154801, rs7750586, rs9647635 and rs9321501). Baseline and final clinical measures for MD patients were assessed through the Hamilton Rating Scale for Depression (HAM-D). Allelic and genotypic frequencies in MD and BD subjects were compared with those of each disorder and healthy group using the χ(2) statistics. Repeated measures ANOVA was used to test possible influences of SNPs on treatment efficacy.

RESULTS

The rs9647635 A/A was more represented in subjects with BD as compared with MD and healthy subjects together. The rs9647635 A/A was also more presented in patients with MD than in healthy subjects. With regard to the allelic analysis, rs9647635 A allele was more represented in subjects with BD compared with healthy subjects, while it was not observed between patients with MD and healthy subjects.

CONCLUSION

Our findings provide potential evidence of an association between some variants of AHI1 and mood disorders susceptibility but not with clinical outcomes. However, we will need to do more adequately-powered and advanced association studies to draw any conclusion due to clear limitations.

Bernard Lerer: recipient of the 2014 inaugural Werner Kalow Responsible Innovation Prize in Global Omics and Personalized Medicine (Pacific Rim Association for Clinical Pharmacogenetics)

This article announces the recipient of the 2014 inaugural Werner Kalow Responsible Innovation Prize in Global Omics and Personalized Medicine by the Pacific Rim Association for Clinical Pharmacogenetics (PRACP): Bernard Lerer, professor of psychiatry and director of the Biological Psychiatry Laboratory, Hadassah-Hebrew University Medical Center, Jerusalem, Israel. The Werner Kalow Responsible Innovation Prize is given to an exceptional interdisciplinary scholar who has made highly innovative and enduring contributions to global omics science and personalized medicine, with both vertical and horizontal (transdisciplinary) impacts. The prize is established in memory of a beloved colleague, mentor, and friend, the late Professor Werner Kalow, who cultivated the idea and practice of pharmacogenetics in modern therapeutics commencing in the 1950s. PRACP, the prize's sponsor, is one of the longest standing learned societies in the Asia-Pacific region, and was founded by Kalow and colleagues more than two decades ago in the then-emerging field of pharmacogenetics. In announcing this inaugural prize and its winner, we seek to highlight the works of prize winner, Professor Lerer. Additionally, we contextualize the significance of the prize by recalling the life and works of Professor Kalow and providing a brief socio-technical history of the rise of pharmacogenetics and personalized medicine as a veritable form of 21(st) century scientific practice. The article also fills a void in previous social science analyses of pharmacogenetics, by bringing to the fore the works of Kalow from 1995 to 2008, when he presciently noted the rise of yet another field of postgenomics inquiry--pharmacoepigenetics--that railed against genetic determinism and underscored the temporal and spatial plasticity of genetic components of drug response, with invention of the repeated drug administration (RDA) method that estimates the dynamic heritabilities of drug response. The prize goes a long way to cultivate transgenerational capacity and broader cognizance of the concept and practice of responsible innovation as an important criterion of 21(st) century omics science and personalized medicine. A new call is presently in place for the 2016 PRACP Werner Kalow prize. Nominations can be made in support of an exceptional individual interdisciplinary scholar, or alternatively, an entire research team, from any region in the world with a record of highly innovative contributions to global omics science and/or personalized medicine, in the spirit of responsible innovation. The application process is straightforward, requiring a signed, 1500-word nomination letter (by the applicant or sponsor) submitted not later than May 31, 2015.

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.

AHI-1: a novel signaling protein and potential therapeutic target in human leukemia and brain disorders

Progress in the understanding of the molecular and cellular mechanisms of human cancer, including human leukemia and lymphomas, has been spurred by cloning of fusion genes created by chromosomal translocations or by retroviral insertional mutagenesis; a number of oncogenes and tumor suppressors involved in development of a number of malignancies have been identified in this manner. The BCR-ABL fusion gene, originating in a multipotent hematopoietic stem cell, is the molecular signature of chronic myeloid leukemia (CML). Discovery of this fusion gene has led to the development of one of the first successful targeted molecular therapies for cancer (Imatinib). It illustrates the advances that can result from an understanding of the molecular basis of disease. However, there still remain many as yet unidentified mutations that may influence the initiation or progression of human diseases. Thus, identification and characterization of the mechanism of action of genes that contribute to human diseases is an important and opportune area of current research. One promising candidate as a potential therapeutic target is Abelson helper integration site-1(Ahi-1/AHI-1) that was identified by retroviral insertional mutagenesis in murine models of leukemia/lymphomas and is highly elevated in certain human lymphoma and leukemia stem/progenitor cells. It encodes a unique protein with a SH3 domain, multiple SH3 binding sites and a WD40-repeat domain, suggesting that the normal protein has novel signaling activities. A new AHI-1-BCR-ABL-JAK2 interaction complex has recently been identified and this complex regulates transforming activities and drug resistance in CML stem/progenitor cells. Importantly, AHI-1 has recently been identified as a susceptibility gene involved in a number of brain disorders, including Joubert syndrome. Therefore, understanding molecular functions of the AHI-1 gene could lead to important and novel insights into disease processes involved in specific types of diseases. Ultimately, this knowledge will set the stage for translation into new and more effective diagnostic and treatment strategies.

Functional genetic variation at the NRGN gene and schizophrenia: evidence from a gene-based case-control study and gene expression analysis

Genome-wide association and follow-up studies have reported an association between schizophrenia and rs12807809 of the NRGN gene on chromosome 11q24.2. We investigated the association of five linkage disequilibrium-tagging SNPs and haplotypes that cover the NRGN gene with schizophrenia in a Japanese sample of 2,019 schizophrenia patients and 2,574 controls to determine whether rs12807809 is the most strongly associated variant for schizophrenia in the vicinity of the NRGN gene. We found that the rs12807809-rs12278912 haplotype of the NRGN gene was associated with schizophrenia (global P = 0.0042). The frequencies of the TG and TA haplotypes of rs12807809-rs12278912 in patients were higher (OR = 1.14, P = 0.0019) and lower (OR = 0.85, P = 0.0053), respectively, than in the controls. We did not detect any evidence of association of schizophrenia with any SNPs; however, two nominal associations of rs12278912 (OR = 1.10, P = 0.057) and rs2075713 (OR = 1.10, P = 0.057) were observed. Furthermore, we detected an association between the rs12807809-rs12278912 haplotype and NRGN expression in immortalized lymphoblasts derived from 45 HapMap JPT subjects (z = 2.69, P = 0.007) and confirmed the association in immortalized lymphoblasts derived from 42 patients with schizophrenia and 44 healthy controls (z = 3.09, P = 0.002). The expression of the high-risk TG haplotype was significantly lower than the protective TA haplotype. The expression was lower in patients with schizophrenia than in controls; however, this difference was not statistically significant. This study provides further evidence of the association of the NRGN gene with schizophrenia, and our results suggest that there is a link between the TG haplotype of rs12807809-rs12278912, decreased expression of NRGN and risk of developing schizophrenia.

The first decade and beyond of transcriptional profiling in schizophrenia

Gene expression changes in brains of individuals with schizophrenia (SZ) have been hypothesized to reflect possible pathways related to pathophysiology and/or medication. Other factors having robust effects on gene expression profiling in brain and possibly influence the schizophrenia transcriptome such as age and pH are examined. Pathways of curated gene expression or gene correlation networks reported in SZ (white matter, apoptosis, neurogenesis, synaptic plasticity, glutamatergic and GABAergic neurotransmission, immune and stress-response, mitochondrial, and neurodevelopment) are not unique to SZ and have been associated with other psychiatric disorders. Suggestions going forward to improve the next decade of profiling: consider multiple brain regions that are carefully dissected, release large datasets from multiple brain regions in controls to better understand neurocircuitry, integrate genetics and gene expression, measure expression variants on genome wide level, peripheral biomarker studies, and analyze the transcriptome across a developmental series of brains. Gene expression, while an important feature of the genomic landscape, requires further systems biology to advance from control brains to a more precise definition of the schizophrenia interactome.

Identification of new schizophrenia susceptibility loci in an ethnically homogeneous, family-based, Arab-Israeli sample

While the use of population-based samples is a common strategy in genome-wide association studies (GWASs), family-based samples have considerable advantages, such as robustness against population stratification and false-positive associations, better quality control, and the possibility to check for both linkage and association. In a genome-wide linkage study of schizophrenia in Arab-Israeli families with multiple affected individuals, we previously reported significant evidence for a susceptibility locus at chromosome 6q23.2-q24.1 and suggestive evidence at chromosomes 10q22.3-26.3, 2q36.1-37.3 and 7p21.1-22.3. To identify schizophrenia susceptibility genes, we applied a family-based GWAS strategy in an enlarged, ethnically homogeneous, Arab-Israeli family sample. We performed genome-wide single nucleotide polymorphism (SNP) genotyping and single SNP transmission disequilibrium test association analysis and found genome-wide significant association (best value of P=1.22×10(-11)) for 8 SNPs within or near highly reasonable functional candidate genes for schizophrenia. Of particular interest are a group of SNPs within and flanking the transcriptional factor LRRFIP1 gene. To determine replicability of the significant associations beyond the Arab-Israeli population, we studied the association of the significant SNPs in a German case-control validation sample and found replication of associations near the UGT1 subfamily and EFHD1 genes. Applying an exploratory homozygosity mapping approach as a complementary strategy to identify schizophrenia susceptibility genes in our Arab Israeli sample, we identified 8 putative disease loci. Overall, this GWAS, which emphasizes the important contribution of family based studies, identifies promising candidate genes for schizophrenia.