G72/G30 (DAOA) and juvenile-onset mood disorders

Gene Polymorphisms and Expression of NRG1, DAOA, and DISC1 Genes in a Chinese Han Population with an Ultra-High Risk for Psychosis

Purpose

Although there is previous evidence supporting that ultra-high risk (UHR) for psychosis transformation is associated with NRG1, DAOA, and DISC1 genes, there have been no relevant studies in the Chinese population. The objective of the current study was to explore the gene polymorphism and expression of NRG1, DAOA, and DISC1 genes in a Han population with UHR for psychosis in China.

Methods

Eighteen UHR individuals, 61 first-degree relatives of patients with schizophrenia (FDR), 55 first-episode psychosis individuals (FEP), and 61 healthy controls (HC) were enrolled in the study. The genotypes at four loci of the NRG1 gene, four loci of the DAOA gene, and two loci of the DISC1 gene were tested for all subjects, and mRNAs of NRG1 and DISC1 were examined and analyzed in a pairwise comparison among the four groups. Statistical analysis of genetics was performed using snpStats software. For the case-control association analysis, a single site association study, epistatic effect analysis, and haplotype analysis were used to explore the association of the above genes.

Results

This study found that rs3918341 in the DAOA gene was associated with susceptibility to UHR by single site association analysis. Epistatic effect analysis results showed that the NRG1 gene interacted with the DAOA gene and DISC1 gene in the susceptibility to UHR. Haplotype association analysis showed that all haplotypes were not significantly associated with UHR. NRG1 mRNA was significantly downregulated in the UHR group compared with the HC group as well as the FEP group.

Conclusion

Our preliminary results show that NRG1, DAOA, and DISC1 genes may play a role in psychosis onset, opening the way to the identification of prognostic biomarkers.

The Genetic Side of the Mood: A Scientometric Review of the Genetic Basis of Mood Disorders

Mood disorders are highly heritable psychiatric disorders. Over the years, many genetic polymorphisms have been identified to pose a higher risk for the development of mood disorders. To overview the literature on the genetics of mood disorders, a scientometric analysis was performed on a sample of 5342 documents downloaded from Scopus. The most active countries and the most impactful documents in the field were identified. Furthermore, a total of 13 main thematic clusters emerged in the literature. From the qualitative inspection of clusters, it emerged that the research interest moved from a monogenic to a polygenic risk framework. Researchers have moved from the study of single genes in the early 1990s to conducting genome-wide association studies around 2015. In this way, genetic overlaps between mood disorders and other psychiatric conditions emerged too. Furthermore, around the 2010s, the interaction between genes and environmental factors emerged as pivotal in understanding the risk for mood disorders. The inspection of thematic clusters provides a valuable insight into the past and recent trends of research in the genetics of mood disorders and sheds light onto future lines of research.

Association of brain-derived neurotrophic factor (BDNF) Val66Met polymorphism with early-onset bipolar disorder

OBJECTIVES

Brain-derived neurotrophic factor (BDNF) Val66Met (rs6265) functional polymorphism has been implicated in early-onset bipolar disorder. However, results of studies are inconsistent. We aimed to further explore this association.

METHODS

DNA samples from the Treatment of Early Age Mania (TEAM) and Mayo Clinic Bipolar Disorder Biobank were investigated for association of rs6265 with early-onset bipolar disorder. Bipolar cases were classified as early onset if the first manic or depressive episode occurred at age ≤19 years (versus adult-onset cases at age >19 years). After quality control, 69 TEAM early-onset bipolar disorder cases, 725 Mayo Clinic bipolar disorder cases (including 189 early-onset cases), and 764 controls were included in the analysis of association, assessed with logistic regression assuming log-additive allele effects.

RESULTS

Comparison of TEAM cases with controls suggested association of early-onset bipolar disorder with the rs6265 minor allele [odds ratio (OR) = 1.55, p = 0.04]. Although comparison of early-onset adult bipolar disorder cases from the Mayo Clinic versus controls was not statistically significant, the OR estimate indicated the same direction of effect (OR = 1.21, p = 0.19). When the early-onset TEAM and Mayo Clinic early-onset adult groups were combined and compared with the control group, the association of the minor allele rs6265 was statistically significant (OR = 1.30, p = 0.04).

CONCLUSIONS

These preliminary analyses of a relatively small sample with early-onset bipolar disorder are suggestive that functional variation in BDNF is implicated in bipolar disorder risk and may have a more significant role in early-onset expression of the disorder.

The role of NMDA receptors in the pathophysiology and treatment of mood disorders

Mood disorders such as major depressive disorder and bipolar disorder are chronic and recurrent illnesses that cause significant disability and affect approximately 350 million people worldwide. Currently available biogenic amine treatments provide relief for many and yet fail to ameliorate symptoms for others, highlighting the need to diversify the search for new therapeutic strategies. Here we present recent evidence implicating the role of N-methyl-D-aspartate receptor (NMDAR) signaling in the pathophysiology of mood disorders. The possible role of NMDARs in mood disorders has been supported by evidence demonstrating that: (i) both BPD and MDD are characterized by altered levels of central excitatory neurotransmitters; (ii) NMDAR expression, distribution, and function are atypical in patients with mood disorders; (iii) NMDAR modulators show positive therapeutic effects in BPD and MDD patients; and (iv) conventional antidepressants/mood stabilizers can modulate NMDAR function. Taken together, this evidence suggests the NMDAR system holds considerable promise as a therapeutic target for developing next generation drugs that may provide more rapid onset relief of symptoms. Identifying the subcircuits involved in mood and elucidating the role of NMDARs subtypes in specific brain circuits would constitute an important step toward the development of more effective therapies with fewer side effects.

Pre-clinical models of neurodevelopmental disorders: focus on the cerebellum

Recent studies have advanced our understanding of the role of the cerebellum in non-motor behaviors. Abnormalities in the cerebellar structure have been demonstrated to produce changes in emotional, cognitive, and social behaviors resembling clinical manifestations observed in patients with autism spectrum disorders (ASD) and schizophrenia. Several animal models have been used to evaluate the effects of relevant environmental and genetic risk factors on the cerebellum development and function. However, very few models of ASD and schizophrenia selectively target the cerebellum and/or specific cell types within this structure. In this review, we critically evaluate the strength and weaknesses of these models. We will propose that the future progress in this field will require time- and cell type-specific manipulations of disease-relevant genes, not only selectively in the cerebellum, but also in frontal brain areas connected with the cerebellum. Such information can advance our knowledge of the cerebellar contribution to non-motor behaviors in mental health and disease.

A method for the determination of D-kynurenine in biological tissues

D-kynurenine (D-KYN), a metabolite of D-tryptophan, can serve as the bioprecursor of kynurenic acid (KYNA) and 3-hydroxykynurenine, two neuroactive compounds that are believed to play a role in the pathophysiology of several neurological and psychiatric diseases. In order to investigate the possible presence of D-KYN in biological tissues, we developed a novel assay based on the conversion of D-KYN to KYNA by purified D-amino acid oxidase (D-AAO). Samples were incubated with D-AAO under optimal conditions for measuring D-AAO activity (100 mM borate buffer, pH 9.0), and newly produced KYNA was detected by high-performance liquid chromatography (HPLC) with fluorimetric detection. The detection limit for D-KYN was 300 fmol, and linearity of the assay was ascertained up to 300 pmol. No assay interference was noted when other D-amino acids, including D-serine and D-aspartate, were present in the incubation mixture at 50-fold higher concentrations than D-KYN. Using this new method, D-KYN was readily detected in the brain, liver, and plasma of mice treated systemically with D-KYN (300 mg/kg). In these experiments, enantioselectivity was confirmed by determining total kynurenine levels in the same samples using a conventional HPLC assay. Availability of a sensitive, specific, and simple method for D-KYN measurement will be instrumental for evaluating whether D-KYN should be considered for a role in physiology and pathology.

Cognitive manic symptoms in bipolar disorder associated with polymorphisms in the DAOA and COMT genes

INTRODUCTION

Bipolar disorder is characterized by severe mood symptoms including major depressive and manic episodes. During manic episodes, many patients show cognitive dysfunction. Dopamine and glutamate are important for cognitive processing, thus the COMT and DAOA genes that modulate the expression of these neurotransmitters are of interest for studies of cognitive function.

METHODOLOGY

Focusing on the most severe episode of mania, a factor was found with the combined symptoms of talkativeness, distractibility, and thought disorder, considered a cognitive manic symptoms (CMS) factor. 488 patients were genotyped, out of which 373 (76%) had talkativeness, 269 (55%) distractibility, and 372 (76%) thought disorder. 215 (44%) patients were positive for all three symptoms, thus showing CMS (Table 1). As population controls, 1,044 anonymous blood donors (ABD) were used. Case-case and case-control design models were used to investigate genetic associations between cognitive manic symptoms in bipolar 1 disorder and SNPs in the COMT and DAOA genes. [Table: see text].

RESULTS

The finding of this study was that cognitive manic symptoms in patients with bipolar 1 disorder was associated with genetic variants in the DAOA and COMT genes. Nominal association for DAOA SNPs and COMT SNPs to cognitive symptoms factor in bipolar 1 disorder was found in both allelic (Table 2) and haplotypic (Table 3) analyses. Genotypic association analyses also supported our findings. However, only one association, when CMS patients were compared to ABD controls, survived correction for multiple testing by max (T) permutation. Data also suggested interaction between SNPs rs2391191 in DAOA and rs5993883 in COMT in the case-control model. [Table: see text] [Table: see text].

CONCLUSION

Identifying genes associated with cognitive functioning has clinical implications for assessment of prognosis and progression. Our finding are consistent with other studies showing genetic associations between the COMT and DAOA genes and impaired cognition both in psychiatric disorders and in the general population.

Genotypic association of the DAOA gene with resting-state brain activity in major depression

Compelling evidence suggests that the glutamatergic system may contribute to the pathophysiology of major depression (MDD). While the D-amino acid oxidase activator (DAOA) gene can affect glutamatergic function, its genetic associations with MDD and abnormal resting-state brain activity have yet to be elucidated. A total of 488 patients with MDD and 480 controls were recruited to examine MDD association for the DAOA gene in a Chinese population, of whom 53 medication-free patients and 46 well-matched controls underwent resting-state functional magnetic resonance imaging for regional homogeneity (ReHo) analysis. The differences in ReHo between genotypes of interest were initially tested by the Student's t test, and the 2 × 2 (genotypes × disease status) ANOVA was then performed to identify the main effects of genotypes, disease status, and their interactions in MDD. Allelic association of the DAOA gene with MDD was observed for rs2391191, rs3918341, and rs778294 and haplotypic association for 2- and 3-SNP haplotypes. Six clusters in the cerebellum, right middle frontal gyrus and left middle temporal gyrus showed genotypic association between altered ReHo and rs2391191. The main effects of rs2391191 genotypes were found in the right culmen and right middle frontal gyrus. The left uvula and left middle temporal gyrus showed a genotypes × disease status interaction. Our results suggest that the DAOA gene may confer genetic risk of MDD. Genotypic effect of rs2391191 and its interaction with disease status may contribute to the altered ReHo in patients with MDD. Glutamatergic modulation may play an important role in alteration of the resting-state brain activities.

Genomics and pharmacogenomics of schizophrenia

Schizophrenia (SCZ) is among the most disabling of mental disorders. Several neurobiological hypotheses have been postulated as responsible for SCZ pathogenesis: polygenic/multifactorial genomic defects, intrauterine and perinatal environment-genome interactions, neurodevelopmental defects, dopaminergic, cholinergic, serotonergic, gamma-aminobutiric acid (GABAergic), neuropeptidergic and glutamatergic/N-Methyl-D-Aspartate (NMDA) dysfunctions, seasonal infection, neuroimmune dysfunction, and epigenetic dysregulation. SCZ has a heritability estimated at 60-90%. Genetic studies in SCZ have revealed the presence of chromosome anomalies, copy number variants, multiple single-nucleotide polymorphisms of susceptibility distributed across the human genome, aberrant single nucleotide polymorphisms (SNPs) in microRNA genes, mitochondrial DNA mutations, and epigenetic phenomena. Pharmacogenetic studies of psychotropic drug response have focused on determining the relationship between variation in specific candidate genes and the positive and adverse effects of drug treatment. Approximately, 18% of neuroleptics are major substrates of CYP1A2 enzymes, 40% of CYP2D6, and 23% of CYP3A4; 24% of antidepressants are major substrates of CYP1A2 enzymes, 5% of CYP2B6, 38% of CYP2C19, 85% of CYP2D6, and 38% of CYP3A4; 7% of benzodiazepines are major substrates of CYP2C19 enzymes, 20% of CYP2D6, and 95% of CYP3A4. About 10-20% of Western populations are defective in genes of the CYP superfamily. Only 26% of Southern Europeans are pure extensive metabolizers for the trigenic cluster integrated by the CYP2D6+CYP2C19+CYP2C9 genes. The pharmacogenomic response of SCZ patients to conventional psychotropic drugs also depends on genetic variants associated with SCZ-related genes. Consequently, the incorporation of pharmacogenomic procedures both to drugs in development and drugs on the market would help to optimize therapeutics in SCZ and other central nervous system (CNS) disorders.

Cognitive manic symptoms associated with the P2RX7 gene in bipolar disorder

OBJECTIVE

  Several genetic loci have been suggested to be associated with bipolar disorder but results have been inconsistent. Studying associations between bipolar symptoms and candidate genes may better expose this relationship. Here we investigate the association between bipolar key symptoms and the P2RX7 gene.

METHODS

  Key symptoms of mania were rated in two sets of medicated bipolar disorder patients (n=171 and n=475) at two specialized outpatient clinics for affective disorders and three regular psychiatric outpatient units in Sweden. The relationships between all manic symptoms according to DSM-IV were entered in a principal component analysis. We used a case-case model to reduce the genetic heterogeneity and tested associations between four factors related to manic symptoms and their association to four single nucleotide polymorphisms in the P2RX7 gene.

RESULTS

  The combination of the cognitive symptoms, distractibility, talkativeness, and thought disorder was significantly associated with rs1718119 in the P2RX7 gene in Set 1 [odds ratio (OR) = 1.78; p=0.011]. The association was re-tested in the second set (OR = 1.42; p=0.009). In the total sample, the association was even stronger (OR = 1.49; p<0.001). None of the other factors was associated with the P2RX7 gene. Within the first factor, the distractibility symptom accounted for a significant portion of the association to rs1718119 (p=0.016).

CONCLUSION

  There is an association between specific symptoms of bipolar disorder and the P2RX7 gene. This finding may open up new approaches to elucidating the neurobiology behind bipolar symptoms.

Possible association of different G72/G30 SNPs with mood episodes and persecutory delusions in bipolar I Romanian patients

The G72/G30 gene is one of the common loci shared both by schizophrenia and bipolar disorder. Studies accumulating since the discovery of this gene complex produced controversial results in both disorders in different populations.

OBJECTIVE

We investigated the association between the G72/G30 gene and bipolar I disorder (BPI) in the Romanian population paying special attention to the association of G72/G30 with lifetime psychosis and in particular with persecutory delusions in BPI patients.

METHOD

Fourteen G72/G30-SNPs were genotyped in a Romanian sample of 198 BPI patients and 180 controls screened for psychiatric disorders. Statistical analysis was performed with FAMHAP and HAPLOVIEW-v3.32. The significance level of the results was corrected through permutations in 100,000 simulations.

RESULTS

None of the fourteen SNPs was associated with the global diagnosis of BPI in our total patient sample or with the psychotic BPI subtype. When confining the psychotic phenotype to persecutory delusions, we observed trends to association for SNPs previously associated with schizophrenia and persecutory delusions in BPI [M21 (P=0.080); M22 (P=0.092; P=0.042 under dominant transmission model); M24 (P=0.092)]. Four SNPs reached nominal significance in the non-psychotic BPI subgroup [rs3916965 (M12) (P=0.044), rs1935057 (P=0.037), rs3916967 (M14) (P=0.043), and rs2391191 (M15, non-synonymous) (P=0.043)]. After correction through permutations, the haploblock GA including M14 and M15 showed a trend to association with BPI (P=0.0524; OR=1.82) in the non-psychotic BPI subgroup.

CONCLUSION

We report a potential association of different G72/G30-SNPs with non-psychotic mood episodes and with persecutory delusions in BPI Romanian patients. The results represent a first partial replication of two studies: Williams et al. (2006) and Schulze et al. (2005). The results have just a suggestive value since the Bonferroni correction for multiple testing was not applied.