Synergistic effects of COMT and TPH2 on social cognition

The associations between cognitive functions and TSNAX genetic variations in patients with schizophrenia

BACKGROUND

The translin-associated factor X (TSNAX) gene, located adjacent to the DISC1 gene, has been implicated in schizophrenia. While cognitive impairment determines long-term the functional outcome of schizophrenia, the role of TSNAX in cognitive dysfunction of schizophrenia patients remains elusive. This study aimed to explore the genetic effect of TSNAX on cognitive functions of schizophrenia.

METHODS

We recruited 286 chronic schizophrenia patients who had been stabilized with antipsychotics for at least 2 months and genotyped three TSNAX SNPs (rs1630250, rs766288, rs6662926). Clinical symptoms and seven cognitive domains were assessed. The score of cognitive tests was standardized to T score.

RESULTS

Clinical symptoms were similar among genotypes of all the three SNPs. The GLM analysis demonstrated that TSNAX genetic polymorphisms influenced cognitive function of schizophrenia patients after adjustment for gender, age, and education. The patients with the rs1630250 C/G genotype performed better than the G/G homozygotes in the Trail Making A (p = 0.034). Those with the rs766288 G/T genotype also performed better than the G/G homozygotes in the Trail Making A (p = 0.012). The patients with the G/G genotype of rs6662926 also performed better than the C/C homozygotes in verbal learning and memory test (p = 0.044).

CONCLUSIONS

This study suggests that the TSNAX gene variation may influence the cognitive functions of the patients with schizophrenia.

Correlation of Expression Changes between Genes Controlling 5-HT Synthesis and Genes Crh and Trh in the Midbrain Raphe Nuclei of Chronically Aggressive and Defeated Male Mice

Midbrain raphe nuclei (MRNs) contain a large number of serotonergic neurons associated with the regulation of numerous types of psychoemotional states and physiological processes. The aim of this work was to study alterations of the MRN transcriptome in mice with prolonged positive or negative fighting experience and to identify key gene networks associated with the regulation of serotonergic system functioning. Numerous genes underwent alterations of transcription in the MRNs of male mice that either manifested aggression or experienced social defeat in daily agonistic interactions. The expression of the Tph2 gene encoding the rate-limiting enzyme of the serotonin synthesis pathway correlated with the expression of many genes, 31 of which were common between aggressive and defeated mice and were downregulated in the MRNs of mice of both experimental groups. Among these common differentially expressed genes (DEGs), there were genes associated with behavior, learning, memory, and synaptic signaling. These results suggested that, in the MRNs of the mice, the transcriptome changes associated with serotonergic regulation of various processes are similar between the two groups (aggressive and defeated). In the MRNs, more DEGs correlating with Tph2 expression were found in defeated mice than in the winners, which is probably a consequence of deeper Tph2 downregulation in the losers. It was shown for the first time that, in both groups of experimental mice, the changes in the transcription of genes controlling the synthesis and transport of serotonin directly correlate with the expression of genes Crh and Trh, which control the synthesis of corticotrophin- and thyrotropin-releasing hormones. Our findings indicate that CRH and TRH locally produced in MRNs are related to serotonergic regulation of brain processes during a chronic social conflict.

Prediction of functional outcomes of schizophrenia with genetic biomarkers using a bagging ensemble machine learning method with feature selection

Genetic variants such as single nucleotide polymorphisms (SNPs) have been suggested as potential molecular biomarkers to predict the functional outcome of psychiatric disorders. To assess the schizophrenia’ functional outcomes such as Quality of Life Scale (QLS) and the Global Assessment of Functioning (GAF), we leveraged a bagging ensemble machine learning method with a feature selection algorithm resulting from the analysis of 11 SNPs (AKT1 rs1130233, COMT rs4680, DISC1 rs821616, DRD3 rs6280, G72 rs1421292, G72 rs2391191, 5-HT2A rs6311, MET rs2237717, MET rs41735, MET rs42336, and TPH2 rs4570625) of 302 schizophrenia patients in the Taiwanese population. We compared our bagging ensemble machine learning algorithm with other state-of-the-art models such as linear regression, support vector machine, multilayer feedforward neural networks, and random forests. The analysis reported that the bagging ensemble algorithm with feature selection outperformed other predictive algorithms to forecast the QLS functional outcome of schizophrenia by using the G72 rs2391191 and MET rs2237717 SNPs. Furthermore, the bagging ensemble algorithm with feature selection surpassed other predictive algorithms to forecast the GAF functional outcome of schizophrenia by using the AKT1 rs1130233 SNP. The study suggests that the bagging ensemble machine learning algorithm with feature selection might present an applicable approach to provide software tools for forecasting the functional outcomes of schizophrenia using molecular biomarkers.

Association Between Lack of Insight and Prefrontal Serotonin Transporter Availability in Antipsychotic-Free Patients with Schizophrenia: A High-Resolution PET Study with [11C]DASB

BACKGROUND

Previous studies suggested a link between serotonergic neurotransmission and impaired insight in schizophrenia. In this study, we examined the relationship between serotonin transporter (SERT) availability in regions of the prefrontal cortex (dorsolateral, ventrolateral, ventromedial, and orbitofrontal cortices) and insight deficits in antipsychotic-free patients with schizophrenia using high-resolution positron emission tomography (PET) with [¹¹C]DASB.

METHODS

Nineteen patients underwent [¹¹C]DASB PET and 7-Tesla magnetic resonance imaging scans. To assess SERT availability, the binding potential with respect to non-displaceable compartment (BP_ND) was derived using the simplified reference tissue model. Patients' level of insight was assessed using the Insight and Treatment Attitude Questionnaire (ITAQ). The relationship between ITAQ scores and [¹¹C]DASB BP_ND values was examined using the region-of-interest (ROI)- and voxel-based analyses with relevant variables as covariates. The prefrontal cortex and its four subregions were selected as a priori ROIs since the prefrontal cortex has been implicated as the critical neuroanatomical substrate of impaired insight in schizophrenia.

RESULTS

The ROI-based analysis revealed that the ITAQ illness insight dimension had significant negative correlations with the [¹¹C]DASB BP_ND in the left dorsolateral, left orbitofrontal, and bilateral ventrolateral prefrontal cortices. The ITAQ treatment insight dimension had significant negative correlations with the [¹¹C]DASB BP_ND in the bilateral dorsolateral, left orbitofrontal, and bilateral ventrolateral prefrontal cortices. The ITAQ total score showed significant negative correlations with the [¹¹C]DASB BP_ND in the bilateral prefrontal cortex and three subregions (dorsolateral, ventrolateral, and orbitofrontal cortices). A supplementary voxel-based analysis corroborated a significant negative association between the ITAQ score and the [¹¹C]DASB BP_ND in the prefrontal cortices.

CONCLUSION

Our study provides in vivo evidence of significant negative correlations between insight deficits and prefrontal SERT availability in patients with schizophrenia, suggesting significant involvement of prefrontal serotonergic signaling in impaired insight, one of the core symptoms of schizophrenia.

A review of neurophysiological and genetic correlates of emotional intelligence

The article is an overview of modern studies of brain organization and genetic correlates of emotional intelligence. Emotional intelligence is becoming the subject of more and more attentive study of psychologists due to the fact that it influences the mental development of humans, plays an important role in many professions, and its impairment is a marker of some disorders. Nevertheless, the brain organization and genetic correlates of emotional intelligence have not been studied enough – first studies appeared only in the early 2000s. A review of the literature on the enceph-alographic showed that in rest, people with higher emotional intelligence show greater excitation of the left anterior regions of the brain. When per-ceiving affective stimuli, participants with high emotional intelligence show stronger synchronization of some EEG rhythms. Brain mapping technique made it possible to identify the areas of the brain involved in activities related to emotional intelligence. In regard to genetic correlates of emotional intelligence, some genes of neurotransmitter systems have been associated to this trait: the catechol-O-methyltransferase gene COMT, the dopamine DRD2 receptor gene, the serotonin receptor gene HTR2A, and the BDNF brain neurotrophic factor gene.

Effect of the catechol-O-methyltransferase Val 158 Met polymorphism on theory of mind in obesity

Obesity is often accompanied with psychosocial adjustment problems, such as difficulties in social interactions and social withdrawal. A key aspect of social cognition is theory of mind, which allows inferring mental states, feelings, motivations, and beliefs of others and to use this information to predict their future behaviour. Theory of mind is highly dependent on prefrontal dopaminergic neurotransmission, which is regulated by catechol-O-methyltransferase (COMT) activity. We aimed at determining whether theory of mind is altered in obesity and if this ability is modulated by COMT. Fifty patients with obesity and 47 normal-weight individuals underwent the Reading the Mind in the Eyes Test, the Wisconsin Card Sorting Test, and the Vocabulary subscale of the Wechsler Adult Intelligence Scale. The genotype for the COMT Val ¹⁵⁸ Met functional polymorphism was determined for all subjects. Patients with obesity obtained significantly lower scores in the negative items of the Reading the Mind in the Eyes Test than normal-weight subjects. Further, an interaction effect was observed between group and COMT genotype. Specifically, the presence of the Met allele was associated to a better identification of negative mental states only in patients with obesity. Our results indicate that obesity is accompanied with difficulties in theory of mind and that this ability is influenced by the COMT genotype.

Adjunctive sarcosine plus benzoate improved cognitive function in chronic schizophrenia patients with constant clinical symptoms: A randomised, double-blind, placebo-controlled trial

Objectives Hypofunction of NMDA receptor is implicated in the pathophysiology, particularly cognitive impairment, of schizophrenia. Sarcosine, a glycine transporter I (GlyT-1) inhibitor, and sodium benzoate, a d-amino acid oxidase (DAAO) inhibitor, can both enhance NMDA receptor-mediated neurotransmission. We proposed simultaneously inhibiting DAAO and GlyT-1 may be more effective than inhibition of either in improving the cognitive and global functioning of schizophrenia patients. Methods This study compared add-on sarcosine (2 g/day) plus benzoate (1 g/day) vs. sarcosine (2 g/day) for the clinical symptoms, as well as the cognitive and global functioning, of chronic schizophrenia patients in a 12-week, double-blind, randomised, placebo-controlled trial. Participants were measured with the Positive and Negative Syndrome Scale and the Global Assessment of Functioning Scale every 3 weeks. Seven cognitive domains, recommended by the Measurement and Treatment Research to Improve Cognition in Schizophrenia Committee, were measured at weeks 0 and 12. Results Adjunctive sarcosine plus benzoate, but not sarcosine alone, improved the cognitive and global functioning of patients with schizophrenia, even when their clinical symptoms had not improved. Conclusions This finding suggests N-methyl-d-aspartate receptor-enhancement therapy can improve the cognitive function of patients with schizophrenia, further indicating this pro-cognitive effect can be primary without improvement in clinical symptoms.

Generation of tryptophan hydroxylase 2 gene knockout pigs by CRISPR/Cas9-mediated gene targeting

Unbalanced brain serotonin (5-HT) levels have implications in various behavioral abnormalities and neuropsychiatric disorders. The biosynthesis of neuronal 5-HT is regulated by the rate-limiting enzyme, tryptophan hydroxylase-2 (TPH2). In the present study, the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas) system was used to target theTph2 gene in Bama mini pig fetal fibroblasts. It was found that CRISPR/Cas9 targeting efficiency could be as high as 61.5%, and the biallelic mutation efficiency reached at 38.5%. The biallelic modified colonies were used as donors for somatic cell nuclear transfer (SCNT) and 10Tph2 targeted piglets were successfully generated. These Tph2 KO piglets were viable and appeared normal at the birth. However, their central 5-HT levels were dramatically reduced, and their survival and growth rates were impaired before weaning. TheseTph2 KO pigs are valuable large-animal models for studies of 5-HT deficiency induced behavior abnomality.

The role of COMT and plasma proline in the variable penetrance of autistic spectrum symptoms in 22q11.2 deletion syndrome

This paper examines how COMT¹⁵⁸ genotypes and plasma proline levels are associated with variable penetrance of social behavioural and social cognitive problems in 22q11.2 deletion syndrome (22q11DS). Severity of autistic spectrum symptoms of 45 participants with 22q11DS was assessed using the Autism Diagnostic Interview Revised. Face and facial emotion recognition was evaluated using standardized computer-based test-paradigms. Associations with COMT¹⁵⁸ genotypes and proline levels were examined. High proline levels and poor face recognition in individuals with the COMT^MET allele, and poor facial emotion recognition, explained almost 50% of the variance in severity of autism symptomatology in individuals with 22q11DS. High proline levels and a decreased capacity to break down dopamine as a result of the COMT^MET variant are both relevant in the expression of the social phenotype in patients. This epistatic interaction effect between the COMT¹⁵⁸ genotype and proline on the expression of social deficits in 22q11DS shows how factors other than the direct effects of the deletion itself can modulate the penetrance of associated cognitive and behavioural outcomes. These findings are not only relevant to our insight into 22q11DS, but also provide a model to better understand the phenomenon of variable penetrance in other pathogenic genetic variants.

Mesocorticolimbic dopamine functioning in primary psychopathy: A source of within-group heterogeneity

Despite similar emotional deficiencies, primary psychopathic individuals can be situated on a continuum that spans from controlled to disinhibited. The constructs on which primary psychopaths are found to diverge, such as self-control, cognitive flexibility, and executive functioning, are crucially regulated by dopamine (DA). As such, the goal of this review is to examine which specific alterations in the meso-cortico-limbic DA system and corresponding genes (e.g., TH, DAT, COMT, DRD2, DRD4) might bias development towards a more controlled or disinhibited expression of primary psychopathy. Based on empirical data, it is argued that primary psychopathy is generally related to a higher tonic and population activity of striatal DA neurons and lower levels of D2-type DA receptors in meso-cortico-limbic projections, which may boost motivational drive towards incentive-laden goals, dampen punishment sensitivity, and increase future reward-expectancy. However, increasingly higher levels of DA activity in the striatum (moderate versus pathological elevations), lower levels of DA functionality in the prefrontal cortex, and higher D1-to-D2-type receptor ratios in meso-cortico-limbic projections may lead to increasingly disinhibited and impetuous phenotypes of primary psychopathy. Finally, in order to provide a more coherent view on etiological mechanisms, we discuss interactions between DA and serotonin that are relevant for primary psychopathy.

Recent advances in the genetics of emotion regulation: a review

Recent attention has been given to the role of emotion regulation in the development and maintenance of psychopathology, and the psychosocial literature on emotion regulation has been growing rapidly over the past decade. However, knowledge about the genetic etiology of emotion regulation facets has been slower to develop. The present paper aims to briefly introduce the various constructs that fall under the umbrella of emotion regulation; provide an overview of behavioral genetic methods; summarize the empirical studies of emotion regulation twin studies; introduce molecular genetic methods; review the recent molecular genetic studies on emotion regulation; and provide future directions for research.