Candidate gene associations with withdrawn behavior

Single nucleotide variations encoding missense mutations in G protein-coupled receptors may contribute to autism

Autism is a neurodevelopmental condition with a range of symptoms that vary in intensity and severity from person to person. Genetic sequencing has identified thousands of genes containing mutations in autistic individuals, which may contribute to the development of autistic symptoms. Several of these genes encode G protein-coupled receptors (GPCRs), which are cell surface expressed proteins that transduce extracellular messages to the intracellular space. Mutations in GPCRs can impact their function, resulting in aberrant signalling within cells and across neurotransmitter systems in the brain. This review summarises the current knowledge on autism-associated single nucleotide variations encoding missense mutations in GPCRs and the impact of these genetic mutations on GPCR function. For some autism-associated mutations, changes in GPCR expression levels, ligand affinity, potency and efficacy have been observed. However, for many the functional consequences remain unknown. Thus, further work to characterise the functional impacts of the genetically identified mutations is required. LINKED ARTICLES: This article is part of a themed issue Therapeutic Targeting of G Protein-Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc.

Withdrawn Behavior in Preschool: Implications for Emotion Knowledge and Broader Emotional Competence

The present study investigated the respective roles of withdrawal, language, and context-inappropriate (CI) anger in the development of emotion knowledge (EK) among a subsample of 4 and 5 year-old preschoolers (n = 74). Measures included parent-reported withdrawn behavior, externalizing behavior, and CI anger, as well as child assessments of receptive language and EK. Ultimately, findings demonstrated that receptive language mediated the relationship between withdrawn behavior and situational EK. However, CI anger significantly interacted with receptive language, and, when incorporated into a second-stage moderated mediation analysis, moderate levels of CI anger rendered the indirect effect of withdrawn behavior on situational EK via receptive language insignificant. Cumulatively, these findings demonstrate a mechanism by which withdrawal may impact EK. They also indicate that such an effect may be attenuated in children with moderate levels of CI anger. Implications of these findings are discussed.

Genetic analysis of suicide: a sample study in Tuscany (Central Italy)

Many studies have examined the genetic contribution to suicide. However, data on suicide in the Italian population are scarce. We therefore aimed to address this gap by investigating a cohort of 111 Italians for whom a verdict of suicide had been declared in court in Florence, Italy between 2007 and 2017. This cohort included 86 men and 25 women. DNA samples were obtained from tissues or blood, and 22 genes from multiple neurobiological pathways previously shown to be associated with the pathogenesis of suicide were analysed. Next-generation sequencing was used to compare these gene sequences with those from a large, normal population. In this study, we identified 19 gene variants that were present at significantly lower frequencies in our Italian cohort than in the general population. In addition, four missense mutations were identified in four different genes: Monoamine Oxidase A (MAOA), 5-Hydroxytryptamine Receptor 2 A (HTR2A), Sodium Voltage-Gated Channel Alpha Subunit 8 (SCN8A), and Nitric Oxide Synthase 3 (NOS3). Our study identified several potential genetic links with suicide in a cohort of Italians and supports a relationship between specific genetic variants and suicidal behaviour in this population.

Influence of Receptor Polymorphisms on the Response to α-Adrenergic Receptor Blockers in Pheochromocytoma Patients

Background: Presurgical treatment with an α-adrenergic receptor blocker is recommended to antagonize the catecholamine-induced α-adrenergic receptor mediated vasoconstriction in patients with pheochromocytoma or sympathetic paraganglioma (PPGL). There is, however, a considerable interindividual variation in the dose-response relationship regarding the magnitude of blood pressure reduction or the occurrence of side effects. We hypothesized that genetically determined differences in α-adrenergic receptor activity contribute to this variability in dose-response relationship. Methods: Thirty-one single-nucleotide polymorphisms (SNPs) of the α1A, α1B, α1D adrenoreceptor (ADRA1A, ADRA1B, ADRA1D) and α2A, α2B adrenoreceptor (ADRA2A, ADRA2B) genes were genotyped in a group of 116 participants of the PRESCRIPT study. Haplotypes were constructed after determining linkage disequilibrium blocks. Results: The ADRA1B SNP rs10515807 and the ADRA2A SNPs rs553668/rs521674 were associated with higher dosages of α-adrenergic receptor blocker (p < 0.05) and with a higher occurrence of side effects (rs10515807) (p = 0.005). Similar associations were found for haplotype block 6, which is predominantly defined by rs10515807. Conclusions: This study suggests that genetic variability of α-adrenergic receptor genes might be associated with the clinically observed variation in beneficial and adverse therapeutic drug responses to α-adrenergic receptor blockers. Further studies in larger cohorts are needed to confirm our observations.

Molecular laterality encodes stress susceptibility in the medial prefrontal cortex

Functional lateralization of the prefrontal cortex has been implicated in stress and emotional disorders, yet underlying gene expression changes remains unknown. Here, we report molecular signatures lateralized by chronic social defeats between the two medial prefrontal cortices (mPFCs). Stressed mice show 526 asymmetrically expressed genes between the mPFCs. This cortical asymmetry selectively occurs in stressed mice with depressed social activity, but not in resilient mice with normal behavior. We have isolated highly asymmetric genes including connective tissue growth factor (CTGF), a molecule that modulates wound healing at the periphery. Knockdown of CTGF gene in the right mPFC by shRNA led to a stress-resistant behavioral phenotype. Overexpression of CTGF in the right mPFC using viral transduction induces social avoidance while the left mPFC thereof prevent stress-induced social avoidance. Our study provides a molecular window into the mechanism of stress-induced socioemotional disorders, which can pave the way for new interventions by targeting cortical asymmetry.

The therapeutic and protective effects of bee pollen against prenatal methylmercury induced neurotoxicity in rat pups

The current study evaluated the protective and therapeutic potency of bee pollen in ameliorating the toxic effects of methylmercury (MeHg), by measuring certain biochemical parameters related to neurotransmission, neuroinflammation, apoptosis, and glutamate excitotoxicity in the male neonate brain. Healthy, pregnant female rats (N = 40) were randomly divided into 5 groups, each comprising10 male neonates, as follows: (i) neonates delivered by control mothers; (ii) neonates delivered by MeHg-treated mothers who received 0.5 mg/kg BW/day MeHg via drinking water from gestational day 7 till postnatal day 7; (iii) neonates delivered by bee pollen treated mothers who received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks; (iv) protective group of neonates delivered by MeHg and bee pollen-treated mothers, who continued to receive bee pollen until day 21 at the same dose, and (v) therapeutic group of neonates delivered by MeHg- treated mothers followed by bee pollen treatment, wherein they received 200-mg/kg BW bee pollen from postnatal day 0 for 4 weeks. Selected biochemical parameters in brain homogenates from each group were measured. MeHg-treated groups exhibited various signs of brain toxicity, such as a marked reduction in neurotransmitters (serotonin (5-HT), nor-adrenalin (NA), dopamine (DA)) and gamma aminobutyric acid (GABA) and elevated levels of interferon gamma (IFN-γ), caspase-3, and glutamate (Glu). Bee pollen effectively reduced the neurotoxic effects of MeHg. Minimal changes in all measured parameters were observed in MeHg-treated animals compared to the control group. Therefore, bee pollen may safely improve neurotransmitter defects, inflammation, apoptosis, and glutamate excitotoxicity.

Association of rs4680 COMT, rs6280 DRD3, and rs7322347 5HT2A With Clinical Features of Youth-Onset Schizophrenia

We investigated the associations of rs4680 COMT, rs6280 DRD3, and rs7322347 5HT2A with youth-onset schizophrenia in the Russian population in a case-control study, and the role of the genotype in the severity of clinical features. The association between rs7322347 and schizophrenia (p = 0.0001) is described for the first time. Furthermore, we found a link with rs6280 and rs4680 in females (p = 0.001 and p = 0.02 respectively) and with rs7322347 in males (p = 0.002). Clinical symptoms were assessed on three scales: the Clinician-Rated Dimensions of Psychosis Symptom Severity scale, Positive and Negative Syndrome Scale, and Frontal Assessment Battery. Gender differences in clinical features are of particular interest. In our study we found gender differences in the severity of clinical features-higher scores for delusions (Positive and Negative Syndrome Scale and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition) in males and higher scores for depression, delusions, somatic concern, motor retardation, poor attention were found in females.

Genetic variant rs3750625 in the 3'UTR of ADRA2A affects stress-dependent acute pain severity after trauma and alters a microRNA-34a regulatory site

α2A adrenergic receptor (α2A-AR) activation has been shown in animal models to play an important role in regulating the balance of acute pain inhibition vs facilitation after both physical and psychological stress. To our knowledge, the influence of genetic variants in the gene encoding α2A-AR, ADRA2A, on acute pain outcomes in humans experiencing traumatic stress has not been assessed. In this study, we tested whether a genetic variant in the 3'UTR of ADRA2A, rs3750625, is associated with acute musculoskeletal pain (MSP) severity following motor vehicle collision (MVC, n = 948) and sexual assault (n = 84), and whether this influence was affected by stress severity. We evaluated rs3750625 because it is located in the seed binding region of miR-34a, a microRNA (miRNA) known to regulate pain and stress responses. In both cohorts, the minor allele at rs3750625 was associated with increased musculoskeletal pain in distressed individuals (stress*rs3750625 P = 0.043 for MVC cohort and P = 0.007 for sexual assault cohort). We further found that (1) miR-34a binds the 3'UTR of ADRA2A, (2) the amount of repression is greater when the minor (risk) allele is present, (3) miR-34a in the IMR-32 adrenergic neuroblastoma cell line affects ADRA2A expression, (4) miR-34a and ADRA2A are expressed in tissues known to play a role in pain and stress, (5) following forced swim stress exposure, rat peripheral nerve tissue expression changes are consistent with miR-34a regulation of ADRA2A. Together, these results suggest that ADRA2A rs3750625 contributes to poststress musculoskeletal pain severity by modulating miR-34a regulation.

The serotonin transporter promoter polymorphism moderates the continuity of behavioral inhibition in early childhood

Persistently elevated behavioral inhibition (BI) in children is a marker of vulnerability to psychopathology. However, little research has considered the joint influences of caregiver and child factors that may moderate the continuity of BI in early childhood, particularly genetic variants that may serve as markers of biological plasticity, such as the serotonin transporter linked polymorphic region (5-HTTLPR). We explored this issue in 371 preschoolers and their caregivers, examining whether parent characteristics (i.e., overinvolvement or anxiety disorder) and child 5-HTTLPR influenced the continuity of BI between ages 3 and 5. Measures were observational ratings of child BI, observational and questionnaire measures of parenting, and parent interviews for anxiety disorder history, and children were genotyped for the 5-HTTLPR. Parent factors did not moderate the association between age 3 and age 5 BI; however, child BI at age 3 interacted with children's 5-HTTLPR variants to predict age 5 BI, such that children with at least one copy of the short allele exhibited less continuity of BI over time relative to children without this putative plasticity variant. Findings are consistent with previous work indicating the 5-HTTLPR short variant increases plasticity to contextual influences, thereby serving to decrease the continuity of BI in early childhood.

The genetics of anxiety-related negative valence system traits

NIMH's Research Domain Criteria (RDoC) domain of negative valence systems (NVS) captures constructs of negative affect such as fear and distress traditionally subsumed under the various internalizing disorders. Through its aims to capture dimensional measures that cut across diagnostic categories and are linked to underlying neurobiological systems, a large number of phenotypic constructs have been proposed as potential research targets. Since "genes" represent a central "unit of analysis" in the RDoC matrix, it is important for studies going forward to apply what is known about the genetics of these phenotypes as well as fill in the gaps of existing knowledge. This article reviews the extant genetic epidemiological data (twin studies, heritability) and molecular genetic association findings for a broad range of putative NVS phenotypic measures. We find that scant genetic epidemiological data is available for experimentally derived measures such as attentional bias, peripheral physiology, or brain-based measures of threat response. The molecular genetic basis of NVS phenotypes is in its infancy, since most studies have focused on a small number of candidate genes selected for putative association to anxiety disorders (ADs). Thus, more research is required to provide a firm understanding of the genetic aspects of anxiety-related NVS constructs. © 2016 Wiley Periodicals, Inc.

Body fluid levels of neuroactive amino acids in autism spectrum disorders: a review of the literature

A review of studies on the body fluid levels of neuroactive amino acids, including glutamate, glutamine, taurine, gamma-aminobutyric acid (GABA), glycine, tryptophan, d-serine, and others, in autism spectrum disorders (ASD) is given. The results reported in the literature are generally inconclusive and contradictory, but there has been considerable variation among the previous studies in terms of factors such as age, gender, number of subjects, intelligence quotient, and psychoactive medication being taken. Future studies should include simultaneous analyses of a large number of amino acids [including d-serine and branched-chain amino acids (BCAAs)] and standardization of the factors mentioned above. It may also be appropriate to use saliva sampling to detect amino acids in ASD patients in the future—this is noninvasive testing that can be done easily more frequently than other sampling, thus providing more dynamic monitoring.

Therapeutic potency of bee pollen against biochemical autistic features induced through acute and sub-acute neurotoxicity of orally administered propionic acid

Background

It is now well documented that postnatal exposure to certain chemicals has been reported to increase the risk of autism spectrum disorder. Propionic acid (PA), as a metabolic product of gut microbiotaandas a commonly used food additive, has been reported to mediate the effects of autism. Results from animal studies may help to identify environmental neurotoxic agents and drugs that can ameliorate neurotoxicity and may thereby aid in the treatment of autism. The present study investigated the ameliorative effects of natural bee pollen against acute and sub-acute brain intoxication induced by (PA) in rats.

Methods

Twenty-four young male Western Albino ratswere enrolled in the present study. They were classified into four equal groups, eachwith6 rats. The control group received only phosphate buffered saline; the oral buffered PA-treated groups (II and III) received a neurotoxic dose of 750 mg/kg body weight divided in 3 dose of 250 mg/kg body weight/day serving asthe acute group and 750 mg/kg body weight divided in 10 equal dose of 75 mg/kg body weight/day as the sub-acute group. The fourth group received 50 mg bee pollen for 30 days after PA-acute intoxication.

Results

The obtained data showed that the PA-treated groups demonstrated multiple signs of brain toxicity, as indicated by a depletion of serotonin (5HT), dopamine and nor-adrenaline, together withan increase in IFN-γ and caspase 3. Bee pollen was effective in ameliorating the neurotoxic effect of PA. All measured parameters demonstrated minimal alteration in comparison with thecontrol animal than did those of acute and sub-acute PA-treated animals.

Conclusions

In conclusion, bee pollen demonstrates anti-inflammatory and anti-apoptotic effects while ameliorating the impaired neurochemistry of PA-intoxicated rats.

Acute dietary tryptophan manipulation differentially alters social behavior, brain serotonin and plasma corticosterone in three inbred mouse strains

Clinical evidence indicates brain serotonin (5-HT) stores and neurotransmission may be inadequate in subpopulations of individuals with autism, and this may contribute to characteristically impaired social behaviors. Findings that depletion of the 5-HT precursor tryptophan (TRP) worsens autism symptoms support this hypothesis. Yet dietetic studies show and parents report that many children with autism consume less TRP than peers. To measure the impact of dietary TRP content on social behavior, we administered either diets devoid of TRP, with standard TRP (0.2 g%), or with 1% added TRP (1.2 g%) overnight to three mouse strains. Of these, BTBRT(+)Itpr3(tf)/J and 129S1/SvImJ consistently exhibit low preference for social interaction relative to C57BL/6. We found that TRP depletion reduced C57BL/6 and 129S social interaction preference, while TRP enhancement improved BTBR sociability (p < 0.05; N = 8-10). Subsequent marble burying did not differ among diets or strains. After behavior tests, brain TRP levels and plasma corticosterone were higher in TRP enhanced C57BL/6 and BTBR, while 5-HT levels were reduced in all strains by TRP depletion (p < 0.05; N = 4-10). Relative hyperactivity of BTBR and hypoactivity of 129S, evident in self-grooming and chamber entries during sociability tests, were uninfluenced by dietary TRP. Our findings demonstrate mouse sociability and brain 5-HT turnover are reduced by acute TRP depletion, and can be enhanced by TRP supplementation. This outcome warrants further basic and clinical studies employing biomarker combinations such as TRP metabolism and 5-HT regulated hormones to characterize conditions wherein TRP supplementation may best ameliorate sociability deficits.

Polymorphism in the serotonin receptor 2a (HTR2A) gene as possible predisposal factor for aggressive traits

Aggressive manifestations and their consequences are a major issue of mankind, highlighting the need for understanding the contributory factors. Still, aggression-related genetic analyses have so far mainly been conducted on small population subsets such as individuals suffering from a certain psychiatric disorder or a narrow-range age cohort, but no data on the general population is yet available. In the present study, our aim was to identify polymorphisms in genes affecting neurobiological processes that might explain some of the inter-individual variation between aggression levels in the non-clinical Caucasian adult population. 55 single nucleotide polymorphisms (SNP) were simultaneously determined in 887 subjects who also filled out the self-report Buss-Perry Aggression Questionnaire (BPAQ). Single marker association analyses between genotypes and aggression scores indicated a significant role of rs7322347 located in the HTR2A gene encoding serotonin receptor 2a following Bonferroni correction for multiple testing (p = 0.0007) both for males and females. Taking the four BPAQ subscales individually, scores for Hostility, Anger and Physical Aggression showed significant association with rs7322347 T allele in themselves, while no association was found with Verbal Aggression. Of the subscales, relationship with rs7322347 was strongest in the case of Hostility, where statistical significance virtually equaled that observed with the whole BPAQ. In conclusion, this is the first study to our knowledge analyzing SNPs in a wide variety of genes in terms of aggression in a large sample-size non-clinical adult population, also describing a novel candidate polymorphism as predisposal to aggressive traits.