Prefrontal cortex VAMP1 gene network moderates the effect of the early environment on cognitive flexibility in children

Exploring the role of environmental enrichment and early life adversity on emotional development

Early life adversity has been linked with a higher probability of developing behavioral impairments and environmental manipulation is a strategy that may reduce the negative effects of exposure to adversity in early life. Here, we focused on exploring the influence of environmental enrichment (EE) as a protective factor in the context of early life adversity. We hypothesized that 24 hours of maternal deprivation (MD), in the second week of life, could induce anxiety-like behavior alterations and that exposure to EE could induce resilience to these behaviors due to alterations in the serotonergic system. Male Wistar rats were exposed to MD, on postnatal days 11 and 13, and to EE, after weaning. In adulthood, we performed a series of behavioral tests for fear, anxiety, and locomotor activity. We also measured the levels of serotonin in the amygdala and dorsal raphe nucleus. Our results revealed that MD does not impact fear behavior or the levels of serotonin, while EE decreases locomotor activity in a novel environment and enhances exploration in the predator odor test. EE also decreases serotonin in the amygdala and increases its turnover rate levels. Our findings provide insights into the critical timeframe during which stress exposure impacts the development and confirm that exposure to EE has an independent and protective effect for anxiety-like behaviors later in life.

Coping with the experience of frustration throughout life: Sex- and age-specific effects of early life stress on the susceptibility to reward devaluation

Early life stress may lead to lifelong impairments in psychophysiological functions, including emotional and reward systems. Unpredicted decrease in reward magnitude generates a negative emotional state (frustration) that may be involved with susceptibility to psychiatric disorders. We evaluated, in adolescents and adult rats of both sexes, whether maternal separation (MS) alters the ability to cope with an unexpected reduction of reward later in life. Litters of Wistar rats were divided into controls (non handled - NH) or subjected to MS. Animals were trained to find sugary cereal pellets; later the amount was reduced. Increased latency to reach the reward-associated area indicates higher inability to regulate frustration. The dorsal hippocampus (dHC) and basolateral amygdala (BLA) were evaluated for protein levels of NMDA receptor subunits (GluN2A/GluN2B), synaptophysin, PSD95, SNAP-25 and CRF1. We found that adult MS males had greater vulnerability to reward reduction, together with decreased GluN2A and increased GluN2B immunocontent in the dHC. MS females and adolescents did not differ from controls. We concluded that MS enhances the response to frustration in adult males. The change in the ratio of GluN2A and GluN2B subunits in dHC could be related to a stronger, more difficult to update memory of the aversive experience.

Maternal aerobic exercise decreases the effects of a perinatal Western diet on the short and long-term memory of CD1 mouse progeny

Maternal nutrition and physical activity during pregnancy and lactation can modify offspring development. Here, we investigated the effects of maternal aerobic exercise (AE) and Western diet (WD) on brain development, cognitive flexibility, and memory of progenies. Sixteen adult female mice were assigned to AE or sedentary groups (SED) and fed a balanced diet (BD) or WD. Offspring were categorized into four groups: WD + AE, WD + SED, BD + AE, and BD + SED. The AE group showed enhanced spontaneous alternation in the T-maze test, suggesting an improvement in working memory and tasks related to cognitive flexibility. The novel object recognition (NOR) test showed that the BD + AE pups improved their absolute discrimination and discrimination index at 24 h, which suggests a delay in memory consolidation without affecting evocation. WD + SED showed poorer discrimination and recognition memory. The pups of AE mothers had better efficiency in short-term memory, whereas WD offspring showed low performance in long-term memory. Interestingly, exercise improved tasks related to cognitive flexibility, regardless of the diet. These findings indicate that maternal diet and physical activity modify offspring development and suggest that maternal AE during pregnancy could be a beneficial intervention to counteract the adverse effects of WD by improving spatial memory and cognitive flexibility in offspring.

A protein-coding gene expression atlas from the brain of pregnant and non-pregnant goats

Background: The brain is an extraordinarily complex organ with multiple anatomical structures involved in highly specialized functions related with behavior and physiological homeostasis. Our goal was to build an atlas of protein-coding gene expression in the goat brain by sequencing the transcriptomes of 12 brain regions in seven female Murciano-Granadina goats, from which three of them were 1-month pregnant. Results: Between 14,889 (cerebellar hemisphere) and 15,592 (pineal gland) protein-coding genes were expressed in goat brain regions, and most of them displayed ubiquitous or broad patterns of expression across tissues. Principal component analysis and hierarchical clustering based on the patterns of mRNA expression revealed that samples from certain brain regions tend to group according to their position in the anterior-posterior axis of the neural tube, i.e., hindbrain (pons and medulla oblongata), midbrain (rostral colliculus) and forebrain (frontal neocortex, olfactory bulb, hypothalamus, and hippocampus). Exceptions to this observation were cerebellum and glandular tissues (pineal gland and hypophysis), which showed highly divergent mRNA expression profiles. Differential expression analysis between pregnant and non-pregnant goats revealed moderate changes of mRNA expression in the frontal neocortex, hippocampus, adenohypophysis and pons, and very dramatic changes in the olfactory bulb. Many genes showing differential expression in this organ are related to olfactory function and behavior in humans. Conclusion: With the exception of cerebellum and glandular tissues, there is a relationship between the cellular origin of sampled regions along the anterior-posterior axis of the neural tube and their mRNA expression patterns in the goat adult brain. Gestation induces substantial changes in the mRNA expression of the olfactory bulb, a finding consistent with the key role of this anatomical structure on the development of maternal behavior.

Serotonin transporter (5-HTT) gene network moderates the impact of prenatal maternal adversity on orbitofrontal cortical thickness in middle childhood

In utero, the developing brain is highly susceptible to the environment. For example, adverse maternal experiences during the prenatal period are associated with outcomes such as altered neurodevelopment and emotion dysregulation. Yet, the underlying biological mechanisms remain unclear. Here, we investigate whether the function of a network of genes co-expressed with the serotonin transporter in the amygdala moderates the impact of prenatal maternal adversity on the structure of the orbitofrontal cortex (OFC) in middle childhood and/or the degree of temperamental inhibition exhibited in toddlerhood. T1-weighted structural MRI scans were acquired from children aged 6-12 years. A cumulative maternal adversity score was used to conceptualize prenatal adversity and a co-expression based polygenic risk score (ePRS) was generated. Behavioural inhibition at 18 months was assessed using the Early Childhood Behaviour Questionnaire (ECBQ). Our results indicate that in the presence of a low functioning serotonin transporter gene network in the amygdala, higher levels of prenatal adversity are associated with greater right OFC thickness at 6-12 years old. The interaction also predicts temperamental inhibition at 18 months. Ultimately, we identified important biological processes and structural modifications that may underlie the link between early adversity and future deviations in cognitive, behavioural, and emotional development.

Examining the biological mechanisms of human mental disorders resulting from gene-environment interdependence using novel functional genomic approaches

We explore how functional genomics approaches that integrate datasets from human and non-human model systems can improve our understanding of the effect of gene-environment interplay on the risk for mental disorders. We start by briefly defining the G-E paradigm and its challenges and then discuss the different levels of regulation of gene expression and the corresponding data existing in humans (genome wide genotyping, transcriptomics, DNA methylation, chromatin modifications, chromosome conformational changes, non-coding RNAs, proteomics and metabolomics), discussing novel approaches to the application of these data in the study of the origins of mental health. Finally, we discuss the multilevel integration of diverse types of data. Advance in the use of functional genomics in the context of a G-E perspective improves the detection of vulnerabilities, informing the development of preventive and therapeutic interventions.

Novel functional genomics approaches bridging neuroscience and psychiatry

The possibility of establishing a metric of individual genetic risk for a particular disease or trait has sparked the interest of the clinical and research communities, with many groups developing and validating genomic profiling methodologies for their potential application in clinical care. Current approaches for calculating genetic risk to specific psychiatric conditions consist of aggregating genome-wide association studies-derived estimates into polygenic risk scores, which broadly represent the number of inherited risk alleles for an individual. While the traditional approach for polygenic risk score calculation aggregates estimates of gene-disease associations, novel alternative approaches have started to consider functional molecular phenotypes that are closer to genetic variation and are less penalized by the multiple testing required in genome-wide association studies. Moving the focus from genotype-disease to genotype-gene regulation frameworks, these novel approaches incorporate prior knowledge regarding biological processes involved in disease and aggregate estimates for the association of genotypes and phenotypes using multi-omics data modalities. In this review, we discuss and list different functional genomics tools that can be used and integrated to inform researchers and clinicians for a better understanding and diagnosis of psychopathology. We suggest that these novel approaches can help generate biologically driven hypotheses for polygenic signals that can ultimately serve the clinical community as potential biomarkers of psychiatric disease susceptibility.

Effects of early life adversities upon memory processes and cognition in rodent models

Exposure to stressors in early postnatal life induces long-lasting modifications in brainfunction.Thisplasticity,an essential characteristic of the brain that enables adaptation to the environment, may also induce impairments in some psychophysiological functions, including learning and memory. Early life stress (ELS) has long-term effects on thehypothalamic-pituitary-adrenal axisresponse to stressors, and has been reported to lead toneuroinflammation,altered levelsof neurotrophic factors, modifications inneurogenesis andsynaptic plasticity,with changes in neurotransmitter systems and network functioning. In this review, we focus on early postnatal stress in animal models and their effects on learning and memory.Many studies have reported ELS-induced impairments in different types of memories, including spatial memory, fear memory, recognition (both for objects and social) memory, working memory and reversal learning. Studies are not always in agreement, however, no effects, or sometimes facilitation, being reported, depending on the nature and intensity of the early intervention, as well as the age when the outcome was evaluated and the sex of the animals. When considering processes occurring after consolidation, related with memory maintenance or modification, there are a very reduced number of reports. Future studies addressing the mechanisms underlying memory changes for ELS should shed some light on the understanding of the different effects induced by stressors of different types and intensities on cognitive functions.