Functional effects of polymorphisms on glucocorticoid receptor modulation of human anxiogenic substance-P gene promoter activity in primary amygdala neurones

Genetic variants in the TAC1 transcriptional regulatory region affect on trainability and excitability levels in Belgian Malinois dogs

BACKGROUND

Trainability in dogs is affected by learning aptitude and memory capacity. While this trait has a heritable basis in canines, the specific genetic loci responsible for it remain unknown. Our previous results suggested that the BDNF, CCK and TAC1 genes are associated with learning and memory in canines. Experimental validation is crucial to confirm the effects of these candidate genes on trainability. Understanding the genetic foundation of this trait would offer insight into the inheritance pattern of complex behavioural characteristics.

OBJECTIVE

This study aimed to assess the genetic variations within candidate genes and explore their potential associations with behavioural phenotypes in dogs.

METHODS

The behavioural characteristics of 123 male Belgian Malinois dogs were assessed using a customised questionnaire. Target regions of candidate genes were screened for genetic variation by single-strand conformational polymorphism (SSCP). Following that, SSCP banding patterns were sequenced, and putative transcription factor binding sites were predicted using bioinformatics tools. Quantitative association analysis between identified genetic variants and behavioural trait scores was performed using the general linear model (GLM).

RESULTS

Sequencing the coding and flanking regions revealed three mutations (c.-89C>T, c.-162G>C and c.*33T>A) in the dog TAC1 gene. Bioinformatics analysis predicted two single nucleotide polymorphisms (SNPs) were located within the putative TAC1 promoter and could disrupt transcription factor binding sites. Statistical tests revealed that the c.-89C>T was significantly associated with excitability (p < 0.01), while the c.-162G>C was significantly associated with trainability level (p < 0.05).

CONCLUSION

In summary, we identified two regulatory SNPs in the 5'-UTR promoter region of the TAC1 gene that are associated with excitability and trainability in Belgian Malinois dogs. These genetic variations have the potential to alter the binding sites of transcription factors NRF1 and OTX1, consequently influencing TAC1 expression and related behavioural characteristics. Our findings implicate TAC1 polymorphisms as candidates influencing breed-specific behavioural characteristics in canines. Further studies on diverse breeds of dogs are necessary to validate these SNPs' effects.

In vitro modeling of the neurobiological effects of glucocorticoids: A review

Hypothalamic-pituitary adrenal (HPA)axis dysregulation has long been implicated in stress-related disorders such as major depression and post-traumatic stress disorder. Glucocorticoids (GCs) are released from the adrenal glands as a result of HPA-axis activation. The release of GCs is implicated with several neurobiological changes that are associated with negative consequences of chronic stress and the onset and course of psychiatric disorders. Investigating the underlying neurobiological effects of GCs may help to better understand the pathophysiology of stress-related psychiatric disorders. GCs impact a plethora of neuronal processes at the genetic, epigenetic, cellular, and molecular levels. Given the scarcity and difficulty in accessing human brain samples, 2D and 3D in vitro neuronal cultures are becoming increasingly useful in studying GC effects. In this review, we provide an overview of in vitro studies investigating the effects of GCs on key neuronal processes such as proliferation and survival of progenitor cells, neurogenesis, synaptic plasticity, neuronal activity, inflammation, genetic vulnerability, and epigenetic alterations. Finally, we discuss the challenges in the field and offer suggestions for improving the use of in vitro models to investigate GC effects.

Modulating the tachykinin: Role of substance P and neurokinin receptor expression in ocular surface disorders

Substance P (SP) is a tachykinin expressed by various cells in the nervous and immune systems. SP is predominantly released by neurons and exerts its biological and immunological effects through the neurokinin receptors, primarily the neurokinin-1 receptor (NK1R). SP is essential for maintaining ocular surface homeostasis, and its reduced levels in disorders like diabetic neuropathy disrupt the corneal tissue. It also plays an essential role in promoting corneal wound healing by promoting the migration of keratocytes. In this review, we briefly discuss the structure, expression, and function of SP and its principal receptor NK1R. In addition, SP induces pro-inflammatory effects through autocrine or paracrine action on the immune cells in various ocular surface pathologies, including dry eye disease, herpes simplex virus keratitis, and Pseudomonas keratitis. We provide an in-depth review of the pathogenic role of SP in various ocular surface diseases and several new approaches developed to counter the immune-mediated effects of SP either through modulating its production or blocking its target receptor.

Maternal diabetes-mediated RORA suppression in mice contributes to autism-like offspring through inhibition of aromatase

Retinoic acid-related orphan receptor alpha (RORA) suppression is associated with autism spectrum disorder (ASD) development, although the mechanism remains unclear. In this study, we aim to investigate the potential effect and mechanisms of RORA suppression on autism-like behavior (ALB) through maternal diabetes-mediated mouse model. Our in vitro study in human neural progenitor cells shows that transient hyperglycemia induces persistent RORA suppression through oxidative stress-mediated epigenetic modifications and subsequent dissociation of octamer-binding transcription factor 3/4 from the RORA promoter, subsequently suppressing the expression of aromatase and superoxide dismutase 2. The in vivo mouse study shows that prenatal RORA deficiency in neuron-specific RORA null mice mimics maternal diabetes-mediated ALB; postnatal RORA expression in the amygdala ameliorates, while postnatal RORA knockdown mimics, maternal diabetes-mediated ALB in offspring. In addition, RORA mRNA levels in peripheral blood mononuclear cells decrease to 34.2% in ASD patients (n = 121) compared to the typically developing group (n = 118), and the related Receiver Operating Characteristic curve shows good sensitivity and specificity with a calculated 84.1% of Area Under the Curve for ASD diagnosis. We conclude that maternal diabetes contributes to ALB in offspring through suppression of RORA and aromatase, RORA expression in PBMC could be a potential marker for ASD screening.

Hong Yu, Yanbin Niu, Guohua Jia et al. integrate in vitro, in vivo, and human experiments to examine a link between RORA expression on autism-like behavior. Their results suggest that maternal diabetes may contribute to autism-like behavior via RORA suppression.

Structural insights into glucocorticoid receptor function

The glucocorticoid receptor (GR) is a steroid hormone-activated transcription factor that binds to various glucocorticoid response elements to up- or down- regulate the transcription of thousands of genes involved in metabolism, development, stress and inflammatory responses. GR consists of two domains enabling interaction with glucocorticoids, DNA response elements and coregulators, as well as a large intrinsically disordered region that mediates condensate formation. A growing body of structural studies during the past decade have shed new light on GR interactions, providing a new understanding of the mechanisms driving context-specific GR activity. Here, we summarize the established and emerging mechanisms of action of GR, primarily from a structural perspective. This minireview also discusses how the current state of knowledge of GR function may guide future glucocorticoid design with an improved therapeutic index for different inflammatory disorders.

Brain-derived neurotrophic factor upregulates synaptic GluA1 in the amygdala to promote depression in response to psychological stress

Psychological stress impairs neuronal structure and function and leads to emotional disorders, but the underlying mechanisms have not yet been fully elucidated. The amygdala is closely correlated with emotional regulation. In the present study, we analyzed whether the amygdala plasticity is regulated by psychological stress and explored their regulatory mechanism. We established a mouse psychological stress model using an improved communication box, wherein mice were exposed to chronic fear and avoided physical stress interference. After the 14-day psychological stress paradigm, mice exhibited significantly increased depressive behaviors (decreased sucrose consumption in the sucrose preference test and longer immobility time in the forced swimming test). HPLC, ELISA, and molecular and morphological evidences showed that psychological stress increased the content of glutamate and the expression of glutamatergic neurons, upregulated the content of the stress hormone corticosterone, and activated the CREB/BDNF pathway in the amygdala. Furthermore, psychological stress induced an increased density of dendritic spines and LTD impairment in the amygdala. Importantly, virus-mediated silencing of BDNF in the basolateral amygdala (BLA) nuclei reversed the depression-like behaviors and the increase of synaptic GluA1 and its phosphorylation at Ser831 and Ser845 sites in psychologically stressed mice. This process was likely achieved through mTOR signaling activation. Finally, we treated primary amygdala neurons with corticosterone to mimic psychological stress; corticosterone-induced upregulation of GluA1 was prevented by BDNF and mTOR antagonists. Thus, activation of the CREB/BDNF pathway in the amygdala following psychological stress upregulates synaptic GluA1 via mTOR signaling, which dysregulates synaptic plasticity of the amygdala, eventually promoting depression.

Perspective: Quality Versus Quantity; Is It Important to Assess the Role of Enhancers in Complex Disease from an In Vivo Perspective?

Sequencing of the human genome has permitted the development of genome-wide association studies (GWAS) to analyze the genetics of a number of complex disorders such as depression, anxiety and substance abuse. Thanks to their ability to analyze huge cohort sizes, these studies have successfully identified thousands of loci associated with a broad spectrum of complex diseases. Disconcertingly, the majority of these GWAS hits occur in non-coding regions of the genome, much of which controls the cell-type-specific expression of genes essential to health. In contrast to gene coding sequences, it is a challenge to understand the function of this non-coding regulatory genome using conventional biochemical techniques in cell lines. The current commentary scrutinizes the field of complex genetics from the standpoint of the large-scale whole-genome functional analysis of the promoters and cis-regulatory elements using chromatin markers. We contrast these large scale quantitative techniques against comparative genomics and in vivo analyses including CRISPR/CAS9 genome editing to determine the functional characteristics of these elements and to understand how polymorphic variation and epigenetic changes within these elements might contribute to complex disease and drug response. Most importantly, we suggest that, although the role of chromatin markers will continue to be important in identifying and characterizing enhancers, more emphasis must be placed on their analysis in relevant in-vivo models that take account of the appropriate cell-type-specific roles of these elements. It is hoped that offering these insights might refocus progress in analyzing the data tsunami of non-coding GWAS and whole-genome sequencing "hits" that threatens to overwhelm progress in the field.

Resveratrol ameliorates prenatal progestin exposure-induced autism-like behavior through ERβ activation

Background

Recent literatures indicate that maternal hormone exposure is a risk factor for autism spectrum disorder (ASD). We hypothesize that prenatal progestin exposure may counteract the neuroprotective effect of estrogen and contribute to ASD development, and we aim to develop a method to ameliorate prenatal progestin exposure-induced autism-like behavior.

Methods

Experiment 1: Prenatal progestin exposure-induced offspring are treated with resveratrol (RSV) through either prenatal or postnatal exposure and then used for autism-like behavior testing and other biomedical analyses. Experiment 2: Prenatal norethindrone (NET) exposure-induced offspring are treated with ERβ knockdown lentivirus together with RSV for further testing. Experiment 3: Pregnant dams are treated with prenatal NET exposure together with RSV, and the offspring are used for further testing.

Results

Eight kinds of clinically relevant progestins were used for prenatal exposure in pregnant dams, and the offspring showed decreased ERβ expression in the amygdala with autism-like behavior. Oral administration of either postnatal or prenatal RSV treatment significantly reversed this effect with ERβ activation and ameliorated autism-like behavior. Further investigation showed that RSV activates ERβ and its target genes by demethylation of DNA and histone on the ERβ promoter, and then minimizes progestin-induced oxidative stress as well as the dysfunction of mitochondria and lipid metabolism in the brain, subsequently ameliorating autism-like behavior.

Conclusions

We conclude that resveratrol ameliorates prenatal progestin exposure-induced autism-like behavior through ERβ activation. Our data suggest that prenatal progestin exposure is a strong risk factor for autism-like behavior. Many potential clinical progestin applications, including oral contraceptive pills, preterm birth drugs, and progestin-contaminated drinking water or seafood, may be risk factors for ASD. In addition, RSV may be a good candidate for clinically rescuing or preventing ASD symptoms in humans, while high doses of resveratrol used in the animals may be a potential limitation for human application.

Substance P signalling in primary motor cortex facilitates motor learning in rats

Among the genes that are up-regulated in response to a reaching training in rats, Tachykinin 1 (Tac1)-a gene that encodes the neuropeptide Substance P (Sub P)-shows an especially strong expression. Using Real-Time RT-PCR, a detailed time-course of Tac1 expression could be defined: a significant peak occurs 7 hours after training ended at the first and second training session, whereas no up-regulation could be detected at a later time-point (sixth training session). To assess the physiological role of Sub P during movement acquisition, microinjections into the primary motor cortex (M1) contralateral to the trained paw were performed. When Sub P was injected before the first three sessions of a reaching training, effectiveness of motor learning became significantly increased. Injections at a time-point when rats already knew the task (i.e. training session ten and eleven) had no effect on reaching performance. Sub P injections did not influence the improvement of performance within a single training session, but retention of performance between sessions became strengthened at a very early stage (i.e. between baseline-training and first training session). Thus, Sub P facilitates motor learning in the very early phase of skill acquisition by supporting memory consolidation. In line with these findings, learning related expression of the precursor Tac1 occurs at early but not at later time-points during reaching training.

Prenatal levonorgestrel exposure induces autism-like behavior in offspring through ERβ suppression in the amygdala

BACKGROUND

Autism spectrum disorder (ASD) is characterized by impairments in social communication and restricted or repetitive behaviors or interests. ASD is now diagnosed in more than one out of 100 children and is biased towards males by a ratio of at least 4:1. Many possible explanations and potential causative factors have been reported, such as genetics, sex, and environmental factors, although the detailed mechanisms of ASD remain unclear.

METHODS

The dams were exposed through oral contraceptives to either vehicle control (VEH) alone, levonorgestrel (LNG) alone, ethinyl estradiol (EE) alone, or a combination of LNG/EE for 21 days during their pregnancy. The subsequent 10-week-old offspring were used for autism-like behavior testing, and the limbic tissues were isolated for analysis. In another experimental group, 8-week-old male offspring were treated by infusion of ERβ overexpression/knockdown lentivirus in the amygdala, and the offspring were analyzed after 2 weeks.

RESULTS

We show that prenatal exposure of either LNG alone or a LNG/EE combination, but not EE alone, results in suppression of ERβ (estrogen receptor β) and its target genes in the amygdala with autism-like behavior in male offspring, while there is a much smaller effect on female offspring. However, we find that there is no effect on the hippocampus and hypothalamus. Further investigation shows that ERβ suppression is due to LNG-mediated altered methylation on the ERβ promoter and results in tissue damage with oxidative stress and the dysfunction of mitochondria and fatty acid metabolism, which subsequently triggers autism-like behavior. Overexpression of ERβ in the amygdala completely restores LNG-induced ERβ suppression and autism-like behaviors in offspring, while ERβ knockdown mimics this effect, indicating that ERβ expression in the amygdala plays an important role in autism-like behavior development.

CONCLUSIONS

We conclude that prenatal levonorgestrel exposure induces autism-like behavior in offspring through ERβ suppression in the amygdala. To our knowledge, this is the first time the potential effect of oral contraceptives on the contribution of autism-like behavior in offspring has been discovered.

High activity of the stress promoter contributes to susceptibility to stress in the tree shrew

Stress is increasingly present in everyday life in our fast-paced society and involved in the pathogenesis of many psychiatric diseases. Corticotrophin-releasing-hormone (CRH) plays a pivotal role in regulating the stress responses. The tree shrews are highly vulnerable to stress which makes them the promising animal models for studying stress responses. However, the mechanisms underlying their high stress-susceptibility remained unknown. Here we confirmed that cortisol was the dominate corticosteroid in tree shrew and was significantly increased after acute stress. Our study showed that the function of tree shrew CRH - hypothalamic-pituitary-adrenal (HPA) axis was nearly identical to human that contributed little to their hyper-responsiveness to stress. Using CRH transcriptional regulation analysis we discovered a peculiar active glucocorticoid receptor response element (aGRE) site within the tree shrew CRH promoter, which continued to recruit co-activators including SRC-1 (steroid receptor co-activator-1) to promote CRH transcription under basal or forskolin/dexamethasone treatment conditions. Basal CRH mRNA increased when the aGRE was knocked into the CRH promoter in human HeLa cells using CAS9/CRISPR. The aGRE functioned critically to form the "Stress promoter" that contributed to the higher CRH expression and susceptibility to stress. These findings implicated novel molecular bases of the stress-related diseases in specific populations.