Corticosterone after early adolescent stress prevents social avoidance, aversive behavior, and morphine-conditioned place preference in adulthood.

RATIONALE: Stress during childhood or adolescence increases vulnerability to psychiatric disorders in adults. In adult rodents, the delayed effects of stress can increase anxiety-like behavior. These effects, however, can be prevented with post-stress administration of corticosterone (CORT). The effectiveness of CORT in preventing adolescent stress-induced emotional behavior alterations in adulthood has yet to be investigated. OBJECTIVES: Here, we investigated the interactions between early adolescent stress and exogenous corticosterone on adult social, aversive, and drug-seeking behavior in mice, which are translationally related to symptoms associated with psychiatric and substance abuse disorders. METHODS AND RESULTS: A single administration of CORT in drinking water (400ug/mL) for 24 h after social defeat or context fear conditioning prevents defeat-induced social avoidance, alters fear processing, prevents adolescent stress-induced anhedonia, and prevents stress-potentiated morphine place preference in adulthood. Exogenous CORT did not immediately prevent stress-induced potentiation of morphine conditioned-place preference in adolescents but did so in adult mice. However, when administered to adolescent mice, CORT also prevented the incubation of morphine-conditioned place preference into adulthood. Lastly, exogenous CORT administration blunted endogenous corticosterone but was unrelated to freezing behavior during a fear test. CONCLUSIONS: This is the first demonstration of adolescent post-stress CORT promoting socio-emotional resilience and preventing drug-seeking behavior. Our data suggest elevated corticosterone after a stress experience promotes resilience for at least 40 days across the developmental transition from adolescence to adulthood and is effective for socio-emotional and drug-seeking behavior. These results are critical for understanding how adolescent stress impacts emotional and drug-seeking behavior into adulthood.

Pathogenic variants in SMARCA1 cause an X-linked neurodevelopmental disorder modulated by NURF complex composition.

Pathogenic variants in ATP-dependent chromatin remodeling proteins are a recurrent cause of neurodevelopmental disorders (NDDs). The NURF complex consists of BPTF and either the SNF2H (SMARCA5) or SNF2L (SMARCA1) ISWI-chromatin remodeling enzyme. Pathogenic variants in BPTF and SMARCA5 were previously implicated in NDDs. Here, we describe 40 individuals from 30 families with de novo or maternally inherited pathogenic variants in SMARCA1. This novel NDD was associated with mild to severe ID/DD, delayed or regressive speech development, and some recurrent facial dysmorphisms. Individuals carrying SMARCA1 loss-of-function variants exhibited a mild genome-wide DNA methylation profile and a high penetrance of macrocephaly. Genetic dissection of the NURF complex using Smarca1, Smarca5, and Bptfsingle and double mouse knockouts revealed the importance of NURF composition and dosage for proper forebrain development. Finally, we propose that genetic alterations affecting different NURF components result in a NDD with a broad clinical spectrum.

Dominant-negative variants in CBX1 cause a neurodevelopmental disorder.

PURPOSE: This study aimed to establish variants in CBX1, encoding heterochromatin protein 1ß (HP1ß), as a cause of a novel syndromic neurodevelopmental disorder. METHODS: Patients with CBX1 variants were identified, and clinician researchers were connected using GeneMatcher and physician referrals. Clinical histories were collected from each patient. To investigate the pathogenicity of identified variants, we performed in vitro cellular assays and neurobehavioral and cytological analyses of neuronal cells obtained from newly generated Cbx1 mutant mouse lines. RESULTS: In 3 unrelated individuals with developmental delay, hypotonia, and autistic features, we identified heterozygous de novo variants in CBX1. The identified variants were in the chromodomain, the functional domain of HP1ß, which mediates interactions with chromatin. Cbx1 chromodomain mutant mice displayed increased latency-to-peak response, suggesting the possibility of synaptic delay or myelination deficits. Cytological and chromatin immunoprecipitation experiments confirmed the reduction of mutant HP1ß binding to heterochromatin, whereas HP1ß interactome analysis demonstrated that the majority of HP1ß-interacting proteins remained unchanged between the wild-type and mutant HP1ß. CONCLUSION: These collective findings confirm the role of CBX1 in developmental disabilities through the disruption of HP1ß chromatin binding during neurocognitive development. Because HP1ß forms homodimers and heterodimers, mutant HP1ß likely sequesters wild-type HP1ß and other HP1 proteins, exerting dominant-negative effects.

De novo missense mutation in GRIA2 in a patient with global developmental delay, autism spectrum disorder, and epileptic encephalopathy.

De novo variants are increasingly recognized as a common cause of early infantile epileptic encephalopathies. We present a 4-year-old male with epileptic encephalopathy characterized by seizures, autism spectrum disorder, and global developmental delay. Whole genome sequencing of the proband and his unaffected parents revealed a novel de novo missense variant in GRIA2 (c.1589A>T; p.Lys530Met; ENST00000264426.14). Variants in the GRIA2 gene were recently reported to cause an autosomal dominant neurodevelopmental disorder with language impairments and behavioral abnormalities (OMIM; MIM #618917), a condition characterized by intellectual disability and developmental delay in which seizures are a common feature. The de novo variant identified in our patient maps to the edge of a key ligand binding domain of the AMPA receptor and has not been previously reported in gnomAD or other public databases, making it novel. Our findings provided a long-sought diagnosis for this patient and support the link between GRIA2 and a dominant neurodevelopmental disorder.

Early adversity and insulin: neuroendocrine programming beyond glucocorticoids.

Exposure to direct or contextual adversities during early life programs the functioning of the brain and other biological systems, contributing to the development of physical as well as mental health issues in the long term. While the role of glucocorticoids in mediating the outcomes of early adversity has been explored for many years, less attention has been given to insulin. Beyond its metabolic effects in the periphery, central insulin action affects synaptic plasticity, brain neurotransmission, and executive functions. Knowledge about the interactions between the peripheral metabolism and brain function from a developmental perspective can contribute to prevention and diagnosis programs, as well as early interventions for vulnerable populations.

Anterior Cingulate Cortex and Ventral Hippocampal Inputs to the Basolateral Amygdala Selectively Control Generalized Fear.

A common symptom of anxiety disorders is the overgeneralization of fear across a broad range of contextual cues. We previously found that the ACC and ventral hippocampus (vHPC) regulate generalized fear. Here, we investigate the functional projections from the ACC and vHPC to the amygdala and their role in governing generalized fear in a preclinical rodent model. A chemogenetic approach (designer receptor exclusively activated by designer drugs) was used to inhibit glutamatergic projections from the ACC or vHPC that terminate within the BLA at recent (1 d) or remote (28 d) time points after contextually fear conditioning male mice. Inactivating ACC or vHPC projections to the BLA significantly reduced generalized fear to a novel, nonthreatening context but had no effect on fear to the training context. Further, our data indicate that the ACC-BLA circuit supports generalization in a time-independent manner. We also identified, for the first time, a strictly time-dependent role of the vHPC-BLA circuit in supporting remote generalized contextual fear. Dysfunctional signaling to the amygdala from the ACC or the HPC could underlie overgeneralized fear responses that are associated with anxiety disorders. Our findings demonstrate that the ACC and vHPC regulate fear expressed in novel, nonthreatening environments via projections to the BLA but do so as a result of training intensity or time, respectively.SIGNIFICANCE STATEMENT Anxiety disorders are characterized by a common symptom that promotes overgeneralization of fear in nonthreatening environments. Dysregulation of the amygdala, ACC, or hippocampus (HPC) has been hypothesized to contribute to increased fear associated with anxiety disorders. Our findings show that the ACC and HPC projections to the BLA regulate generalized fear in nonthreatening, environments. However, descending ACC projections control fear generalization independent of time, whereas HPC projections play a strictly time-dependent role in regulating generalized fear. Thus, dysfunctional ACC/HPC signaling to the BLA may be a predominant underlying mechanism of nonspecific fear associated with anxiety disorders. Our data have important implications for predictions made by theories about aging memories and interactions between the HPC and cortical regions.

A Novel Interaction between Tryptophan Hydroxylase 2 (TPH2) Gene Polymorphism (rs4570625) and BDNF Val66Met Predicts a High-Risk Emotional Phenotype in Healthy Subjects.

Poor inhibitory processing of negative emotional content is central to many psychiatric disorders, including depression and anxiety. Moreover, increasing evidence suggests that core aspects of emotion-inhibitory processing are largely inherited and as such may represent a key intermediate or risk-related phenotype for common affective diseases (e.g., unipolar depressive, anxiety disorders). The current study employed a candidate-gene approach in order to most effectively examine this complex behavioral phenotype. We examined the novel interaction between BDNF (Val66Met) and TPH2 (rs4570625) polymorphisms and their influence on behavioral inhibition of negative emotion in two independent investigations of healthy adults. BDNF Met carriers consistently report greater symptoms of affective disease and display corresponding behavioral rigidity, while TPH2 T carriers display poor inhibitory processing. These genotypes are traditionally perceived as 'risk' genotypes when compared to their respective major Val and G homozygous genotypes, but evidence is mixed. Recent studies in humans and mutant mouse models suggest biological epistasis between BDNF and genes involved in serotonin regulation. Moreover, polymorphisms in the TPH2 gene may have greater influence on serotonergic function than other more commonly studied polymorphisms (e.g., 5-HTTLPR). We observed consistent evidence across two different emotion-inhibition paradigms, one with high internal validity (Study 1, n = 119) and one with high ecological validity (Study 2, n = 115) that the combination of Val/Val and G/G genotypes was clearly associated with impaired inhibition of negative emotional content. This was followed by individuals carrying the BDNF-Met allele (including Met/Val and Met/Met) when combined with the TPH2-T allele (including T/G and T/T combinations). The consistency of these results across tasks and studies suggests that these two groups may be particularly vulnerable to the most common psychiatric disorders and should be targets for future clinical investigation.

Aromatized testosterone attenuates contextual generalization of fear in male rats.

Generalization is a common symptom of many anxiety disorders, and females are 60% more likely to suffer from an anxiety disorder than males. We have previously demonstrated that female rats display significantly accelerated rates of contextual fear generalization compared to male rats; a process driven, in part, by activation of ERß. The current study was designed to determine the impact of estrogens on contextual fear generalization in male rats. For experiment 1, adult male rats were gonadectomized (GDX) and implanted with a capsule containing testosterone proprionate, estradiol, dihydrotestosterone proprionate (DHT), or an empty capsule. Treatment with testosterone or estradiol maintained memory precision when rats were tested in a different (neutral) context 1day after training. However, male rats treated with DHT or empty capsules displayed significant levels of fear generalization, exhibiting high levels of fear in the neutral context. In Experiment 2, we used acute injections of gonadal hormones at a time known to elicit fear generalization in female rats (e.g. 24h before testing). Injection treatment followed the same pattern of results seen in Experiment 1. Finally, animals given daily injections of the aromatase inhibitor, Fadrozole, displayed significant fear generalization. These data suggest that testosterone attenuates fear generalization likely through the aromatization testosterone into estradiol as animals treated with the non-aromatizable androgen, DHT, or animals treated with Fadrozole, displayed significant generalized fear. Overall, these results demonstrate a sex-dependent effect of estradiol on the generalization of contextual fear.

Corticosterone may interact with peripubertal development to shape adult resistance to social defeat.

Studies of social stress in adult mice have revealed two distinct defeat-responsive behavioral phenotypes; "susceptible" and "resistant," characterized by social avoidance and social interaction, respectively. Typically, these phenotypes are observed at least 1day after the last defeat in adults, but may extend up to 30days later. The current study examined the impact of peripubertal social defeat on immediate (1day) and adult (30day) social stress phenotypes and neuroendocrine function in male C57BL/6 mice. Initially, peripubertal (P32) mice were resistant to social defeat. When the same mice were tested for social interaction again as adults (P62), two phenotypes emerged; a group of mice were characterized as susceptible evidenced by significantly lower social interaction, whereas the remaining mice exhibited normal social interaction, characteristic of resistance. A repeated analysis of corticosterone revealed that the adult (P62) resistant mice had elevated corticosterone following the social interaction test as juveniles. This was when all mice, regardless of adult phenotype, displayed equivalent levels of social interaction. Peripubertal corticosterone was positively correlated with adult social interaction levels in defeated mice, suggesting early life stress responsiveness impacts adult social behavior. In addition, adult corticotropin-releasing factor (CRF) mRNA in the paraventricular nucleus of the hypothalamus (PVN) was elevated in all defeated mice, but there were no differences in CRF mRNA expression between the phenotypes. Thus, there is a delayed appearance of social stress-responsive phenotypes suggesting that early life stress exposure, combined with the resultant physiological responses, may interact with pubertal development to influence adult social behavior.

Contextual Modulation of Vocal Behavior in Mouse: Newly Identified 12 kHz "Mid-Frequency" Vocalization Emitted during Restraint.

While several studies have investigated mouse ultrasonic vocalizations (USVs) emitted by isolated pups or by males in mating contexts, studies of behavioral contexts other than mating and vocalization categories other than USVs have been limited. By improving our understanding of the vocalizations emitted by mice across behavioral contexts, we will better understand the natural vocal behavior of mice and better interpret vocalizations from mouse models of disease. Hypothesizing that mouse vocal behavior would differ depending on behavioral context, we recorded vocalizations from male CBA/CaJ mice across three behavioral contexts including mating, isolation, and restraint. We found that brief restraint elevated blood corticosterone levels of mice, indicating increased stress relative to isolation. Further, after 3 days of brief restraint, mice displayed behavioral changes indicative of stress. These persisted for at least 2 days after restraint. Contextual differences in mouse vocal behavior were striking and robust across animals. Thus, while USVs were the most common vocalization type across contexts, the spectrotemporal features of USVs were context-dependent. Compared to the mating context, vocalizations during isolation and restraint displayed a broader frequency range, with a greater emphasis on frequencies below 50 kHz. These contexts also included more non-USV vocal categories and different vocal patterns. We identified a new Mid-Frequency Vocalization, a tonal vocalization with fundamental frequencies below 18 kHz, which was almost exclusively emitted by mice undergoing restraint stress. These differences combine to form vocal behavior that is grossly different among behavioral contexts and may reflect the level of anxiety in these contexts.

Phenotypic responses to social defeat are associated with differences in cued and contextual fear discrimination.

Conflict among individuals is one of the most common forms of stressors experienced across a variety of species, including humans. Social defeat models in mice produce two phenotypic behavioral responses characterized by prolonged social avoidance (susceptibility) or continued social interaction (resistance). The resistant phenotype has been proposed as a model of resilience to chronic stress-induced depression in humans. Previously, we have found that mice that are resistant to social defeat stress display significant impairments in extinction learning and retention, suggesting that continued social interaction following the experience of social defeat may be associated with maladaptive fear responses. Here, we examined how individual differences in response to social defeat may be related to differences in cued and context fear discrimination. Following defeat, resistant mice showed increased fear to a neutral cued stimulus (CS-) compared to control and susceptible mice, but were still able to significantly discriminate between the CS+ and CS-. Likewise, both phenotypes were generally able to discriminate between the training context and neutral context at all retention intervals tested (1, 5, 14 days). However, susceptible mice displayed significantly better discrimination compared to resistant and non-defeated control mice when assessing the discrimination ratio. Thus, at a time when most animals begin exhibiting generalization to contextual cues, susceptible mice retain the ability to discriminate between fearful and neutral contexts. These data suggest that the differences observed in context and cued discrimination between susceptible and resistant mice may be related to differences in their coping strategies in response to social defeat. In particular, resistance or resilience to social defeat as traditionally characterized may be associated with altered inhibitory learning. Understanding why individual differences arise in response to stress, including social confrontation is important in understanding the development and treatment of stress related pathologies such as PTSD.