Medial prefrontal cortex: genes linked to bipolar disorder and schizophrenia have altered expression in the highly social maternal phenotype

Plasticity in auditory cortex during parenthood

Most animals display robust parental behaviors that support the survival and well-being of their offspring. The manifestation of parental behaviors is accompanied by physiological and hormonal changes, which affect both the body and the brain for better care giving. Rodents exhibit a behavior called pup retrieval - a stereotyped sequence of perception and action - used to identify and retrieve their newborn pups back to the nest. Pup retrieval consists of a significant auditory component, which depends on plasticity in the auditory cortex (ACx). We review the evidence of neural changes taking place in the ACx of rodents during the transition to parenthood. We discuss how the plastic changes both in and out of the ACx support the encoding of pup vocalizations. Key players in the mechanism of this plasticity are hormones and experience, both of which have a clear dynamic signature during the transition to parenthood. Mothers, co caring females, and fathers have been used as models to understand parental plasticity at disparate levels of organization. Yet, common principles of cortical plasticity and the biological mechanisms underlying its involvement in parental behavior are just beginning to be unpacked.

Experience-Regulated Neuronal Signaling in Maternal Behavior

Maternal behavior is shaped and challenged by the changing developmental needs of offspring and a broad range of environmental factors, with evidence indicating that the maternal brain exhibits a high degree of plasticity. This plasticity is displayed within cellular and molecular systems, including both intra- and intercellular signaling processes as well as transcriptional profiles. This experience-associated plasticity may have significant overlap with the mechanisms controlling memory processes, in particular those that are activity-dependent. While a significant body of work has identified various molecules and intracellular processes regulating maternal care, the role of activity- and experience-dependent processes remains unclear. We discuss recent progress in studying activity-dependent changes occurring at the synapse, in the nucleus, and during the transport between these two structures in relation to maternal behavior. Several pre- and postsynaptic molecules as well as transcription factors have been found to be critical in these processes. This role reflects the principal importance of the molecular and cellular mechanisms of memory formation to maternal and other behavioral adaptations.

An epigenomic shift in amygdala marks the transition to maternal behaviors in alloparenting virgin female mice

Adults of many species will care for young offspring that are not their own, a phenomenon called alloparenting. However, in many cases, nonparental adults must be sensitized by repeated or extended exposures to newborns before they will robustly display parental-like behaviors. To capture neurogenomic events underlying the transition to active parental caring behaviors, we analyzed brain gene expression and chromatin profiles of virgin female mice co-housed with pregnant dams during pregnancy and after birth. After an initial display of antagonistic behaviors and a surge of defense-related gene expression, we observed a dramatic shift in the chromatin landscape specifically in amygdala of the pup-exposed virgin females compared to females co-housed with mother before birth, accompanied by a dampening of anxiety-related gene expression. This epigenetic shift coincided with hypothalamic expression of the oxytocin gene and the emergence of behaviors and gene expression patterns classically associated with maternal care. The results outline a neurogenomic program associated with dramatic behavioral changes and suggest molecular networks relevant to human postpartum mental health.

Immune System Alterations and Postpartum Mental Illness: Evidence From Basic and Clinical Research

The postpartum period is a time associated with high rates of depression and anxiety as well as greater risk for psychosis in some women. A growing number of studies point to aberrations in immune system function as contributing to postpartum mental illness. Here we review evidence from both clinical and animal models suggesting an immune component to postpartum depression, postpartum anxiety, and postpartum psychosis. Thus far, clinical data primarily highlights changes in peripheral cytokine signaling in disease etiology, while animal models have begun to provide insight into the immune environment of the maternal brain and how central inflammation may also be contributing to postpartum mental illnesses. Further research investigating peripheral and central immune function, along with neural and endocrine interactions, will be important in successfully developing novel prevention and treatment strategies for these serious disorders that impact a large portion of new mothers.

Evaluation of animal model congruence to human depression based on large-scale gene expression patterns of the CNS

Depression is a complex mental health disorder that is difficult to study. A wide range of animal models exist and for many of these data on large-scale gene expression patterns in the CNS are available. The goal of this study was to evaluate how well animal models match human depression by evaluating congruence and discordance of large-scale gene expression patterns in the CNS between almost 300 animal models and a portrait of human depression created from male and female datasets. Multiple approaches were used, including a hypergeometric based scoring system that rewards common gene expression patterns (e.g., up-up or down-down in both model and human depression), but penalizes opposing gene expression patterns. RRHO heat maps, Uniform Manifold Approximation Plot (UMAP), and machine learning were used to evaluate matching of models to depression. The top ranked model was a histone deacetylase (HDAC2) conditional knockout in forebrain neurons. Also highly ranked were various models for Alzheimer’s, including APPsa knock-in (2nd overall), APP knockout, and an APP/PS1 humanized double mutant. Other top models were the mitochondrial gene HTRA2 knockout (that is lethal in adulthood), a modified acetylcholinesterase, a Huntington’s disease model, and the CRTC1 knockout. Over 30 stress related models were evaluated and while some matched highly with depression, others did not. In most of the top models, a consistent dysregulation of MAP kinase pathway was identified and the genes NR4A1, BDNF, ARC, EGR2, and PDE7B were consistently downregulated as in humans with depression. Separate male and female portraits of depression were also evaluated to identify potential sex specific depression matches with models. Individual human depression datasets were also evaluated to allow for comparisons across the same brain regions. Heatmap, UMAP, and machine learning results supported the hypergeometric ranking findings. Together, this study provides new insights into how large-scale gene expression patterns may be similarly dysregulated in some animals models and humans with depression that may provide new avenues for understanding and treating depression.

miR-506-loaded gelatin nanospheres target PENK and inactivate the ERK/Fos signaling pathway to suppress triple-negative breast cancer aggressiveness

Triple-negative breast cancer (TNBC) is the most malignant subtype of breast cancer. Some microRNAs (miRNAs) were abnormally expressed in TNBC, and they are closely related to the occurrence and progression of TNBC. Here, we found that miR-506 was significantly downregulated in TNBC and relatively lower miR-506 expression predicted a poorer prognosis. Moreover, we found that miR-506 could inhibit MDA-MB-231 cell viability, colony formation, migration, and invasion, and suppress the ERK/Fos oncogenic signaling pathway through upregulating its direct target protein proenkephalin (PENK). Therefore, miR-506 was proposed as a nucleic acid drug for TNBC therapy. However, miRNA is unstable in vivo, which limiting its application as a therapeutic drug via conventional oral or injected therapies. Here, a gelatin nanosphere (GN) delivery system was applied for the first time to load exogenous miRNA. Exogenous miR-506 mimic was loaded on GNs and injected into the in situ TNBC animal model, and the miR-506 could achieve sustained and controlled release. The results confirmed that overexpression of miR-506 and PENK in vivo through loading on GNs inhibited in situ triple-negative breast tumor growth and metastasis significantly in the xenograft model. Moreover, we indicated that the ERK/Fos signaling pathway was intensively inactivated after overexpression of miR-506 and PENK both in vitro and in vivo, which was further validated by the ERK1/2-specific inhibitor SCH772984. In conclusion, this study demonstrates that miR-506-loaded GNs have great potential in anti-TNBC aggressiveness therapy.

Neocortical Microdissection at Columnar and Laminar Resolution for Molecular Interrogation

The heterogeneous organization of the mammalian neocortex poses a challenge for elucidating the molecular mechanisms underlying its physiological processes. Although high-throughput molecular methods are increasingly deployed in neuroscience, their anatomical specificity is often lacking. In this unit, we introduce a targeted microdissection technique that enables extraction of high-quality RNA and proteins at high anatomical resolution from acutely prepared brain slices. We exemplify its utility by isolating single cortical columns and laminae from the mouse primary somatosensory (barrel) cortex. Tissues can be isolated from living slices in minutes, and the extracted RNA and protein are of sufficient quantity and quality to be used for RNA sequencing and mass spectrometry. This technique will help to increase the anatomical specificity of molecular studies of the neocortex, and the brain in general, as it is applicable to any brain structure that can be identified using optical landmarks in living slices. © 2018 by John Wiley & Sons, Inc.

Down-regulation of fatty acid binding protein 7 (Fabp7) is a hallmark of the postpartum brain

Fatty acid binding protein 7 (Fabp7) is a versatile protein that is linked to glial differentiation and proliferation, neurogenesis, and multiple mental health disorders. Recent microarray studies identified a robust decrease in Fabp7 expression in key brain regions of the postpartum rodents. Given its diverse functions, Fabp7 could play a critical role in sculpting the maternal brain and promoting the maternal phenotype. The present study aimed at investigating the expression profile of Fabp7 across the postpartum CNS. Quantitative real-time PCR (qPCR) analysis showed that Fabp7 mRNA was consistently down-regulated across the postpartum brain. Of the 9 maternal care-related regions tested, seven exhibited significant decreases in Fabp7 in postpartum (relative to virgin) females, including medial prefrontal cortex (mPFC), nucleus accumbens (NA), lateral septum (LS), bed nucleus of stria terminalis dorsal (BnSTd), paraventricular nucleus (PVN), lateral hypothalamus (LH), and basolateral and central amygdala (BLA/CeA). For both ventral tegmental area (VTA) and medial preoptic area (MPOA) levels of Fabp7 were lower in mothers, but levels of changes did not reach significance. Confocal microscopy revealed that protein expression of Fabp7 in the LS paralleled mRNA findings. Specifically, the caudal LS exhibited a significant reduction in Fabp7 immunoreactivity, while decreases in medial LS were just above significance. Double fluorescent immunolabeling confirmed the astrocytic phenotype of Fabp7-expressing cells. Collectively, this research demonstrates a broad and marked reduction in Fabp7 expression in the postpartum brain, suggesting that down-regulation of Fabp7 may serve as a hallmark of the postpartum brain and contribute to the maternal phenotype.

The circadian gene Nr1d1 in the mouse nucleus accumbens modulates sociability and anxiety-related behaviour

Nuclear receptor subfamily 1, group D, member 1 (Nr1d1) (also known as Rev-erb alpha) has been linked to circadian rhythm regulation, mood-related behaviour and disorders associated with social deficits. Recent work from our laboratory found striking decreases in Nr1d1 in the nucleus accumbens (NAc) in the maternal condition and indirect evidence that Nr1d1 was interacting with numerous addiction and reward-related genes to modulate social reward. In this study, we applied our insights from the maternal state to nonparental adult mice to determine whether decreases in Nr1d1 expression in the NAc via adeno-associated viral (AAV) vectors and short hairpin RNA (shRNA)-mediated gene knockdown were sufficient to modulate social behaviours and mood-related behaviours. Knockdown of Nr1d1 in the NAc enhanced sociability and reduced anxiety, but did not affect depressive-like traits in female mice. In male mice, Nr1d1 knockdown had no significant behavioural effects. Microarray analysis of Nr1d1 knockdown in females identified changes in circadian rhythm and histone deacetylase genes and suggested possible drugs, including histone deacetylase inhibitors, that could mimic actions of Nr1d1 knockdown. Quantitative real-time PCR (qPCR) analysis confirmed expression upregulation of gene period circadian clock 1 (Per1) and period circadian clock 2 (Per2) with Nr1d1 knockdown. The evidence for roles for opioid-related genes opioid receptor, delta 1 (Oprd1) and preproenkephalin (Penk) was also found. Together, these results suggest that Nr1d1 in the NAc modulates sociability and anxiety-related behaviour in a sex-specific manner, and circadian, histone deacetylase and opioid-related genes may be involved in the expression of these behavioural phenotypes.

Association Study of Tumor Necrosis Factor Receptor 1 (TNFR1) Gene Polymorphisms with Schizophrenia in the Polish Population

Schizophrenia is a devastating mental disorder with undetermined aetiology. Previous research has suggested that dysregulation of proinflammatory cytokines and their receptors plays a role in developing schizophrenia. We examined the association of the three single nucleotide polymorphisms (SNPs; rs4149576, rs4149577, and rs1860545) in the tumor necrosis factor receptor 1 (TNFR1) gene with the development and psychopathology of paranoid schizophrenia in the Polish Caucasian sample consisting of 388 patients and 657 control subjects. The psychopathology was assessed using a five-factor model of the Positive and Negative Syndrome Scale (PANSS). SNPs were genotyped using the TaqMan 5'-exonuclease allelic discrimination assay. The SNPs tested were not associated with a predisposition to paranoid schizophrenia in either the entire sample or after stratification according to gender. However, rs4149577 and rs1860545 SNPs were associated with the intensity of the PANSS excitement symptoms in men, which may contribute to the risk of violent behavior. Polymorphisms in the TNFR1 gene may have an impact on the symptomatology of schizophrenia in men.

Genetic and neuroendocrine regulation of the postpartum brain

Changes in expression of hundreds of genes occur during the production and function of the maternal brain that support a wide range of processes. In this review, we synthesize findings from four microarray studies of different maternal brain regions and identify a core group of 700 maternal genes that show significant expression changes across multiple regions. With those maternal genes, we provide new insights into reward-related pathways (maternal bonding), postpartum depression, social behaviors, mental health disorders, and nervous system plasticity/developmental events. We also integrate the new genes into well-studied maternal signaling pathways, including those for prolactin, oxytocin/vasopressin, endogenous opioids, and steroid receptors (estradiol, progesterone, cortisol). A newer transcriptional regulation model for the maternal brain is provided that incorporates recent work on maternal microRNAs. We also compare the top 700 genes with other maternal gene expression studies. Together, we highlight new genes and new directions for studies on the postpartum brain.

Genetic mechanisms of parenting

This article is part of a Special Issue "Parental Care". The complexities of parenting behavior in humans have been studied for decades. Only recently did we begin to probe the genetic and epigenetic mechanisms underlying these complexities. Much of the research in this field continues to be informed by animal studies, where genetic manipulations and invasive tools allow to peek into and directly observe the brain during the expression of maternal behavior. In humans, studies of adult twins who are parents can suggest dimensions of parenting that might be more amenable to a genetic influence. Candidate gene studies can test specific genes in association with parental behavior based on prior knowledge of those genes' function. Gene-by-environment interactions of a specific kind indicating differential susceptibility to the environment might explain why some parents are more resilient and others are more vulnerable to stressful life events. Epigenetic studies can provide the bridge often necessary to explain why some individuals behave differently from others despite common genetic influences. There is a much-needed expansion in parenting research to include not only mothers as the focus-as has been the case almost exclusively to date-but also fathers, grandparents, and other caregivers.

MicroRNA expression is altered in lateral septum across reproductive stages

MicroRNAs (miRNAs) inhibit RNA targets and may contribute to postpartum central nervous system (CNS) gene expression changes, although this has never been tested. In the present study, we directly evaluated miRNA levels using RNA sequencing during reproduction in female mice in the lateral septum (LS). We found the reliable and robust changes of miRNAs away from the virgin stage at the three other stages, namely pregnant, day 1 postpartum, and day 8 postpartum. For a given miRNA that was significantly different from the virgin condition in more than one group, the direction of change was always the same. Overall, we identified 32 upregulated miRNAs and 25 downregulated miRNAs that were consistently different from the virgin state. 'Arm switching' occurs for miR-433-3 and miR-7b. Unexpectedly, a third of upregulated miRNAs (relative to virgin) were highly localized within the 12qF1 region of chromosome 12 that includes the Dlk1-Dio3 gene cluster implicated in stem cell and neuronal differentiation. Over 1500 genes were targeted by multiple upregulated miRNAs with about 100 genes targeted by five or more miRNAs. Over 1000 genes were targeted by multiple downregulated miRNAs with about 50 genes targeted by five or more miRNAs. Half of the target genes were regulated by up and downregulated miRNAs, indicating homeostatic regulation. Transcriptional regulation was the most enriched pathway for genes linked to up or down regulated miRNAs. Other enriched pathways included protein kinase activity (e.g., MAP kinase), CNS development, axon guidance, neurotrophin signaling, neuron development/differentiation, and neurogenesis. Previously published postpartum LS gene expression changes were enrichment for LS miRNA targets, as expected. Surprisingly, postpartum gene expression changes from other regions were also enriched against LS miRNA targets, suggesting a core group of miRNAs may act across the CNS during reproduction. Together, we directly examine miRNAs and find significant alterations in the postpartum brain.

A novel relationship for schizophrenia, bipolar and major depressive disorder Part 7: A hint from chromosome 7 high density association screen

Convergent evidence from genetics, symptology and psychopharmacology imply that there are intrinsic connection between schizophrenia (SCZ), bipolar disorder (BPD) and major depressive disorder (MDD). Also, any two or even three of these disorders could co-existe in some families. A total of 47,144 single nucleotide polymorphism (SNPs) on chromosome 7 were genotyped by Affymetrix Genome-Wide Human SNP array 6.0 on 119 SCZ, 253 BPD (type-I), 177 MDD, and 1000 controls. Associated SNP loci were comprehensively revealed and outstanding susceptibility genes were identified including CNTNAP2. a neurexin family gene. Unexpectedly, flanking genes for up to 94.74 % of of the associated SNPs were replicated (P≤9.9 E-8) in an enlarged cohort of 986 SCZ patients. Considering other convergent evidence, our results further implicate that BPD and MDD are subtypes of SCZ.

Coexpression networks identify brain region-specific enhancer RNAs in the human brain

Despite major progress in identifying enhancer regions on a genome-wide scale, the majority of available data are limited to model organisms and human transformed cell lines. We have identified a robust set of enhancer RNAs (eRNAs) expressed in the human brain and constructed networks assessing eRNA-gene coexpression interactions across human fetal brain and multiple adult brain regions. Our data identify brain region-specific eRNAs and show that enhancer regions expressing eRNAs are enriched for genetic variants associated with autism spectrum disorders.

Metabotropic glutamate receptor 3 is downregulated and its expression is shifted from neurons to astrocytes in the mouse lateral septum during the postpartum period

The inhibitory metabotropic glutamate receptor 3 (mGluR3) plays diverse and complex roles in brain function, including synaptic plasticity and neurotransmission. We recently found that mGluR3 is downregulated in the lateral septum (LS) of postpartum females using microarray and qPCR analysis. In this study, we used double fluorescence immunohistochemical approaches to characterize mGluR3 changes in LS of the postpartum brain. The number of mGluR3-immunoractive cells was significantly reduced in the dorsal (LSD) and intermediate (LSI) but not ventral (LSV) parts of the LS in postpartum versus virgin females. mGluR3 immunoreactivity in the LS was found predominantly in neurons (~70%), with a smaller portion (~20%-30%) in astrocytes. Colocalization analysis revealed a reduced mGluR3 expression in neurons but an increased astrocytic localization in postpartum LSI. This change in the pattern of expression suggests that mGluR3 expression is shifted from neurons to astrocytes in postpartum LS, and the decrease in mGluR3 is neuron-specific. Because mGluR3 is inhibitory and negatively regulates glutamate and GABA release, decreases in neuronal expression would increase glutamate and GABA signaling. Given our recent finding that ~90% of LS neurons are GABAergic, the present data suggest that decreases in mGluR3 are a mechanism for elevated GABA in LS in the postpartum state.

Addiction and reward-related genes show altered expression in the postpartum nucleus accumbens

Motherhood involves a switch in natural rewards, whereby offspring become highly rewarding. Nucleus accumbens (NAC) is a key CNS region for natural rewards and addictions, but to date no study has evaluated on a large scale the events in NAC that underlie the maternal change in natural rewards. In this study we utilized microarray and bioinformatics approaches to evaluate postpartum NAC gene expression changes in mice. Modular Single-set Enrichment Test (MSET) indicated that postpartum (relative to virgin) NAC gene expression profile was significantly enriched for genes related to addiction and reward in five of five independently curated databases (e.g., Malacards, Phenopedia). Over 100 addiction/reward related genes were identified and these included: Per1, Per2, Arc, Homer2, Creb1, Grm3, Fosb, Gabrb3, Adra2a, Ntrk2, Cry1, Penk, Cartpt, Adcy1, Npy1r, Htr1a, Drd1a, Gria1, and Pdyn. ToppCluster analysis found maternal NAC expression profile to be significantly enriched for genes related to the drug action of nicotine, ketamine, and dronabinol. Pathway analysis indicated postpartum NAC as enriched for RNA processing, CNS development/differentiation, and transcriptional regulation. Weighted Gene Coexpression Network Analysis (WGCNA) identified possible networks for transcription factors, including Nr1d1, Per2, Fosb, Egr1, and Nr4a1. The postpartum state involves increased risk for mental health disorders and MSET analysis indicated postpartum NAC to be enriched for genes related to depression, bipolar disorder (BPD), and schizophrenia. Mental health related genes included: Fabp7, Grm3, Penk, and Nr1d1. We confirmed via quantitative PCR Nr1d1, Per2, Grm3, Penk, Drd1a, and Pdyn. This study indicates for the first time that postpartum NAC involves large scale gene expression alterations linked to addiction and reward. Because the postpartum state also involves decreased response to drugs, the findings could provide insights into how to mitigate addictions.