Project description:Early-life adversity (ELA) is associated with lifelong memory deficits, yet the responsible mechanisms remain unclear. We imposed ELA by rearing rat pups in simulated poverty, assessed hippocampal memory, and probed changes in gene expression, their transcriptional regulation and the consequent changes in hippocampal neuronal structure. ELA rats had poor hippocampal memory and stunted hippocampal pyramidal neurons, associated with ~140 differentially expressed genes. Upstream regulators of the altered genes included glucocorticoid receptor and, unexpectedly, the transcription factor neuron-restrictive silencer factor (NRSF/REST). NRSF contributed critically to the memory deficits because blocking its function transiently following ELA rescued spatial memory and restored the dendritic arborization of hippocampal pyramidal neurons in ELA rats. Blocking NRSF function in vitro augmented dendritic complexity of developing hippocampal neurons, suggesting that NRSF represses genes involved in neuronal maturation. These findings establish important, surprising contributions of NRSF to ELA-induced transcriptional programming that disrupts hippocampal maturation and memory function.
Project description:Early life adversity has been linked to altered reproductive development in humans, including changes in the timing of pubertal onset and sexual activity. One common form of early life adversity is having limited access to resources. This form of early life adversity can be modeled in rodents using the limited bedding and nesting model (LBN), in which rat dams and pups are placed in a low resource environment from postnatal day (PND) 2 through 9. Our laboratory has previously shown that male rats raised in LBN conditions have elevated levels of plasma estradiol compared to control males. Female rats, on the other hand, show no effect of LBN on plasma hormone levels, pubertal timing, or estrous cycle duration in adulthood. Here, we find that LBN males also show changes in adult reproductive behaviors. LBN males acquired the suite of reproductive behaviors more quickly than their control counterparts over the course of 3 weeks of testing, showing shorter latencies to mount, intromit, and ejaculate compared to controls prior to the final week of testing. We also characterized LBN-induced gene transcription changes across sex in the medial preoptic area (mPOA) which underlies reproductive behaviors. Interestingly, there was no effect of LBN on puberty onset (as measured by preputial separation) or masculinization of the sexually dimorphic nucleus of the preoptic area (SDN/POA; as measured by calbindin immunoreactivity) in males, suggesting LBN may not exert effects on hormone-dependent measures until after puberty.
Project description:Early adversity in the form of neglect, abuse, and unpredictable stress impairs hippocampal development across diverse mammalian species. Individuals exposed to multiple adversities are more impacted compared to those exposed to a single adversity. However, the mechanisms responsible for this dose-dependent effect are unclear and have not been investigated in animal models. Here we assess the effects of a single stressor (i.e. limited bedding/nesting) abbreviated as LB and unpredictable multiple stressors (limited bedding/nesting, unpredictable maternal separation, and nest disruption) abbreviated as UPS on gene expression in the hippocampus of 17-day old pups (P17).
Project description:Early life social experiences are believed to confer persistent effects on individual’s biology and subsequent functioning and health. Using a diverse, longitudinal community sample of 178 children, we show that three different types of early life social experience: family income, parental education, and family psychosocial adversity, each predict DNA methylation within buccal epithelial cells. Each predictor was significantly associated with DNA methylation within a unique set of genomic CpG sites, with income showing the greatest number of associations. Findings were independently verified using pyrosequencing. Our results provide evidence for longitudinal associations between early life social environment and variation in DNA methylation during childhood, after adjusting for genetic ancestry and self-reported ethnic minority status. Gene ontology analyses of top, differentially methylated CpG sites point to genes serving immune and developmental regulation functions, suggesting potential pathways for the biological embedding of early life stress and its association with later development and health.
Project description:In this study we hypothesize that early life stress perturbs the normal function of microglial in the developing hippocampus and that this effect is responsible for the ability of early life tress to disrupt normal synaptic maturation, myelination, and axonal growth in the developing hippocampus. To test this hypothesis we used the mouse immune panel from NanoString in order to identify immune-related genes whose expression is modified by BDS, a mouse model of early life stress, in microglia isolated from the hippocampus of 28-day old male pups. This project is part of a manuscript that is currently under preparation (Delpech J.C. et al. Early life stress perturbs the maturation of microglia in the developing hippocampus, Brain, Behavior and Immunity, 2016)
Project description:In this study we hypothesize that early life stress perturbs the normal function of microglia in the developing hippocampus and that this effect is responsible for the ability of early life tress to disrupt normal synaptic maturation, myelination, and axonal growth in the developing hippocampus. To test this hypothesis we used the mouse immune panel from NanoString in order to identify immune-related genes whose expression is modified by BDS, a mouse model of early life stress, in microglia isolated from the hippocampus of 14-day old male pups. This project is part of a manuscript that is currently under preparation (Delpech J.C. et al. Early life stress perturbs the maturation of microglia in the developing hippocampus, Brain, Behavior and Immunity, 2016)
Project description:Social anxiety disorder (SAD) is a psychiatric disorder characterized by extensive fear in social situations. Multiple genetic and environmental factors are known to contribute to its pathogenesis. One of the main environmental risk factors is early life adversity (ELA). Evidence is emerging that epigenetic mechanisms such as DNA methylation might play an important role in the biological mechanisms underlying SAD and ELA. To investigate the relationship between ELA, DNA methylation, and SAD, we performed an epigenome-wide association study for SAD and ELA examining DNA from whole blood of a cohort of 143 individuals using DNA methylation arrays. We identified two differentially methylated regions (DMRs) associated with SAD located within the genes SLC43A2 and TNXB. As this was the first epigenome-wide association study for SAD, it is worth noting that both genes have previously been associated with panic disorder. Further, we identified two DMRs associated with ELA within the SLC17A3 promoter region and the SIAH3 gene and several DMRs that were associated with the interaction of SAD and ELA. Of these, the regions within C2CD2L and MRPL28 showed the largest difference in DNA methylation. Lastly, we found that two DMRs were associated with both the severity of social anxiety and ELA, however, neither of them was found to mediate the contribution of ELA to SAD later in life. Future studies are needed to replicate our findings in independent cohorts and to investigate the biological pathways underlying these effects.
Project description:Mental and cognitive health, as well as vulnerability to neuropsychiatric disorders, involve the interplay of genes with the environment during sensitive developmental periods. Genetic and environmental factors contribute to the development and maturation of neurons, synapses, and the resulting brain circuits. Within the hypothalamus, early-life experiences cause changes in the number of excitatory synapses onto corticotropin-releasing hormone (CRH)-expressing neurons in the paraventricular nucleus (PVN). Further, such synaptic changes suffice to induce enduring epigenomic changes within these cells, influencing programs of gene expression. However, the epigenetic mechanisms by which early-life experiences orchestrate transcriptional programs within individual CRH-expressing neurons, with enduring functional consequences, remain unknown. We utilize animal models of an impoverished environment and unpredictable maternal care (in a limited bedding and nesting [LBN] paradigm), which provokes major alterations in cognitive and emotional outcomes. We are focused on the change in gene expression profiles of stress-sensitive CRH-neurons in the PVN following early-life adversity (ELA). Because of the known heterogeneity of CRH-expressing neuronal populations, we are using single-cell RNA sequencing (RNA-seq) to determine differential gene expression associated with early-life adversity and establish the upstream mechanisms and downstream consequences. We found that CRH-expressing populations of neurons in the PVN can be clustered by both their gene expression profiles as well as by their neurotransmitter phenotype. ELA significantly modified gene expression programs in some neuronal clusters more than others, reducing programs of neuronal development and differentiation and enhancing gene families involved in responses to stress and inflammation. The use of single-cell transcriptomics revealed that ELA impacts gene expression profiles in a cell-type specific manner, with distinctive influence on the different clusters and subpopulations of CRH neurons.