Annette M. Vogl

Glutamatergic and Dopaminergic Neurons Mediate Anxiogenic and Anxiolytic Effects of CRHR1

An imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disturbances. The corticotropin-releasing hormone receptor 1 (CRHR1) critically controls behavioral adaptation to stress and is causally linked to emotional disorders. Using neurochemical and genetic tools, we determined that CRHR1 is expressed in forebrain glutamatergic and γ-aminobutyric acid–containing (GABAergic) neurons as well as in midbrain dopaminergic neurons. Via specific CRHR1 deletions in glutamatergic, GABAergic, dopaminergic, and serotonergic cells, we found that the lack of CRHR1 in forebrain glutamatergic circuits reduces anxiety and impairs neurotransmission in the amygdala and hippocampus. Selective deletion of CRHR1 in midbrain dopaminergic neurons increases anxiety-like behavior and reduces dopamine release in the prefrontal cortex. These results define a bidirectional model for the role of CRHR1 in anxiety and suggest that an imbalance between CRHR1-controlled anxiogenic glutamatergic and anxiolytic dopaminergic systems might lead to emotional disorders.

MicroRNA-9 controls dendritic development by targeting REST

MicroRNAs (miRNAs) are conserved noncoding RNAs that function as posttranscriptional regulators of gene expression. miR-9 is one of the most abundant miRNAs in the brain. Although the function of miR-9 has been well characterized in neural progenitors, its role in dendritic and synaptic development remains largely unknown. In order to target miR-9 in vivo, we developed a transgenic miRNA sponge mouse line allowing conditional inactivation of the miR-9 family in a spatio-temporal-controlled manner. Using this novel approach, we found that miR-9 controls dendritic growth and synaptic transmission in vivo. Furthermore, we demonstrate that miR-9-mediated downregulation of the transcriptional repressor REST is essential for proper dendritic growth. DOI: http://dx.doi.org/10.7554/eLife.02755.001

Neddylation inhibition impairs spine development, destabilizes synapses and deteriorates cognition.

Neddylation is a ubiquitylation-like pathway that controls cell cycle and proliferation by covalently conjugating Nedd8 to specific targets. However, its role in neurons, nonreplicating postmitotic cells, remains unexplored. Here we report that Nedd8 conjugation increased during postnatal brain development and is active in mature synapses, where many proteins are neddylated. We show that neddylation controls spine development during neuronal maturation and spine stability in mature neurons. We found that neddylated PSD-95 was present in spines and that neddylation on Lys202 of PSD-95 is required for the proactive role of the scaffolding protein in spine maturation and synaptic transmission. Finally, we developed Nae1CamKIIα-CreERT2 mice, in which neddylation is conditionally ablated in adult excitatory forebrain neurons. These mice showed synaptic loss, impaired neurotransmission and severe cognitive deficits. In summary, our results establish neddylation as an active post-translational modification in the synapse regulating the maturation, stability and function of dendritic spines.

Behavioral phenotyping of Nestin-Cre mice: Implications for genetic mouse models of psychiatric disorders

Genetic mouse models based on the Cre-loxP system have been extensively used to explore the influence of specific gene deletions on different aspects of behavioral neurobiology. However, the interpretation of the effects attributed to the gene deletion might be obscured by potential side effects secondary to the Cre recombinase transgene insertion or Cre activity, usually neither controlled nor reported. Here, we performed a comprehensive behavioral analysis of endophenotypes of neuropsychiatric disorders in the extensively used Nestin(Cre) mouse line, commonly employed to restrict genetic modifications to the CNS. We observed no alterations in locomotion, general exploratory activity, learning and memory, sociability, startle response and sensorimotor gating. Although the overall response to stimuli triggering anxiety-like behaviors remained unaltered in Nestin(Cre) mice, a strong impairment in the acquisition of both contextual- and cued-conditioned fear was observed. These results underline the importance of adequately controlling the behavioral performance of the employed Cre-lines per-se in pre-clinical neurobehavioral research.

Conditional CRH overexpressing mice: an animal model for stress-elicited pathologies and treatments that target the central CRH system.

Conditional CRH overexpressing mice: an animal model for stress-elicited pathologies and treatments that target the central CRH system

AMYGDALOID pERK1/2 IN CORTICOTROPIN-RELEASING HORMONE OVEREXPRESSING MICE UNDER BASAL AND ACUTE STRESS CONDITIONS

Corticotropin-releasing hormone (CRH) coordinates neuroendocrine and behavioral adaptations to stress. Acute CRH administration in vivo activates extracellular signal-regulated kinase 1/2 (ERK1/2) in limbic brain areas, acting through the CRH receptor type 1 (CRH-R1). In the present study, we used CRH-COE-Cam mice that overexpress CRH in limbic-restricted areas, to analyze the effect of chronic CRH overexpression on ERK1/2 activation. By immunohistochemistry and confocal microscopy analysis we found that pERK1/2 levels in the basolateral amygdala (BLA) were similar in control and CRH overexpressing mice under basal conditions. Acute stress caused comparably increased levels of corticosterone in both control (CRH-COEcon-Cam) and CRH overexpressing (CRH-COEhom-Cam) animals. CRH-COEhom-Cam mice after stress showed reduced pERK1/2 immunoreactivity in the BLA compared to CRH-COEhom-Cam animals under basal conditions. Radioligand binding and in situ hybridization revealed higher density of CRH-R1 in the amygdala of CRH-COEhom mice under basal conditions compared to control littermates. A significant reduction of the receptor levels was observed in this area after acute stress, suggesting that stress may trigger CRH-R1 internalization/downregulation in these CRH overexpressing mice. Chronic CRH overexpression leads to reduced ERK1/2 activation in response to acute stress in the BLA.

Immunology, Signal Transduction, and Behavior in Hypothalamic-Pituitary-Adrenal Axis-related Genetic Mouse Models

A classical view of the neuroendocrine–immune network assumes bidirectional interactions where pro‐inflammatory cytokines influence hypothalamic–pituitary–adrenal (HPA) axis‐derived hormones that subsequently affect cytokines in a permanently servo‐controlled circle. Nevertheless, this picture has been continuously evolving over the last years as a result of the discovery of redundant expression and extended functions of many of the molecules implicated. Thus, cytokines are not only expressed in cells of the immune system but also in the central nervous system, and many hormones present at hypothalamic–pituitary level are also functionally expressed in the brain as well as in other peripheral organs, including immune cells. Because of this intermingled network of molecules redundantly expressed, the elucidation of the unique roles of HPA axis‐related molecules at every level of complexity is one of the major challenges in the field. Genetic engineering in the mouse offers the most convincing method for dissecting in vivo the specific roles of distinct molecules acting in complex networks. Thus, various immunological, behavioral, and signal transduction studies performed with different HPA axis‐related mutant mouse lines to delineate the roles of β‐endorphin, the type 1 receptor of corticotropin‐releasing hormone (CRHR1), and its ligand CRH will be discussed here.

Vitamin D3 signalling in the brain enhances the function of phosphoprotein enriched in astrocytes – 15 kD (PEA-15)

In spite of growing evidence linking vitamin D3 levels to mental health disorders, little is known about its direct targets in the brain. This study set out to investigate targets of vitamin D3 in a human brain stem cell line. We employed arrays with antibodies directed against more than 600 structural and signalling proteins, including phospho‐variants. Over 180 proteins responded to vitamin D3, such as cyclin‐dependent protein‐serine kinase 1/2, epidermal growth factor receptor‐tyrosine kinase, protein kinase A, protein‐serine kinase Bγ and protein‐serine kinase Cα. PEA‐15 (phosphoprotein enriched in astrocytes‐15 kD, also known as PED), known to be involved in various anti‐proliferative and anti‐apoptotic effects, was strongly up‐regulated. In silico promoter analysis revealed conserved binding sites for vitamin D3 receptor, suggesting a strong vitamin D3 dependency of the PEA‐15 promoter. PEA‐15 up‐regulation by vitamin D3 could be confirmed by Western blot in two different cell lines. Analysis of mRNA and protein phosphorylation status of PEA‐15 suggests that increased PEA‐15 promoter activity and increased protein stabilization contribute to the overall rise of PEA‐15 protein. In a functional test of this novel pathway, we demonstrated that vitamin D3 was able to rescue cells from TRAIL‐induced apoptosis through regulation of the PEA‐15 expression and function. Summarized, our study presents novel targets of vitamin D3 relevant for apoptosis and cell proliferation, and thus strongly supports a function of vitamin D3 in the brain that impacts on processes highly relevant for major neurological disorders.

Chronic CRH depletion from GABAergic, long-range projection neurons in the extended amygdala reduces dopamine release and increases anxiety

The interplay between corticotropin-releasing hormone (CRH) and the dopaminergic system has predominantly been studied in addiction and reward, while CRH–dopamine interactions in anxiety are scarcely understood. We describe a new population of CRH-expressing, GABAergic, long-range-projecting neurons in the extended amygdala that innervate the ventral tegmental area and alter anxiety following chronic CRH depletion. These neurons are part of a distinct CRH circuit that acts anxiolytically by positively modulating dopamine release.The neuropeptide CRH is believed to induce aversive, stress-like behavioral responses. Here the authors describe a distinct population of CRH neurons in the extended amygdala that act to suppress anxiety by positively modulating dopamine release.