Specific ablation of the transcription factor CREB in sympathetic neurons surprisingly protects against developmentally regulated apoptosis

Division of Molecular Biology of the Cell II , German Cancer Research Center, Heidelburg, Baden-Württemberg, Germany
Development (Impact Factor: 6.46). 06/2007; 134(9):1663-70. DOI: 10.1242/dev.02838
Source: PubMed


The cyclic-AMP response element-binding (CREB) protein family of transcription factors plays a crucial role in supporting the survival of neurons. However, a cell-autonomous role has not been addressed in vivo. To investigate the cell-specific role of CREB, we used as a model developing sympathetic neurons, whose survival in vitro is dependent on CREB activity. We generated mice lacking CREB in noradrenergic (NA) and adrenergic neurons and compared them with the phenotype of the germline CREB mutant. Whereas the germline CREB mutant revealed increased apoptosis of NA neurons and misplacement of sympathetic precursors, the NA neuron-specific mutation unexpectedly led to reduced levels of caspase-3-dependent apoptosis in sympathetic ganglia during the period of naturally occurring neuronal death. A reduced level of p75 neurotrophin receptor expression in the absence of CREB was shown to be responsible. Thus, our analysis indicates that the activity of cell-autonomous pro-survival signalling is operative in developing sympathetic neurons in the absence of CREB.

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Available from: Rosanna Parlato
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    • "All experiments were conducted using separate cohorts of male and female animals, which originated from our own transgenic mouse colonies maintained in the C57BL/6N background. Transgenic animals with selective ablation of GR in the noradrenergic system (GR DBHCre ) were obtained by crossing animals that hosted Cre recombinase under the dopamine beta-hydroxylase (DBH) promoter with animals that harbored a floxed GR gene as previously described (Parlato et al., 2007, 2009). The animals were maintained with their control (Cre-negative ) littermates of the same sex in self-ventilated cages under standard laboratory conditions (12 h light/dark cycle, food and water ad libitum) until 12 weeks of age. "
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    ABSTRACT: Recently, we have demonstrated that conditional inactivation of glucocorticoid receptors (GRs) in the noradrenergic system, may evoke depressive-like behavior in female but not male mutant mice (GR(DBHCre) mice). The aim of the current study was to dissect how selective ablation of glucocorticoid signaling in the noradrenergic system influences the previously reported depressive-like phenotype and whether it might be linked to neurotrophic alterations or secondary changes in the serotonergic system. We demonstrated that selective depletion of GRs enhances brain derived neurotrophic factor (BDNF) expression in female but not male GR(DBHCre) mice on both the mRNA and protein levels. The possible impact of the mutation on brain noradrenergic and serotonergic systems was addressed by investigating the tissue neurotransmitter levels under basal conditions and after acute restraint stress. The findings indicated a stress-provoked differential response in tissue noradrenaline content in the GR(DBHCre) female but not male mutant mice. An analogous gender-specific effect was identified in the diminished content of 5-hydroxyindoleacetic acid, the main metabolite of serotonin, in the prefrontal cortex, which suggests down-regulation of this monoamine system in female GR(DBHCre) mice. The lack of GR also resulted in an up-regulation of alpha2-adrenergic receptor (α2-AR) density in the female but not male mutants in the locus coeruleus. We have also confirmed the utility of the investigated model in pharmacological studies, which demonstrates that the depressive-like phenotype of GR(DBHCre) female mice can be reversed by antidepressant treatment with desipramine or fluoxetine, with the latter drug evoking more pronounced effects. Overall, our study validates the use of female GR(DBHCre) mice as an interesting and novel genetic tool for the investigation of the cross-connected mechanisms of depression that is not only based on behavioral phenotypes.
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    • "Conserved features of gene expression during neuronal development are the delayed induction of Syt1 as compared to neurofilament expression during early differentiation stages [15] as well as the slow increase in synaptic protein mRNA levels during advanced stages of neuronal development. To search for evidence of microRNA-mediated regulation in these processes, Dicer 1 was conditionally inactivated by DBH promoter-driven Cre recombinase [50-52]. "
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    ABSTRACT: Neurons in sympathetic ganglia and neuroendocrine cells in the adrenal medulla share not only their embryonic origin from sympathoadrenal precursors in the neural crest but also a range of functional features. These include the capacity for noradrenaline biosynthesis, vesicular storage and regulated release. Yet the regulation of neuronal properties in early neuroendocrine differentiation is a matter of debate and the developmental expression of the vesicle fusion machinery, which includes components found in both neurons and neuroendocrine cells, is not resolved. Analysis of synaptic protein and pan-neuronal marker mRNA expression during mouse development uncovers profound differences between sympathetic neurons and adrenal chromaffin cells, which result in qualitatively similar but quantitatively divergent transcript profiles. In sympathetic neurons embryonic upregulation of synaptic protein mRNA follows early and persistent induction of pan-neuronal marker transcripts. In adrenal chromaffin cells pan-neuronal marker expression occurs only transiently and synaptic protein messages remain at distinctly low levels throughout embryogenesis. Embryonic induction of synaptotagmin I (Syt1) in sympathetic ganglia and postnatal upregulation of synaptotagmin VII (Syt7) in adrenal medulla results in a cell type-specific difference in isoform prevalence. Dicer 1 inactivation in catecholaminergic cells reduces high neuronal synaptic protein mRNA levels but not their neuroendocrine low level expression. Pan-neuronal marker mRNAs are induced in chromaffin cells to yield a more neuron-like transcript pattern, while ultrastructure is not altered. Our study demonstrates that remarkably different gene regulatory programs govern the expression of synaptic proteins in the neuronal and neuroendocrine branch of the sympathoadrenal system. They result in overlapping but quantitatively divergent transcript profiles. Dicer 1-dependent regulation is required to establish high neuronal mRNA levels for synaptic proteins and to maintain repression of neurofilament messages in neuroendocrine cells.
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    • "Selective ablation of GRs in the noradrenergic system (GRDBHCre mice) was achieved using the Cre/loxP approach. Transgenic mice hosting Cre recombinase under the dopamine beta-hydroxylase (DBH) promoter were crossed with animals harboring the floxed GR gene as described previously [12]. Previous studies performed on GRDBHCre mice revealed the crucial role of GRs in postnatal maintenance of chromaffin cells, resulting in the inhibition of adrenaline synthesis [13]. "
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