Elevated P75NTR expression causes death of engrailed-deficient midbrain dopaminergic neurons by Erk1/2 suppression

<p>Abstract</p> <p>Background</p> <p>The homeodomain transcription factors <it>Engrailed-1 </it>and <it>Engrailed-2 </it>are required for the survival of mesencephalic dopaminergic (mesDA) neurons in a cell-autonomous and gene-dose-dependent manner. Homozygote mutant mice, deficient of both genes (<it>En1-/-;En2-/-</it>), die at birth and exhibit a loss of all mesDA neurons by mid-gestation. In heterozygote animals (<it>En1+/-;En2-/-</it>), which are viable and fertile, postnatal maintenance of the nigrostriatal dopaminergic system is afflicted, leading to a progressive degeneration specific to this subpopulation and Parkinson's disease-like molecular and behavioral deficits.</p> <p>Results</p> <p>In this work, we show that the dose of <it>Engrailed </it>is inversely correlated to the expression level of the pan-neurotrophin receptor gene <it>P75</it>^{<it>NTR </it>}(<it>Ngfr</it>). Loss of mesDA neurons in the <it>Engrailed</it>-null mutant embryos is caused by elevated expression of this neurotrophin receptor: Unusually, in this case, the cell death signal of P75^NTRis mediated by suppression of Erk1/2 (extracellular-signal-regulated kinase 1/2) activity. The reduction in expression of <it>Engrailed</it>, possibly related to the higher levels of P75^NTR, also decreases mitochondrial stability. In particular, the dose of <it>Engrailed </it>determines the sensitivity to cell death induced by the classic Parkinson-model toxin MPTP and to inhibition of the anti-apoptotic members of the Bcl-2 family of proteins.</p> <p>Conclusion</p> <p>Our study links the survival function of the <it>Engrailed </it>genes in developing mesDA neurons to the regulation of <it>P75</it>^{<it>NTR </it>}and the sensitivity of these neurons to mitochondrial insult. The similarities to the disease etiology in combination with the nigral phenotype of <it>En1+/-;En2-/- </it>mice suggests that haplotype variations in the <it>Engrailed </it>genes and/or <it>P75</it>^{<it>NTR </it>}that alter their expression levels could, in part, determine susceptibility to Parkinson's disease.</p

Parkinson's disease candidate gene prioritization based on expression profile of midbrain dopaminergic neurons

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease is the second most common neurodegenerative disorder. The pathological hallmark of the disease is degeneration of midbrain dopaminergic neurons. Genetic association studies have linked 13 human chromosomal loci to Parkinson's disease. Identification of gene(s), as part of the etiology of Parkinson's disease, within the large number of genes residing in these loci can be achieved through several approaches, including screening methods, and considering appropriate criteria. Since several of the indentified Parkinson's disease genes are expressed in substantia nigra pars compact of the midbrain, expression within the neurons of this area could be a suitable criterion to limit the number of candidates and identify PD genes.</p> <p>Methods</p> <p>In this work we have used the combination of findings from six rodent transcriptome analysis studies on the gene expression profile of midbrain dopaminergic neurons and the PARK loci in OMIM (Online Mendelian Inheritance in Man) database, to identify new candidate genes for Parkinson's disease.</p> <p>Results</p> <p>Merging the two datasets, we identified 20 genes within PARK loci, 7 of which are located in an orphan Parkinson's disease locus and one, which had been identified as a disease gene. In addition to identifying a set of candidates for further genetic association studies, these results show that the criteria of expression in midbrain dopaminergic neurons may be used to narrow down the number of genes in PARK loci for such studies.</p

The lifelong maintenance of mesencephalic dopaminergic neurons by Nurr1 and engrailed

Specific vulnerability and degeneration of the dopaminergic neurons in the substantia nigra pars compacta of the midbrain is the pathological hallmark of Parkinson’s disease. A number of transcription factors regulate the birth and development of this set of neurons and some remain constitutively expressed throughout life. These maintenance transcription factors are closely associated with essential neurophysiological functions and are required ultimately for the long-term survival of the midbrain dopaminergic neurons. The current review describes the role of two such factors, Nurr1 and engrailed, in differentiation, maturation, and in normal physiological functions including acquisition of neurotransmitter identity. The review will also elucidate the relationship of these factors with life, vulnerability, degeneration and death of mesencephalic dopaminergic neurons in the context of Parkinson’s disease

Bcl-xL regulates mitochondrial energetics by stabilizing the inner membrane potential

To promote cell survival, the antiapoptotic factor Bcl-xL both inhibits Bax-induced mitochondrial outer membrane permeabilization and stabilizes mitochondrial inner membrane ion flux and thus overall mitochondrial energetic capacity

Decreased SGK1 Expression and Function Contributes to Behavioral Deficits Induced by Traumatic Stress

Exposure to extreme stress can trigger the development of major depressive disorder (MDD) as well as post-traumatic stress disorder (PTSD). The molecular mechanisms underlying the structural and functional alterations within corticolimbic brain regions, including the prefrontal cortex (PFC) and amygdala of individuals subjected to traumatic stress, remain unknown. In this study, we show that serum and glucocorticoid regulated kinase 1 (SGK1) expression is down-regulated in the postmortem PFC of PTSD subjects. Furthermore, we demonstrate that inhibition of SGK1 in the rat medial PFC results in helplessness- and anhedonic-like behaviors in rodent models. These behavioral changes are accompanied by abnormal dendritic spine morphology and synaptic dysfunction. Together, the results are consistent with the possibility that altered SGK1 signaling contributes to the behavioral and morphological phenotypes associated with traumatic stress pathophysiology

Linkage of cDNA expression profiles of mesencephalic dopaminergic neurons to a genome-wide in situ hybridization database

<p>Abstract</p> <p>Midbrain dopaminergic neurons are involved in control of emotion, motivation and motor behavior. The loss of one of the subpopulations, substantia nigra pars compacta, is the pathological hallmark of one of the most prominent neurological disorders, Parkinson's disease. Several groups have looked at the molecular identity of midbrain dopaminergic neurons and have suggested the gene expression profile of these neurons. Here, after determining the efficiency of each screen, we provide a linked database of the genes, expressed in this neuronal population, by combining and comparing the results of six previous studies and verification of expression of each gene in dopaminergic neurons, using the collection of in situ hybridization in the Allen Brain Atlas.</p