Monoamine oxidase A expression is vital for embryonic brain development by modulating developmental apoptosis

Monoamine oxidases (MAO-A, MAO-B) metabolize biogenic amines and have been implicated in neuronal apoptosis. Although apoptosis is an important process in embryo development, the role of MAO isoenzymes has not been investigated in detail. We found that expression of MAO-A and MAO-B can be detected early on during embryo development. Expression levels remained constant until around midgestation but then dropped to almost undetectable levels toward birth. Similar expression kinetics were observed in the brain. Isoform-specific expression silencing of MAO-A mediated by siRNA during in vitro embryogenesis induced developmental defects, as indicated by a reduction of the crown rump length and impaired cerebral development. These alterations were paralleled by elevated serotonin levels. Similar abnormalities were observed when embryos were cultured in the presence of the MAO-A inhibitor clorgyline or when the transcriptional inhibitor of MAO-A expression Rl was overexpressed. In contrast, no such alterations were detected when expression of MAO-B was knocked down. To explore the underlying mechanisms for the developmental abnormalities in MAO-A knockdown embryos, we quantified the degree of developmental apoptosis in the developing brain. MAO-A knockdown reduced the number of apoptotic cells in the neuroepithelium, which coincided with impaired activation of caspases 3 and 9. Moreover, we observed reduced cyclin Dl levels as an indicator of impaired cell proliferation in MAO-A knockdown embryos. This data highlights MAO-A as a vital regulator of embryonic brain development

Genome-Wide Bovine H3K27me3 Modifications and the Regulatory Effects on Genes Expressions in Peripheral Blood Lymphocytes

Gene expression of lymphocytes was found to be influenced by histone methylation in mammals and trimethylation of lysine 27 on histone H3 (H3K27me3) normally represses genes expressions. Peripheral blood lymphocytes are the main source of somatic cells in the milk of dairy cows that vary frequently in response to the infection or injury of mammary gland and number of parities.The genome-wide status of H3K27me3 modifications on blood lymphocytes in lactating Holsteins was performed via ChIP-Seq approach. Combined with digital gene expression (DGE) technique, the regulation effects of H3K27me3 on genes expressions were analyzed.The ChIP-seq results showed that the peaks of H3K27me3 in cows lymphocytes were mainly enriched in the regions of up20K (~50%), down20K (~30%) and intron (~28%) of the genes. Only ~3% peaks were enriched in exon regions. Moreover, the highest H3K27me3 modification levels were mainly around the 2 Kb upstream of transcriptional start sites (TSS) of the genes. Using conjoint analysis with DGE data, we found that H3K27me3 marks tended to repress target genes expressions throughout whole gene regions especially acting on the promoter region. A total of 53 differential expressed genes were detected in third parity cows compared to first parity, and the 25 down-regulated genes (PSEN2 etc.) were negatively correlated with H3K27me3 levels on up2Kb to up1Kb of the genes, while the up-regulated genes were not showed in this relationship.The first blueprint of bovine H3K27me3 marks that mediates gene silencing was generated. H3K27me3 plays its repressed role mainly in the regulatory region in bovine lymphocytes. The up2Kb to up1Kb region of the down-regulated genes in third parity cows could be potential target of H3K27me3 regulation. Further studies are warranted to understand the regulation mechanisms of H3K27me3 on somatic cell count increases and milk losses in latter parities of cows

Presenilin 2 Is the Predominant γ-Secretase in Microglia and Modulates Cytokine Release

Presenilin 1 (PS1) and Presenilin 2 (PS2) are the enzymatic component of the γ-secretase complex that cleaves amyloid precursor protein (APP) to release amyloid beta (Aβ) peptide. PS deficiency in mice results in neuroinflammation and neurodegeneration in the absence of accumulated Aβ. We hypothesize that PS influences neuroinflammation through its γ-secretase action in CNS innate immune cells. We exposed primary murine microglia to a pharmacological γ-secretase inhibitor which resulted in exaggerated release of TNFα and IL-6 in response to lipopolysaccharide. To determine if this response was mediated by PS1, PS2 or both we used shRNA to knockdown each PS in a murine microglia cell line. Knockdown of PS1 did not lead to decreased γ-secretase activity while PS2 knockdown caused markedly decreased γ-secretase activity. Augmented proinflammatory cytokine release was observed after knockdown of PS2 but not PS1. Proinflammatory stimuli increased microglial PS2 gene transcription and protein in vitro. This is the first demonstration that PS2 regulates CNS innate immunity. Taken together, our findings suggest that PS2 is the predominant γ-secretase in microglia and modulates release of proinflammatory cytokines. We propose PS2 may participate in a negative feedback loop regulating inflammatory behavior in microglia

Accelerated long-term forgetting in presymptomatic autosomal dominant Alzheimer's disease: a cross-sectional study.

Tests sensitive to presymptomatic changes in Alzheimer's disease could be valuable for clinical trials. Accelerated long-term forgetting-during which memory impairment becomes apparent over longer periods than usually assessed, despite normal performance on standard cognitive testing-has been identified in other temporal lobe disorders. We assessed whether accelerated long-term forgetting is a feature of presymptomatic autosomal dominant (familial) Alzheimer's disease, and whether there is an association between accelerated long-term forgetting and early subjective memory changes.This article is available via Open Access. Click on the Additional Link above to access the full-text via the publisher's site

Mitochondria in Memory Retrieval in Wild‐Type Mice and in the Impairment of Memory Retrieval in Amyloid Precursor Protein Transgenic Mice

AbstractBackgroundTreatment of Alzheimer’s disease (AD) would benefit from earlier diagnosis and a better understanding of the biochemical and cellular events underlying memory loss. This study, which follows our previous work identifying early deficits in long‐term memory retrieval and memory‐associated glucose uptake in amyloid precursor protein transgenic (APPtg) mice, aims to a) test our hypothesis of stimulus‐dependent synaptic mitochondrial activity as a mechanism underlying memory retrieval, and b) investigate any mitochondrial abnormalities possibly associated with the impairment of memory retrieval in APPtg mice (and possibly in presymptomatic AD).MethodThe J20 APPtg mouse line has been used. Two genotypes (APPtg and wild‐type) and two behavioral groups have been analysed, a) a group subject to criterion‐based watermaze training, sacrificed 20 sec following a probe trial seven days after learning the task (the memory retrieval group), and b) a group with no behavioral training (the basal levels group). Synaptosome forebrain samples (enriched in synapses) from 16 mice (four mice from each of the genotype/behavioral combinations) have been subjected to proteomics, Western blot and electron microscopy analyses. Oxygen consumption and enzymatic activity assay analyses are ongoing.ResultOur previous behavioral result of significantly impaired 7‐day memory retrieval has been reproduced. Our proteomics analysis has suggested higher synaptic levels of mitochondrial proteins during memory retrieval, compared to basal levels in wild‐type mice, a phenotype also present but less evident in APPtg mice. Western analysis has indicated lower synaptic levels of proteins involved in mitochondrial fusion and fission during memory retrieval, compared to basal levels. No difference was identified by electron microscopy in a) numbers of synaptic mitochondria or b) synaptic mitochondrial area. Our oxygen consumption and enzymatic activity assay results are planned to be collected on time for this presentation.ConclusionOur data provide evidence supporting our hypothesis of mitochondrial involvement a) in memory retrieval and b) in the impairment of memory retrieval in APPtg mice and possibly in early AD. They also provide some clues on the exact mitochondrial mechanisms, which is the focus of our current research

Gene-Targeting Technologies for the Study of Neurological Disorders

Studies using genetic manipulations have proven invaluable in the research of neurological disorders. In the forefront of these approaches is the knockout technology that engineers a targeted gene mutation in mice resulting in inactivation of gene expression. In many cases, important roles of a particular gene in embryonic development have precluded the in vivo study of its function in the adult brain, which is usually the most relevant experimental context for the study of neurological disorders. The conditional knockout technology has provided a tool to overcome this restriction and has been used successfully to generate viable mouse models with gene inactivation patterns in certain regions or cell types of the postnatal brain. This review first describes the methodology of gene targeting in mice, detailing the aspects of designing a targeting vector, introducing it into embryonic stem cells in culture and screening for correct recombination events, and generating chimeric and null mutant mice from the positive clones. It then discusses the special issues and considerations for the generation of conditional knockout mice, including a section about approaches for inducible gene inactivation in the brain and some of their applications. An overview of gene-targeted mouse models that have been used in the study of several neurological disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, seizure disorders, and schizophrenia, is also presented. The importance of the results obtained by these models for the understanding of the pathogenic mechanism underlying the disorders is discussed

Regulation of CRE-dependent transcription by presenilins: prospects for therapy of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder and is characterized by memory loss and other cognitive disabilities. Mutations in the presenilin genes are the major cause of familial AD. Analysis of conditional knockout mice has shown that inactivation of presenilins results in progressive memory impairment and age-dependent neurodegeneration, suggesting that reduced presenilin activity might represent an important pathogenic mechanism. Presenilins positively regulate the transcription of cAMP response element (CRE)-containing genes, some of which are known to be important for memory formation and neuronal survival. Phosphodiesterase 4 and histone deacetylase inhibitors, which can enhance CRE-dependent gene expression, have been shown to ameliorate memory deficits and neurodegeneration in animal models. Thus, modulation of CRE-dependent transcription might be beneficial for the treatment of dementia in AD