VEGF counteracts amyloid-β-induced synaptic dysfunction

The vascular endothelial growth factor (VEGF) pathway regulates key processes in synapse function, which are disrupted in early stages of Alzheimer's disease (AD) by toxic-soluble amyloid-beta oligomers (Aβo). Here, we show that VEGF accumulates in and around Aβ plaques in postmortem brains of patients with AD and in APP/PS1 mice, an AD mouse model. We uncover specific binding domains involved in direct interaction between Aβo and VEGF and reveal that this interaction jeopardizes VEGFR2 activation in neurons. Notably, we demonstrate that VEGF gain of function rescues basal synaptic transmission, long-term potentiation (LTP), and dendritic spine alterations, and blocks long-term depression (LTD) facilitation triggered by Aβo. We further decipher underlying mechanisms and find that VEGF inhibits the caspase-3-calcineurin pathway responsible for postsynaptic glutamate receptor loss due to Aβo. These findings provide evidence for alterations of the VEGF pathway in AD models and suggest that restoring VEGF action on neurons may rescue synaptic dysfunction in AD.

Transcriptional regulation of CRMP5 controls neurite outgrowth through Sox5

Transcriptional regulation of proteins involved in neuronal polarity is a key process that underlies the ability of neurons to transfer information in the central nervous system. The Collapsin Response Mediator Protein (CRMP) family is best known for its role in neurite outgrowth regulation conducting to neuronal polarity and axonal guidance, including CRMP5 that drives dendrite differentiation. Although CRMP5 is able to control dendritic development, the regulation of its expression remains poorly understood. Here we identify a Sox5 consensus binding sequence in the putative promoter sequence upstream of the CRMP5 gene. By luciferase assays we show that Sox5 increases CRMP5 promoter activity, but not if the putative Sox5 binding site is mutated. We demonstrate that Sox5 can physically bind to the CRMP5 promoter DNA in gel mobility shift and chromatin immunoprecipitation assays. Using a combination of real-time RT-PCR and quantitative immunocytochemistry, we provide further evidence for a Sox5-dependent upregulation of CRMP5 transcription and protein expression in N1E115 cells: a commonly used cell line model for neuronal differentiation. Furthermore, we report that increasing Sox5 levels in this neuronal cell line inhibits neurite outgrowth. This inhibition requires CRMP5 because CRMP5 knockdown prevents the Sox5-dependent effect. We confirm the physiological relevance of the Sox5-CRMP5 pathway in the regulation of neurite outgrowth using mouse primary hippocampal neurons. These findings identify Sox5 as a critical modulator of neurite outgrowth through the selective activation of CRMP5 expression.

Disequilibrium of BMP2 levels in the breast stem cell niche launches epithelial transformation by overamplifying BMPR1B cell response

Understanding the mechanisms of cancer initiation will help to prevent and manage the disease. At present, the role of the breast microenvironment in transformation remains unknown. As BMP2 and BMP4 are important regulators of stem cells and their niches in many tissues, we investigated their function in early phases of breast cancer. BMP2 production by tumor microenvironment appeared to be specifically upregulated in luminal tumors. Chronic exposure of immature human mammary epithelial cells to high BMP2 levels initiated transformation toward a luminal tumor-like phenotype, mediated by the receptor BMPR1B. Under physiological conditions, BMP2 controlled the maintenance and differentiation of early luminal progenitors, while BMP4 acted on stem cells/myoepithelial progenitors. Our data also suggest that microenvironment-induced overexpression of BMP2 may result from carcinogenic exposure. We reveal a role for BMP2 and the breast microenvironment in the initiation of stem cell transformation, thus providing insight into the etiology of luminal breast cancer.

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High BMP2 levels are provided by endothelial and stroma cells in luminal tumors

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Chronic exposure to high BMP2 levels initiate mammary epithelial transformation

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Luminal tumors likely arise from an amplified BMP2/BMPR1B-mediated normal response

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Radiation and bisphenols perturbed BMP2 production by the mammary niche stroma

Upstream ORF affects MYCN translation depending on exon 1b alternative splicing

Background

The MYCN gene is transcribed into two major mRNAs: one full-length (MYCN) and one exon 1b-spliced (MYCN^Δ1b) mRNA. But nothing is known about their respective ability to translate the MYCN protein.

Methods

Plasmids were prepared to enable translation from the upstream (uORF) and major ORF of the two MYCN transcripts. Translation was studied after transfection in neuroblastoma SH-EP cell line. Impact of the upstream AUG on translation was evaluated after directed mutagenesis. Functional study with the two MYCN mRNAs was conducted by a cell viability assay. Existence of a new protein encoded by the MYCN^Δ1b uORF was explored by designing a rabbit polyclonal antibody against a specific epitope of this protein.

Results

Both are translated, but higher levels of protein were seen with MYCN^Δ1b mRNA. An upstream ORF was shown to have positive cis-regulatory activity on translation from MYCN but not from MYCN^Δ1b mRNA. In transfected SH-EP neuroblastoma cells, high MYCN dosage obtained with MYCN^Δ1b mRNA translation induces an antiapoptotic effect after serum deprivation that was not observed with low MYCN expression obtained with MYCN mRNA. Here, we showed that MYCNOT: MYCN Overlap Transcript, a new protein of unknown function is translated from the upstream AUG of MYCN^Δ1b mRNA.

Conclusions

Existence of upstream ORF in MYCN transcripts leads to a new level of MYCN regulation. The resulting MYCN dosage has a weak but significant anti-apoptotic activity after intrinsic apoptosis induction.

Missense mutation in exon 11 (Codon 378) of the presenilin-1 gene in a French family with early-onset Alzheimer's disease and transmission study by mismatch enhanced allele specific amplification. Mutations in brief no. 141. Online. besancon@rockefeller1.univ.lyon1.fr

Mutations in the presenilin-1 (PS1) gene account for the majority of familial early-onset Alzheimer's disease (EOAD) cases. We screened the coding part of the PS1 gene for the present of mutations in a French family with EOAD, using single strand conformation polymorphism (SSCP) analysis. Patients in the pedigree showed a missense mutation in exon 11 of the PS1 gene involving a transition of G to A, altering glycine to glutamate at codon 378. The cosegregation of the mutation with EOAD in the family was studied by allele specific amplification, enhanced by the introduction of a mismatch at the penultimate position near the 3' primer end. The mutation has not been described before and is located within the third large cytoplasmic loop and may lead to the appearance of a short additional a-helix.

Alternative exon 3 splicing of the human major protein zero gene in white blood cells and peripheral nerve tissue

The major protein zero (MPZ) is involved in peripheral myelin folding. Using nested reverse transcription-PCR, we amplified several fragments of MPZ mRNAs in white blood cells and in peripheral nerve tissue. Cloning of PCR products revealed the existence of three alternative splicing patterns: one resulted in the complete loss of exon 3 and two others induced partial skipping of the exon 3 sequence. All three alternative splicing mechanisms produced a frame-shift and created an identical premature stop codon in exon 4. We conclude that the existence of these MPZ RNA transcript variants may be the result of deliberate splicing decisions and may have functional implications in the cell.

Tryptophan hydroxylase mRNAs analysis by RT-PCR: preliminary report on the effect of noradrenaline in the neonatal rat pineal gland

The levels of mRNAs coding for tryptophan hydroxylase (TPOH), the first enzyme in melatonin synthesis, have been investigated by quantitative reverse transcription of RNA, followed by polymerase chain reaction (RT-PCR), after stimulation of neonatal pineal organ cultures with Noradrenaline (NA). TPOH mRNAs were specifically amplified from various adult tissues, namely the pineal gland, raphe, retina, and kidney, but not the lung. PCR signals for TPOH were detected in the neonatal pineal gland in the absence of stimulation. Stimulation of neonatal pineal organ culture with 0.1 microM NA resulted in a significant increase (x2.5) in expression of TPOH mRNAs, whereas higher doses (1 and 10 microM) had no effect. All concentrations of NA enhanced melatonin secretion. Our results suggest that the level of TPOH mRNAs can be controlled by NA and that this effect might be implicated in the gene level regulation of the daily enzyme rhythm in the rat pineal gland.

Evidence for tryptophan hydroxylase and hydroxy-indol-O-methyl-transferase mRNAs in human blood platelets

Human blood platelets were tested for the presence of mRNAs coding for tryptophan hydroxylase (TPOH) and hydroxy-indol-o-methyl-transferase (HIOMT). Total RNA was extracted from platelets (12.9 +/- 3.3 mg RNA/100 ml blood, mean +/- SEM of 6 preparations) and cDNA synthesized by reverse transcription using random hexamers, oligo-dT or TPOH- or HIOMT-specific primers, designed to amplify a 254 bp fragment for TPOH and a 301 bp fragment for HIOMT. Positive controls were performed using RNA extracted from human normal or tumoral pineal glands. The PCR products were analyzed by gel electrophoresis, transferred to a nylon membrane and hybridized with a 32P-labeled internal probe. When random hexamers, oligo-dT or specific primers were used for reverse transcription, amplification products of the predicted sizes were detectable following electrophoresis in the case of pineal glands and following transfer and hybridization in the case of platelets. These results show TPOH and HIOMT mRNAs to be present in human blood and support the hypothesis that serotonin and melatonin may be synthesized in blood and, more particularly, in platelets.

Nycthemeral expression of tryptophan hydroxylase mRNAs in the rat pineal gland

The expression of mRNAs coding for tryptophan hydroxylase (TPOH), the first enzyme involved in melatonin synthesis, has been studied in the rat adult pineal gland at four different circadian time points by in-situ hybridization using an oligonucleotide probe. TPOH mRNAs were detected at all chosen time-points. The lowest level was seen at 13:00 h. Quantification of the hybridization signals demonstrated a significant increase in expression (+16.5%) between 13:00 h and 19:30 h, with the values at 23:30 h and 09:00 h being similar to that of 19:30 h. These results coincide with the nycthemeral rhythm of TPOH activity. Day/night rhythms in the rat pineal gland are controlled by noradrenaline release at lights-off, which results in an increase in cAMP levels and in gene activation. This study suggests that the TPOH gene might be one such gene whose activation is stimulated in this way.

Rapid in situ hybridization using digoxigenin probe and microwave oven

In situ hybridization has been developed with probes labelled with a non-radioactive nucleotide, especially digoxigenin-coupled nucleotides. These non-radioactive probes significantly reduce safety problems and experimentation time. In this paper, we have studied by in situ hybridization the messenger RNA (mRNA) of the neuropeptide pro-opiomelanocortin (POMC), in the rat pituitary gland using digoxigenin labelled oligonucleotide and a microwave oven. Our protocol permitted us to visualize POMC mRNA in all cells of the intermediate lobe and a few corticotroph cells in the anterior lobe, as it has been already demonstrated and to complete the experiment in less than 24 hrs.

Developmental expression of tryptophan hydroxylase mRNAs in the rat pineal gland: an in situ hybridization study

The expression of messenger RNAs encoding for tryptophan hydroxylase (TPOH), the first enzyme involved in serotonin and melatonin synthesis, has been investigated by in situ hybridization during the development of the rat pineal gland. TPOH mRNAs were detected as early as the twentieth day of gestation (E20) in the rat embryo before any nerve ending was observed in the pineal gland. After birth, their expression increased strongly, and attained a plateau during the second week. This coincides with the setting up of sympathetic innervation. From day 17 (D17), the TPOH mRNA expression diminished. These results indicate that noradrenergic innervation is not involved in the initiation of rat pinealocyte differentiation, but might modulate cell maturation. This study showed the existence of three types of cells arranged in patches in the young rat pineal gland (D6): regions in which cells expressed TPOH mRNAs, regions in which cells expressed vimentin, an intermediate filament protein present in the cytoskeleton of immature cells, and regions in which both TPOH mRNAs and vimentin are expressed. In older rat pineal gland (D20), almost all cells express TPOH mRNAs, and some cells still express vimentin. This suggests that all cells do not reach the same level of differentiation at the same time in the rat pineal gland.

Structural and ultrastructural characteristics of human pineal gland, and pineal parenchymal tumors

We have studied 20 pineal parenchymal tumors (PPT) and 4 normal or cystic pineal glands both by light and electron microscopy and immunohistochemistry with antibodies against glial markers [glial fibrillary acidic protein (GFAP) and protein S-100] or neural/neuroendocrine markers [neurofilaments (NF), synaptophysin and chromogranin A]. Light microscopy revealed the cellular organization of pinealocytes in the normal gland and in different morphological types of pineal tumors (typical pineocytomas, PPT with intermediate differentiation, mixed PPT exhibiting elements of both pineocytoma and pineoblastoma and pineoblastomas). Immunohistochemistry showed the presence of GFAP and protein S-100 in interstitial cells in non-neoplastic pineal gland. Cell processes were labeled with anti-synaptophysin and anti-NF antibodies. No immunoreactivity was found for chromogranin A in non-neoplastic pineal gland. In pineocytomas, GFAP and protein S-100 were observed in interstitial cells. Synaptophysin and NF were present in the large rosettes of pineocytomas. Synaptophysin, NF and chromogranin A were present in pineocytomas with a lobular arrangement of cells. Anti-chromogranin A immunoreactivity was also seen in lobular areas of some PPT with intermediate differentiation. Analysis of normal human pineal gland by electron microscopy showed the presence of vesicle-crowned rodlets (VCR or synaptic ribbons), fibrous filaments (F), paired twisted filaments but few dense-core vesicles (DCV) in normal pinealocytes. Tumoral pineal cells appeared to differentiate either towards a neurosensory pathway characterized by the presence of sensory cells elements (VCR and F), or towards a neuroendocrine pathway, with the occurrence of many DCV. Immunogold labeling demonstrated the presence of chromogranin A in neurosecretory granules.

Pharmacology of human dopamine D3 receptor expressed in a mammalian cell line: comparison with D2 receptor

Two cell lines were created by transfecting cDNAs of the human D2 receptor or the recently cloned human D3 receptor to CHO cells, and the properties of [125I]iodosulpride binding to membranes of these cells were compared. In cell lines expressing the D2 receptor subtype where the selectable marker, a phleomycin-resistance gene, was cotransfected in a different plasmid, a stable expression could be maintained for only few passages. In cell lines expressing the D3 receptor subtype, the selectable marker, a dihydrofolate reductase gene, was cotransfected in the same plasmid and a stable expression could be obtained. In addition, the D3 receptor gene could be amplified in these latter cell lines and a high expression level reached (up to 10(6) binding sites per cell). Sodium and, to a lesser extent, lithium similarly increased [125I]iodosulpride binding to D2 and D3 receptors. In the absence of guanylnucleotide, dopamine had a 24-fold higher apparent affinity at D3 than at D2 receptors. Gpp(NH)p induced rightward shift and steepening of dopamine competition curves at either subtype but the effects were more marked at D2 than at D3 receptors. Several agonists and antagonists, previously regarded as autoreceptor-selective, displayed higher affinities at D3 than at D2 receptors. Although most antagonists used as antipsychotics displayed high affinities at the D3 receptor, all were more potent at the D2 receptor. However, the ratio of Ki values varied over about 10-fold among these compounds, suggesting that they realize differential dopamine receptor subtype occupancy during treatments and that this might be reflected in their clinical profile.