Impact of Preanalytical Procedures on Complement Biomarkers in Cerebrospinal Fluid and Plasma from Controls and Alzheimer's Disease Patients.

Background: Studies comparing cerebrospinal fluid (CSF) and plasma complement proteins in Alzheimer's disease (AD) patients versus healthy controls (HC) have yielded inconsistent results. Discrepancies in the preanalytical sample handling could contribute to the heterogeneity in the reported findings.

Objective: Using qualified immunoassays, we aimed at assessing the impact of preanalytical procedures on complement proteins in blood and CSF from AD patients and HCs.

Primate cerebrospinal fluid CHI3L1 reflects brain TREM2 agonism.

Introduction: Triggering receptor expressed on myeloid cells 2 (TREM2) agonists are being clinically evaluated as disease-modifying therapeutics for Alzheimer's disease. Clinically translatable pharmacodynamic (PD) biomarkers are needed to confirm drug activity and select the appropriate therapeutic dose in clinical trials.

Methods: We conducted multi-omic analyses on paired non-human primate brain and cerebrospinal fluid (CSF), and stimulation of human induced pluripotent stem cell-derived microglia cultures after TREM2 agonist treatment, followed by validation of candidate fluid PD biomarkers using immunoassays.

The translatome of neuronal cell bodies, dendrites, and axons.

To form synaptic connections and store information, neurons continuously remodel their proteomes. The impressive length of dendrites and axons imposes logistical challenges to maintain synaptic proteins at locations remote from the transcription source (the nucleus). The discovery of thousands of messenger RNAs (mRNAs) near synapses suggested that neurons overcome distance and gain autonomy by producing proteins locally.

Monosomes actively translate synaptic mRNAs in neuronal processes.

To accommodate their complex morphology, neurons localize messenger RNAs (mRNAs) and ribosomes near synapses to produce proteins locally. However, a relative paucity of polysomes (considered the active sites of translation) detected in electron micrographs of neuronal processes has suggested a limited capacity for local protein synthesis. In this study, we used polysome profiling together with ribosome footprinting of microdissected rodent synaptic regions to reveal a surprisingly high number of dendritic and/or axonal transcripts preferentially associated with monosomes (single ribosomes).

Author Correction: A genetically encodable cell-type-specific protein synthesis inhibitor.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A genetically encodable cell-type-specific protein synthesis inhibitor.

Chemical inhibitors have revealed requirements for protein synthesis that drive cellular plasticity. We developed a genetically encodable protein synthesis inhibitor (gePSI) to achieve cell-type-specific temporal control of protein synthesis. Controlled expression of the gePSI in neurons or glia resulted in rapid, potent and reversible cell-autonomous inhibition of protein synthesis.

Dopamine signaling in the striatum.

The striatum integrates dopamine-mediated reward signals to generate appropriate behavior in response to glutamate-mediated sensory cues. Such associative learning relies on enduring neural plasticity in striatal GABAergic spiny projection neurons which, when altered, can lead to the development of a wide variety of pathological states. Considerable progress has been made in our understanding of the intracellular signaling mechanisms in dopamine-related behaviors and pathologies.

Local translation in neuronal processes.

Neurons exhibit a unique degree of spatial compartmentalization and are able to maintain and remodel their proteomes independently from the cell body. While much effort has been devoted to understanding the capacity and role for local protein synthesis in dendrites and spines, local mRNA translation in mature axons, projecting over distances up to a meter, has received much less attention. Also, little is known about the spatio-temporal dynamics of axonal and dendritic gene expression as function of mRNA abundance, protein synthesis and degradation.

Alternative 3' UTRs Modify the Localization, Regulatory Potential, Stability, and Plasticity of mRNAs in Neuronal Compartments.

Neurons localize mRNAs near synapses where their translation can be regulated by synaptic demand and activity. Differences in the 3' UTRs of mRNAs can change their localization, stability, and translational regulation. Using 3' end RNA sequencing of microdissected rat brain slices, we discovered a huge diversity in mRNA 3' UTRs, with many transcripts showing enrichment for a particular 3' UTR isoform in either somata or the neuropil.

Ribosomal Protein S6 Phosphorylation Is Involved in Novelty-Induced Locomotion, Synaptic Plasticity and mRNA Translation.

The phosphorylation of the ribosomal protein S6 (rpS6) is widely used to track neuronal activity. Although it is generally assumed that rpS6 phosphorylation has a stimulatory effect on global protein synthesis in neurons, its exact biological function remains unknown. By using a phospho-deficient rpS6 knockin mouse model, we directly tested the role of phospho-rpS6 in mRNA translation, plasticity and behavior.

Repeated Exposure to D-Amphetamine Decreases Global Protein Synthesis and Regulates the Translation of a Subset of mRNAs in the Striatum.

Repeated psychostimulant exposure induces persistent gene expression modifications that contribute to enduring changes in striatal GABAergic spiny projecting neurons (SPNs). However, it remains unclear whether changes in the control of mRNA translation are required for the establishment of these durable modifications. Here we report that repeated exposure to D-amphetamine decreases global striatal mRNA translation.

Ribosomal Protein S6 Phosphorylation in the Nervous System: From Regulation to Function.

Since the discovery of the phosphorylation of the 40S ribosomal protein S6 (rpS6) about four decades ago, much effort has been made to uncover the molecular mechanisms underlying the regulation of this post-translational modification. In the field of neuroscience, rpS6 phosphorylation is commonly used as a readout of the mammalian target of rapamycin complex 1 signaling activation or as a marker for neuronal activity. Nevertheless, its biological role in neurons still remains puzzling.

PKA-dependent phosphorylation of ribosomal protein S6 does not correlate with translation efficiency in striatonigral and striatopallidal medium-sized spiny neurons.

Ribosomal protein S6 (rpS6), a component of the 40S ribosomal subunit, is phosphorylated on several residues in response to numerous stimuli. Although commonly used as a marker for neuronal activity, its upstream mechanisms of regulation are poorly studied and its role in protein synthesis remains largely debated. Here, we demonstrate that the psychostimulant d-amphetamine (d-amph) markedly increases rpS6 phosphorylation at Ser235/236 sites in both crude and synaptoneurosomal preparations of the mouse striatum.

drd2-cre:ribotag mouse line unravels the possible diversity of dopamine d2 receptor-expressing cells of the dorsal mouse hippocampus.

Increasing evidences suggest that dopamine facilitates the encoding of novel memories by the hippocampus. However, the role of dopamine D2 receptors (D2R) in such regulations remains elusive due to the lack of the precise identification of hippocampal D2R-expressing cells. To address this issue, mice expressing the ribosomal protein Rpl22 tagged with the hemagglutinin (HA) epitope were crossed with Drd2-Cre mice allowing the selective expression of HA in D2R-containing cells (Drd2-Cre:RiboTag mice).

Cognitive dysfunction, elevated anxiety, and reduced cocaine response in circadian clock-deficient cryptochrome knockout mice.

The circadian clock comprises a set of genes involved in cell-autonomous transcriptional feedback loops that orchestrate the expression of a range of downstream genes, driving circadian patterns of behavior. Cognitive dysfunction, mood disorders, anxiety disorders, and substance abuse disorders have been associated with disruptions in circadian rhythm and circadian clock genes, but the causal relationship of these associations is still poorly understood. In the present study, we investigate the effect of genetic disruption of the circadian clock, through deletion of both paralogs of the core gene cryptochrome (Cry1 and Cry2).