Impact of actin filament stabilization on adult hippocampal and olfactory bulb neurogenesis

Human dermal fibroblast-derived secretory proteins for regulating nerve restoration: A bioinformatic approach

BACKGROUND

Human dermal fibroblasts secrete diverse proteins that regulate wound repair and tissue regeneration.

METHODS

In this study, dermal fibroblast-conditioned medium (DFCM) proteins potentially regulating nerve restoration were bioinformatically selected among the 337 protein lists identified by quantitative liquid chromatography-tandem mass spectrometry. Using these proteins, protein-protein interaction network analysis was conducted. In addition, the roles of DFCM proteins were reviewed according to their protein classifications.

RESULTS

Gene Ontology protein classification categorized these 57 DFCM proteins into various classes, including protein-binding activity modulator (N = 11), cytoskeletal protein (N = 8), extracellular matrix protein (N = 6), metabolite interconversion enzyme (N = 5), chaperone (N = 4), scaffold/adapter protein (N = 4), calcium-binding protein (N = 3), cell adhesion molecule (N = 2), intercellular signal molecule (N = 2), protein modifying enzyme (N = 2), transfer/carrier protein (N = 2), membrane traffic protein (N = 1), translational protein (N = 1), and unclassified proteins (N = 6). Further protein-protein interaction network analysis of 57 proteins revealed significant interactions among the proteins that varied according to the settings of confidence score.

CONCLUSIONS

Our bioinformatic analysis demonstrated that DFCM contains many secretory proteins that form significant protein-protein interaction networks crucial for regulating nerve restoration. These findings underscore DFCM proteins' critical roles in various nerve restoration stages during the wound repair process.

Mapping dynamic molecular changes in hippocampal subregions after traumatic brain injury through spatial proteomics

BACKGROUND

Traumatic brain injury (TBI) often results in diverse molecular responses, challenging traditional proteomic studies that measure average changes at tissue levels and fail to capture the complexity and heterogeneity of the affected tissues. Spatial proteomics offers a solution by providing insights into sub-region-specific alterations within tissues. This study focuses on the hippocampal sub-regions, analyzing proteomic expression profiles in mice at the acute (1 day) and subacute (7 days) phases of post-TBI to understand subregion-specific vulnerabilities and long-term consequences.

METHODS

Three mice brains were collected from each group, including Sham, 1-day post-TBI and 7-day post-TBI. Hippocampal subregions were extracted using Laser Microdissection (LMD) and subsequently analyzed by label-free quantitative proteomics.

RESULTS

The spatial analysis reveals region-specific protein abundance changes, highlighting the elevation of FN1, LGALS3BP, HP, and MUG-1 in the stratum moleculare (SM), suggesting potential immune cell enrichment post-TBI. Notably, established markers of chronic traumatic encephalopathy, IGHM and B2M, exhibit specific upregulation in the dentate gyrus bottom (DG2) independent of direct mechanical injury. Metabolic pathway analysis identifies disturbances in glucose and lipid metabolism, coupled with activated cholesterol synthesis pathways enriched in SM at 7-Day post-TBI and subsequently in deeper DG1 and DG2 suggesting a role in neurogenesis and the onset of recovery. Coordinated activation of neuroglia and microtubule dynamics in DG2 suggest recovery mechanisms in less affected regions. Cluster analysis revealed spatial variations post-TBI, indicative of dysregulated neuronal plasticity and neurogenesis and further predisposition to neurological disorders. TBI-induced protein upregulation (MUG-1, PZP, GFAP, TJP, STAT-1, and CD44) across hippocampal sub-regions indicates shared molecular responses and links to neurological disorders. Spatial variations were demonstrated by proteins dysregulated in both or either of the time-points exclusively in each subregion (ELAVL2, CLIC1 in PL, CD44 and MUG-1 in SM, and SHOC2, LGALS3 in DG).

CONCLUSIONS

Utilizing advanced spatial proteomics techniques, the study unveils the dynamic molecular responses in distinct hippocampal subregions post-TBI. It uncovers region-specific vulnerabilities and dysregulated neuronal processes, and potential recovery-related pathways that contribute to our understanding of TBI's neurological consequences and provides valuable insights for biomarker discovery and therapeutic targets.

Cytochalasins as Modulators of Stem Cell Differentiation

Regenerative medicine aims to identify new research strategies for the repair and restoration of tissues damaged by pathological or accidental events. Mesenchymal stem cells (MSCs) play a key role in regenerative medicine approaches due to their specific properties, such as the high rate of proliferation, the ability to differentiate into several cell lineages, the immunomodulatory potential, and their easy isolation with minimal ethical issues. One of the main goals of regenerative medicine is to modulate, both in vitro and in vivo, the differentiation potential of MSCs to improve their use in the repair of damaged tissues. Over the years, much evidence has been collected about the ability of cytochalasins, a large family of 60 metabolites isolated mainly from fungi, to modulate multiple properties of stem cells (SCs), such as proliferation, migration, and differentiation, by altering the organization of the cyto- and the nucleo-skeleton. In this review, we discussed the ability of two different cytochalasins, cytochalasins D and B, to influence specific SC differentiation programs modulated by several agents (chemical or physical) or intra- and extra-cellular factors, with particular attention to human MSCs (hMSCs).

Role of Nasal Nitric Oxide in Primary Ciliary Dyskinesia and Other Respiratory Conditions in Children

Nitric oxide (NO) is produced within the airways and released with exhalation. Nasal NO (nNO) can be measured in a non-invasive way, with different devices and techniques according to the age and cooperation of the patients. Here, we conducted a narrative review of the literature to examine the relationship between nNO and some respiratory diseases with a particular focus on primary ciliary dyskinesia (PCD). A total of 115 papers were assessed, and 50 were eventually included in the review. nNO in PCD is low (below 77 nL/min), and its measurement has a clear diagnostic value when evaluated in a clinically suggestive phenotype. Many studies have evaluated the role of NO as a molecular mediator as well as the association between nNO values and genotype or ciliary function. As far as other respiratory diseases are concerned, nNO is low in chronic rhinosinusitis and cystic fibrosis, while increased values have been found in allergic rhinitis. Nonetheless, the role in the diagnosis and prognosis of these conditions has not been fully clarified.

Regulation of young-adult neurogenesis and neuronal differentiation by neural cell adhesion molecule 2 (NCAM2)

Adult neurogenesis persists in mammals in the neurogenic zones, where newborn neurons are incorporated into preexisting circuits to preserve and improve learning and memory tasks. Relevant structural elements of the neurogenic niches include the family of cell adhesion molecules (CAMs), which participate in signal transduction and regulate the survival, division, and differentiation of radial glial progenitors (RGPs). Here we analyzed the functions of neural cell adhesion molecule 2 (NCAM2) in the regulation of RGPs in adult neurogenesis and during corticogenesis. We characterized the presence of NCAM2 across the main cell types of the neurogenic process in the dentate gyrus, revealing different levels of NCAM2 amid the progression of RGPs and the formation of neurons. We showed that Ncam2 overexpression in adult mice arrested progenitors in an RGP-like state, affecting the normal course of young-adult neurogenesis. Furthermore, changes in Ncam2 levels during corticogenesis led to transient migratory deficits but did not affect the survival and proliferation of RGPs, suggesting a differential role of NCAM2 in adult and embryonic stages. Our data reinforce the relevance of CAMs in the neurogenic process by revealing a significant role of Ncam2 levels in the regulation of RGPs during young-adult neurogenesis in the hippocampus.

Chitinase-like protein 3: A novel niche factor for mouse neural stem cells

The concept of a perivascular niche has been proposed for neural stem cells (NSCs). This study examined endothelial colony-forming cell (ECFC)-secreted proteins as potential niche factors for NSCs. Intraventricle infusion with ECFC-secreted proteins increased the number of NSCs. ECFC-secreted proteins were more effective in promoting NSC self-renewal than marrow stromal cell (MSC)-secreted proteins. Differential proteomics analysis of MSC-secreted and ECFC-secreted proteins was performed, which revealed chitinase-like protein 3 (CHIL3; also called ECF-L or Ym1) as a candidate niche factor for NSCs. Experiments with recombinant CHIL3, small interfering RNA, and neutralizing antibodies demonstrated that CHIL3 stimulated NSC self-renewal with neurogenic propensity. CHIL3 was endogenously expressed in the neurogenic niche of the brain and retina as well as in the injured brain and retina. Transcriptome and phosphoproteome analyses revealed that CHIL3 activated various genes and proteins associated with NSC maintenance or neurogenesis. Thus, CHIL3 is a novel niche factor for NSCs.

Proteomic characterization of spontaneously regrowing spinal cord following injury in the teleost fish Apteronotus leptorhynchus, a regeneration-competent vertebrate

In adult mammals, spontaneous repair after spinal cord injury (SCI) is severely limited. By contrast, teleost fish successfully regenerate injured axons and produce new neurons from adult neural stem cells after SCI. The molecular mechanisms underlying this high regenerative capacity are largely unknown. The present study addresses this gap by examining the temporal dynamics of proteome changes in response to SCI in the brown ghost knifefish (Apteronotus leptorhynchus). Two-dimensional difference gel electrophoresis (2D DIGE) was combined with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and tandem mass spectrometry (MS/MS) to collect data during early (1 day), mid (10 days), and late (30 days) phases of regeneration following caudal amputation SCI. Forty-two unique proteins with significant differences in abundance between injured and intact control samples were identified. Correlation analysis uncovered six clusters of spots with similar expression patterns over time and strong conditional dependences, typically within functional families or between isoforms. Significantly regulated proteins were associated with axon development and regeneration; proliferation and morphogenesis; neuronal differentiation and re-establishment of neural connections; promotion of neuroprotection, redox homeostasis, and membrane repair; and metabolism or energy supply. Notably, at all three time points examined, significant regulation of proteins involved in inflammatory responses was absent.

Adult Neurogenesis and Stroke: A Tale of Two Neurogenic Niches

In the aftermath of an acute stroke, numerous signaling cascades that reshape the brain both in the perilesional zone as well as in more distal regions are activated. Despite continuous improvement in the acute treatment of stroke and the sustained research efforts into the pathophysiology of stroke, we critically lag in our integrated understanding of the delayed and chronic responses to ischemic injury. As such, the beneficial or maladaptive effect of some stroke-induced cellular responses is unclear, restricting the advancement of therapeutic strategies to target long-term complications. A prominent delayed effect of stroke is the robust increase in adult neurogenesis, which raises hopes for a regenerative strategy to counter neurological deficits in stroke survivors. In the adult brain, two regions are known to generate new neurons from endogenous stem cells: the subventricular zone (SVZ) and the dentate subgranular zone (SGZ) of the hippocampus. While both niches respond with an increase in neurogenesis post-stroke, there are significant regional differences in the ensuing stages of survival, migration, and maturation, which may differently influence functional outcome. External interventions such as rehabilitative training add a further layer of complexity by independently modulating the process of adult neurogenesis. In this review we summarize the current knowledge regarding the effects of ischemic stroke on neurogenesis in the SVZ and in the SGZ, and the influence of exogenous stimuli such as motor activity or enriched environment (EE). In addition, we discuss the contribution of SVZ or SGZ post-stroke neurogenesis to sensory, motor and cognitive recovery.

Correlation between Serum Platelet Count and Cognitive Function in Patients with Atrial Fibrillation: A Cross-Sectional Study

BACKGROUND

The risk of cognitive impairment in patients with atrial fibrillation is significantly increased. Its occurrence may be related to blood hypercoagulable state and immune inflammatory reaction. Platelets can mediate immune inflammatory response, but there is no evidence about the relationship between platelet count and cognitive function in patients with atrial fibrillation.

PURPOSE

To explore whether there is a certain correlation between platelet count and cognitive function in patients with atrial fibrillation.

METHODS

A cross-sectional study was conducted in a single center in China, including 254 patients with atrial fibrillation. Cognitive function assessment and clinical and laboratory examinations were performed on all participants. After adjusting the related confounding factors, the relationship between platelet count and cognitive function was analyzed.

RESULTS

A total of 254 subjects with an average age of 59.71 ± 11.14 years were included. The average platelet count was 208.15 ± 68.30, and the average score of cognitive function was 19.29 ± 6.78. Result of fully adjusted binary logistic regression showed platelet count was negatively associated with the cognitive function score after adjusting confounders (hazard ratio (HR) = 0.000, 95%CI -0.01, 0.01). A nonlinear relationship was detected between platelet count and the cognitive function score, whose point was 230. The effect sizes and the confidence intervals of the left and right sides of the inflection point were 0.03 (0.01-0.05, P for nonlinearity = 0.011) and -0.03 (-0.05-0.00, P for nonlinearity = 0.023), respectively.

CONCLUSION

Platelets have a nonlinear relationship with cognitive function in patients with atrial fibrillation. This finding suggests that, in patients with atrial fibrillation, platelets should be maintained at about 230.

Bortezomib at therapeutic doses poorly passes the blood-brain barrier and does not impair cognition

The 26S proteasome inhibitor bortezomib is currently used to treat multiple myeloma but also is effective in the treatment of antibody-mediated autoimmune disorders. One clinical concern is bortezomib's toxicity towards the (central) nervous system. We used standardized neuropsychological testing to assess cognitive function in six patients with myasthenia gravis and systemic lupus erythematodes before and after treatment with a mean cumulative dose of 9.4 mg m^-2 bortezomib. In addition, cognitive performance was measured in adult C57Bl/6 mice after treatment with a human equivalent cumulative dose of 15.6 mg m^-2. Bortezomib concentrations were analysed in the human CSF as well as the brain tissue and serum of adult C57Bl/6 mice at various time points after the injection of 1.3 mg m^-2 bortezomib with liquid chromatography-tandem mass spectrometry. Neither patients nor mice showed signs of cognitive impairment after bortezomib therapy. Bortezomib concentrations in the human CSF and murine brain tissue reached only 5-7% of serum concentrations with comparable concentrations measured in the hippocampus and the neocortex. Five-fold higher concentrations were needed to damage neuronal cells in vitro. In conclusion, penetration of the intact blood-brain barrier by bortezomib is low. Overall, our data show that bortezomib is a safe medication in terms of central nervous system toxicity.

Platelets: The missing link between the blood and brain?

It is becoming increasingly clear that interactions between the peripheral immune system and the central nervous system are important in maintaining healthy brain function. Platelets are small blood cells traditionally known for their role in wound healing. However, platelets have recently been shown to exhibit many alternative functions. In this perspective, we summarize the repertoire of platelet functions, focusing on how these cells contribute to the maintenance of brain homeostasis and propose the mechanisms via which they could communicate with brain cells, including exosome and microparticle release and receptor interactions at local sites. In particular, we highlight the potential role that platelets play in maintaining brain plasticity via the modulation of new neuron generation from neural precursor cells, an interaction which could have important implications in the development of therapeutic interventions to promote cognitive function in aging and disease.

Chronic Lithium Treatment Increases Telomere Length in Parietal Cortex and Hippocampus of Triple-Transgenic Alzheimer's Disease Mice

Telomere length (TL) is a biomarker of cell aging, and its shortening has been linked to several age-related diseases. In Alzheimer's disease (AD), telomere shortening has been associated with neuroinflammation and oxidative stress. The majority of studies on TL in AD were based on leucocyte DNA, with little information about its status in the central nervous system. In addition to other neuroprotective effects, lithium has been implicated in the maintenance of TL. The present study aims to determine the effect of chronic lithium treatment on TL in different regions of the mouse brain, using a triple-transgenic mouse model (3xTg-AD). Eighteen transgenic and 22 wild-type (Wt) male mice were treated for eight months with chow containing 1.0 g (Li1) or 2.0 g (Li2) of lithium carbonate/kg, or standard chow (Li0). DNA was extracted from parietal cortex, hippocampus and olfactory epithelium and TL was quantified by real-time PCR. Chronic lithium treatment was associated with longer telomeres in the hippocampus (Li2, p = 0.0159) and in the parietal cortex (Li1, p = 0.0375) of 3xTg-AD compared to Wt. Our findings suggest that chronic lithium treatment does affect telomere maintenance, but the magnitude and nature of this effect depend on the working concentrations of lithium and characteristics of the tissue. This effect was observed when comparing 3xTg-AD with Wt mice, suggesting that the presence of AD pathology was required for the lithium modulation of TL.

Reduced Hippocampal Neurogenesis in Mice Deficient in Apoptosis Repressor with Caspase Recruitment Domain (ARC)

In the adult hippocampal dentate gyrus (DG), the majority of newly generated cells are eliminated by apoptotic mechanisms. The apoptosis repressor with caspase recruitment domain (ARC), encoded by the Nol3 gene, is a potent and multifunctional death repressor that inhibits both death receptor and mitochondrial apoptotic signaling. The aim of the present study was to parse the role of ARC in the development of new granule cell neurons. Nol3 gene expression as revealed by in situ hybridization is present in the entire dentate granule cell layer. Moreover, a comparison of Nol3 expression between FACS-sorted Sox2-positive neural stem cells and Doublecortin (DCX)-positive immature neurons demonstrates upregulation of Nol3 during neurogenesis. Using ARC-deficient mice, we show that proliferation and survival of BrdU birth-dated cells are strongly reduced in the absence of ARC while neuronal-glial fate choice is not affected. Both the number of DCX-positive cells and the number of calretinin (CR)-positive immature postmitotic neurons are reduced in the hippocampus of ARC^-/- mice. ARC knockout is not associated with increased numbers of microglia or with microglia activation. However, hippocampal brain-derived neurotrophic factor (BDNF) protein content is significantly increased in ARC^-/- mice, possibly representing a compensatory response. Collectively, our results suggest that ARC plays a critical cell-autonomous role in preventing cell death during adult granule cell neogenesis.

miR-124-3p is a chronic regulator of gene expression after brain injury

Traumatic brain injury (TBI) initiates molecular and cellular pathologies that underlie post-injury morbidities, including hippocampus-related memory decline and epileptogenesis. Non-coding small RNAs are master regulators of gene expression with the potential to affect multiple molecular pathways. To evaluate whether hippocampal gene expression networks are chronically regulated by microRNAs after TBI, we sampled the dentate gyrus of rats with severe TBI induced by lateral fluid-percussion injury 3 months earlier. Ingenuity pathway analysis revealed 30 upregulated miR-124-3p targets, suggesting that miR-124-3p is downregulated post-TBI (z-score = - 5.146, p < 0.05). Droplet digital polymerase chain reaction (ddPCR) and in situ hybridization confirmed the chronic downregulation of miR-124-3p (p < 0.05). Quantitative PCR analysis of two targets, Plp2 and Stat3, indicated that their upregulation correlated with the miR-124-3p downregulation (r = - 0.647, p < 0.05; r = - 0.629, p < 0.05, respectively). Immunohistochemical staining of STAT3 confirmed the increased protein expression. STRING analysis showed that 9 of the 30 miR-124-3p targets belonged to a STAT3 network. Reactome analysis and data mining connected the targets especially to inflammation and signal transduction. L1000CDS2 software revealed drugs (e.g., importazole, trichostatin A, and IKK-16) that could reverse the observed molecular changes. The translational value of our data was emphasized by in situ hybridization showing chronic post-traumatic downregulation of miR-124-3p in the dentate gyrus of TBI patients. Analysis of another brain injury model, status epilepticus, highlighted the fact that chronic downregulation of miR-124 is a common phenomenon after brain injury. Together, our findings indicate that miR-124-3p is a chronic modulator of molecular networks relevant to post-injury hippocampal pathologies in experimental models and in humans.

Dendritic spine actin cytoskeleton in autism spectrum disorder

Dendritic spines are small actin-rich protrusions from neuronal dendrites that form the postsynaptic part of most excitatory synapses. Changes in the shape and size of dendritic spines correlate with the functional changes in excitatory synapses and are heavily dependent on the remodeling of the underlying actin cytoskeleton. Recent evidence implicates synapses at dendritic spines as important substrates of pathogenesis in neuropsychiatric disorders, including autism spectrum disorder (ASD). Although synaptic perturbations are not the only alterations relevant for these diseases, understanding the molecular underpinnings of the spine and synapse pathology may provide insight into their etiologies and could reveal new drug targets. In this review, we will discuss recent findings of defective actin regulation in dendritic spines associated with ASD.

Identification of Genes Enriched in GnRH Neurons by Translating Ribosome Affinity Purification and RNAseq in Mice

Gonadotropin-releasing hormone (GnRH) neurons are a nexus of fertility regulation. We used translating ribosome affinity purification coupled with RNA sequencing to examine messenger RNAs of GnRH neurons in adult intact and gonadectomized (GDX) male and female mice. GnRH neuron ribosomes were tagged with green fluorescent protein (GFP) and GFP-labeled polysomes isolated by immunoprecipitation, producing one RNA fraction enhanced for GnRH neuron transcripts and one RNA fraction depleted. Complementary DNA libraries were created from each fraction and 50-base, paired-end sequencing done and differential expression (enhanced fraction/depleted fraction) determined with a threshold of >1.5- or <0.66-fold (false discovery rate P ≤ 0.05). A core of ∼840 genes was differentially expressed in GnRH neurons in all treatments, including enrichment for Gnrh1 (∼40-fold), and genes critical for GnRH neuron and/or gonadotrope development. In contrast, non-neuronal transcripts were not enriched or were de-enriched. Several epithelial markers were also enriched, consistent with the olfactory epithelial origins of GnRH neurons. Interestingly, many synaptic transmission pathways were de-enriched, in accordance with relatively low innervation of GnRH neurons. The most striking difference between intact and GDX mice of both sexes was a marked downregulation of genes associated with oxidative phosphorylation and upregulation of glucose transporters in GnRH neurons from GDX mice. This may suggest that GnRH neurons switch to an alternate fuel to increase adenosine triphosphate production in the absence of negative feedback when GnRH release is elevated. Knowledge of the GnRH neuron translatome and its regulation can guide functional studies and can be extended to disease states, such as polycystic ovary syndrome.

Olfactory dysfunction is worse in primary ciliary dyskinesia compared with other causes of chronic sinusitis in children

Cilia have multiple functions including olfaction. We hypothesised that olfactory function could be impaired in primary ciliary dyskinesia (PCD). Olfaction, nasal nitric oxide (nNO) and sinus CT were assessed in patients with PCD and non-PCD sinus disease, and healthy controls (no CT scan). PCD and non-PCD patients had similar severity of sinus disease. Despite this, defective olfaction was more common in patients with PCD (P<0.0001) and more severe in patients with PCD with major Transmission Electron Microscopy (TEM) abnormalities. Only in classical PCD did olfaction inversely correlate with sinusitis and nNO. We speculate that defective olfaction in PCD is primary in nature.

A novel preventive therapy for paclitaxel-induced cognitive deficits: preclinical evidence from C57BL/6 mice

Chemotherapy-induced central nervous system (CNS) neurotoxicity presents an unmet medical need. Patients often report a cognitive decline in temporal correlation to chemotherapy, particularly for hippocampus-dependent verbal and visuo-spatial abilities. We treated adult C57Bl/6 mice with 12 × 20 mg kg^-1 paclitaxel (PTX), mimicking clinical conditions of dose-dense chemotherapy, followed by a pulse of bromodesoxyuridine (BrdU) to label dividing cells. In this model, mice developed visuo-spatial memory impairments, and we measured peak PTX concentrations in the hippocampus of 230 nm l^-1, which was sevenfold higher compared with the neocortex. Histologic analysis revealed a reduced hippocampal cell proliferation. In vitro, we observed severe toxicity in slowly proliferating neural stem cells (NSC) as well as human neuronal progenitor cells after 2 h exposure to low nanomolar concentrations of PTX. In comparison, mature post-mitotic hippocampal neurons and cell lines of malignant cells were less vulnerable. In PTX-treated NSC, we observed an increase of intracellular calcium levels, as well as an increased activity of calpain- and caspase 3/7, suggesting a calcium-dependent mechanism. This cell death pathway could be specifically inhibited with lithium, but not glycogen synthase kinase 3 inhibitors, which protected NSC in vitro. In vivo, preemptive treatment of mice with lithium prevented PTX-induced memory deficits and abnormal adult hippocampal neurogenesis. In summary, we identified a molecular pathomechanism, which invokes PTX-induced cytotoxicity in NSC independent of cell cycle status. This pathway could be pharmacologically inhibited with lithium without impairing paclitaxel's tubulin-dependent cytostatic mode of action, enabling a potential translational clinical approach.

Overexpression of GSN could decrease inflammation and apoptosis in EAE and may enhance vitamin D therapy on EAE/MS

The decrease of gelsolin (GSN) in the blood has been reported in multiple sclerosis (MS) patients and experimental allergic encephalomyelitis (EAE) animals, but the protective effect of GSN on EAE/MS lacks of evidence. In our study, we increased the GSN level in EAE by injecting GSN-overexpress lentivirus (LV-GSN) into the lateral ventricle and caudal vein and found that GSN administration can delay the onset and decrease the severity of EAE. Vitamin D is proven to have a therapeutic effect on MS/EAE; however, we previously found that vitamin D caused a downregulation of GSN, which might limit vitamin D efficacy. In our current research, we obtained a better symptom and a slowing down progression in EAE after combining vitamin D treatment with a proper increase of GSN. Furthermore, we discovered that the mediation of vitamin D on GSN might occur through the vitamin D receptor (VDR) by using gene interruption and overexpression to regulate the level of VDR in PC12 cells (a rat sympathetic nerve cell line). We also confirmed the anti-apoptotic function of GSN by GSN RNA interference in PC12. Collectively, these results support the therapeutic effect of GSN in EAE, which might enhance Vitamin D therapy in EAE/MS.

LINGO-1 Regulates Oligodendrocyte Differentiation through the Cytoplasmic Gelsolin Signaling Pathway

Differentiation and maturation of oligodendrocyte progenitor cells (OPCs) involve the assembly and disassembly of actin microfilaments. However, how actin dynamics are regulated during this process remains poorly understood. Leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of OPC differentiation. We discovered that anti-LINGO-1 antibody-promoted OPC differentiation was accompanied by upregulation of cytoplasmic gelsolin (cGSN), an abundant actin-severing protein involved in the depolymerization of actin filaments. Treating rat OPCs with cGSN siRNA reduced OPC differentiation, whereas overexpression of cGSN promoted OPC differentiation in vitro and remyelination in vivo Furthermore, coexpression of cGSN and LINGO-1 blocked the inhibitory effect of LINGO-1. Our study demonstrates that cGSN works downstream of LINGO-1 signaling pathway, which enhances actin dynamics and is essential for OPC morphogenesis and differentiation. This finding may lead to novel therapeutic approaches for the treatment of demyelinating diseases such as multiple sclerosis (MS).SIGNIFICANCE STATEMENT Myelin loss and subsequent axon degeneration contributes to a variety of neurological diseases, such as multiple sclerosis (MS). Understanding the regulation of myelination by oligodendrocytes is therefore critical for developing therapies for the treatment of MS. We previously demonstrated that leucine-rich repeat and Ig-like domain-containing Nogo receptor interacting protein 1 (LINGO-1) is a negative regulator of oligodendrocyte differentiation and that anti-LINGO-1 promotes remyelination in preclinical animal models for MS and in a phase II acute optic neuritis clinical trial (RENEW). The mechanism by which LINGO-1 regulates oligodendrocyte differentiation is unknown. Here, we demonstrate that LINGO-1 regulates oligodendrocyte differentiation and maturation through the cytoplasmic gelsolin signaling pathway, providing new drug targets for the treatment of demyelination diseases.

Decreased demand for olfactory periglomerular cells impacts on neural precursor cell viability in the rostral migratory stream

The subventricular zone (SVZ) provides a constant supply of new neurons to the olfactory bulb (OB). Different studies have investigated the role of olfactory sensory input to neural precursor cell (NPC) turnover in the SVZ but it was not addressed if a reduced demand specifically for periglomerular neurons impacts on NPC-traits in the rostral migratory stream (RMS). We here report that membrane type-1 matrix metalloproteinase (MT1-MMP) deficient mice have reduced complexity of the nasal turbinates, decreased sensory innervation of the OB, reduced numbers of olfactory glomeruli and reduced OB-size without alterations in SVZ neurogenesis. Large parts of the RMS were fully preserved in MT1-MMP-deficient mice, but we detected an increase in cell death-levels and a decrease in SVZ-derived neuroblasts in the distal RMS, as compared to controls. BrdU-tracking experiments showed that homing of NPCs specifically to the glomerular layer was reduced in MT1-MMP-deficient mice in contrast to controls while numbers of tracked cells remained equal in other OB-layers throughout all experimental groups. Altogether, our data show the demand for olfactory interneurons in the glomerular layer modulates cell turnover in the RMS, but has no impact on subventricular neurogenesis.

BAR-SH3 sorting nexins are conserved interacting proteins of Nervous wreck that organize synapses and promote neurotransmission

Nervous wreck (Nwk) is a conserved F-BAR protein that attenuates synaptic growth and promotes synaptic function in Drosophila. In an effort to understand how Nwk carries out its dual roles, we isolated interacting proteins using mass spectrometry. We report a conserved interaction between Nwk proteins and BAR-SH3 sorting nexins, a family of membrane-binding proteins implicated in diverse intracellular trafficking processes. In mammalian cells, BAR-SH3 sorting nexins induce plasma membrane tubules that localize NWK2, consistent with a possible functional interaction during the early stages of endocytic trafficking. To study the role of BAR-SH3 sorting nexins in vivo, we took advantage of the lack of genetic redundancy in Drosophila and employed CRISPR-based genome engineering to generate null and endogenously tagged alleles of SH3PX1. SH3PX1 localizes to neuromuscular junctions where it regulates synaptic ultrastructure, but not synapse number. Consistently, neurotransmitter release was significantly diminished in SH3PX1 mutants. Double-mutant and tissue-specific-rescue experiments indicate that SH3PX1 promotes neurotransmitter release presynaptically, at least in part through functional interactions with Nwk, and might act to distinguish the roles of Nwk in regulating synaptic growth and function.

Photoperiod affects the cerebrospinal fluid proteome: a comparison between short day- and long day-treated ewes

Photoperiod is the main physical synchronizer of seasonal functions and a key factor in the modulation of molecule access to cerebrospinal fluid (CSF) in animals. Previous work has shown that photoperiod affects the transfer rate of steroids and protein hormones from blood to CSF and modulates choroid plexus tight junction protein content. We hypothesized that the CSF proteome would also be modified by photoperiod. We tested this hypothesis by comparing CSF obtained from the third ventricle of mature, ovariectomized, estradiol-replaced ewes exposed to long day length (LD) or short day length (SD). Variations in CSF protein expression between SD- or LD-treated ewes were studied in pools of CSF collected for 48 h. Proteins were precipitated, concentrated, and included in a polyacrylamide gel without protein fractionation. After in-gel tryptic digestion of total protein samples, we analyzed the resulting peptides by nanoliquid chromatography coupled with high-resolution tandem mass spectrometry (GeLC-MS/MS). Quantitative analysis was performed using 2 methods based on spectral counting and extracted ion chromatograms. Among 103 identified proteins, 41 were differentially expressed between LD and SD ewes (with P < 0.05 and at least a 1.5-fold difference). Of the 41 differentially expressed proteins, 22 were identified by both methods and 19 using extracted ion chromatograms only. Eighteen proteins were more abundant in LD ewes and 23 were more abundant in SD ewes. These proteins are involved in numerous functions including hormone transport, immune system activity, metabolism, and angiogenesis. To confirm proteomic results, 2 proteins, pigment epithelium-derived factor (PEDF) and gelsolin, for each individual sample of CSF collected under SD or LD were analyzed with Western blots. These results suggest an important photoperiod-dependent change in CSF proteome composition. Nevertheless, additional studies are required to assess the role of each protein in seasonal functions.

CNS myelin wrapping is driven by actin disassembly

Myelin is essential in vertebrates for the rapid propagation of action potentials, but the molecular mechanisms driving its formation remain largely unknown. Here we show that the initial stage of process extension and axon ensheathment by oligodendrocytes requires dynamic actin filament assembly by the Arp2/3 complex. Unexpectedly, subsequent myelin wrapping coincides with the upregulation of actin disassembly proteins and rapid disassembly of the oligodendrocyte actin cytoskeleton and does not require Arp2/3. Inducing loss of actin filaments drives oligodendrocyte membrane spreading and myelin wrapping in vivo, and the actin disassembly factor gelsolin is required for normal wrapping. We show that myelin basic protein, a protein essential for CNS myelin wrapping whose role has been unclear, is required for actin disassembly, and its loss phenocopies loss of actin disassembly proteins. Together, these findings provide insight into the molecular mechanism of myelin wrapping and identify it as an actin-independent form of mammalian cell motility.

Actin dynamics shape microglia effector functions

Impaired actin filament dynamics have been associated with cellular senescence. Microglia, the resident immune cells of the brain, are emerging as a central pathophysiological player in neurodegeneration. Microglia activation, which ranges on a continuum between classical and alternative, may be of critical importance to brain disease. Using genetic and pharmacological manipulations, we studied the effects of alterations in actin dynamics on microglia effector functions. Disruption of actin dynamics did not affect transcription of genes involved in the LPS-triggered classical inflammatory response. By contrast, in consequence of impaired nuclear translocation of phospho-STAT6, genes involved in IL-4 induced alternative activation were strongly downregulated. Functionally, impaired actin dynamics resulted in reduced NO secretion and reduced release of TNFalpha and IL-6 from LPS-stimulated microglia and of IGF-1 from IL-4 stimulated microglia. However, pathological stabilization of the actin cytoskeleton increased LPS-induced release of IL-1beta and IL-18, which belong to an unconventional secretory pathway. Reduced NO release was associated with decreased cytoplasmic iNOS protein expression and decreased intracellular arginine uptake. Furthermore, disruption of actin dynamics resulted in reduced microglia migration, proliferation and phagocytosis. Finally, baseline and ATP-induced [Ca(2+)]int levels were significantly increased in microglia lacking gelsolin, a key actin-severing protein. Together, the dynamic state of the actin cytoskeleton profoundly and distinctly affects microglia behaviours. Disruption of actin dynamics attenuates M2 polarization by inhibiting transcription of alternative activation genes. In classical activation, the role of actin remodelling is complex, does not relate to gene transcription and shows a major divergence between cytokines following conventional and unconventional secretion.

Tropomyosin Tm5NM1 spatially restricts src kinase activity through perturbation of Rab11 vesicle trafficking

In order for cells to stop moving, they must synchronously stabilize actin filaments and their associated focal adhesions. How these two structures are coordinated in time and space is not known. We show here that the actin association protein Tm5NM1, which induces stable actin filaments, concurrently suppresses the trafficking of focal-adhesion-regulatory molecules. Using combinations of fluorescent biosensors and fluorescence recovery after photobleaching (FRAP), we demonstrate that Tm5NM1 reduces the level of delivery of Src kinase to focal adhesions, resulting in reduced phosphorylation of adhesion-resident Src substrates. Live imaging of Rab11-positive recycling endosomes that carry Src to focal adhesions reveals disruption of this pathway. We propose that tropomyosin synchronizes adhesion dynamics with the cytoskeleton by regulating actin-dependent trafficking of essential focal-adhesion molecules.

Invasive cells in animals and plants: searching for LECA machineries in later eukaryotic life

Invasive cell growth and migration is usually considered a specifically metazoan phenomenon. However, common features and mechanisms of cytoskeletal rearrangements, membrane trafficking and signalling processes contribute to cellular invasiveness in organisms as diverse as metazoans and plants – two eukaryotic realms genealogically connected only through the last common eukaryotic ancestor (LECA). By comparing current understanding of cell invasiveness in model cell types of both metazoan and plant origin (invadopodia of transformed metazoan cells, neurites, pollen tubes and root hairs), we document that invasive cell behavior in both lineages depends on similar mechanisms. While some superficially analogous processes may have arisen independently by convergent evolution (e.g. secretion of substrate- or tissue-macerating enzymes by both animal and plant cells), at the heart of cell invasion is an evolutionarily conserved machinery of cellular polarization and oriented cell mobilization, involving the actin cytoskeleton and the secretory pathway. Its central components - small GTPases (in particular RHO, but also ARF and Rab), their specialized effectors, actin and associated proteins, the exocyst complex essential for polarized secretion, or components of the phospholipid- and redox- based signalling circuits (inositol-phospholipid kinases/PIP2, NADPH oxidases) are aparently homologous among plants and metazoans, indicating that they were present already in LECA.

Reviewer: This article was reviewed by Arcady Mushegian, Valerian Dolja and Purificacion Lopez-Garcia.

Burn injury induces gelsolin expression and cleavage in the brain of mice

Gelsolin is an actin filament-severing and capping protein, affecting cellular motility, adhesiveness and apoptosis. Whether it is expressed in the brain of burned mice has not yet been characterized. Mice were subjected to a 15% total body surface area scald injury. Neuropathology was examined by hematoxylin and eosin staining. Cerebral gelsolin mRNA, distribution and cleavage were demonstrated by quantitative polymerase chain reaction (QPCR), immunohistochemistry and Western blot, respectively. Cysteinyl aspartate-specific protease (caspase)-3-positive cells and activity were also measured. Burn injury could induce pathological alterations in the brain including leukocyte infiltration, necrosis, microabscess and gliosis. Compared with sham-injured mice, gelsolin mRNA was up-regulated at 8h post-burn (pb) in a transient manner in the cortex and striatum of burned mice, while it remained at higher levels in the hippocampus up to 72 hpb. Of interest, gelsolin was further cleaved into 42 and 48 kDa (kilo Dalton) fragments as illustrated in the hippocampus at 24 hpb, and was widely expressed in the brain by activated monocyte/macrophages, astrocytes and damaged neurons. In the meantime, caspase-3-positive cells were noted in the striatum of burned mice and its activity peaked at 24 hpb. To clarify inflammation-induced gelsolin expression and cleavage in the brain, rat pheochromocytoma cells were exposed to lipopolysaccharide to show increased gelsolin expression and caspase-3-dependent cleavage. The results suggest that burn-induced cerebral gelsolin expression would be involved in the activation of both the monocytes and astroglial cells, thereby playing a crucial role in the subsequent inflammation-induced neural apoptosis following burn injury.

Exofocal dopaminergic degeneration as antidepressant target in mouse model of poststroke depression

BACKGROUND

Although poststroke depression (PSD) is a frequent chronic complication of stroke with high relevance for outcome and survival, underlying pathomechanisms remain inadequately understood. This may be because suitable animal models are largely lacking and existing models are poorly characterized.

METHODS

Male 129/SV mice were subjected to 30-min middle cerebral artery occlusion (MCAo)/reperfusion and serial magnetic resonance imaging scans. A subset of animals received selective serotonin reuptake inhibitor citalopram starting 7 days after MCAo. Behavioral assessment was performed at 14 weeks. To identify biological correlates of PSD, we quantified corticosterone levels in serum and brain-derived neurotrophic factor levels in brain. The integrity of the mesolimbic dopaminergic system was assessed using tyrosine hydroxylase and dynorphin in situ hybridizations as well as dopamine transporter autoradiography.

RESULTS

Left, but not right, MCAo, elicited anhedonia and increased anxiety and despair. This depression-like syndrome was associated with alterations in the mesolimbic reward system. MCAo resulted in delayed degeneration of dopaminergic neurons in ipsilateral midbrain, which was accompanied by reduced dopamine concentrations and decreased levels of dopamine transporter density along with increased brain-derived neurotrophic factor protein levels in ischemic striatum and increased dynorphin messenger RNA expression in nucleus accumbens. Chronic antidepressant treatment initiated as late as 7 days after stroke reversed the behavioral phenotype, prevented degeneration of dopaminergic midbrain neurons, and attenuated striatal atrophy at 4 months.

CONCLUSIONS

Our results highlight the importance of the dopaminergic system for the development of PSD. Prevention of secondary neurodegeneration by antidepressants may provide a novel target for subacute stroke therapy.

Leucine-rich repeat kinase 2 modulates retinoic acid-induced neuronal differentiation of murine embryonic stem cells

Background

Dominant mutations in the leucine-rich repeat kinase 2 (LRRK2) gene are the most prevalent cause of Parkinson's disease, however, little is known about the biological function of LRRK2 protein. LRRK2 is expressed in neural precursor cells suggesting a role in neurodevelopment.

Methodology/Principal Findings

In the present study, differential gene expression profiling revealed a faster silencing of pluripotency-associated genes, like Nanog, Oct4, and Lin28, during retinoic acid-induced neuronal differentiation of LRRK2-deficient mouse embryonic stem cells compared to wildtype cultures. By contrast, expression of neurotransmitter receptors and neurotransmitter release was increased in LRRK2+/− cultures indicating that LRRK2 promotes neuronal differentiation. Consistently, the number of neural progenitor cells was higher in the hippocampal dentate gyrus of adult LRRK2-deficient mice. Alterations in phosphorylation of the putative LRRK2 substrates, translation initiation factor 4E binding protein 1 and moesin, do not appear to be involved in altered differentiation, rather there is indirect evidence that a regulatory signaling network comprising retinoic acid receptors, let-7 miRNA and downstream target genes/mRNAs may be affected in LRRK2-deficient stem cells in culture.

Conclusion/Significance

Parkinson's disease-linked LRRK2 mutations that associated with enhanced kinase activity may affect retinoic acid receptor signaling during neurodevelopment and/or neuronal maintenance as has been shown in other mouse models of chronic neurodegenerative diseases.

Electric field-guided neuron migration: a novel approach in neurogenesis

Effective directional neuron migration is crucial in development of the central nervous system and for neurogenesis. Endogenous electrical signals are present in many developing systems and crucial cellular behaviors such as neuronal cell division, cell migration, and cell differentiation are all under the influence of such endogenous electrical cues. Preclinical in vivo studies have used electric fields (EFs) to attempt to enhance regrowth of damaged spinal cord axons with some success. Recent evidence shows that small EFs not only guide axonal growth, but also direct the earlier events of neuronal migration and neuronal cell division. This raises the possibility that applied or endogenous EFs, perhaps in combination, may direct transplanted neural stem cells, or regenerating neurons, to the desired site after brain injury or neuron degeneration. The high complexity of both structure and function of the nervous system, however, poses significant challenges to techniques for applying EFs to promote neurogenesis. The evolution of functional biomaterials and nanotechnology may provide promising solutions for the application of EFs in guiding neuron migration and neurogenesis within the central nervous system.