The role of neural cell adhesion molecules in plasticity and repair

Genome-wide selection signatures address trait specific candidate genes in cattle indigenous to arid regions of India

The peculiarity of Indian cattle lies in milk quality, resistance to diseases and stressors as well as adaptability. The investigation addressed selection signatures in Gir and Tharparkar cattle, belonging to arid ecotypes of India. Double digest restriction-site associated DNA sequencing (ddRAD-seq) yielded nearly 26 million high-quality reads from unrelated seven Gir and seven Tharparkar cows. In all, 19,127 high-quality SNPs were processed for selection signature analysis. An approach involving within-population composite likelihood ratio (CLR) statistics and between-population FST statistics was used to capture selection signatures within and between the breeds, respectively. A total of 191 selection signatures were addressed using CLR and FST approaches. Selection signatures overlapping 86 and 73 genes were detected as Gir- and Tharparkar-specific, respectively. Notably, genes related to production (CACNA1D, GHRHR), reproduction (ESR1, RBMS3), immunity (NOSTRIN, IL12B) and adaptation (ADAM22, ASL) were annotated to selection signatures. Gene pathway analysis revealed genes in insulin/IGF pathway for milk production, gonadotropin releasing hormone pathway for reproduction, Wnt signalling pathway and chemokine and cytokine signalling pathway for adaptation. This is the first study where selection signatures are identified using ddRAD-seq in indicine cattle breeds. The study shall help in conservation and leveraging genetic improvements in Gir and Tharparkar cattle.

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

Identification of potential biomarkers for neuromyelitis optica by quantitative proteomics

OBJECTIVE

Neuromyelitis optica (NMO) was a serious autoimmune inflammatory condition affecting the central nervous system. Currently, there was a lack of diagnostic biomarkers for AQP4-IgG-negative NMO patients.

METHODS

A comparative proteomic analysis was conducted on the CSF of 10 patients with NMO and 10 patients with non-inflammatory neurological disorders (NND) using tandem mass tagging technology. Differentially expressed proteins (DEPs) were analyzed using bioinformatic methods. The candidate proteins were then validated through ELISAs in a subsequent cohort of 160 samples, consisting of paired CSF and plasma samples from 50 NMO patients, CSF samples from 30 NND patients, and plasma samples from 30 healthy individuals.

RESULTS

We identified 389 proteins via proteomics, screening 79 DEPs. NCAM1, SST and AHSG were selected as candidate molecules for further validation. Compared to NND patients, there were decreased levels of AHSG in CSF and increased levels of NCAM1 and SST in NMO patients. The ELISA results revealed significantly higher levels of AHSG, SST and NCAM1 in the CSF of the NMO group compared to the NND group. Similarly, the serum levels of these three proteins were also higher in the NMO group compared to the healthy control group. It was found that serum NCAM1 levels significantly decreased in patients with non-relapsed NMO compared to patients with relapsed NMO and CSF NCAM1 level increased in patients with bilateral NMO compared to patients with unilateral NMO. Furthermore, CSF SST levels increased in AQP4 antibody-positive NMO patients compared to AQP4 antibody-negative patients.

INTERPRETATION

CSF NCAM1, serum NCAM1 and serum SST may serve as potential biomarkers for NMO patients and aid in the diagnosis of AQP4 antibody-negative NMO patients.

Revealing cell-cell communication pathways with their spatially coupled gene programs

Inference of cell-cell communication (CCC) provides valuable information in understanding the mechanisms of many important life processes. With the rise of spatial transcriptomics in recent years, many methods have emerged to predict CCCs using spatial information of cells. However, most existing methods only describe CCCs based on ligand-receptor interactions, but lack the exploration of their upstream/downstream pathways. In this paper, we proposed a new method to infer CCCs, called Intercellular Gene Association Network (IGAN). Specifically, it is for the first time that we can estimate the gene associations/network between two specific single spatially adjacent cells. By using the IGAN method, we can not only infer CCCs in an accurate manner, but also explore the upstream/downstream pathways of ligands/receptors from the network perspective, which are actually exhibited as a new panoramic cell-interaction-pathway graph, and thus provide extensive information for the regulatory mechanisms behind CCCs. In addition, IGAN can measure the CCC activity at single cell/spot resolution, and help to discover the CCC spatial heterogeneity. Interestingly, we found that CCC patterns from IGAN are highly consistent with the spatial microenvironment patterns for each cell type, which further indicated the accuracy of our method. Analyses on several public datasets validated the advantages of IGAN.

The Effect of Deep and Slow Breathing on Retention and Cognitive Function in the Elderly Population

The purpose of this study was to apply deep and slow breathing to the elderly, who can be classified as potential dementia patients, to confirm changes in the cognitive functions of learning and memory. Forty-five elderly subjects were randomly and evenly divided into a rest group (RG), a before group (BG), and an after group (AG). Measurements of their cognitive abilities were obtained before testing (PT), 30 min after learning (STT), and 24 h after learning (LTT). After PT measurements were obtained from all three groups, the RG and AG conducted new cognitive skills learning, while the BG performed deep and slow breathing (DSB) for 30 min before learning new cognitive skills. After all the three groups underwent 30 min of learning, the STT was performed. Subsequently, the AG performed DSB for 30 min. Finally, 24 h after learning, the LTT was conducted for all three groups. Changes were compared and analyzed by measuring the retention of new cognitive skills and attention, working memory, and spatial perception of cognitive functions. A two-way repeated measure analysis of variance measured the effect of the application of DSB in the three groups. These results demonstrated a significant interaction of time and time*group in all measurements of retention and attention, working memory, and spatial perception. This study confirms the benefit of DSB as part of a dementia prevention training protocol.

Single-Cell Quantification of the Mechanical Stability of Cell-Cell Adherens Junction Using Glass Micropipettes

Micropipette-based methods have been widely used for the manipulation of cells and characterization of the mechanical properties at the cell or tissue level. Here, we introduce the glass micropipette-based mechanical assays for the stability of cell-cell adhesion. A probing microbead coated with specific adhesion ligands, captured by a glass micropipette, is manipulated to form the adhesion complexes with the corresponding receptors on a single cell. Once the cell is moving away from the micropipette, forces are generated from 20 pN to 100 nN to the adhesion complexes, which are quantified in real-time based on the bending of the glass micropipette. We specifically emphasize the principle and method to probe the rupturing forces of the adhesion complexes at controlled force loading rates, the ligand coating on the probe microbeads, the force calibration of the glass micropipette, and the applications of the method to probe the E-cadherin-based cell-cell adhesions. The principles can be broadly applied to other cell adhesions such as cell-matrix adhesions, neuronal synapses, and bacterial-cell adhesions.

Cerebrospinal fluid YKL-40 level evolution is associated with autoimmune encephalitis remission

Objective

Because of its heterogeneity in clinical presentation and course, predicting autoimmune encephalitis (AIE) evolution remains challenging. Hence, our aim was to explore the correlation of several biomarkers with the clinical course of disease.

Methods

Thirty-seven cases of AIE were selected retrospectively and divided into active (N = 9), improved (N = 12) and remission (N = 16) AIE according to their disease evolution. Nine proteins were tested in both serum and cerebrospinal fluid (CSF) at diagnosis (T0) and during the follow-up (T1), in particular activated MMP-9 (MMP-9A) and YKL-40 (or chitinase 3-like 1).

Results

From diagnosis to revaluation, AIE remission was associated with decreased YKL-40 and MMP-9A levels in the CSF, and with decreased NfL and NfH levels in the serum. The changes in YKL-40 concentrations in the CSF were associated with (1) still active AIE when increasing >10% (P-value = 0.0093); (2) partial improvement or remission when the changes were between +9% and -20% (P-value = 0.0173); and remission with a reduction > -20% (P-value = 0.0072; overall difference between the three groups: P-value = 0.0088). At T1, the CSF YKL-40 levels were significantly decreased between active and improved as well as improved and remission AIE groups but with no calculable threshold because of patient heterogeneity.

Conclusion

The concentration of YKL-40, a cytokine-like proinflammatory protein produced by glial cells, is correlated in the CSF with the clinical course of AIE. Its introduction as a biomarker may assist in following disease activity and in evaluating therapeutic response.

Acquisition-dependent modulation of hippocampal neural cell adhesion molecules by associative motor learning

It is widely accepted that some types of learning involve structural and functional changes of hippocampal synapses. Cell adhesion molecules neural cell adhesion molecule (NCAM), its polysialylated form polysialic acid to NCAM (PSA-NCAM), and L1 are prominent modulators of those changes. On the other hand, trace eyeblink conditioning, an associative motor learning task, requires the active participation of hippocampal circuits. However, the involvement of NCAM, PSA-NCAM, and L1 in this type of learning is not fully known. Here, we aimed to investigate the possible time sequence modifications of such neural cell adhesion molecules in the hippocampus during the acquisition of a trace eyeblink conditioning. To do so, the hippocampal expression of NCAM, PSA-NCAM, and L1 was assessed at three different time points during conditioning: after one (initial acquisition), three (partial acquisition), and six (complete acquisition) sessions of the conditioning paradigm. The conditioned stimulus (CS) was a weak electrical pulse separated by a 250-ms time interval from the unconditioned stimuli (US, a strong electrical pulse). An acquisition-dependent regulation of these adhesion molecules was found in the hippocampus. During the initial acquisition of the conditioning eyeblink paradigm (12 h after 1 and 3 days of training), synaptic expression of L1 and PSA-NCAM was transiently increased in the contralateral hippocampus to the paired CS-US presentations, whereas, when the associative learning was completed, such increase disappeared, but a marked and bilateral upregulation of NCAM was found. In conclusion, our findings show a specific temporal pattern of hippocampal CAMs expression during the acquisition process, highlighting the relevance of NCAM, PSA-NCAM, and L1 as learning-modulated molecules critically involved in remodeling processes underlying associative motor-memories formation.

The use of viral vectors to promote repair after spinal cord injury

Spinal cord injury (SCI) is a devastating event that can permanently disrupt multiple modalities. Unfortunately, the combination of the inhibitory environment at a central nervous system (CNS) injury site and the diminished intrinsic capacity of adult axons for growth results in the failure for robust axonal regeneration, limiting the ability for repair. Delivering genetic material that can either positively or negatively modulate gene expression has the potential to counter the obstacles that hinder axon growth within the spinal cord after injury. A popular gene therapy method is to deliver the genetic material using viral vectors. There are considerations when deciding on a viral vector approach for a particular application, including the type of vector, as well as serotypes, and promoters. In this review, we will discuss some of the aspects to consider when utilizing a viral vector approach to as a therapy for SCI. Additionally, we will discuss some recent applications of gene therapy to target extrinsic and/or intrinsic barriers to promote axon regeneration after SCI in preclinical models. While still in early stages, this approach has potential to treat those living with SCI.

Potential biomarkers identified by tandem mass tags based quantitative proteomics for diagnosis and classification of Guillain-Barré syndrome

BACKGROUND AND PURPOSE

Guillain-Barré syndrome (GBS) is an acute inflammatory autoimmune and demyelinating disease of the peripheral nervous system. Currently, valid biomarkers are unavailable for the diagnosis of GBS.

METHODS

A comparative proteomics analysis was performed on the cerebrospinal fluid (CSF) from 10 patients with GBS and 10 patients with noninflammatory neurological disease (NND) using the tandem mass tags technique. The differentially expressed proteins were analyzed by bioinformatics, and then the candidate proteins were validated by the enzyme-linked immunosorbent assay method in another cohort containing 160 samples (paired CSF and plasma of 40 patients with GBS, CSF of 40 NND patients and plasma of 40 healthy individuals).

RESULTS

In all, 298 proteins were successfully identified in the CSF samples, of which 97 differentially expressed proteins were identified in the GBS and NND groups. Three key molecules were identified as candidate molecules for further validation. The CSF levels of TGOLN2 and NCAM1 decreased in GBS patients compared with NND patients, whereas the CSF levels of APOC3 increased. The enzyme-linked immunosorbent assay results were consistent with our proteomics analysis. Interestingly, in the validation cohort, serum APOC3 levels in the GBS group were consistent with those in the CSF samples and significantly higher than those in the healthy control group.

CONCLUSIONS

Our preliminary data suggest that the CSF protein expression profile of patients with GBS is different from that of patients with NND. Moreover, alterations of TGOLN2, NCAM1and APOC3 may be used as novel biomarkers for identifying patients with GBS.

Evolutionary conserved role of neural cell adhesion molecule-1 in memory

The neural cell adhesion molecule 1 (NCAM-1) has been implicated in several brain-related biological processes, including neuronal migration, axonal branching, fasciculation, and synaptogenesis, with a pivotal role in synaptic plasticity. Here, we investigated the evolutionary conserved role of NCAM-1 in learning and memory. First, we investigated sustained changes in ncam-1 expression following aversive olfactory conditioning in C. elegans using molecular genetic methods. Furthermore, we examined the link between epigenetic signatures of the NCAM1 gene and memory in two human samples of healthy individuals (N = 568 and N = 319) and in two samples of traumatized individuals (N = 350 and N = 463). We found that olfactory conditioning in C. elegans induced ncam-1 expression and that loss of ncam-1 function selectively impaired associative long-term memory, without causing acquisition, sensory, or short-term memory deficits. Reintroduction of the C. elegans or human NCAM1 fully rescued memory impairment, suggesting a conserved role of NCAM1 for memory. In parallel, DNA methylation of the NCAM1 promoter in two independent healthy Swiss cohorts was associated with memory performance. In two independent Sub-Saharan populations of conflict zone survivors who had faced severe trauma, DNA methylation at an alternative promoter of the NCAM1 gene was associated with traumatic memories. Our results support a role of NCAM1 in associative memory in nematodes and humans, and might, ultimately, be helpful in elucidating diagnostic markers or suggest novel therapy targets for memory-related disorders, like PTSD.

Assessing genetic architecture and signatures of selection of dual purpose Gir cattle populations using genomic information

Gir is one of the main cattle breeds raised in tropical South American countries. Strong artificial selection through its domestication resulted in increased genetic differentiation among the countries in recent years. Over the years, genomic studies in Gir have become more common. However, studies of population structure and signatures of selection in divergent Gir populations are scarce and need more attention to better understand genetic differentiation, gene flow, and genetic distance. Genotypes of 173 animals selected for growth traits and 273 animals selected for milk production were used in this study. Clear genetic differentiation between beef and dairy populations was observed. Different criteria led to genetic divergence and genetic differences in allele frequencies between the two populations. Gene segregation in each population was forced by artificial selection, promoting isolation, and increasing genetic variation between them. Results showed evidence of selective forces in different regions of the genome. A total of 282 genes were detected under selection in the test population based on the fixation index (Fst), integrated haplotype score (iHS), and cross-population extend haplotype homozygosity (XP-EHH) approaches. The QTL mapping identified 35 genes associated with reproduction, milk composition, growth, meat and carcass, health, or body conformation traits. The investigation of genes and pathways showed that quantitative traits associated to fertility, milk production, beef quality, and growth were involved in the process of differentiation of these populations. These results would support further investigations of population structure and differentiation in the Gir breed.

Cell adhesion and matricellular support by astrocytes of the tripartite synapse

Astrocytes contribute to the formation, function, and plasticity of synapses. Their processes enwrap the neuronal components of the tripartite synapse, and due to this close interaction they are perfectly positioned to modulate neuronal communication. The interaction between astrocytes and synapses is facilitated by cell adhesion molecules and matricellular proteins, which have been implicated in the formation and functioning of tripartite synapses. The importance of such neuron-astrocyte integration at the synapse is underscored by the emerging role of astrocyte dysfunction in synaptic pathologies such as autism and schizophrenia. Here we review astrocyte-expressed cell adhesion molecules and matricellular molecules that play a role in integration of neurons and astrocytes within the tripartite synapse.

Disturbances of systemic and hippocampal insulin sensitivity in macrophage migration inhibitory factor (MIF) knockout male mice lead to behavioral changes associated with decreased PSA-NCAM levels

Macrophage migration inhibitory factor (MIF) is a multifunctional cytokine well known for its role in inflammation enhancement. However, a growing body of evidence is emerging on its role in energy metabolism in insulin sensitive tissues such as hippocampus, a brain region implicated in cognition, learning and memory. We hypothesized that genetic deletion of MIF may result in the specific behavioral changes, which may be linked tо impairments in brain or systemic insulin sensitivity by possible changes of the hippocampal synaptic plasticity. To assess memory, exploratory behavior and anxiety, three behavioral tests were applied on Mif gene-deficient (MIF^-/-) and "wild type" C57BL/6J mice (WT). The parameters of systemic and hippocampal insulin sensitivity were also determined. The impact of MIF deficiency on hippocampal plasticity was evaluated by analyzing the level of synaptosomal polysialylated-neural cell adhesion molecule (PSA-NCAM) plasticity marker and mRNA levels of different neurotrophic factors. The results showed that MIF^-/- mice exhibit emphasized anxiety-like behaviors, as well as impaired recognition memory, which may be hippocampus-dependent. This behavioral phenotype was associated with impaired systemic insulin sensitivity and attenuated hippocampal insulin sensitivity, characterized by increased inhibitory Ser³⁰⁷ phosphorylation of insulin receptor substrate 1 (IRS1). Finally, MIF^-/- mice displayed a decreased hippocampal PSA-NCAM level and unchanged Bdnf, NT-3, NT-4 and Igf-1 mRNA levels. The results suggest that the lack of MIF leads to disturbances of systemic and hippocampal insulin sensitivity, which are possibly responsible for memory deficits and anxiety, most likely through decreased PSA-NCAM-mediated neuroplasticity rather than through neurotrophic factors.

PSA-NCAM expression in the teleost optic tectum is related to ecological niche and use of vision in finding food

In this study, tangential migration and neuronal connectivity organization were analysed in the optic tectum of seven different teleosts through the expression of polysialylated neural cell adhesion molecule (PSA-NCAM) in response to ecological niche and use of vision. Reduced PSA-NCAM expression in rainbow trout Oncorhynchus mykiss optic tectum occurred in efferent layers, while in pike Esox lucius and zebrafish Danio rerio it occurred in afferent and efferent layers. Zander Sander lucioperca and European eel Anguilla anguilla had very low PSA-NCAM expression in all tectal layers except in the stratum marginale. Common carp Cyprinus carpio and wels catfish Silurus glanis had the same intensity of PSA-NCAM expression in all tectal layers. The optic tectum of all studied fishes was also a site of tangential migration with sustained PSA-NCAM and c-series ganglioside expression. Anti-c-series ganglioside immunoreactivity was observed in all tectal layers of all analysed fishes, even in layers where PSA-NCAM expression was reduced. Since the optic tectum is indispensable for visually guided prey capture, stabilization of synaptic contact and decrease of neurogenesis and tangential migration in the visual map are an expected adjustment to ecological niche. The authors hypothesize that this stabilization would probably be achieved by down-regulation of PSA-NCAM rather than c-series of ganglioside.

Deep Breathing Practice Facilitates Retention of Newly Learned Motor Skills

Paced deep breathing practices, a core component of a number of meditation programs, have been shown to enhance a variety of cognitive functions. However, their effects on complex processes such as memory, and in particular, formation and retention of motor memories, remain unknown. Here we show that a 30-minute session of deep, alternate-nostril breathing remarkably enhances retention of a newly learned motor skill. Healthy humans learned to accurately trace a given path within a fixed time duration. Following learning, one group of subjects (n = 16) underwent the 30-minute breathing practice while another control group (n = 14) rested for the same duration. The breathing-practice group retained the motor skill strikingly better than controls, both immediately after the breathing session and also at 24 hours. These effects were confirmed in another group (n = 10) that rested for 30 minutes post-learning, but practiced breathing after their first retention test; these subjects showed significantly better retention at 24 hours but not 30 minutes. Our results thus uncover for the first time the remarkable facilitatory effects of simple breathing practices on complex functions such as motor memory, and have important implications for sports training and neuromotor rehabilitation in which better retention of learned motor skills is highly desirable.

Cross-Phenotype Polygenic Risk Score Analysis of Persistent Post-Concussive Symptoms in U.S. Army Soldiers with Deployment-Acquired Traumatic Brain Injury

Traumatic brain injury (TBI) contributes to the increased rates of suicide and post-traumatic stress disorder in military personnel and veterans, and it is also associated with the risk for neurodegenerative and psychiatric disorders. A cross-phenotype high-resolution polygenic risk score (PRS) analysis of persistent post-concussive symptoms (PCS) was conducted in 845 U.S. Army soldiers who sustained TBI during their deployment. We used a prospective longitudinal survey of three brigade combat teams to assess deployment-acquired TBI and persistent physical, cognitive, and emotional PCS. PRS was derived from summary statistics of large genome-wide association studies of Alzheimer's disease, Parkinson's disease, schizophrenia, bipolar disorder, and major depressive disorder (MDD); and for years of schooling, college completion, childhood intelligence, infant head circumference (IHC), and adult intracranial volume. Although our study had more than 95% of statistical power to detect moderate-to-large effect sizes, no association was observed with neurodegenerative and psychiatric disorders, suggesting that persistent PCS does not share genetic components with these traits to a moderate-to-large degree. We observed a significant finding: subjects with high IHC PRS recovered better from cognitive/emotional persistent PCS than the other individuals (R² = 1.11%; p = 3.37 × 10^-3). Enrichment analysis identified two significant Gene Ontology (GO) terms related to this result: GO:0050839∼Cell adhesion molecule binding (p = 8.9 × 10^-6) and GO:0050905∼Neuromuscular process (p = 9.8 × 10^-5). In summary, our study indicated that the genetic predisposition to persistent PCS after TBI does not have substantial overlap with neurodegenerative and psychiatric diseases, but mechanisms related to early brain growth may be involved.

Impact of neural cell adhesion molecule deletion on regeneration after mouse spinal cord injury

The neural cell adhesion molecule (NCAM) plays important functional roles in development of the nervous system. We investigated the influence of a constitutive ablation of NCAM on the outcome of spinal cord injury. Transgenic mice lacking NCAM (NCAM-/-) were subjected to severe compression injury of the lower thoracic spinal cord using wild-type (NCAM+/+) littermates as controls. According to the single-frame motion analysis, the NCAM-/- mice showed reduced locomotor recovery in comparison to control mice at 3 and 6 weeks after injury, indicating an overall positive impact of NCAM on recovery after injury. Also the Basso Mouse Scale score was lower in NCAM-/- mice at 3 weeks after injury, whereas at 6 weeks after injury the difference between genotypes was not statistically significant. Worse locomotor function was associated with decreased monoaminergic and cholinergic innervation of the spinal cord caudal to the injury site and decreased axonal regrowth/sprouting at the site of injury. Astrocytic scar formation at the injury site, as assessed by immunohistology for glial fibrillary acidic protein at and around the lesion site was increased in NCAM-/- compared with NCAM+/+ mice. Migration of cultured monolayer astrocytes from NCAM-/- mice was reduced as assayed by scratch wounding. Numbers of Iba-1 immunopositive microglia were not different between genotypes. We conclude that constitutive NCAM deletion in young adult mice reduces recovery after spinal cord injury, validating the hypothesized beneficial role of this molecule in recovery after injury.

The effects of morphine treatment on the NCAM and its signaling in the MLDS of rats

Prolonged exposure to opiates induces a constellation of neuroadaptations, especially in the mesolimbic dopamine system (MLDS), which leads to alteration in the function of motivational circuitry. The neural cell adhesion molecule (NCAM) mediates cell-cell interactions and plays an important role in processes associated with neural plasticity. Moreover, it has been shown that NCAM were related to risk of alcoholism in human populations. Here, coimmunoprecipitation and western blotting were used to investigate whether morphine treatment induced alteration of the expression of NCAM or its signaling level in MLDS. The rats receiving escalating dose of morphine treatment were divided into three groups: morphine 1d, 3d and 5d group, which were injected subcutaneously with morphine hydrochloride for 1 day, 3 days and 5 days, respectively. Twelve hours after the last injection, animals were sacrificed and the tissues of ventral tegmental area (VTA), prefrontal cortex (PFC) and nucleus accumbens (NAc) were punched out to examine the expression of NCAM or its signaling level. The results showed that morphine treatment had no significant effect on the expression of NCAM, but downregulated the phosphorylation of NCAM-associated focal adhesion kinase (FAK) in the VTA and PFC of rats. In the NAc of rats, however, the expression of NCAM and its signaling were not altered significantly by morphine treatment. These results indicated that the downregulation of NCAM signaling in the VTA and PFC might be involved in the formation of morphine addiction.

Role of F3/contactin expression profile in synaptic plasticity and memory in aged mice

We have recently shown that overexpression of the F3/contactin adhesive glycoprotein (also known as Contactin-1) promotes neurogenesis in adult hippocampus, which correlates with improved synaptic plasticity and memory. Because F3/contactin levels physiologically decrease with age, here, we aim at investigating whether its overexpression might counteract the cognitive decline in aged animals. For this we use 20- to 24-month-old TAG/F3 transgenic mice in which F3/contactin overexpression is driven by regulatory sequences from the gene encoding the transient axonal glycoprotein TAG-1 throughout development. We show that aged TAG/F3 mice display improved hippocampal long-term potentiation and memory compared with wild-type littermates. The same mice undergo a decrease of neuronal apoptosis at the hippocampal level, which correlated to a decrease of active caspase-3; by contrast, procaspase-3 and Bax as well as the anti-apoptotic and plasticity-related pathway BDNF/CREB/Bcl-2 were rather increased. Interestingly, amyloid-precursor protein processing was shifted toward sAPPα generation, with a decrease of sAPPβ and amyloid-beta levels. Our data confirm that F3/contactin plays a role in hippocampal synaptic plasticity and memory also in aged mice, suggesting that it acts on molecular pathways related to apoptosis and amyloid-beta production.

Identification of molecular pathways facilitating glioma cell invasion in situ

Gliomas are mostly incurable secondary to their diffuse infiltrative nature. Thus, specific therapeutic targeting of invasive glioma cells is an attractive concept. As cells exit the tumor mass and infiltrate brain parenchyma, they closely interact with a changing micro-environmental landscape that sustains tumor cell invasion.

In this study, we used a unique microarray profiling approach on a human glioma stem cell (GSC) xenograft model to explore gene expression changes in situ in Invading Glioma Cells (IGCs) compared to tumor core, as well as changes in host cells residing within the infiltrated microenvironment relative to the unaffected cortex. IGCs were found to have reduced expression of genes within the extracellular matrix compartment, and genes involved in cell adhesion, cell polarity and epithelial to mesenchymal transition (EMT) processes. The infiltrated microenvironment showed activation of wound repair and tissue remodeling networks. We confirmed by protein analysis the downregulation of EMT and polarity related genes such as CD44 and PARD3 in IGCs, and EFNB3, a tissue-remodeling agent enriched at the infiltrated microenvironment. OLIG2, a proliferation regulator and glioma progenitor cell marker upregulated in IGCs was found to function in enhancing migration and stemness of GSCs. Overall, our results unveiled a more comprehensive picture of the complex and dynamic cell autonomous and tumor-host interactive pathways of glioma invasion than has been previously demonstrated. This suggests targeting of multiple pathways at the junction of invading tumor and microenvironment as a viable option for glioma therapy.

Distinctive PSA-NCAM and NCAM hallmarks in glutamate-induced dendritic atrophy and synaptic disassembly

Dendritic and synapse remodeling are forms of structural plasticity that play a critical role in normal hippocampal function. Neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) participate in neurite outgrowth and synapse formation and plasticity. However, it remains unclear whether they contribute to dendritic retraction and synaptic disassembly. Cultured hippocampal neurons exposed to glutamate (5 µM) showed a reduced MAP-2 (+) area in the absence of neuronal death 24 h after the insult. Concomitantly, synapse loss, revealed by decreased synaptophysin and post-synaptic density-95 cluster number and area, together with changes in NCAM and PSA-NCAM levels were found. Dendritic atrophy and PSA-NCAM reduction proved NMDA-receptor dependent. Live-imaging experiments evidenced dendritic atrophy 4 h after the insult; this effect was preceded by smaller NCAM clusters (1 h) and decreased surface and total PSA-NCAM levels (3 h). Simultaneously, total NCAM cluster number and area remained unchanged. The subsequent synapse disassembly (6 h) was accompanied by reductions in total NCAM cluster number and area. A PSA mimetic peptide prevented both the dendritic atrophy and the subsequent synaptic changes (6 h) but had no effect on the earliest synaptic remodeling (3 h). Thus, NCAM-synaptic reorganization and PSA-NCAM level decrease precede glutamate-induced dendritic atrophy, whereas the NCAM level reduction is a delayed event related to synapse loss. Consequently, distinctive stages in PSA-NCAM/NCAM balance seem to accompany glutamate-induced dendritic atrophy and synapse loss.

NCAM140 and pCREB Expression after Tianeptine Treatment of SH-SY5Y Cells

OBJECTIVE

Antidepressants Modulate Neuronal Plasticity. Tianeptine, An Atypical Antidepressant, Might Be Involved In The Restoration Of Neuronal Plasticity; It Primarily Enhances The Synaptic Reuptake Of Serotonin. Ncam140 Is Involved In Neuronal Development Processes, Synaptogenesis And Synaptic Plasticity. We Investigated The Effect Of Tianeptine On The Expression Of Ncam140 And Its Downstream Signaling Molecule In The Human Neuroblastoma Cell Line Sh-sy5y.

METHODS

NCAM protein expression was measured in human neuroblastoma SH-SY5Y cells that were cultivated in serum-free media and treated with 0, 10, or 20 µM tianeptine for 6, 24, or 72 hours. NCAM140 expression in the tianeptine treatment group was confirmed by Western blot, and quantified through measurement of band intensity by absorbance. CREB and pCREB expression was identified after treatment with 20 µM tianeptine for 6, 24, and 72 hours by Western blot.

RESULTS

Compared to cells treated for 6 hours, cells treated with 0 or 10 µM tianeptine for 72 hours showed a significant increase in NCAM140 expression and cells treated with 20 µM tianeptine showed a significant increase after 24 and 72 hours. The pCREB level in cells treated with 20 µM tianeptine increased in time-dependent manner.

CONCLUSION

Our findings indicated that the tianeptine antidepressant effect may occur by induction of NCAM140 expression and CREB phosphorylation.

Specific protein markers for stem cell cross-talk with neighboring cells in the environment

A stem cell interacts with the neighboring cells in its environment. To maintain a living organism's metabolism, either cell-cell or cell-environment interactions may be significant. Usually, these cells communicate with each other through biological signaling by interactive behaviors of primary proteins or complementary chemicals. The signaling intermediates offer the stem cell's functionality on its metabolism. With the rapid advent of omics technologies, various specific markers by which stem cells cooperate with their surroundings have been discovered and established. In this article, we review several stem cell markers used to communicate with either cancer or immune cells in the human body.

A role for hippocampal PSA-NCAM and NMDA-NR2B receptor function in flavonoid-induced spatial memory improvements in young rats

The increase in incidence and prevalence of neurodegenerative diseases highlights the need for a more comprehensive understanding of how food components may affect neural systems. In particular, flavonoids have been recognized as promising agents capable of influencing different aspects of synaptic plasticity resulting in improvements in memory and learning in both animals and humans. Our previous studies highlight the efficacy of flavonoids in reversing memory impairments in aged rats, yet little is known about the effects of these compounds in healthy animals, particularly with respect to the molecular mechanisms by which flavonoids might alter the underlying synaptic modifications responsible for behavioral changes. We demonstrate that a 3-week intervention with two dietary doses of flavonoids (Dose I: 8.7 mg/day and Dose II: 17.4 mg/day) facilitates spatial memory acquisition and consolidation (24 recall) (p < 0.05) in young healthy rats. We show for the first time that these behavioral improvements are linked to increased levels in the polysialylated form of the neural adhesion molecule (PSA-NCAM) in the dentate gyrus (DG) of the hippocampus, which is known to be required for the establishment of durable memories. We observed parallel increases in hippocampal NMDA receptors containing the NR2B subunit for both 8.7 mg/day (p < 0.05) and 17.4 mg/day (p < 0.001) doses, suggesting an enhancement of glutamate signaling following flavonoid intervention. This is further strengthened by the simultaneous modulation of hippocampal ERK/CREB/BDNF signaling and the activation of the Akt/mTOR/Arc pathway, which are crucial in inducing changes in the strength of hippocampal synaptic connections that underlie learning. Collectively, the present data supports a new role for PSA-NCAM and NMDA-NR2B receptor on flavonoid-induced improvements in learning and memory, contributing further to the growing body of evidence suggesting beneficial effects of flavonoids in cognition and brain health.

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We have identified novel targets for the flavonoid actions in the brain.

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Flavonoid ingestion facilitates hippocampal-dependent learning in healthy animals.

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Flavonoids regulate hippocampal PSA-NCAM in the Dentate Gyrus of the hippocampus.

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Flavonoids modulate the levels of hippocampal glutamate receptors (NMDA-NR2B).

Effects of chronic stress in adolescence on learned fear, anxiety, and synaptic transmission in the rat prelimbic cortex

The prelimbic cortex and amygdala regulate the extinction of conditioned fear and anxiety, respectively. In adult rats, chronic stress affects the dendritic morphology of these brain areas, slowing extinction of learned fear and enhancing anxiety. The aim of this study was to determine whether rats subjected to chronic stress in adolescence show changes in learned fear, anxiety, and synaptic transmission in the prelimbic cortex during adulthood. Male Sprague Dawley rats were subjected to seven days of restraint stress on postnatal day forty-two (PND 42, adolescence). Afterward, the fear-conditioning paradigm was used to study conditioned fear extinction. Anxiety-like behavior was measured one day (PND 50) and twenty-one days (PND 70, adulthood) after stress using the elevated-plus maze and dark-light box tests, respectively. With another set of rats, excitatory synaptic transmission was analyzed with slices of the prelimbic cortex. Rats that had been stressed during adolescence and adulthood had higher anxiety-like behavior levels than did controls, while stress-induced slowing of learned fear extinction in adolescence was reversed during adulthood. As well, the field excitatory postsynaptic potentials of stressed adolescent rats had significantly lower amplitudes than those of controls, although the amplitudes were higher in adulthood. Our results demonstrate that short-term stress in adolescence induces strong effects on excitatory synaptic transmission in the prelimbic cortex and extinction of learned fear, where the effect of stress on anxiety is more persistent than on the extinction of learned fear. These data contribute to the understanding of stress neurobiology.

Neuronal adhesion and synapse organization in recovery after brain injury

Few specific therapeutic targets exist to manage brain injury, despite the prevalence of stroke or traumatic brain injury. With traumatic brain injury, characteristic neuronal changes include axonal swelling and degeneration, and the loss of synapses, the sites of communication between neurons. This is followed by axonal sprouting and alterations in synaptic markers in recovery. The resulting changes in neuronal connectivity are likely to contribute to the effects of traumatic brain injury on cognitive functions and the underlying mechanisms may represent points of therapeutic intervention. In agreement, animal studies implicate adhesion and signaling molecules that organize synapses as molecular players in neuronal recovery. In this article, the authors focus on the role of cell surface interactions in the recovery after brain injury in humans and animals. The authors review cellular and synaptic alterations that occur with injury and how changes in cell adhesion, protein expression and modification may be involved in recovery. The changes in neuronal surface interactions as potential targets and their possible value for the development of therapeutics are also discussed.

Effects of low-level organic selenium on lead-induced alterations in neural cell adhesion molecules

Low-level lead (Pb) exposure has been reported to impair the formation and consolidation of learning and memory by inhibiting the expression of neural cell adhesion molecules (NCAMs) and altering the temporal profile of its polysialylation state. In this study, we investigated whether administration of low-level organic selenium (selenomethionine, Se) at different time points could affect Pb-induced changes of NCAMs in female Wistar rats. Here we reported that the exposure of Se (60μg/kg body weight/day) at different time points significantly alleviated Pb-induced reductions in the mRNA and protein levels of NCAMs, and increases in the mRNA levels of two polysialyltransferases (St8sia II, Stx; St8sia IV, Pst) as well as the sialyltransferase activity (p<0.05). The concentrations of Pb in blood and hippocampi of Wistar rats treated with the combination of Se and Pb were significantly lower than those treated with Pb alone (p<0.05). Our results suggest that low-level organic Se can not only prevent but also reverse Pb-induced alterations in the expression and polysialylated state of NCAMs as well as the concentration of Pb in rat blood and hippocampus.

Long-term social isolation in the adulthood results in CA1 shrinkage and cognitive impairment

Social isolation in adulthood is a psychosocial stressor that can result in endocrinological and behavioral alterations in different species. In rodents, controversial results have been obtained in fear conditioning after social isolation at adulthood, while neural substrates underlying these differences are largely unknown. Neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) are prominent modulators of synaptic plasticity underlying memory processes in many tasks, including fear conditioning. In this study, we used adult female Octodon degus to investigate the effects of long-term social isolation on contextual and cued fear conditioning, and the possible modulation of the synaptic levels of NCAM and PSA-NCAM in the hippocampus. After 6½ months of social isolation, adult female degus showed a normal auditory-cued fear memory, but a deficit in contextual fear memory, a hippocampal dependent task. Subsequently, we observed reduced hippocampal synaptic levels of PSA-NCAM in isolated compared to grouped-housed female degus. No significant differences were found between experimental groups in hippocampal levels of the three main isoforms of NCAM (NCAM180, NCAM140 and NCAM120). Interestingly, social isolation reduced the volume of the hippocampal CA1 subfield, without affecting the volume of the CA3 subregion or the total hippocampus. Moreover, attenuated body weight gain and reduced number of granulocytes were detected in isolated animals. Our findings indicate for the first time, that long-term social isolation of adult female animals induces a specific shrinkage of CA1 and a decrease in synaptic levels of PSA-NCAM in the hippocampus. These effects may be related to the deficit in contextual fear memory observed in isolated female degus.

Long-term ω-3 fatty acid supplementation induces anti-stress effects and improves learning in rats

Chronic stress leads to secretion of the adrenal steroid hormone corticosterone, inducing hippocampal atrophy and dendritic hypertrophy in the rat amygdala. Both alterations have been correlated with memory impairment and increased anxiety. Supplementation with ω-3 fatty acids improves memory and learning in rats. The aim of this study was to evaluate the effects of ω-3 supplementation on learning and major biological and behavioral stress markers. Male Sprague-Dawley rats were randomly assigned to three experimental groups: 1) Control, 2) Vehicle, animals supplemented with water, and 3) ω-3, rats supplemented with ω-3 (100 mg of DHA+25 mg of EPA). Each experimental group was divided into two subgroups: one of which was not subjected to stress while the other was subjected to a restraint stress paradigm. Afterwards, learning was analyzed by avoidance conditioning. As well, plasma corticosterone levels and anxiety were evaluated as stress markers, respectively by ELISA and the plus-maze test. Restraint stress impaired learning and increased both corticosterone levels and the number of entries into the open-arm (elevated plus-maze). These alterations were prevented by ω-3 supplementation. Thus, our results demonstrate that ω-3 supplementation had two beneficial effects on the stressed rats, a strong anti-stress effect and improved learning.

Repeated restraint stress impairs auditory attention and GABAergic synaptic efficacy in the rat auditory cortex

Chronic stress induces dendritic atrophy in the rat primary auditory cortex (A1), a key brain area for auditory attention. The aim of this study was to determine whether repeated restraint stress affects auditory attention and synaptic transmission in A1. Male Sprague-Dawley rats were trained in a two-alternative choice task (2-ACT), a behavioral paradigm to study auditory attention in rats. Trained animals that reached a performance over 80% of correct trials in the 2-ACT were randomly assigned to control and restraint stress experimental groups. To analyze the effects of restraint stress on the auditory attention, trained rats of both groups were subjected to 50 2-ACT trials one day before and one day after of the stress period. A difference score was determined by subtracting the number of correct trials after from those before the stress protocol. Another set of rats was used to study the synaptic transmission in A1. Restraint stress decreased the number of correct trials by 28% compared to the performance of control animals (p < 0.001). Furthermore, stress reduced the frequency of spontaneous inhibitory postsynaptic currents (sIPSC) and miniature IPSC in A1, whereas glutamatergic efficacy was not affected. Our results demonstrate that restraint stress decreased auditory attention and GABAergic synaptic efficacy in A1.

Psychological stress and aging: role of glucocorticoids (GCs)

Psychological stress has extreme adverse consequences on health. However, the molecular mechanisms that mediate and accelerate the process of aging due to stress hormone are not well defined. This review has focused on diverse molecular paths that come out in response to chronic psychological stress via releasing of excessive glucocorticoids (GCs), involved in the aging process. GCs suppress transcription of nuclear cell adhesion molecules which impair synaptic plasticity, memory formation, and cognitive ability. Again, GCs promote muscle atrophy by means of motivating ubiquitin proteasome system and can repress muscle protein synthesis by inhibition of PI3-kinase/Akt pathway. GCs also inhibit interleukin-2 synthesis through suppressing T cell receptor signal that leads to loss of T cell activation, proliferation, and B-cell activation. Moreover, GCs increase the expression of collagenase-3, RANK ligand, and colony stimulating factor-1 that induce bone resorption. In general, stress-induced GCs can play causal role for aging and age-related disorders.

Brain-derived neurotrophic factor and the course of experimental cerebral malaria

The role of neurotrophic factors on the integrity of the central nervous system (CNS) during cerebral malaria (CM) infection remains obscure, but the long-standing neurocognitive sequelae often observed in rescued children can be attributed in part to the modulation of neuronal survival and synaptic plasticity. To discriminate the contribution of key responses in the time-sequence of the pathogenic events that trigger the development of neurocognitive malaria syndrome we defined four stages (I-IV) of the neurological progression of CM in C57BL/6 mice infected with Plasmodium berghei ANKA. Upregulation of ICAM-1, VCAM-1, e-selectin and p-selectin expression was detected in all cerebral regions before parasitized red blood cells (pRBC) accumulation. As the severity of symptoms increased, BDNF mRNA progressively diminished in several brain regions, earliest in the thalamus-hypothalamus, cerebellum, brainstem and cortex, and correlated with a four-stage disease sequence. Immunohistochemical confocal microscopy revealed changes in the BDNF distribution pattern, suggesting altered axonal transport. During CM progression, molecular markers of neurological infection and inflammation in the parasite and the host, respectively, were accompanied by a switch in the brain constitutive proteasome to the immunoproteasome, which could impede normal protein turnover. In parallel with BDNF downregulation, NCAM expression also diminished with increased CM severity. Together, these data suggest that changes in BDNF availability could be involved in the pathogenesis of CM.

Corticosterone treatment impairs auditory fear learning and the dendritic morphology of the rat inferior colliculus

Stress leads to secretion of the adrenal steroid hormone corticosterone (CORT). The aim of this study was to determine the effects of chronic CORT administration on auditory and visual fear conditioning. Male Sprague-Dawley rats received CORT (400 mg/ml) in their drinking water for 10 consecutive days; this treatment induces stress levels of serum CORT. CORT impaired fear conditioning (F((1,28)) = 11.52, p < 0.01) and extinction (F((1,28)) = 4.86, p < 0.05) of auditory fear learning, but did not affect visual fear conditioning. In addition, we analyzed the CORT effects on the neuronal morphology of the inferior colliculus (flat neurons, auditory mesencephalon, a key brain area for auditory processing) and superior colliculus (wide-field neurons, related to visual processing) by Golgi stain. CORT decreased dendritic arborization of inferior colliculus neurons by approximately 50%, but did not affect superior colliculus neurons. Thus, CORT had more deleterious effects on the auditory fear processing than the visual system in the brain.

Flavonoids as modulators of memory and learning: molecular interactions resulting in behavioural effects

There is considerable interest in the potential of a group of dietary-derived phytochemicals known as flavonoids in modulating neuronal function and thereby influencing memory, learning and cognitive function. The present review begins by detailing the molecular events that underlie the acquisition and consolidation of new memories in the brain in order to provide a critical background to understanding the impact of flavonoid-rich diets or pure flavonoids on memory. Data suggests that despite limited brain bioavailability, dietary supplementation with flavonoid-rich foods, such as blueberry, green tea and Ginkgo biloba lead to significant reversals of age-related deficits on spatial memory and learning. Furthermore, animal and cellular studies suggest that the mechanisms underpinning their ability to induce improvements in memory are linked to the potential of absorbed flavonoids and their metabolites to interact with and modulate critical signalling pathways, transcription factors and gene and/or protein expression which control memory and learning processes in the hippocampus; the brain structure where spatial learning occurs. Overall, current evidence suggests that human translation of these animal investigations are warranted, as are further studies, to better understand the precise cause-and-effect relationship between flavonoid intake and cognitive outputs.

Bidirectional remodeling of β1-integrin adhesions during chemotropic regulation of nerve growth

Background

Chemotropic factors in the extracellular microenvironment guide nerve growth by acting on the growth cone located at the tip of extending axons. Growth cone extension requires the coordination of cytoskeleton-dependent membrane protrusion and dynamic adhesion to the extracellular matrix, yet how chemotropic factors regulate these events remains an outstanding question. We demonstrated previously that the inhibitory factor myelin-associated glycoprotein (MAG) triggers endocytic removal of the adhesion receptor β1-integrin from the growth cone surface membrane to negatively remodel substrate adhesions during chemorepulsion. Here, we tested how a neurotrophin might affect integrin adhesions.

Results

We report that brain-derived neurotropic factor (BDNF) positively regulates the formation of substrate adhesions in axonal growth cones during stimulated outgrowth and prevents removal of β1-integrin adhesions by MAG. Treatment of Xenopus spinal neurons with BDNF rapidly triggered β1-integrin clustering and induced the dynamic formation of nascent vinculin-containing adhesion complexes in the growth cone periphery. Both the formation of nascent β1-integrin adhesions and the stimulation of axon extension by BDNF required cytoplasmic calcium ion signaling and integrin activation at the cell surface. Exposure to MAG decreased the number of β1-integrin adhesions in the growth cone during inhibition of axon extension. In contrast, the BDNF-induced adhesions were resistant to negative remodeling by MAG, correlating with the ability of BDNF pretreatment to counteract MAG-inhibition of axon extension. Pre-exposure to MAG prevented the BDNF-induced formation of β1-integrin adhesions and blocked the stimulation of axon extension by BDNF.

Conclusions

Altogether, these findings demonstrate the neurotrophin-dependent formation of integrin-based adhesions in the growth cone and reveal how a positive regulator of substrate adhesions can block the negative remodeling and growth inhibitory effects of MAG. Such bidirectional remodeling may allow the growth cone to rapidly adjust adhesiveness to the extracellular matrix as a general mechanism for governing axon extension. Techniques for manipulating integrin internalization and activation state may be important for overcoming local inhibitory factors after traumatic injury or neurodegenerative disease to enhance regenerative nerve growth.

Melatonin controls photoperiodic changes in tanycyte vimentin and neural cell adhesion molecule expression in the Djungarian hamster (Phodopus sungorus)

The Djungarian hamster displays photoperiodic variations in gonadal size synchronized to the seasons by the nightly secretion of the pineal hormone melatonin. In short photoperiod (SP), the gonads regress in size, and circulating sex steroids levels decline. Thus, the brain is subject to seasonal variations of both melatonin and sex steroids. Tanycytes are specialized glial cells located in the ependymal lining of the third ventricle. They send processes either to the meninges or to blood vessels of the medio-basal hypothalamus. Furthermore, they are known to locally modulate GnRH release in the median eminence and to display seasonal structural changes. Seasonal changes in tanycyte morphology might be mediated either through melatonin or sex steroids. Therefore, we analyzed the effects of photoperiod, melatonin, and sex steroids 1) on tanycyte vimentin expression by immunohistochemistry and 2) on the expression of the neural cell adhesion molecule (NCAM) and polysialic acid as markers of brain plasticity. Vimentin immunostaining was reduced in tanycyte cell bodies and processes in SP. Similarly, tanycytes and their processes contained lower amounts of NCAM in SP. These changes induced by SP exposure could not be restored to long photoperiod (LP) levels by testosterone supplementation. Likewise, castration in LP did not affect tanycyte vimentin or NCAM expression. By contrast, late afternoon melatonin injections mimicking a SP-like melatonin peak in LP hamsters reduced vimentin and NCAM expression. Thus, the seasonal changes in vimentin and NCAM expression in tanycytes are regulated by melatonin independently of seasonal sex steroid changes.

A peptide mimetic targeting trans-homophilic NCAM binding sites promotes spatial learning and neural plasticity in the hippocampus

The key roles played by the neural cell adhesion molecule (NCAM) in plasticity and cognition underscore this membrane protein as a relevant target to develop cognitive-enhancing drugs. However, NCAM is a structurally and functionally complex molecule with multiple domains engaged in a variety of actions, which raise the question as to which NCAM fragment should be targeted. Synthetic NCAM mimetic peptides that mimic NCAM sequences relevant to specific interactions allow identification of the most promising targets within NCAM. Recently, a decapeptide ligand of NCAM—plannexin, which mimics a homophilic trans-binding site in Ig2 and binds to Ig3—was developed as a tool for studying NCAM's trans-interactions. In this study, we investigated plannexin's ability to affect neural plasticity and memory formation. We found that plannexin facilitates neurite outgrowth in primary hippocampal neuronal cultures and improves spatial learning in rats, both under basal conditions and under conditions involving a deficit in a key plasticity-promoting posttranslational modification of NCAM, its polysialylation. We also found that plannexin enhances excitatory synaptic transmission in hippocampal area CA1, where it also increases the number of mushroom spines and the synaptic expression of the AMPAR subunits GluA1 and GluA2. Altogether, these findings provide compelling evidence that plannexin is an important facilitator of synaptic functional, structural and molecular plasticity in the hippocampal CA1 region, highlighting the fragment in NCAM's Ig3 module where plannexin binds as a novel target for the development of cognition-enhancing drugs.

Sacral nerve stimulation increases activation of the primary somatosensory cortex by anal canal stimulation in an experimental model

BACKGROUND

Sacral and posterior tibial nerve stimulation may be used to treat faecal incontinence; however, the mechanism of action is unknown. The aim of this study was to establish whether sensory activation of the cerebral cortex by anal canal stimulation was increased by peripheral neuromodulation.

METHODS

A multielectrode array was positioned over the right primary somatosensory cortex of anaesthetized rats. A brief burst of electrical stimulation was applied to either the left sacral root or the left posterior tibial nerve, and evoked potentials from anal canal stimulation were signal-averaged at intervals over 1 h. At the end of the experiment, the cerebral cortex was removed and probed for polysialylated neural cell adhesion molecule (PSA-NCAM).

RESULTS

Sacral nerve root and posterior tibial nerve stimulation significantly increased the peak amplitude of primary cortical evoked potentials by 54.0 and 45.1 per cent respectively. This change persisted throughout the period of observation. The density of PSA-NCAM-positive cells in the somatosensory cortex underlying the electrode array was increased by approximately 50 per cent in the sacral nerve-stimulated group.

CONCLUSION

Brief sacral neuromodulation induces profound changes in anal canal representation on the primary somatosensory cortex, providing a plausible hypothesis concerning the mechanism of action of neuromodulation in the treatment of faecal incontinence.

Sequences at the interface of the fifth immunoglobulin domain and first fibronectin type III repeat of the neural cell adhesion molecule are critical for its polysialylation

Polysialic acid is an anti-adhesive glycan that modifies a select group of mammalian proteins. The primary substrate of the polysialyltransferases (polySTs) is the neural cell adhesion molecule (NCAM). Polysialic acid negatively regulates cell adhesion, is required for proper brain development, and is expressed in specific areas of the adult brain where it promotes on-going cell migration and synaptic plasticity. The first fibronectin type III repeat (FN1) of NCAM is required for polysialylation of the N-glycans on the adjacent immunoglobulin-like domain (Ig5), and acidic residues on the surface of FN1 play a role in polyST recognition. Recent work demonstrated that the FN1 domain from the unpolysialylated olfactory cell adhesion molecule (OCAM) was able to partially replace NCAM FN1 (Foley, D. A., Swartzentruber, K. G., Thompson, M. G., Mendiratta, S. S., and Colley, K. J. (2010) J. Biol. Chem. 285, 35056-35067). Here we demonstrate that individually replacing three identical regions shared by NCAM and OCAM FN1, (500)PSSP(503) (PSSP), (526)GGVPI(530) (GGVPI), and (580)NGKG(583) (NGKG), dramatically reduces NCAM polysialylation. In addition, we show that the polyST, ST8SiaIV/PST, specifically binds NCAM and that this binding requires the FN1 domain. Replacing the FN1 PSSP sequences and the acidic patch residues decreases NCAM-polyST binding, whereas replacing the GGVPI and NGKG sequences has no effect. The location of GGVPI and NGKG in loops that flank the Ig5-FN1 linker and the proximity of PSSP to this linker suggest that GGVPI and NGKG sequences may be critical for stabilizing the Ig5-FN1 linker, whereas PSSP may play a dual role maintaining the Ig5-FN1 interface and a polyST recognition site.

Sequences from the first fibronectin type III repeat of the neural cell adhesion molecule allow O-glycan polysialylation of an adhesion molecule chimera

Polysialic acid is a developmentally regulated, anti-adhesive polymer that is added to N-glycans on the fifth immunoglobulin domain (Ig5) of the neural cell adhesion molecule (NCAM). We found that the first fibronectin type III repeat (FN1) of NCAM is required for the polysialylation of N-glycans on the adjacent Ig5 domain, and we proposed that the polysialyltransferases recognize specific sequences in FN1 to position themselves for Ig5 N-glycan polysialylation. Other studies identified a novel FN1 acidic surface patch and α-helix that play roles in NCAM polysialylation. Here, we characterize the contribution of two additional FN1 sequences, Pro(510)-Tyr(511)-Ser(512) (PYS) and Gln(516)-Val(517)-Gln(518) (QVQ). Replacing PYS or the acidic patch dramatically decreases the O-glycan polysialylation of a truncated NCAM protein, and replacing the α-helix or QVQ shifts polysialic acid to FN1 O-glycans in full-length NCAM. We also found that the FN1 domain of the olfactory cell adhesion molecule, a homologous but unpolysialylated protein, could partially replace NCAM FN1. Inserting Pro(510)-Tyr(511) eliminated N-glycan polysialylation and enhanced O-glycosylation of an NCAM- olfactory cell adhesion molecule chimera, and inserting other FN1 sequences unique to NCAM, predominantly the acidic patch, created a new polysialyltransferase recognition site. Taken together, our results highlight the role of the FN1 α-helix and QVQ sequences in N-glycan polysialylation and demonstrate that the acidic patch primarily functions in O-glycan polysialylation.

Brain-derived neurotrophic factor (BDNF) and polysialylated-neural cell adhesion molecule (PSA-NCAM): codistribution in the human brainstem precerebellar nuclei from prenatal to adult age

Occurrence and distribution of the neurotrophin brain-derived neurotrophic factor (BDNF) and polysialylated-neural cell adhesion molecule (PSA-NCAM), a neuroplasticity marker known to modulate BDNF signalling, were examined by immunohistochemistry in the human brainstem precerebellar nuclei at prenatal, perinatal and adult age. Western blot analysis performed in human brainstem showed for both molecules a single protein band compatible with the molecular weight of the dimeric form of mature BDNF and with that of PSA-NCAM. Detectability of both molecules up to 72h post-mortem was also assessed in rat brain. In neuronal perikarya, BDNF-like immunoreactivity (LI) appeared as intracytoplasmic granules, whereas PSA-NCAM-LI appeared mostly as peripheral staining, indicative of membrane labelling; immunoreactivity to both substances also labelled nerve fibres and terminals. BDNF- and PSA-NCAM-LI occurred in the external cuneate nucleus, perihypoglossal nuclei, inferior olive complex, arcuate nucleus, lateral reticular formation, vestibular nuclei, pontine reticulotegmental and paramedian reticular nuclei, and pontine basilar nuclei. With few exceptions, for both substances the distribution pattern detected at prenatal age persisted later on, though the immunoreactivity appeared often higher in pre- and full-term newborns than in adult specimens. The results obtained suggest that BDNF operates in the development, maturation, maintenance and plasticity of human brainstem precerebellar neuronal systems. They also imply a multiple origin for the BDNF-LI of the human cerebellum. The codistribution of BDNF- and PSA-NCAM-LI in analyzed regions suggests that PSA-NCAM may modulate the functional interaction between BDNF and its high and low affinity receptors, an issue worth further analysis, particularly in view of the possible clinical significance of neuronal trophism in cerebellar neurodegenerative disorders.