The interaction of Synapsin 2a and Synaptogyrin-3 regulates fear extinction in mice.

The mechanisms behind a lack of efficient fear extinction in some individuals are unclear. Here, by employing a principal components analysis-based approach, we differentiated the mice into extinction-resistant and susceptible groups. We determined that elevated synapsin 2a (Syn2a) in the infralimbic cortex (IL) to basolateral amygdala (BLA) circuit disrupted presynaptic orchestration, leading to an excitatory/inhibitory imbalance in the BLA region and causing extinction resistance. Overexpression or silencing of Syn2a levels in IL neurons replicated or alleviated behavioral, electrophysiological, and biochemical phenotypes in resistant mice. We further identified that the proline-rich domain H in the C-terminus of Syn2a was indispensable for the interaction with synaptogyrin-3 (Syngr3) and demonstrated that disrupting this interaction restored extinction impairments. Molecular docking revealed that ritonavir, an FDA-approved HIV drug, could disrupt Syn2a-Syngr3 binding and rescue fear extinction behavior in Syn2a-elevated mice. In summary, the aberrant elevation of Syn2a expression and its interaction with Syngr3 at the presynaptic site were crucial in fear extinction resistance, suggesting a potential therapeutic avenue for related disorders.

Functional and evolutionary analysis of host Synaptogyrin-2 in porcine circovirus type 2 susceptibility.

Mammalian evolution has been influenced by viruses for millions of years, leaving signatures of adaptive evolution within genes encoding for viral interacting proteins. Synaptogyrin-2 (SYNGR2) is a transmembrane protein implicated in promoting bacterial and viral infections. A genome-wide association study of pigs experimentally infected with porcine circovirus type 2b (PCV2b) uncovered a missense mutation (SYNGR2 p.Arg63Cys) associated with viral load. In this study, CRISPR/Cas9-mediated gene editing of the porcine kidney 15 (PK15, wtSYNGR2+p.63Arg) cell line generated clones homozygous for the favorable SYNGR2 p.63Cys allele (emSYNGR2+p.63Cys). Infection of edited clones resulted in decreased PCV2 replication compared to wildtype PK15 (P<0.05), with consistent effects across genetically distinct PCV2b and PCV2d isolates. Sequence analyses of wild and domestic pigs (n>700) revealed the favorable SYNGR2 p.63Cys allele is unique to domestic pigs and more predominant in European than Asian breeds. A haplotype defined by the SYNGR2 p.63Cys allele was likely derived from an ancestral haplotype nearly fixed within European (0.977) but absent from Asian wild boar. We hypothesize that the SYNGR2 p.63Cys allele arose post-domestication in ancestral European swine. Decreased genetic diversity in homozygotes for the SYNGR2 p.63Cys allele compared to SYNGR2 p.63Arg, corroborates a rapid increase in frequency of SYGNR2 p.63Cys via positive selection. Signatures of adaptive evolution across mammalian species were also identified within SYNGR2 intraluminal loop domains, coinciding with the location of SYNGR2 p.Arg63Cys. Therefore, SYNGR2 may reflect a novel component of the host-virus evolutionary arms race across mammals with SYNGR2 p.Arg63Cys representing a species-specific example of putative adaptive evolution.

Pan-cancer analysis of SYNGR2 with a focus on clinical implications and immune landscape in liver hepatocellular carcinoma.

BACKGROUND: Synaptogyrin-2 (SYNGR2), as a member of synaptogyrin gene family, is overexpressed in several types of cancer. However, the role of SYNGR2 in pan-cancer is largely unexplored. METHODS: From the TCGA and GEO databases, we obtained bulk transcriptomes, and clinical information. We examined the expression patterns, prognostic values, and diagnostic value of SYNGR2 in pan-cancer, and investigated the relationship of SYNGR2 expression with tumor mutation burden (TMB), microsatellite instability (MSI), immune infiltration, and immune checkpoint (ICP) genes. The gene set enrichment analysis (GSEA) software was used to perform pathway analysis. Besides, we built a nomogram of liver hepatocellular carcinoma patients (LIHC) and validated its prediction accuracy. RESULTS: SYNGR2 was highly expressed in most cancers. The high expression of SYNGR2 significantly reduced the overall survival (OS), disease-specific survival (DSS), disease-free interval (DFI), and progression-free interval (PFI) in multiple types of cancer. Also, receiver operating characteristic (ROC) curve analysis demonstrated that SYNGR2 showed high accuracy in distinguishing cancerous tissues from normal ones. Moreover, SYNGR2 expression was correlated with TMB, MSI, immune scores, and immune cell infiltrations. We also analyzed the association of SYNGR2 with immunotherapy response in LIHC. Finally, a nomogram including SYNGR2 and pathologic T, N, M stage was built and exhibited good predictive power for the OS, DSS, and PFI of LIHC patients. CONCLUSION: Overall, SYNGR2 is a critical oncogene in various tumors. SYNGR2 participates in the carcinogenic progression, and may contribute to the immune infiltration in tumor microenvironment. Our study suggests that SYNGR2 can serve as a predictor related to prognosis in pan-cancer, especially LIHC.

Phosphatidylserine-dependent structure of synaptogyrin remodels the synaptic vesicle membrane.

Synaptic vesicles are small membrane-enclosed organelles that store neurotransmitters at presynaptic terminals. The uniform morphology of synaptic vesicles is important for brain function, because it enables the storage of well-defined amounts of neurotransmitters and thus reliable synaptic transmission. Here, we show that the synaptic vesicle membrane protein synaptogyrin cooperates with the lipid phosphatidylserine to remodel the synaptic vesicle membrane. Using NMR spectroscopy, we determine the high-resolution structure of synaptogyrin and identify specific binding sites for phosphatidylserine. We further show that phosphatidylserine binding changes the transmembrane structure of synaptogyrin and is critical for membrane bending and the formation of small vesicles. Cooperative binding of phosphatidylserine to both a cytoplasmic and intravesicular lysine-arginine cluster in synaptogyrin is required for the formation of small vesicles. Together with other synaptic vesicle proteins, synaptogyrin thus can sculpt the membrane of synaptic vesicles.

In vivo overexpression of synaptogyrin-3 promotes striatal synaptic dopamine uptake in LRRK2R1441G mutant mouse model of Parkinson's disease.

BACKGROUND: Leucine-rich repeat kinase 2 (LRRK2) mutation is a common genetic risk factor of Parkinson's disease (PD). Presynaptic dysfunction is an early pathogenic event associated with dopamine (DA) dysregulation in striatum of the brain. DA uptake activity of DA uptake transporter (DAT) affects synaptic plasticity and motor and non-motor behavior. Synaptogyrin-3 (SYNGR3) is part of the synaptogyrin family, especially abundant in brain. Previous in vitro studies demonstrated interaction between SYNGR3 and DAT. Reduced SYNGR3 expression was observed in human PD brains with unclear reasons. METHODS: Here, we further explored whether inducing SYNGR3 expression can influence (i) cellular DA uptake using differentiated human SH-SY5Y neuronal cells, (ii) striatal synaptosomal DA uptake in a mutant LRRK2R1441G  knockin mouse model of PD, and (iii) innate rodent behavior using the marble burying test. RESULTS: Young LRRK2 mutant mice exhibited significantly lower SYNGR3 levels in striatum compared to age-matched wild-type (WT) controls, resembling level in aged WT mice. SYNGR3 is spatially co-localized with DAT at striatal presynaptic terminals, visualized by immuno-gold transmission electron microscopy and immunohistochemistry. Their protein-protein interaction was confirmed by co-immunoprecipitation. Transient overexpression of SYNGR3 in differentiated SH-SY5Y cells increased cellular DA uptake activity without affecting total DAT levels. Inducing SYNGR3 overexpression by adeno-associated virus-7 (AAV7) injection in vivo into striatum increased ex vivo synaptosomal DA uptake in LRRK2 mutant mice and improved their innate marble burying behavior. CONCLUSION: Brain SYNGR3 expression may be an important determinant to striatal DA homeostasis and synaptic function. Our preliminary behavioral test showed improved innate behavior after SYNGR3 overexpression in LRRK2 mutant mice, advocating further studies to determine the influence of SYNGR3 in the pathophysiology of DA neurons in PD.

Tumor Cell Extrinsic Synaptogyrin 3 Expression as a Diagnostic and Prognostic Biomarker in Head and Neck Cancer.

Over 70% of oropharyngeal head and neck squamous cell carcinoma (HNSC) cases in the United States are positive for human papillomavirus (HPV) yet biomarkers for stratifying oropharyngeal head and neck squamous cell carcinoma (HNSC) patient risk are limited. We used immunogenomics to identify differentially expressed genes in immune cells of HPV(+) and HPV(-) squamous carcinomas. Candidate genes were tested in clinical specimens using both quantitative RT-PCR and IHC and validated by IHC using the Carolina Head and Neck Cancer Study (CHANCE) tissue microarray of HNSC cases. We performed multiplex immunofluorescent staining to confirm expression within the immune cells of HPV(+) tumors, receiver operating characteristic (ROC) curve analyses, and assessed survival outcomes. The neuronal gene Synaptogyrin-3 (SYNGR3) is robustly expressed in immune cells of HPV(+) squamous cancers. Multiplex immunostaining and single cell RNA-seq analyses confirmed SYNGR3 expression in T cells, but also unexpectedly in B cells of HPV(+) tumors. ROC curve analyses revealed that combining SYNGR3 and p16 provides more sensitivity and specificity for HPV detection compared to p16 IHC alone. SYNGR3-high HNSC patients have significantly better prognosis with five-year OS and DSS rates of 60% and 71%, respectively. Moreover, combining p16 localization and SYNGR3 expression can further risk stratify HPV(+) patients such that high cytoplasmic, low nuclear p16 do significantly worse (Hazard Ratio, 8.6; P = 0.032) compared to patients with high cytoplasmic, high nuclear p16. SYNGR3 expression in T and B cells is associated with HPV status and enhanced survival outcomes of HNSC patients.

Transcriptional Regulation of the Synaptic Vesicle Protein Synaptogyrin-3 (SYNGR3) Gene: The Effects of NURR1 on Its Expression.

Synaptogyrin-3 (SYNGR3) is a synaptic vesicular membrane protein. Amongst four homologues (SYNGR1 to 4), SYNGR1 and 3 are especially abundant in the brain. SYNGR3 interacts with the dopamine transporter (DAT) to facilitate dopamine (DA) uptake and synaptic DA turnover in dopaminergic transmission. Perturbed SYNGR3 expression is observed in Parkinson's disease (PD). The regulatory elements which affect SYNGR3 expression are unknown. Nuclear-receptor-related-1 protein (NURR1) can regulate dopaminergic neuronal differentiation and maintenance via binding to NGFI-B response elements (NBRE). We explored whether NURR1 can regulate SYNGR3 expression using an in silico analysis of the 5'-flanking region of the human SYNGR3 gene, reporter gene activity and an electrophoretic mobility shift assay (EMSA) of potential cis-acting sites. In silico analysis of two genomic DNA segments (1870 bp 5'-flanking region and 1870 + 159 bp of first exon) revealed one X Core Promoter Element 1 (XCPE1), two SP1, and three potential non-canonical NBRE response elements (ncNBRE) but no CAAT or TATA box. The longer segment exhibited gene promoter activity in luciferase reporter assays. Site-directed mutagenesis of XCPE1 decreased promoter activity in human neuroblastoma SH-SY5Y (↓43.2%) and human embryonic kidney HEK293 cells (↓39.7%). EMSA demonstrated NURR1 binding to these three ncNBRE. Site-directed mutagenesis of these ncNBRE reduced promoter activity by 11-17% in SH-SY5Y (neuronal) but not in HEK293 (non-neuronal) cells. C-DIM12 (Nurr1 activator) increased SYNGR3 protein expression in SH-SY5Y cells and its promoter activity using a real-time luciferase assay. As perturbed vesicular function is a feature of major neurodegenerative diseases, inducing SYNGR3 expression by NURR1 activators may be a potential therapeutic target to attenuate synaptic dysfunction in PD.

Methotrexate Treatment of Newly Diagnosed RA Patients Is Associated With DNA Methylation Differences at Genes Relevant for Disease Pathogenesis and Pharmacological Action.

Background: Methotrexate (MTX) is the first line treatment of rheumatoid arthritis (RA), and methylation changes in bulk T cells have been reported after treatment with MTX. We have investigated cell-type specific DNA methylation changes across the genome in naïve and memory CD4+ T cells before and after MTX treatment of RA patients. DNA methylation profiles of newly diagnosed RA patients (N=9) were assessed by reduced representation bisulfite sequencing. Results: We found that MTX treatment significantly influenced DNA methylation levels at multiple CpG sites in both cell populations. Interestingly, we identified differentially methylated sites annotated to two genes; TRIM15 and SORC2, previously reported to predict treatment outcome in RA patients when measured in bulk T cells. Furthermore, several of the genes, including STAT3, annotated to the significant CpG sites are relevant for RA susceptibility or the action of MTX. Conclusion: We detected CpG sites that were associated with MTX treatment in CD4+ naïve and memory T cells isolated from RA patients. Several of these sites overlap genetic regions previously associated with RA risk and MTX treatment outcome.

Synaptophysin Regulates Fusion Pores and Exocytosis Mode in Chromaffin Cells.

Synaptophysin (syp) is a major integral membrane protein of secretory vesicles. Previous work has demonstrated functions for syp in synaptic vesicle cycling, endocytosis, and synaptic plasticity, but the role of syp in the process of membrane fusion during Ca2+-triggered exocytosis remains poorly understood. Furthermore, although syp resides on both large dense-core and small synaptic vesicles, its role in dense-core vesicle function has received less attention compared with synaptic vesicle function. To explore the role of syp in membrane fusion and dense-core vesicle function, we used amperometry to measure catecholamine release from single vesicles in male and female mouse chromaffin cells with altered levels of syp and the related tetraspanner protein synaptogyrin (syg). Knocking out syp slightly reduced the frequency of vesicle fusion events below wild-type (WT) levels, but knocking out both syp and syg reduced the frequency 2-fold. Knocking out both proteins stabilized initial fusion pores, promoted fusion pore closure (kiss-and-run), and reduced late-stage fusion pore expansion. Introduction of a syp construct lacking its C-terminal dynamin-binding domain in syp knock-outs (KOs) increased the duration and fraction of kiss-and-run events, increased total catecholamine release per event, and reduced late-stage fusion pore expansion. These results demonstrated that syp and syg regulate dense-core vesicle function at multiple stages to initiate fusion, control the choice of mode between full-fusion and kiss-and-run, and influence the dynamics of both initial and late-stage fusion pores. The transmembrane domain (TMD) influences small initial fusion pores, and the C-terminal domain influences large late-stage fusion pores, possibly through an interaction with dynamin.SIGNIFICANCE STATEMENT The secretory vesicle protein synaptophysin (syp) is known to function in synaptic vesicle cycling, but its roles in dense-core vesicle functions, and in controlling membrane fusion during Ca2+-triggered exocytosis remain unclear. The present study used amperometry recording of catecholamine release from endocrine cells to assess the impact of syp and related proteins on membrane fusion. A detailed analysis of amperometric spikes arising from the exocytosis of single vesicles showed that these proteins influence fusion pores at multiple stages and control the choice between kiss-and-run and full-fusion. Experiments with a syp construct lacking its C terminus indicated that the transmembrane domain (TMD) influences the initial fusion pore, while the C-terminal domain influences later stages after fusion pore expansion.

Targeting pre-synaptic tau accumulation: a new strategy to counteract tau-mediated synaptic loss and memory deficits.

Synaptic tau accumulation is believed to promote synaptic loss, which contributes to cognitive deficits in Alzheimer's disease and tauopathies. In this issue of Neuron, Largo-Barrientos et al. report that synaptic loss can be mitigated by lowering Synaptogyrin-3, a known mediator of tau binding to synaptic vesicles.

Global discovery of lupus genetic risk variant allelic enhancer activity.

Genome-wide association studies of Systemic Lupus Erythematosus (SLE) nominate 3073 genetic variants at 91 risk loci. To systematically screen these variants for allelic transcriptional enhancer activity, we construct a massively parallel reporter assay (MPRA) library comprising 12,396 DNA oligonucleotides containing the genomic context around every allele of each SLE variant. Transfection into the Epstein-Barr virus-transformed B cell line GM12878 reveals 482 variants with enhancer activity, with 51 variants showing genotype-dependent (allelic) enhancer activity at 27 risk loci. Comparison of MPRA results in GM12878 and Jurkat T cell lines highlights shared and unique allelic transcriptional regulatory mechanisms at SLE risk loci. In-depth analysis of allelic transcription factor (TF) binding at and around allelic variants identifies one class of TFs whose DNA-binding motif tends to be directly altered by the risk variant and a second class of TFs that bind allelically without direct alteration of their motif by the variant. Collectively, our approach provides a blueprint for the discovery of allelic gene regulation at risk loci for any disease and offers insight into the transcriptional regulatory mechanisms underlying SLE.

Lowering Synaptogyrin-3 expression rescues Tau-induced memory defects and synaptic loss in the presence of microglial activation.

Tau is a major driver of neurodegeneration and is implicated in over 20 diseases. Tauopathies are characterized by synaptic loss and neuroinflammation, but it is unclear if these pathological events are causally linked. Tau binds to Synaptogyrin-3 on synaptic vesicles. Here, we interfered with this function to determine the role of pathogenic Tau at pre-synaptic terminals. We show that heterozygous knockout of synaptogyrin-3 is benign in mice but strongly rescues mutant Tau-induced defects in long-term synaptic plasticity and working memory. It also significantly rescues the pre- and post-synaptic loss caused by mutant Tau. However, Tau-induced neuroinflammation remains clearly upregulated when we remove the expression of one allele of synaptogyrin-3. Hence neuroinflammation is not sufficient to cause synaptic loss, and these processes are separately induced in response to mutant Tau. In addition, the pre-synaptic defects caused by mutant Tau are enough to drive defects in cognitive tasks.

Rab5a Promotes Cytolethal Distending Toxin B-Induced Cytotoxicity and Inflammation.

The cytolethal distending toxin B subunit (CdtB) induces significant cytotoxicity and inflammation in many cell types that are involved in the pathogenesis of postinfectious irritable bowel syndrome (PI-IBS). However, the underlying mechanisms remain unclear. This study tested the potential role of Rab small GTPase 5a (Rab5a) in the process. We tested mRNA and protein expression of proinflammatory cytokines (interleukin-1ß [IL-1ß] and IL-6) in THP-1 macrophages by quantitative PCR (qPCR) and enzyme-linked immunosorbent assays (ELISAs), respectively. In the primary colonic epithelial cells, Cdt treatment induced a CdtB-Rab5a-cellugyrin association. Rab5a silencing, by target small hairpin RNAs (shRNAs), largely inhibited CdtB-induced cytotoxicity and apoptosis in colon epithelial cells. CRISPR/Cas9-mediated Rab5a knockout also attenuated CdtB-induced colon epithelial cell death. Conversely, forced overexpression of Rab5a intensified CdtB-induced cytotoxicity. In THP-1 human macrophages, Rab5a shRNA or knockout significantly inhibited CdtB-induced mRNA expression and production of proinflammatory cytokines (IL-1ß and IL-6). Rab5a depletion inhibited activation of nuclear factor-κB (NF-κB) and Jun N-terminal protein kinase (JNK) signaling in CdtB-treated THP-1 macrophages. Rab5a appears essential for CdtB-induced cytotoxicity in colonic epithelial cells and proinflammatory responses in THP-1 macrophages.

Internalization and Intoxication of Human Macrophages by the Active Subunit of the Aggregatibacter actinomycetemcomitans Cytolethal Distending Toxin Is Dependent Upon Cellugyrin (Synaptogyrin-2).

The Aggregatibacter actinomycetemcomitans cytolethal distending toxin (Cdt) is a heterotrimeric AB2 toxin capable of inducing cell cycle arrest and apoptosis in lymphocytes and other cell types. Recently, we have demonstrated that human macrophages are resistant to Cdt-induced apoptosis but are susceptible to toxin-induced pro-inflammatory cytokine response involving activation of the NLRP3 inflammasome. Exposure to Cdt results in binding to the cell surface followed by internalization and translocation of the active subunit, CdtB, to intracellular compartments. Internalization involves hijacking of retrograde pathways; treatment of cells with Retro-2 leads to a decrease in CdtB-Golgi association. These events are dependent upon toxin binding to cholesterol in the context of lipid rich membrane microdomains often referred to as lipid rafts. We now demonstrate that within 1 h of exposure of macrophages to Cdt, CdtB is internalized and found primarily within lipid rafts; concurrently, cellugyrin (synaptogyrin-2) also translocates into lipid rafts. Further analysis by immunoprecipitation indicates that CdtB associates with complexes containing both cellugyrin and Derlin-2. Moreover, a human macrophage cell line deficient in cellugyrin expression (THP-1Cg-) challenged with Cdt failed to internalize CdtB and was resistant to the Cdt-induced pro-inflammatory response. We propose that lipid rafts along with cellugyrin play a critical role in the internalization and translocation of CdtB to critical intracellular target sites in human macrophages. These studies provide the first evidence that cellugyrin is expressed in human macrophages and plays a critical role in Cdt toxicity of these cells.

Motor neuron translatome reveals deregulation of SYNGR4 and PLEKHB1 in mutant TDP-43 amyotrophic lateral sclerosis models.

Amyotrophic lateral sclerosis (ALS) is an incurable neurological disease with progressive loss of motor neuron (MN) function in the brain and spinal cord. Mutations in TARDBP, encoding the RNA-binding protein TDP-43, are one cause of ALS, and TDP-43 mislocalization in MNs is a key pathological feature of >95% of ALS cases. While numerous studies support altered RNA regulation by TDP-43 as a major cause of disease, specific changes within MNs that trigger disease onset remain unclear. Here, we combined translating ribosome affinity purification (TRAP) with RNA sequencing to identify molecular changes in spinal MNs of TDP-43-driven ALS at motor symptom onset. By comparing the MN translatome of hTDP-43A315T mice to littermate controls and to mice expressing wild type hTDP-43, we identified hundreds of mRNAs that were selectively up- or downregulated in MNs. We validated the deregulated candidates Tex26, Syngr4, and Plekhb1 mRNAs in an independent TRAP experiment. Moreover, by quantitative immunostaining of spinal cord MNs, we found corresponding protein level changes for SYNGR4 and PLEKHB1. We also observed these changes in spinal MNs of an independent ALS mouse model caused by a different patient mutant allele of TDP-43, suggesting that they are general features of TDP-43-driven ALS. Thus, we identified SYNGR4 and PLEKHB1 to be deregulated in MNs at motor symptom onset in TDP-43-driven ALS models. This spatial and temporal pattern suggests that these proteins could be functionally important for driving the transition to the symptomatic phase of the disease.

Enhanced functional recovery by levodopa is associated with decreased levels of synaptogyrin following stroke in aged mice.

Levodopa is a precursor to dopamine that has been shown to improve functional recovery following stroke partly achieved through mechanisms of brain plasticity. This study investigates if dopamine might affect plasticity by having a direct effect on synaptic plasticity through alterations in neurotransmitter release and re-uptake. Synaptogyrin is a synaptic vesicle protein that has been suggested to be involved in dopamine re-uptake in the synaptic terminal. Therefore, we investigated if levodopa has an effect on the expression of synaptogyrin 1. Thy1-YFP mice were subjected to photothrombosis as an experimental model of stroke. Starting two days after surgery they were treated with either levodopa or a vehicle solution (saline) on a daily basis until day seven following surgery. On day seven they were sacrificed and their brains stained for Dopamine 1 receptor (D1R), Dopamine 2 receptor (D2R) and Parvalbumin (PV). Neu-N stainings were used to estimate infarct size. A second group of mice were subjected to photothrombosis and also treated with either levodopa or a vehicle solution in the same manner as previously mentioned. On day seven they were then sacrificed, and samples of brain tissue were taken for protein determination. Western blots were carried out to investigate possible differences in synaptogyrin expression between the two groups. Immunofluorescent stains showed the presence of dopamine receptors on the YFP-positive neurons and on PV-expressing neurones. Our Western Blot analysis showed a significant decrease in the expression of synaptogyrin in levodopa-treated mice. Our stains showed co-localisation with Thy-1 neurones and PV-expressing neurones for both D1 and D2 receptors. This indicates that dopamine has the ability to bind to, and directly influence cortical neurons, as well as inhibitory interneurons. We discovered a considerable decrease in synaptogyrin expression through levodopa treatment, suggesting that this might be a mechanism for regulating brain plasticity.

Elevated synaptic vesicle release probability in synaptophysin/gyrin family quadruple knockouts.

Synaptophysins 1 and 2 and synaptogyrins 1 and 3 constitute a major family of synaptic vesicle membrane proteins. Unlike other widely expressed synaptic vesicle proteins such as vSNAREs and synaptotagmins, the primary function has not been resolved. Here, we report robust elevation in the probability of release of readily releasable vesicles with both high and low release probabilities at a variety of synapse types from knockout mice missing all four family members. Neither the number of readily releasable vesicles, nor the timing of recruitment to the readily releasable pool was affected. The results suggest that family members serve as negative regulators of neurotransmission, acting directly at the level of exocytosis to dampen connection strength selectively when presynaptic action potentials fire at low frequency. The widespread expression suggests that chemical synapses may play a frequency filtering role in biological computation that is more elemental than presently envisioned. Editorial note: This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

Expression and significance of phosphodiesterase 4B gene in peripheral blood of patients with oral lichen planus.

BACKGROUND: The pathogenesis of oral lichen planus (OLP) may be related to mental factors. In this study, we investigated the molecular mechanism of mental factors in the development of OLP. METHODS: The normal control group and OLP patients were tested and evaluated by Zung self-rating anxiety scale and self-rating depression scale. Secondly, Agilent human LncRNA chip technology was used to detect differential genes in the total RNA of the normal control group and OLP patients, and to screen out the differentially expressed genes related to anxiety and depression. Thirdly, we verified the genes at gene level and protein level, respectively. RESULTS: Zung self-rating anxiety scale and self-rating depression scale showed that tendency of anxiety and depression in OLP patients is significantly higher than that in normal controls, but there was no significant difference between the erosion form group and the reticular form group; the duration of OLP showed significant negative correlations between degree of anxiety and depression. Microarray analysis showed there were four differential genes (PDE4B, RGS2, SYNGR1, and SYNE1) related to anxiety and depression in OLP patients; real-time qPCR confirmed the expression of PDE4B mRNA was lower in the peripheral blood of normal control group (P < 0.001). The expression of RGS2, SYNGR1, and SYNE1 mRNA was higher in the normal control group (P < 0.05, P < 0.05, P < 0.05). Wes automatic western blot confirmed that the expression of PDE4B protein was lower in the peripheral blood of the normal control group (P < 0.01). CONCLUSION: PDE4B gene may play a role in the pathogenesis of OLP.

Synaptogyrin-2 influences replication of Porcine circovirus 2.

Porcine circovirus 2 (PCV2) is a circular single-stranded DNA virus responsible for a group of diseases collectively known as PCV2 Associated Diseases (PCVAD). Variation in the incidence and severity of PCVAD exists between pigs suggesting a host genetic component involved in pathogenesis. A large-scale genome-wide association study of experimentally infected pigs (n = 974), provided evidence of a host genetic role in PCV2 viremia, immune response and growth during challenge. Host genotype explained 64% of the phenotypic variation for overall viral load, with two major Quantitative Trait Loci (QTL) identified on chromosome 7 (SSC7) near the swine leukocyte antigen complex class II locus and on the proximal end of chromosome 12 (SSC12). The SNP having the strongest association, ALGA0110477 (SSC12), explained 9.3% of the genetic and 6.2% of the phenotypic variance for viral load. Dissection of the SSC12 QTL based on gene annotation, genomic and RNA-sequencing, suggested that a missense mutation in the SYNGR2 (SYNGR2 p.Arg63Cys) gene is potentially responsible for the variation in viremia. This polymorphism, located within a protein domain conserved across mammals, results in an amino acid variant SYNGR2 p.63Cys only observed in swine. PCV2 titer in PK15 cells decreased when the expression of SYNGR2 was silenced by specific-siRNA, indicating a role of SYNGR2 in viral replication. Additionally, a PK15 edited clone generated by CRISPR-Cas9, carrying a partial deletion of the second exon that harbors a key domain and the SYNGR2 p.Arg63Cys, was associated with a lower viral titer compared to wildtype PK15 cells (>24 hpi) and supernatant (>48hpi)(P < 0.05). Identification of a non-conservative substitution in this key domain of SYNGR2 suggests that the SYNGR2 p.Arg63Cys variant may underlie the observed genetic effect on viral load.

Synaptogyrin-3 Mediates Presynaptic Dysfunction Induced by Tau.

Synaptic dysfunction is an early pathological feature of neurodegenerative diseases associated with Tau, including Alzheimer's disease. Interfering with early synaptic dysfunction may be therapeutically beneficial to prevent cognitive decline and disease progression, but the mechanisms underlying synaptic defects associated with Tau are unclear. In disease conditions, Tau mislocalizes into pre- and postsynaptic compartments; here we show that, under pathological conditions, Tau binds to presynaptic vesicles in Alzheimer's disease patient brain. We define that the binding of Tau to synaptic vesicles is mediated by the transmembrane vesicle protein Synaptogyrin-3. In fly and mouse models of Tauopathy, reduction of Synaptogyrin-3 prevents the association of presynaptic Tau with vesicles, alleviates Tau-induced defects in vesicle mobility, and restores neurotransmitter release. This work therefore identifies Synaptogyrin-3 as the binding partner of Tau on synaptic vesicles, revealing a new presynapse-specific Tau interactor, which may contribute to early synaptic dysfunction in neurodegenerative diseases associated with Tau.