PPP1R9B (Neurabin 2): Involvement and dynamics in the NK immunological synapse

Peripheral control of psychiatric disorders: Focus on OCD. Are we there yet?

"We are all in this together" - we often hear this phrase when we want to flag up a problem that is not for a single individual but concerns us all. A similar reflection has been recently made in the field of mental disorders where brain-centric scientists have started to zoom out their brain-focused graphical representations of the mechanisms regulating psychiatric diseases to include other organs or mediators that did not belong historically to the world of neuroscience. The brain itself - that has long been seen as a master in command secluded in its fortress (the blood brain barrier), has now become a collection of Airbnb(s) where all sorts of cells come in and out and sometimes even rearrange the furniture! Under this new framework of reference, mental disorders have become multisystem pathologies where different biological systems - not just the CNS -contribute 'all together' to the development and severity of the disease. In this narrative review article, we will focus on one of the most popular biological systems that has been shown to influence the functioning of the CNS: the immune system. We will specifically highlight the two main features of the immune system and the CNS that we think are important in the context of mental disorders: plasticity and memory.

Candidate genes and sequence variants for susceptibility to mycobacterial infection identified by whole-exome sequencing

Inborn errors of immunity are known to influence susceptibility to mycobacterial infections. The aim of this study was to characterize the genetic profile of nine patients with mycobacterial infections (eight with BCGitis and one with disseminated tuberculosis) from the Republic of Moldova using whole-exome sequencing. In total, 12 variants in eight genes known to be associated with Mendelian Susceptibility to Mycobacterial Disease (MSMD) were detected in six out of nine patients examined. In particular, a novel splice site mutation c.373–2A>C in STAT1 gene was found and functionally confirmed in a patient with disseminated tuberculosis. Trio analysis was possible for seven out of nine patients, and resulted in 23 candidate variants in 15 novel genes. Four of these genes - GBP2, HEATR3, PPP1R9B and KDM6A were further prioritized, considering their elevated expression in immune-related tissues. Compound heterozygosity was found in GBP2 in a single patient, comprising a maternally inherited missense variant c.412G>A/p.(Ala138Thr) predicted to be deleterious and a paternally inherited intronic mutation c.1149+14T>C. Functional studies demonstrated that the intronic mutation affects splicing and the level of transcript. Finally, we analyzed pathogenicity of variant combinations in gene pairs and identified five patients with putative oligogenic inheritance. In summary, our study expands the spectrum of genetic variation contributing to susceptibility to mycobacterial infections in children and provides insight into the complex/oligogenic disease-causing mode.

Viral targeting of PDZ polarity proteins in the immune system as a potential evasion mechanism

PDZ proteins are highly conserved through evolution; the principal function of this large family of proteins is to assemble protein complexes that are involved in many cellular processes, such as cell-cell junctions, cell polarity, recycling, or trafficking. Many PDZ proteins that have been identified as targets of viral pathogens by promoting viral replication and spread are also involved in epithelial cell polarity. Here, we briefly review the PDZ polarity proteins in cells of the immune system to subsequently focus on our hypothesis that the viral PDZ-dependent targeting of PDZ polarity proteins in these cells may alter the cellular fitness of the host to favor that of the virus; we further hypothesize that this modification of the cellular fitness landscape occurs as a common and widespread mechanism for immune evasion by viruses and possibly other pathogens.-Gutiérrez-González, L. H., Santos-Mendoza, T. Viral targeting of PDZ polarity proteins in the immune system as a potential evasion mechanism.

Initial findings of striatum tripartite model in OCD brain samples based on transcriptome analysis

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by obsessions and/or compulsions. Different striatal subregions belonging to the cortico-striato-thalamic circuitry (CSTC) play an important role in the pathophysiology of OCD. The transcriptomes of 3 separate striatal areas (putamen (PT), caudate nucleus (CN) and accumbens nucleus (NAC)) from postmortem brain tissue were compared between 6 OCD and 8 control cases. In addition to network connectivity deregulation, different biological processes are specific to each striatum region according to the tripartite model of the striatum and contribute in various ways to OCD pathophysiology. Specifically, regulation of neurotransmitter levels and presynaptic processes involved in chemical synaptic transmission were shared between NAC and PT. The Gene Ontology terms cellular response to chemical stimulus, response to external stimulus, response to organic substance, regulation of synaptic plasticity, and modulation of synaptic transmission were shared between CN and PT. Most genes harboring common and/or rare variants previously associated with OCD that were differentially expressed or part of a least preserved coexpression module in our study also suggest striatum subregion specificity. At the transcriptional level, our study supports differences in the 3 circuit CSTC model associated with OCD.

Genome-wide association study reveals genetic architecture of eating behavior in pigs and its implications for humans obesity by comparative mapping

This study was aimed at identifying genomic regions controlling feeding behavior in Danish Duroc boars and its potential implications for eating behavior in humans. Data regarding individual daily feed intake (DFI), total daily time spent in feeder (TPD), number of daily visits to feeder (NVD), average duration of each visit (TPV), mean feed intake per visit (FPV) and mean feed intake rate (FR) were available for 1130 boars. All boars were genotyped using the Illumina Porcine SNP60 BeadChip. The association analyses were performed using the GenABEL package in the R program. Sixteen SNPs were found to have moderate genome-wide significance (p<5E-05) and 76 SNPs had suggestive (p<5E-04) association with feeding behavior traits. MSI2 gene on chromosome (SSC) 14 was very strongly associated with NVD. Thirty-six SNPs were located in genome regions where QTLs have previously been reported for behavior and/or feed intake traits in pigs. The regions: 64–65 Mb on SSC 1, 124–130 Mb on SSC 8, 63–68 Mb on SSC 11, 32–39 Mb and 59–60 Mb on SSC 12 harbored several signifcant SNPs. Synapse genes (GABRR2, PPP1R9B, SYT1, GABRR1, CADPS2, DLGAP2 and GOPC), dephosphorylation genes (PPM1E, DAPP1, PTPN18, PTPRZ1, PTPN4, MTMR4 and RNGTT) and positive regulation of peptide secretion genes (GHRH, NNAT and TCF7L2) were highly significantly associated with feeding behavior traits. This is the first GWAS to identify genetic variants and biological mechanisms for eating behavior in pigs and these results are important for genetic improvement of pig feed efficiency. We have also conducted pig-human comparative gene mapping to reveal key genomic regions and/or genes on the human genome that may influence eating behavior in human beings and consequently affect the development of obesity and metabolic syndrome. This is the first translational genomics study of its kind to report potential candidate genes for eating behavior in humans.

Interrogation of brain miRNA and mRNA expression profiles reveals a molecular regulatory network that is perturbed by mutant huntingtin

Emerging evidence indicates that microRNAs (miRNAs) may play an important role in the pathogenesis of Huntington's disease (HD). To identify the individual miRNAs that are altered in HD and may therefore regulate a gene network underlying mutant huntingtin-induced neuronal dysfunction in HD, we performed miRNA array analysis combined with mRNA profiling in the cerebral cortex from N171-82Q HD mice. Expression profiles of miRNAs as well as mRNAs in HD mouse cerebral cortex were analyzed and confirmed at different stages of disease progression; the most significant changes of miRNAs in the cerebral cortex were also detected in the striatum of HD mice. Our results revealed a significant alteration of miR-200 family members, miR-200a, and miR-200c in the cerebral cortex and the striatum, at the early stage of disease progression in N171-82Q HD mice. We used a coordinated approach to integrate miRNA and mRNA profiling, and applied bioinformatics to predict a target gene network potentially regulated by these significantly altered miRNAs that might be involved in HD disease progression. Interestingly, miR-200a and miR-200c are predicted to target genes regulating synaptic function, neurodevelopment, and neuronal survival. Our results suggest that altered expression of miR-200a and miR-200c may interrupt the production of proteins involved in neuronal plasticity and survival, and further investigation of the involvement of perturbed miRNA expression in HD pathogenesis is warranted, and may lead to reveal novel approaches for HD therapy.

IQGAP1 involvement in MTOC and granule polarization in NK-cell cytotoxicity

Natural killer (NK) cells form a region of tight contact called the NK immunological synapse (NKIS) with their target cells. This is a dynamic region serving as a platform for targeted signaling and exocytotic events. We previously identified IQGAP1 as a cytoskeletal component of the NK-like cell line YTS. The present study was undertaken to determine the role of IQGAP1 in the function of NK cells. Silencing of IQGAP1 expression resulted in almost complete loss of the cytotoxic activity of YTS cells. Loss of IQGAP1 did not prevent conjugate formation with target cells but it did result in a failure to reorient the microtubule organizing centre to the immune synapse. Significantly, IQGAP1 expression was required for the perigranular accumulation of an F-actin network. IQGAP1 was shown to undergo marked rearrangements during synapse maturation in effector target conjugates of YTS or primary NK cells. These results suggest previously undescribed role(s) for IQGAP1 in regulating multiple aspects of cytoskeletal organization and granule polarization in NK cells.

Molecular mechanisms of natural killer cell activation

With an array of activating and inhibitory receptors, natural killer (NK) cells can specifically eradicate infected and transformed cells. Target cell killing is achieved through directed release of lytic granules. Recognition of target cells also induces production of chemokines and cytokines that can coordinate immune responses. Upon contact with susceptible cells, a multiplicity of activating receptors can induce signals for adhesion. Engagement of the integrin leukocyte functional antigen-1 mediates firm adhesion, provides signals for granule polarization and orchestrates the structure of an immunological synapse that facilitates efficient target cell killing. Other activating receptors apart from leukocyte functional antigen-1 signal for lytic granule exocytosis, a process that requires overcoming a threshold for activation of phospholipase C-γ, which in turn induces STIM1- and ORAI1-dependent store-operated Ca²+ entry as well as exocytosis mediated by the SNARE-containing protein syntaxin-11 and regulators thereof. Cytokine and chemokine release follows a different secretory pathway which also requires phospholipase C-γ activation and store-operated Ca²+ entry. Recent studies of human NK cells have provided insights into a hierarchy of effector functions that result in graded responses by NK cell populations. Responses display cellular heterogeneity and are influenced by environmental cues. This review highlights recent knowledge gained on the molecular pathways for and regulation of NK cell activation.

Defining the membrane proteome of NK cells

The present study was initiated to define the composition of the membrane proteome of the Natural Killer (NK) like cell line YTS. Isolated membranes were treated with reagents that have been reported to remove peripheral membrane proteins. Additional steps involving trifluoroethanol (TFE) were introduced in an effort to remove remaining nonintegral membrane proteins. This treatment resulted in the release of a subset of proteins without any apparent disruption of membrane integrity. The membranes were solubilized and digested with trypsin in 25% TFE. The resulting peptides were separated using an off-line two-dimensional reversed phase LC technique at alkaline and acidic pHs. Mass spectrometric analysis identified 1843 proteins with high confidence scores. On the basis of the presence of transmembrane regions or evidence of posttranslational modifications and prediction algorithms, approximately 40% of the identified proteins were predicted as plausible membrane proteins. The remaining species were largely involved in cellular processes and molecular functions that could be predicted to be transiently associated with membranes. The analytical approaches presented in this study offer robust generic methods for the identification and characterization of membrane proteins. These observations highlight the fact that the membrane is a dynamic entity that is composed of integral and stably associated proteins.