The triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial innate immune receptor associated with a lethal form of early, progressive dementia, Nasu-Hakola disease, and with an increased risk of Alzheimer's disease. Microglial defects in phagocytosis of toxic aggregates or apoptotic membranes were proposed to be at the origin of the pathological processes in the presence of Trem2 inactivating mutations. Here, we show that TREM2 is essential for microglia-mediated synaptic refinement during the early stages of brain development. The absence of Trem2 resulted in impaired synapse elimination, accompanied by enhanced excitatory neurotransmission and reduced long-range functional connectivity. Trem2 mice displayed repetitive behavior and altered sociability. TREM2 protein levels were also negatively correlated with the severity of symptoms in humans affected by autism. These data unveil the role of TREM2 in neuronal circuit sculpting and provide the evidence for the receptor's involvement in neurodevelopmental diseases.

These findings identify myeloid MVs as a marker and therapeutic target of brain inflammation.

A hallmark of synaptic specializations is their dependence on highly organized complexes of proteins that interact with each other. The loss or modification of key synaptic proteins directly affects the properties of such networks, ultimately impacting synaptic function. SNAP-25 is a component of the SNARE complex, which is central to synaptic vesicle exocytosis, and, by directly interacting with different calcium channels subunits, it negatively modulates neuronal voltage-gated calcium channels, thus regulating intracellular calcium dynamics. The SNAP-25 gene has been associated with distinct brain diseases, including Attention Deficit Hyperactivity Disorder (ADHD), schizophrenia and bipolar disorder, indicating that the protein may act as a shared biological substrate among different “synaptopathies”. The mechanisms by which alterations in SNAP-25 may concur to these psychiatric diseases are still undefined, although alterations in neurotransmitter release have been indicated as potential causative processes. This review summarizes recent work showing that SNAP-25 not only controls exo/endocytic processes at the presynaptic terminal, but also regulates postsynaptic receptor trafficking, spine morphogenesis, and plasticity, thus opening the possibility that SNAP-25 defects may contribute to psychiatric diseases by impacting not only presynaptic but also postsynaptic functions.

We provide evidence that maternal immune activation hits a key neurodevelopmental process, the excitatory-to-inhibitory gamma-aminobutyric acid switch; defects in this switch have been unequivocally linked to diseases such as autism spectrum disorder or epilepsy. These data open the avenue for a safe pharmacological treatment that may prevent the neurodevelopmental defects caused by prenatal immune activation in a specific pregnancy time window.

Transformation of primary B lymphocytes by Epstein-Barr Virus (EBV) requires the establishment of a latent infection, the expression of several latent viral proteins and a sustained telomerase activity. We investigated the interplay between the activation of human telomerase reverse transcriptase (hTERT), the catalytic rate-limiting component of the telomerase complex, and the expression of latent/lytic EBV genes during the establishment of a stably latent EBV infection of normal B lymphocytes. Cell cultures at early passages after EBV infection greatly differed in their timing of hTERT expression and telomerase activation. Induction of hTERT was dependent on the balance between latent and lytic EBV gene expression, being positively associated with a high ratio of latent/lytic isoforms of latent membrane protein 1, and negatively associated with the expression of BZLF1 gene, the main activator of the viral lytic cycle. In turn, hTERT expression was followed by a decrease in EBV lytic gene expression and virus production. Ectopic expression of hTERT in BZLF1-positive B cell cultures resulted in BZLF1 down-regulation, increased resistance to lytic cycle induction, and enhanced in vitro growth properties, whereas hTERT inhibition by siRNA triggered the activation of the EBV lytic cycle. These findings indicate that hTERT contributes by multiple mechanisms to the EBV-driven transformation of B lymphocytes and suggest that hTERT may constitute a therapeutic target for EBV-associated B cell lymphomas. ' 2007 Wiley-Liss, Inc. Key words: hTERT; EBV latent infection; B lymphocytesEpstein-Barr virus (EBV) is closely associated with a broad spectrum of malignancies in vivo, and EBV infection of resting B cells in vitro results in the generation of immortalized, continuously proliferating lymphoblastoid cell lines (LCLs). Similar to other gammaherpesviruses, EBV has both latent and lytic stages in its life cycle. Viral replication is triggered by the expression of the BZLF1 gene, which initiates a cascade of viral lytic gene expression that culminates in the release of infectious virus and the death of host cells.1 In vitro grown LCLs, like most of the EBV-related tumors associated with immune suppression, harbor EBV mainly in its latent state and express several latent proteins, including 6 nuclear antigens (EBNAs) and 3 latent membrane proteins (LMP1, LMP2A and LMP2B). Expression of LMP1 is key to the ability of EBV to transform B cells.2 LMP1 functions as a constitutively active tumor necrosis factor receptor, and triggers multiple cell signaling pathways in a ligand-independent manner. 3-6Notably, LMP1 is also expressed early during EBV replication, being activated by the lytic transactivator protein Rta.7 In addition, the LMP1 gene of several EBV strains also contains a late lytic cycle promoter, EDL1A, driving the expression of an amino-terminally truncated form of LMP1, the lytic LMP1 (lyLMP1), 8,9 which can affect the ability of LMP1 to activate cell signaling pathways. 9,10Expression of latent EBV proteins is not s...

In this paper, we describe the effects of the combination of topographical, mechanical, chemical and intracellular electrical stimuli on a co-culture of fibroblasts and skeletal muscle cells. The co-culture was anisotropically grown onto an engineered micro-grooved (10 µm-wide grooves) polyacrylamide substrate, showing a precisely tuned Young’s modulus (∼ 14 kPa) and a small thickness (∼ 12 µm). We enhanced the co-culture properties through intracellular stimulation produced by piezoelectric nanostructures (i.e., boron nitride nanotubes) activated by ultrasounds, thus exploiting the ability of boron nitride nanotubes to convert outer mechanical waves (such as ultrasounds) in intracellular electrical stimuli, by exploiting the direct piezoelectric effect. We demonstrated that nanotubes were internalized by muscle cells and localized in both early and late endosomes, while they were not internalized by the underneath fibroblast layer. Muscle cell differentiation benefited from the synergic combination of topographical, mechanical, chemical and nanoparticle-based stimuli, showing good myotube development and alignment towards a preferential direction, as well as high expression of genes encoding key proteins for muscle contraction (i.e., actin and myosin). We also clarified the possible role of fibroblasts in this process, highlighting their response to the above mentioned physical stimuli in terms of gene expression and cytokine production. Finally, calcium imaging-based experiments demonstrated a higher functionality of the stimulated co-cultures.

Synaptosomal-associated protein of 25 kDa (SNAP-25) is a protein that participates in the regulation of synaptic vesicle exocytosis through the formation of the soluble NSF attachment protein receptor complex and modulates voltage-gated calcium channels activity. The Snap25 gene has been associated with schizophrenia, attention deficit hyperactivity disorder, and bipolar disorder, and lower levels of SNAP-25 have been described in patients with schizophrenia. We used SNAP-25 heterozygous (SNAP-25(+/-)) mice to investigate at which extent the reduction of the protein levels affects neuronal network function and mouse behavior. As interactions of genotype with the specific laboratory conditions may impact behavioral results, the study was performed through a multilaboratory study in which behavioral tests were replicated in at least 2 of 3 distinct European laboratories. Reductions of SNAP-25 levels were associated with a moderate hyperactivity, which disappeared in the adult animals, and with impaired associative learning and memory. Electroencephalographic recordings revealed the occurrence of frequent spikes, suggesting a diffuse network hyperexcitability. Consistently, SNAP-25(+/-) mice displayed higher susceptibility to kainate-induced seizures, paralleled by degeneration of hilar neurons. Notably, both EEG profile and cognitive defects were improved by antiepileptic drugs. These results indicate that reduction of SNAP-25 expression is associated to generation of epileptiform discharges and cognitive dysfunctions, which can be effectively treated by antiepileptic drugs.

SNAP-25 is plasma membrane protein which, together with syntaxin and the synaptic vesicle protein VAMP/synaptobrevin, forms the SNARE docking complex for regulated exocytosis. SNAP-25 also modulates different voltage-gated calcium channels, representing therefore a multifunctional protein that plays essential roles in neurotransmitter release at different steps. Recent genetic studies of human populations and of some mouse models implicate that alterations in SNAP-25 gene structure, expression and/or function may contribute directly to these distinct neuropsychiatric and neurological disorders. KeywordsSNAP-25; schizophrenia; epilepsy; ADHD; calcium channels SNAP-25: A MULTIFUNCTIONAL PROTEIN REGULATING SYNAPTIC TRANSMISSIONSNAP-25 (synaptosomal-associated protein of 25 kDa) is a SNARE protein that participates in the regulation of synaptic vesicle exocytosis. It is a membrane bound protein anchored to the membranes of neurons via palmitoyl side chains located in the central region of the molecule, and together with syntaxin and the synaptic vesicle protein VAMP/synaptobrevin constitutes the initial SNARE docking complex for regulated exocytosis. Clostridial toxins, which specifically cleave SNAP-25 have unequivocally demonstrated the requirement of the protein for vesicle exocytosis.1 -3 Furthermore generation of SNAP-25 null mutant mice revealed that SNAP-25 is essential for evoked synaptic transmission, although it is not required for stimulus-independent neurotransmitter release.4 Besides its well characterized role in regulating exocytosis, there is increasing evidence that SNAP-25 also modulates various voltage gated ion channels.5 , 6 In particular, SNAP-25 interacts with different types of voltage-gated calcium channels (VGCCs), including N type,7 P/Q type,8 , 9 and L type,10 through a channel region known as the synaptic protein interaction (synprint) site. In line with these data, SNAP-25 negatively controls neuronal calcium responsiveness to depolarization11 by specifically inhibiting, upon phosphorylation of Ser 187, neuronal VGCCs.12 SNAP-25 therefore represents a multifunctional synaptic protein that plays an