Characterization of 22q12 Microdeletions Causing Position Effect in Rare NF2 Patients with Complex Phenotypes.

Neurofibromatosis type 2 is an autosomal dominant tumor-prone disorder mainly caused by NF2 point mutations or intragenic deletions. Few individuals with a complex phenotype and 22q12 microdeletions have been described. The 22q12 microdeletions' pathogenic effects at the genetic and epigenetic levels are currently unknown. We here report on 22q12 microdeletions' characterization in three NF2 patients with different phenotype complexities. A possible effect of the position was investigated by in silico analysis of 22q12 topologically associated domains (TADs) and regulatory elements, and by expression analysis of 12 genes flanking patients' deletions. A 147 Kb microdeletion was identified in the patient with the mildest phenotype, while two large deletions of 561 Kb and 1.8 Mb were found in the other two patients, showing a more severe symptomatology. The last two patients displayed intellectual disability, possibly related to AP1B1 gene deletion. The microdeletions change from one to five TADs, and the 22q12 chromatin regulatory landscape, according to the altered expression levels of four deletion-flanking genes, including PIK3IP1, are likely associated with an early ischemic event occurring in the patient with the largest deletion. Our results suggest that the identification of the deletion extent can provide prognostic markers, predictive of NF2 phenotypes, and potential therapeutic targets, thus overall improving patient management.

The epilepsy-associated protein PCDH19 undergoes NMDA receptor-dependent proteolytic cleavage and regulates the expression of immediate-early genes.

Protocadherin-19 (PCDH19) is a synaptic cell-adhesion molecule encoded by X-linked PCDH19, a gene linked with epilepsy. Here, we report a synapse-to-nucleus signaling pathway through which PCDH19 bridges neuronal activity with gene expression. In particular, we describe the NMDA receptor (NMDAR)-dependent proteolytic cleavage of PCDH19, which leads to the generation of a PCDH19 C-terminal fragment (CTF) able to enter the nucleus. We demonstrate that PCDH19 CTF associates with chromatin and with the chromatin remodeler lysine-specific demethylase 1 (LSD1) and regulates expression of immediate-early genes (IEGs). Our results are consistent with a model whereby PCDH19 favors maintenance of neuronal homeostasis via negative feedback regulation of IEG expression and provide a key to interpreting PCDH19-related hyperexcitability.

Human airway organoids and microplastic fibers: A new exposure model for emerging contaminants.

Three-dimensional (3D) structured organoids are the most advanced in vitro models for studying human health effects, but their application to evaluate the biological effects associated with microplastic exposure was neglected until now. Fibers from synthetic clothes and fabrics are a major source of airborne microplastics, and their release from dryer machines is poorly understood. We quantified and characterized the microplastic fibers (MPFs) released in the exhaust filter of a household dryer and tested their effects on airway organoids (1, 10, and 50 µg mL-1) by optical microscopy, scanning electron microscopy (SEM), confocal microscopy and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). While the presence of MPFs did not inhibit organoid growth, we observed a significant reduction of SCGB1A1 gene expression related to club cell functionality and a polarized cell growth along the fibers. The MPFs did not cause relevant inflammation or oxidative stress but were coated with a cellular layer, resulting in the inclusion of fibers in the organoid. This effect could have long-term implications regarding lung epithelial cells undergoing repair. This exposure study using human airway organoids proved suitability of the model for studying the effects of airborne microplastic contamination on humans and could form the basis for further research regarding the toxicological assessment of emerging contaminants such as micro- or nanoplastics.

Evolution Increases Primates Brain Complexity Extending RbFOX1 Splicing Activity to LSD1 Modulation.

Recent branching (100 MYA) of the mammalian evolutionary tree has enhanced brain complexity and functions at the putative cost of increased emotional circuitry vulnerability. Thus, to better understand psychopathology, a burden for the modern society, novel approaches should exploit evolutionary aspects of psychiatric-relevant molecular pathways. A handful of genes is nowadays tightly associated to psychiatric disorders. Among them, neuronal-enriched RbFOX1 modifies the activity of synaptic regulators in response to neuronal activity, keeping excitability within healthy domains. We here dissect a higher primates-restricted interaction between RbFOX1 and the transcriptional corepressor Lysine Specific Demethylase 1 (LSD1/KDM1A). A single nucleotide variation (AA to AG) in LSD1 gene appeared in higher primates and humans, endowing RbFOX1 with the ability to promote the alternative usage of a novel 3' AG splice site, which extends LSD1 exon E9 in the upstream intron (E9-long). Exon E9-long regulates LSD1 levels by Nonsense-Mediated mRNA Decay. As reintroduction of the archaic LSD1 variant (AA) abolishes E9-long splicing, the novel 3' AG splice site is necessary for RbFOX1 to control LSD1 levels. LSD1 is a homeostatic immediate early genes (IEGs) regulator playing a relevant part in environmental stress-response. In primates and humans, inclusion of LSD1 as RbFOX1 target provides RbFOX1 with the additional ability to regulate the IEGs. These data, together with extensive RbFOX1 involvement in psychiatric disorders and its stress-dependent regulation in male mice, suggest the RbFOX1-LSD1-IEGs axis as an evolutionary recent psychiatric-relevant pathway. Notably, outside the nervous system, RbFOX2-dependent LSD1 modulation could be a candidate deregulated mechanism in cancer.SIGNIFICANCE STATEMENT To be better understood, anxiety and depression need large human genetics studies aimed at further resolving the often ambiguous, aberrant neuronal pathomechanisms that impact corticolimbic circuitry physiology. Several genetic associations of the alternative splicing regulator RbFOX1 with psychiatric conditions suggest homeostatic unbalance as a neuronal signature of psychopathology. Here we move a step forward, characterizing a disease-relevant higher primates-specific pathway by which RbFOX1 acquires the ability to regulate neuronal levels of Lysine Specific Demethylase 1, an epigenetic modulator of environmental stress response. Thus, two brain-enriched enzymes, independently shown to homeostatically protect neurons with a clear readout in terms of emotional behavior in lower mammals, establish in higher primates and humans a new functional cooperation enhancing the complexity of environmental adaptation and stress vulnerability.

Identification of the best housekeeping gene for RT-qPCR analysis of human pancreatic organoids.

In the last few years, there has been a considerable increase in the use of organoids, which is a new three-dimensional culture technology applied in scientific research. The main reasons for their extensive use are their plasticity and multiple applications, including in regenerative medicine and the screening of new drugs. The aim of this study was to better understand these structures by focusing on the choice of the best housekeeping gene (HKG) to perform accurate molecular analysis on such a heterogeneous system. This feature should not be underestimated because the inappropriate use of a HKG can lead to misleading data and incorrect results, especially when the subject of the study is innovative and not totally explored like organoids. We focused our attention on the newly described human pancreatic organoids (hPOs) and compared 12 well-known HKGs (ACTB, B2M, EF1α, GAPDH, GUSB, HPRT, PPIA, RNA18S, RPL13A TBP, UBC and YWHAZ). Four different statistical algorithms (NormFinder, geNorm, BestKeeper and ΔCt) were applied to estimate the expression stability of each HKG, and RefFinder was used to identify the most suitable genes for RT-qPCR data normalization. Our results showed that the intragroup and intergroup comparisons could influence the best choice of the HKG, making clear that the identification of a stable reference gene for accurate and reproducible RT-qPCR data normalization remains a critical issue. In summary, this is the first report on HKGs in human organoids, and this work provides a strong basis to pave the way for further gene analysis in hPOs.

Optical tuning of dielectric nanoantennas for thermo-optically reconfigurable nonlinear metasurfaces.

We demonstrate optically tunable control of second-harmonic generation in all-dielectric nanoantennas: by using a control beam that is absorbed by the nanoresonator, we thermo-optically change the refractive index of the radiating element to modulate the amplitude of the second-harmonic signal. For a moderate temperature increase of roughly 40 K, modulation of the efficiency up to 60% is demonstrated; this large tunability of the single meta-atom response paves the way to exciting avenues for reconfigurable homogeneous and heterogeneous metasurfaces.

Chondrogenic and BMP-4 primings confer osteogenesis potential to human cord blood mesenchymal stromal cells delivered with biphasic calcium phosphate ceramics.

Bone marrow mesenchymal stem/stromal cells (BMSCs) show great promise for bone repair, however they are isolated by an invasive bone marrow harvest and their regenerative potential decreases with age. Conversely, cord blood can be collected non-invasively after birth and contains MSCs (CBMSCs) that can be stored for future use. However, whether CBMSCs can replace BMSCs targeting bone repair is unknown. This study evaluates the in vitro osteogenic potential of unprimed, osteogenically primed, or chondrogenically primed CBMSCs and BMSCs and their in vivo bone forming capacity following ectopic implantation on biphasic calcium phosphate ceramics in nude mice. In vitro, alkaline phosphatase (intracellular, extracellular, and gene expression), and secretion of osteogenic cytokines (osteoprotegerin and osteocalcin) was significantly higher in BMSCs compared with CBMSCs, while CBMSCs demonstrated superior chondrogenic differentiation and secretion of interleukins IL-6 and IL-8. BMSCs yielded significantly more cell engraftment and ectopic bone formation compared to CBMSCs. However, priming of CBMSCs with either chondrogenic or BMP-4 supplements led to bone formation by CBMSCs. This study is the first direct quantification of the bone forming abilities of BMSCs and CBMSCs in vivo and, while revealing the innate superiority of BMSCs for bone repair, it provides avenues to induce osteogenesis by CBMSCs.

Rationale, Relevance, and Limits of Stress-Induced Psychopathology in Rodents as Models for Psychiatry Research: An Introductory Overview.

Emotional and cognitive information processing represent higher-order brain functions. They require coordinated interaction of specialized brain areas via a complex spatial and temporal equilibrium among neuronal cell-autonomous, circuitry, and network mechanisms. The delicate balance can be corrupted by stressful experiences, increasing the risk of developing psychopathologies in vulnerable individuals. Neuropsychiatric disorders affect twenty percent of the western world population, but therapies are still not effective for some patients. Elusive knowledge of molecular pathomechanisms and scarcity of objective biomarkers in humans present complex challenges, while the adoption of rodent models helps to improve our understanding of disease correlate and aids the search for novel pharmacological targets. Stress administration represents a strategy to induce, trace, and modify molecular and behavioral endophenotypes of mood disorders in animals. However, a mouse or rat model will only display one or a few endophenotypes of a specific human psychopathology, which cannot be in any case recapitulated as a whole. To override this issue, shared criteria have been adopted to deconstruct neuropsychiatric disorders, i.e., depression, into specific behavioral aspects, and inherent neurobiological substrates, also recognizable in lower mammals. In this work, we provide a rationale for rodent models of stress administration. In particular, comparing each rodent model with a real-life human traumatic experience, we intend to suggest an introductive guide to better comprehend and interpret these paradigms.

Endocannabinoid-Epigenetic Cross-Talk: A Bridge toward Stress Coping.

There is no argument with regard to the physical and psychological stress-related nature of neuropsychiatric disorders. Yet, the mechanisms that facilitate disease onset starting from molecular stress responses are elusive. Environmental stress challenges individuals' equilibrium, enhancing homeostatic request in the attempt to steer down arousal-instrumental molecular pathways that underlie hypervigilance and anxiety. A relevant homeostatic pathway is the endocannabinoid system (ECS). In this review, we summarize recent discoveries unambiguously listing ECS as a stress coping mechanism. As stress evokes huge excitatory responses in emotional-relevant limbic areas, the ECS limits glutamate release via 2-arachydonilglycerol (2-AG) stress-induced synthesis and retrograde cannabinoid 1 (CB1)-receptor activation at the synapse. However, ECS shows intrinsic vulnerability as 2-AG overstimulation by chronic stress rapidly leads to CB1-receptor desensitization. In this review, we emphasize the protective role of 2-AG in stress-response termination and stress resiliency. Interestingly, we discuss ECS regulation with a further nuclear homeostatic system whose nature is exquisitely epigenetic, orchestrated by Lysine Specific Demethylase 1. We here emphasize a remarkable example of stress-coping network where transcriptional homeostasis subserves synaptic and behavioral adaptation, aiming at reducing psychiatric effects of traumatic experiences.

Characterization of integrated waveguides by atomic-force-microscopy-assisted mid-infrared imaging and spectroscopy.

A novel spectroscopy technique to enable the rapid characterization of discrete mid-infrared integrated photonic waveguides is demonstrated. The technique utilizes lithography patterned polymer blocks that absorb light strongly within the molecular fingerprint region. These act as integrated waveguide detectors when combined with an atomic force microscope that measures the photothermal expansion when infrared light is guided to the block. As a proof of concept, the technique is used to experimentally characterize propagation loss and grating coupler response of Ge-on-Si waveguides at wavelengths from 6 to 10 µm. In addition, when the microscope is operated in scanning mode at fixed wavelength, the guided mode exiting the output facet is imaged with a lateral resolution better than 500 nm i.e. below the diffraction limit. The characterization technique can be applied to any mid-infrared waveguide platform and can provide non-destructive in-situ testing of discrete waveguide components.

From Food Waste to Innovative Biomaterial: Sea Urchin-Derived Collagen for Applications in Skin Regenerative Medicine.

Collagen-based skin-like scaffolds (CBSS) are promising alternatives to skin grafts to repair wounds and injuries. In this work, we propose that the common marine invertebrate sea urchin represents a promising and eco-friendly source of native collagen to develop innovative CBSS for skin injury treatment. Sea urchin food waste after gonad removal was here used to extract fibrillar glycosaminoglycan (GAG)-rich collagen to produce bilayer (2D + 3D) CBSS. Microstructure, mechanical stability, permeability to water and proteins, ability to exclude bacteria and act as scaffolding for fibroblasts were evaluated. Our data show that the thin and dense 2D collagen membrane strongly reduces water evaporation (less than 5% of water passes through the membrane after 7 days) and protein diffusion (less than 2% of BSA passes after 7 days), and acts as a barrier against bacterial infiltration (more than 99% of the different tested bacterial species is retained by the 2D collagen membrane up to 48 h), thus functionally mimicking the epidermal layer. The thick sponge-like 3D collagen scaffold, structurally and functionally resembling the dermal layer, is mechanically stable in wet conditions, biocompatible in vitro (seeded fibroblasts are viable and proliferate), and efficiently acts as a scaffold for fibroblast infiltration. Thus, thanks to their chemical and biological properties, CBSS derived from sea urchins might represent a promising, eco-friendly, and economically sustainable biomaterial for tissue regenerative medicine.

Psychiatric Disorders and lncRNAs: A Synaptic Match.

Psychiatric disorders represent a heterogeneous class of multifactorial mental diseases whose origin entails a pathogenic integration of genetic and environmental influences. Incidence of these pathologies is dangerously high, as more than 20% of the Western population is affected. Despite the diverse origins of specific molecular dysfunctions, these pathologies entail disruption of fine synaptic regulation, which is fundamental to behavioral adaptation to the environment. The synapses, as functional units of cognition, represent major evolutionary targets. Consistently, fine synaptic tuning occurs at several levels, involving a novel class of molecular regulators known as long non-coding RNAs (lncRNAs). Non-coding RNAs operate mainly in mammals as epigenetic modifiers and enhancers of proteome diversity. The prominent evolutionary expansion of the gene number of lncRNAs in mammals, particularly in primates and humans, and their preferential neuronal expression does represent a driving force that enhanced the layering of synaptic control mechanisms. In the last few years, remarkable alterations of the expression of lncRNAs have been reported in psychiatric conditions such as schizophrenia, autism, and depression, suggesting unprecedented mechanistic insights into disruption of fine synaptic tuning underlying severe behavioral manifestations of psychosis. In this review, we integrate literature data from rodent pathological models and human evidence that proposes the biology of lncRNAs as a promising field of neuropsychiatric investigation.

Termination of acute stress response by the endocannabinoid system is regulated through lysine-specific demethylase 1-mediated transcriptional repression of 2-AG hydrolases ABHD6 and MAGL.

Acute environmental stress rarely implies long-lasting neurophysiological and behavioral alterations. On the contrary, chronic stress exerts a potent toxic effect at the glutamatergic synapse whose altered physiology has been recognized as a core trait of neuropsychiatric disorders. The endocannabinoid system (ECS) plays an important role in the homeostatic response to acute stress. In particular, stress induces synthesis of endocannabinoid (eCB) 2-arachidonyl glycerol (2-AG). 2-AG stimulates presynaptic cannabinoid 1 (CB1) receptor contributing to stress response termination through inhibition of glutamate release, restraining thereafter anxiety arousal. We employ mouse models of stress response coupled to gene expression analyses, unravelling that in response to acute psychosocial stress in the mouse hippocampus, ECS-mediated synaptic modulation is enhanced via transcriptional repression of two enzymes involved in 2-AG degradation: α/ß-hydrolase domain containing 6 (ABHD6) and monoacylglycerol lipase (MAGL). Such a process is orchestrated by the epigenetic corepressor LSD1 who directly interacts with promoter regulatory regions of Abhd6 and Magl. Remarkably, negative transcriptional control of Abhd6 and Magl is lost in the hippocampus upon chronic psychosocial stress, possibly contributing to trauma-induced drift of synapse physiology toward uncontrolled glutamate transmission. We previously showed that in mice lysine-specific demethylase 1 (LSD1) increases its hippocampal expression in response to psychosocial stress preventing excessive consolidation of anxiety-related plasticity. In this work, we unravel a nodal epigenetic modulation of eCB turn over, shedding new light on the molecular substrate of converging stress-terminating effects displayed by ECS and LSD1.

SRF and SRFΔ5 Splicing Isoform Recruit Corepressor LSD1/KDM1A Modifying Structural Neuroplasticity and Environmental Stress Response.

Ten to 20% of western countries population suffers from major depression disorder (MDD). Stressful life events represent the main environmental risk factor contributing to the onset of MDD and other stress-related neuropsychiatric disorders. In this regard, investigating brain physiology of stress response underlying the remarkable individual variability in terms of behavioral outcome may uncover stress-vulnerability pathways as a source of candidate targets for conceptually new antidepressant treatments. Serum response factor (SRF) has been addressed as a stress transducer via promoting inherent experience-induced Immediate Early Genes (IEGs) expression in neurons. However, in resting conditions, SRF also represents a transcriptional repressor able to assemble the core LSD1/CoREST/HDAC2 corepressor complex, including demethylase and deacetylase activities. We here show that dominant negative SRF splicing isoform lacking most part of the transactivation domain, namely SRFΔ5, owes its transcriptional repressive behavior to the ability of assembling LSD1/CoREST/HDAC2 corepressor complex meanwhile losing its affinity for transcription-permissive cofactor ELK1. SRFΔ5 is highly expressed in the brain and developmentally regulated. In the light of its activity as negative modulator of dendritic spine density, SRFΔ5 increase along with brain maturation suggests a role in synaptic pruning. Upon acute psychosocial stress, SRFΔ5 isoform transiently increases its levels. Remarkably, when stress is chronically repeated, a different picture occurs where SRF protein becomes stably upregulated in vulnerable mice but not in resilient animals. These data suggest a role for SRFΔ5 that is restricted to acute stress response, while positive modulation of SRF during chronic stress matches the criteria for stress-vulnerability hallmark.

FOXP1 circular RNA sustains mesenchymal stem cell identity via microRNA inhibition.

Stem cell identity and plasticity are controlled by master regulatory genes and complex circuits also involving non-coding RNAs. Circular RNAs (circRNAs) are a class of RNAs generated from protein-coding genes by backsplicing, resulting in stable RNA structures devoid of free 5' and 3' ends. Little is known of the mechanisms of action of circRNAs, let alone in stem cell biology. In this study, for the first time, we determined that a circRNA controls mesenchymal stem cell (MSC) identity and differentiation. High-throughput MSC expression profiling from different tissues revealed a large number of expressed circRNAs. Among those, circFOXP1 was enriched in MSCs compared to differentiated mesodermal derivatives. Silencing of circFOXP1 dramatically impaired MSC differentiation in culture and in vivo. Furthermore, we demonstrated a direct interaction between circFOXP1 and miR-17-3p/miR-127-5p, which results in the modulation of non-canonical Wnt and EGFR pathways. Finally, we addressed the interplay between canonical and non-canonical Wnt pathways. Reprogramming to pluripotency of MSCs reduced circFOXP1 and non-canonical Wnt, whereas canonical Wnt was boosted. The opposing effect was observed during generation of MSCs from human pluripotent stem cells. Our results provide unprecedented evidence for a regulatory role for circFOXP1 as a gatekeeper of pivotal stem cell molecular networks.

Tip-Enhanced Infrared Difference-Nanospectroscopy of the Proton Pump Activity of Bacteriorhodopsin in Single Purple Membrane Patches.

Photosensitive proteins embedded in the cell membrane (about 5 nm thickness) act as photoactivated proton pumps, ion gates, enzymes, or more generally, as initiators of stimuli for the cell activity. They are composed of a protein backbone and a covalently bound cofactor (e.g. the retinal chromophore in bacteriorhodopsin (BR), channelrhodopsin, and other opsins). The light-induced conformational changes of both the cofactor and the protein are at the basis of the physiological functions of photosensitive proteins. Despite the dramatic development of microscopy techniques, investigating conformational changes of proteins at the membrane monolayer level is still a big challenge. Techniques based on atomic force microscopy (AFM) can detect electric currents through protein monolayers and even molecular binding forces in single-protein molecules but not the conformational changes. For the latter, Fourier-transform infrared spectroscopy (FTIR) using difference-spectroscopy mode is typically employed, but it is performed on macroscopic liquid suspensions or thick films containing large amounts of purified photosensitive proteins. In this work, we develop AFM-assisted, tip-enhanced infrared difference-nanospectroscopy to investigate light-induced conformational changes of the bacteriorhodopsin mutant D96N in single submicrometric native purple membrane patches. We obtain a significant improvement compared with the signal-to-noise ratio of standard IR nanospectroscopy techniques by exploiting the field enhancement in the plasmonic nanogap that forms between a gold-coated AFM probe tip and an ultraflat gold surface, as further supported by electromagnetic and thermal simulations. IR difference-spectra in the 1450-1800 cm-1 range are recorded from individual patches as thin as 10 nm, with a diameter of less than 500 nm, well beyond the diffraction limit for FTIR microspectroscopy. We find clear spectroscopic evidence of a branching of the photocycle for BR molecules in direct contact with the gold surfaces, with equal amounts of proteins either following the standard proton-pump photocycle or being trapped in an intermediate state not directly contributing to light-induced proton transport. Our results are particularly relevant for BR-based optoelectronic and energy-harvesting devices, where BR molecular monolayers are put in contact with metal surfaces, and, more generally, for AFM-based IR spectroscopy studies of conformational changes of proteins embedded in intrinsically heterogeneous native cell membranes.

Multiple Layers of CDK5R1 Regulation in Alzheimer's Disease Implicate Long Non-Coding RNAs.

Cyclin-dependent kinase 5 regulatory subunit 1 (CDK5R1) gene encodes for p35, the main activator of Cyclin-dependent kinase 5 (CDK5). The active p35/CDK5 complex is involved in numerous aspects of brain development and function, and its deregulation is closely associated to Alzheimer's disease (AD) onset and progression. We recently showed that miR-15/107 family can negatively regulate CDK5R1 expression modifying mRNA stability. Interestingly, miRNAs belonging to miR-15/107 family are downregulated in AD brain while CDK5R1 is upregulated. Long non-coding RNAs (lncRNAs) are emerging as master regulators of gene expression, including miRNAs, and their dysregulation has been implicated in the pathogenesis of AD. Here, we evaluated the existence of an additional layer of CDK5R1 expression regulation provided by lncRNAs. In particular, we focused on three lncRNAs potentially regulating CDK5R1 expression levels, based on existing data: NEAT1, HOTAIR, and MALAT1. We demonstrated that NEAT1 and HOTAIR negatively regulate CDK5R1 mRNA levels, while MALAT1 has a positive effect. We also showed that all three lncRNAs positively control miR-15/107 family of miRNAs. Moreover, we evaluated the expression of NEAT1, HOTAIR, and MALAT1 in AD and control brain tissues. Interestingly, NEAT1 displayed increased expression levels in temporal cortex and hippocampus of AD patients. Interestingly, we observed a strong positive correlation between CDK5R1 and NEAT1 expression levels in brain tissues, suggesting a possible neuroprotective role of NEAT1 in AD to compensate for increased CDK5R1 levels. Overall, our work provides evidence of another level of CDK5R1 expression regulation mediated by lncRNAs and points to NEAT1 as a biomarker, as well as a potential pharmacological target for AD therapy.

Acute Stress-Induced Epigenetic Modulations and Their Potential Protective Role Toward Depression.

Psychiatric disorders entail maladaptive processes impairing individuals' ability to appropriately interface with environment. Among them, depression is characterized by diverse debilitating symptoms including hopelessness and anhedonia, dramatically impacting the propensity to live a social and active life and seriously affecting working capability. Relevantly, besides genetic predisposition, foremost risk factors are stress-related, such as experiencing chronic psychosocial stress-including bullying, mobbing and abuse-, and undergoing economic crisis or chronic illnesses. In the last few years the field of epigenetics promised to understand core mechanisms of gene-environment crosstalk, contributing to get into pathogenic processes of many disorders highly influenced by stressful life conditions. However, still very little is known about mechanisms that tune gene expression to adapt to the external milieu. In this Perspective article, we discuss a set of protective, functionally convergent epigenetic processes induced by acute stress in the rodent hippocampus and devoted to the negative modulation of stress-induced immediate early genes (IEGs) transcription, hindering stress-driven morphostructural modifications of corticolimbic circuitry. We also suggest that chronic stress damaging protective epigenetic mechanisms, could bias the functional trajectory of stress-induced neuronal morphostructural modification from adaptive to maladaptive, contributing to the onset of depression in vulnerable individuals. A better understanding of the epigenetic response to stress will be pivotal to new avenues of therapeutic intervention to treat depression, especially in light of limited efficacy of available antidepressant drugs.

Identification of an atypical microdeletion generating the RNF135-SUZ12 chimeric gene and causing a position effect in an NF1 patient with overgrowth.

Neurofibromatosis type I (NF1) microdeletion syndrome, which is present in 4-11% of NF1 patients, is associated with a severe phenotype as it is caused by the deletion of NF1 and other genes in the 17q11.2 region. The variable expressivity of the disease makes it challenging to establish genotype-phenotype correlations, which also affects prognosis and counselling. We here describe a 3-year-old NF1 patient with an atypical deletion and a complex phenotype. The patient showed overgrowth, café au lait spots, inguinal freckling, and neurological abnormalities. The extent of the deletion was determined by means of array comparative genomic hybridisation, and its breakpoints were isolated by means of long-range polymerase chain reaction. Sequence analysis of the deletion junction fragment revealed the occurrence of an Alu-mediated recombination that led to the generation of a chimeric gene consisting of three exons of RNF135 and eleven exons of SUZ12. Interestingly, the deletion shares a common RNF135-centred region with another deletion described in a non-NF1 patient with overgrowth. In comparison with the normal RNF135 allele, the chimeric transcript was 350-fold over-expressed in peripheral blood, and the ADAP2 gene located upstream of RNF135 was also up-regulated. In line with this, the deletion causes the loss of a chromatin TD boundary, which entails the aberrant adoption of distal cis-acting regulatory elements. These findings suggest that RNF135 haploinsufficiency is related to overgrowth in patients with NF1 microdeletion syndrome and, for the first time, strongly indicate a position effect that warrants further genotype-phenotype correlation studies to investigate the possible existence of previously unknown pathogenic mechanisms.

eEF2K/eEF2 Pathway Controls the Excitation/Inhibition Balance and Susceptibility to Epileptic Seizures.

Alterations in the balance of inhibitory and excitatory synaptic transmission have been implicated in the pathogenesis of neurological disorders such as epilepsy. Eukaryotic elongation factor 2 kinase (eEF2K) is a highly regulated, ubiquitous kinase involved in the control of protein translation. Here, we show that eEF2K activity negatively regulates GABAergic synaptic transmission. Indeed, loss of eEF2K increases GABAergic synaptic transmission by upregulating the presynaptic protein Synapsin 2b and α5-containing GABAA receptors and thus interferes with the excitation/inhibition balance. This cellular phenotype is accompanied by an increased resistance to epilepsy and an impairment of only a specific hippocampal-dependent fear conditioning. From a clinical perspective, our results identify eEF2K as a potential novel target for antiepileptic drugs, since pharmacological and genetic inhibition of eEF2K can revert the epileptic phenotype in a mouse model of human epilepsy.