miRNA Dysregulation Drives Neuronal Intracellular Chloride Accumulation in Down Syndrome

Down syndrome (DS) is caused by the presence of an extra-copy of chromosome 21 and is the most frequent genetic cause of mental retardation. DS cognitive disabilities primary arise from the triplication of dosage-sensitive genes on chromosome 21. However, a global dysregulation in the expression of extra-chromosome 21 genes greatly complicates the understanding of the underling pathological mechanisms. We have recently found that cognitive impairment in the Ts65Dn mouse model of DS depends on the upregulation of a non-triplicated gene encoding for the chloride importer NKCC1, which we found increased also in brain tissue from individuals with DS. Consequently, the intracellular chloride concentration is increased and GABAergic signaling, through chloride-permeable GABAA receptors, is depolarizing rather than hyperpolarizing. Here, we aimed at addressing the molecular mechanisms responsible for NKCC1 overexpression in DS. Real-time qPRC and Western Blot analysis showed that NKCC1 overexpression in trisomic neurons does not derive from greater mRNA transcription or decreased protein turnover but rather from a diminished translational repression exerted on the 3\u2019 untranslated region (3'UTR) of the gene. As 3\u2019 UTRs are the preferred sites of action of microRNAs (miRs), we applied a combination of bioinformatics prediction tools and gene expression screening to identify candidate miRs downregulated in trisomic samples that could mediate NKCC1 overexpression. Our results show that different candidates miRs interact with NKCC1 3\u2019UTR and repress its expression. Additionally, overexpression of the same miRs can normalize NKCC1 levels and intracellular chloride concentration in trisomic neurons, restoring GABAergic inhibitory signaling at the network level as shown by Multi-Electrode Array recordings. Our findings will help to elucidate molecular pathways dysregulated in DS and suggest possible targets for future therapeutic intervention

53 a neuro specific gene therapy approach to treat cognitive impairment in down syndrome by rna interference

Down syndrome (DS) is a genetic disorder caused by the presence of a third copy of chromosome 21. DS affects multiple organs, resulting in characteristic facial features, muscular hypotonia, heart defects, brain development impairment, and varying degrees of intellectual disability. Trisomic mouse models of DS reproduce the main cognitive disabilities of the human syndrome. In particular, DS mice show structural and functional synaptic impairment as well as learning and memory deficits, largely determined by altered GABAergic transmission through chloride-permeable GABAa receptors (GABAaR). In particular, we have recently found that intracellular chloride accumulation shifts GABAAR-mediated signaling from inhibitory to excitatory in the adult brain of the Ts65Dn mouse model of DS. Accordingly, intracellular chloride accumulation was paralleled by increased expression of the chloride importer NKCC1 (Na-K-Cl cotransporter) in the brains of both trisomic mice and DS patients.Our findings on NKCC1 as a pivotal molecular target for the rescue of cognitive deficits in DS opens the possibility of a gene therapy approach to treat the disease. Here, to normalize NKCC1 expression and rescue synaptic dysfunctions as well as cognitive deficits in Ts65Dn mice we have developed and characterized a knock-down approach to normalize NKCC1 activity. Reducing the expression of the chloride importer NKCC1 by RNA interference restored GABAAR-mediated inhibition and also rescued the structural dendritic deficits found in trisomic neurons in vitro. Most importantly, focal administration of an AAV expressing a silencing RNA under the transcriptional control of a neuron-specific promoter in the hippocampus of Ts65Dn animals mediated NKCC1 knockdown in vivo and rescued behavioral performance on different learning and memory tests at levels undistinguishable from those of WT mice.Our findings demonstrate that NKCC1 overexpression drives excitatory GABAAR signaling in trisomic cells, leading to structural neuronal abnormalities and behavioral impairments in DS mice. Moreover, our study identifies a new gene therapy target for treatments aimed at rescuing cognitive disabilities in individuals with DS

Neurotrophic-mimetic strategy to rescue synaptic plasticity and cognitive functions in a mouse model of Down syndrome

Down syndrome (DS) or trisomy 21 is the most frequent genetic cause of intellectual disability in children and adults. Although numerous studies have shown that cognitive impairment possibly arises from dysfunction of the hippocampal circuit, there has been little progress in defining effective treatments. Previous studies have shown that impaired synaptic plasticity of mature hippocampal neurons and decreased hippocampal adult neurogenesis are main determinants in reducing cognitive functions in DS animal models. Currently, most preclinical therapeutic approaches in DS mice have focused on rescuing either one or the other of these impairments. Here, we have found that the expression of Brain-Derived Neurotrophic Factor (BDNF) is decreased in the brains of individuals with DS. Interestingly, a large body of literature indicates that BDNF signaling modulates both synaptic plasticity, and adult neurogenesis. Therefore, we propose here to promote BDNF/TrkB signaling using a BDNF-mimetic drug with the twofold aim of rescuing synaptic plasticity and increase adult neurogenesis toward the rescue of cognitive functions in the Ts65Dn mouse model of DS. Our results indicate that indeed promoting BDNF/TrkB signaling rescued hippocampal synaptic plasticity, increased hippocampal adult neurogenesis and restored cognitive performances in different behavioral tasks in Ts65Dn mice. The molecular mechanisms of impaired BDNF/TrkB signaling in trisomic mice are currently under investigation. Overall, our experiments show in a reliable animal model of DS the efficacy of a novel and multifaceted therapeutic approach with good potential to be translated into clinical practice

Assessing across-scale optical diversity and productivity relationships in grasslands of the Italian alps

The linearity and scale-dependency of ecosystem biodiversity and productivity relationships (BPRs) have been under intense debate. In a changing climate, monitoring BPRs within and across different ecosystem types is crucial, and novel remote sensing tools such as the Sentinel-2 (S2) may be adopted to retrieve ecosystem diversity information and to investigate optical diversity and productivity patterns. But are the S2 spectral and spatial resolutions suitable to detect relationships between optical diversity and productivity? In this study, we implemented an integrated analysis of spatial patterns of grassland productivity and optical diversity using optical remote sensing and Eddy Covariance data. Across-scale optical diversity and ecosystem productivity patterns were analyzed for different grassland associations with a wide range of productivity. Using airborne optical data to simulate S2, we provided empirical evidence that the best optical proxies of ecosystem productivity were linearly correlated with optical diversity. Correlation analysis at increasing pixel sizes proved an evident scale-dependency of the relationships between optical diversity and productivity. The results indicate the strong potential of S2 for future large-scale assessment of across-ecosystem dynamics at upper levels of observation

Neurotrophic-mimetic strategy to rescue synaptic plasticity and cognitive functions in a mouse model of Down syndrome

Down syndrome (DS) is caused by the triplication of human chromosome 21, and it is the most frequent genetic cause of cognitive disabilities. Although numerous studies have shown that cognitive impairment possibly arises from dysfunction of the hippocampal circuit, there is little insight into neurobiological bases of these abnormalities, and thus, there has been little progress in defining effective treatments. The trisomic Ts65Dn mouse model of DS reproduces the essential cognitive disabilities of the human syndrome. Previous studies in this model have shown that impaired synaptic plasticity of mature hippocampal neurons and decreased hippocampal adult neurogenesis are main determinants in reducing cognitive functions in DS animal models. Currently, most preclinical therapeutic approaches in the DS mouse models have focused on rescuing either one or the other of these impairments. Interestingly, we have found that the expression of Brain-Derived Neurotrophic Factor (BDNF) is decreased in the brains of DS patients. On the other hand, BDNF signaling modulates both synaptic plasticity, and adult neurogenesis. Therefore, we propose to promote BDNF/TrkB signaling using a BDNF-mimetic drug with the twofold aim of rescuing synaptic plasticity and increase adult neurogenesis toward the rescue of cognitive functions in Ts65Dn mice. Our results indicate that indeed promoting BDNF/TrkB signaling rescued hippocampal synaptic plasticity, increased dentate adult neurogenesis and restored cognitive performances in different behavioral tasks in Ts65Dn mice. Overall, our experiments show in a reliable animal model of DS the efficacy of a novel and multifaceted therapeutic approach with good potential to be translated into clinical practice

Aerobic exercise and a BDNF-mimetic therapy rescue learning and memory in a mouse model of Down syndrome

Abstract Down syndrome (DS) is caused by the triplication of human chromosome 21 and represents the most frequent genetic cause of intellectual disability. The trisomic Ts65Dn mouse model of DS shows synaptic deficits and reproduces the essential cognitive disabilities of the human syndrome. Aerobic exercise improved various neurophysiological dysfunctions in Ts65Dn mice, including hippocampal synaptic deficits, by promoting synaptogenesis and neurotransmission at glutamatergic terminals. Most importantly, the same intervention also prompted the recovery of hippocampal adult neurogenesis and synaptic plasticity and restored cognitive performance in trisomic mice. Additionally, the expression of brain-derived neurotrophic factor (BDNF) was markedly decreased in the hippocampus of patients with DS. Since the positive effect of exercise was paralleled by increased BDNF expression in trisomic mice, we investigated the effectiveness of a BDNF-mimetic treatment with 7,8-dihydroxyflavone at alleviating intellectual disabilities in the DS model. Pharmacological stimulation of BDNF signaling rescued synaptic plasticity and memory deficits in Ts65Dn mice. Based on our findings, Ts65Dn mice benefit from interventions aimed at promoting brain plasticity, and we provide evidence that BDNF signaling represents a potentially new pharmacological target for treatments aimed at rescuing cognitive disabilities in patients with DS

Integral representation of functionals defined on curves of W^1,p

Let I ⊂ ℝ be a bounded open interval, (I) be the family of all open subintervals of I and let p > 1. The aim of this paper is to give an integral representation result for abstract functionals F: W1,p(I;ℝn) × (I) → [0, + ∞) which are lower semicontinuous and satisfy suitable properties. In particular, we prove an integral representation theorem for the Г-limit of a sequence {Fh}h, of functionals of the form S0308210500012749_eqnU1 where each fh is a Borel function satisfying proper growth condition

Monitoring the evolution of plant photosynthetic performances using ground sun-induced fluorescence measurements

Plants subjected to biotic or abiotic stress factors can respond with adjustments in their biochemical and physiological processes. These adjustments are often accompanied by changes in reflectance, transmittance, and absorbance at leaf and canopy level.This contribution aims to understand how optical signals linked to plant physiology changes after the application of two different chemical agents: an herbicide blocking the electron-transfer mechanisms in the photosynthetic apparatus (Chlortoluron) and an anti-transpirant chemical known to reduce plant transpiration (Vapor Gard) by sealing the stomata. The chemicals have been applied on 9 grass plots with different concentrations. Three plots have been kept not-treated and used as control. Canopy high resolution spectral measurements and CO2 fluxes have been collected daily on the same sampling area in each plot for the entire duration of the experiment to monitor the temporal evolution of the stress effects.Spectral measurements have been used to estimate the sun-induced chlorophyll fluorescence in both the red (SIF687) and far-red region (SIF760), the Photochemical Reflectance Index (PRI) linked to the xanthophyll-related heat dissipation and several traditional vegetation indices related to canopy greenness and chlorophyll concentration. SIF687 and SIF760 were estimated with spectral fitting methods spectrally modeling the radiance collected with very high resolution spectrometers in the oxygen absorption O2-A and O2-B bands.The applied treatments induced a variation of plant photosynthetic functioning modulated according to the level of herbicide concentration. Both SIF687 and SIF760 measured in Chlortoluron-treated grass plots were significantly higher than in the control plots. The highest dose caused fluorescence values to double in less than 3 hours while the reflectance signal at the same time was not affected confirming that the increase in fluorescence emission was only related to variations in the plant functional status not associated to changes in pigment content and composition. F687 and F760 values of treated plots decreased steeply in the following days. Fluorescence decline was accompanied by a decrease in chlorophyll content. Grass photosynthesis began to decline immediately after the herbicide application and continued in the following days. This result implies that fluorescence was negatively correlated to plant photosynthesis in an early phase of stress reaction and then the relation became positive in the following days. Thus the translation of fluorescence values to photosynthesis is not straightforward in this experiment. Lower doses affected fluorescence signal similarly but with a different temporal dynamic in both the initial rise and the recovery. Chlortoluron also caused an initial increase of PRI values followed by a gradual decline associated to the degradation of the pigment pool. The application of the anti-transpirant agent only slightly affected fluorescence emission and PRI probably because the photosynthetic system was not directly compromised.Sun-induced chlorophyll fluorescence allowed to monitor the temporal dynamics of plants’ functioning and recovery after the application of temporarily blocking photosynthesis agents. Further studies are ongoing to better understand the effects of stress on the fluorescence signal and the link to heat dissipation and photosynthesis