Neuroproteomic Analysis after SARS-CoV-2 Infection Reveals Overrepresented Neurodegeneration Pathways and Disrupted Metabolic Pathways.

Besides respiratory illness, SARS-CoV-2, the causative agent of COVID-19, leads to neurological symptoms. The molecular mechanisms leading to neuropathology after SARS-CoV-2 infection are sparsely explored. SARS-CoV-2 enters human cells via different receptors, including ACE-2, TMPRSS2, and TMEM106B. In this study, we used a human-induced pluripotent stem cell-derived neuronal model, which expresses ACE-2, TMPRSS2, TMEM106B, and other possible SARS-CoV-2 receptors, to evaluate its susceptibility to SARS-CoV-2 infection. The neurons were exposed to SARS-CoV-2, followed by RT-qPCR, immunocytochemistry, and proteomic analyses of the infected neurons. Our findings showed that SARS-CoV-2 infects neurons at a lower rate than other human cells; however, the virus could not replicate or produce infectious virions in this neuronal model. Despite the aborted SARS-CoV-2 replication, the infected neuronal nuclei showed irregular morphology compared to other human cells. Since cytokine storm is a significant effect of SARS-CoV-2 infection in COVID-19 patients, in addition to the direct neuronal infection, the neurons were treated with pre-conditioned media from SARS-CoV-2-infected lung cells, and the neuroproteomic changes were investigated. The limited SARS-CoV-2 infection in the neurons and the neurons treated with the pre-conditioned media showed changes in the neuroproteomic profile, particularly affecting mitochondrial proteins and apoptotic and metabolic pathways, which may lead to the development of neurological complications. The findings from our study uncover a possible mechanism behind SARS-CoV-2-mediated neuropathology that might contribute to the lingering effects of the virus on the human brain.

Secreted Amyloid Precursor Protein Alpha (sAPPα) Regulates the Cellular Proteome and Secretome of Mouse Primary Astrocytes.

Secreted amyloid precursor protein alpha (sAPPα), processed from a parent mammalian brain protein, amyloid precursor protein, can modulate learning and memory. Recently it has been shown to modulate the transcriptome and proteome of human neurons, including proteins with neurological functions. Here, we analysed whether the acute administration of sAPPα facilitated changes in the proteome and secretome of mouse primary astrocytes in culture. Astrocytes contribute to the neuronal processes of neurogenesis, synaptogenesis and synaptic plasticity. Cortical mouse astrocytes in culture were exposed to 1 nM sAPPα, and changes in both the whole-cell proteome (2 h) and the secretome (6 h) were identified with Sequential Window Acquisition of All Theoretical Fragment Ion Spectra-Mass Spectrometry (SWATH-MS). Differentially regulated proteins were identified in both the cellular proteome and secretome that are involved with neurologically related functions of the normal physiology of the brain and central nervous system. Groups of proteins have a relationship to APP and have roles in the modulation of cell morphology, vesicle dynamics and the myelin sheath. Some are related to pathways containing proteins whose genes have been previously implicated in Alzheimer's disease (AD). The secretome is also enriched in proteins related to Insulin Growth Factor 2 (IGF2) signaling and the extracellular matrix (ECM). There is the promise that a more specific investigation of these proteins will help to understand the mechanisms of how sAPPα signaling affects memory formation.

Effects of chronic cannabidiol in a mouse model of naturally occurring neuroinflammation, neurodegeneration, and spontaneous seizures.

Cannabidiol (CBD) has gained attention as a therapeutic agent and is purported to have immunomodulatory, neuroprotective, and anti-seizure effects. Here, we determined the effects of chronic CBD administration in a mouse model of CLN1 disease (Cln1-/-) that simultaneously exhibits neuroinflammation, neurodegeneration, and spontaneous seizures. Proteomic analysis showed that putative CBD receptors are expressed at similar levels in the brains of Cln1-/- mice compared to normal animals. Cln1-/- mice received an oral dose (100 mg/kg/day) of CBD for six months and were evaluated for changes in pathological markers of disease and seizures. Chronic cannabidiol administration was well-tolerated, high levels of CBD were detected in the brain, and markers of astrocytosis and microgliosis were reduced. However, CBD had no apparent effect on seizure frequency or neuron survival. These data are consistent with CBD having immunomodulatory effects. It is possible that a higher dose of CBD could also reduce neurodegeneration and seizure frequency.

Neutrophil-vascular interactions drive myeloperoxidase accumulation in the brain in Alzheimer's disease.

INTRODUCTION: Neutrophil accumulation is a well-established feature of Alzheimer's disease (AD) and has been linked to cognitive impairment by modulating disease-relevant neuroinflammatory and vascular pathways. Neutrophils express high levels of the oxidant-generating enzyme myeloperoxidase (MPO), however there has been controversy regarding the cellular source and localisation of MPO in the AD brain. MATERIALS AND METHODS: We used immunostaining and immunoassays to quantify the accumulation of neutrophils in human AD tissue microarrays and in the brains of APP/PS1 mice. We also used multiplexed immunolabelling to define the presence of NETs in AD. RESULTS: There was an increase in neutrophils in AD brains as well as in the murine APP/PS1 model of AD. Indeed, MPO expression was almost exclusively confined to S100A8-positive neutrophils in both human AD and murine APP/PS1 brains. The vascular localisation of neutrophils in both human AD and mouse models of AD was striking and driven by enhanced neutrophil adhesion to small vessels. We also observed rare infiltrating neutrophils and deposits of MPO around plaques. Citrullinated histone H3, a marker of neutrophil extracellular traps (NETs), was also detected in human AD cases at these sites, indicating the presence of extracellular MPO in the vasculature. Finally, there was a reduction in the endothelial glycocalyx in AD that may be responsible for non-productive neutrophil adhesion to the vasculature. CONCLUSION: Our report indicates that vascular changes may drive neutrophil adhesion and NETosis, and that neutrophil-derived MPO may lead to vascular oxidative stress and be a relevant therapeutic target in AD.

Effect of soluble amyloid precursor protein-alpha on adult hippocampal neurogenesis in a mouse model of Alzheimer's disease.

Soluble amyloid precursor protein-alpha (sAPPα) is a regulator of neuronal and memory mechanisms, while also having neurogenic and neuroprotective effects in the brain. As adult hippocampal neurogenesis is impaired in Alzheimer's disease, we tested the hypothesis that sAPPα delivery would rescue adult hippocampal neurogenesis in an APP/PS1 mouse model of Alzheimer's disease. An adeno-associated virus-9 (AAV9) encoding murine sAPPα was injected into the hippocampus of 8-month-old wild-type and APP/PS1 mice, and later two different thymidine analogues (XdU) were systemically injected to label adult-born cells at different time points after viral transduction. The proliferation of adult-born cells, cell survival after eight weeks, and cell differentiation into either neurons or astrocytes was studied. Proliferation was impaired in APP/PS1 mice but was restored to wild-type levels by viral expression of sAPPα. In contrast, sAPPα overexpression failed to rescue the survival of XdU+-labelled cells that was impaired in APP/PS1 mice, although it did cause a significant increase in the area density of astrocytes in the granule cell layer across both genotypes. Finally, viral expression of sAPPα reduced amyloid-beta plaque load in APP/PS1 mice in the dentate gyrus and somatosensory cortex. These data add further evidence that increased levels of sAPPα could be therapeutic for the cognitive decline in AD, in part through restoration of the proliferation of neural progenitor cells in adults.

Deficiency of the Lysosomal Protein CLN5 Alters Lysosomal Function and Movement.

Batten disease is a devastating, childhood, rare neurodegenerative disease characterised by the rapid deterioration of cognition and movement, leading to death within ten to thirty years of age. One of the thirteen Batten disease forms, CLN5 Batten disease, is caused by mutations in the CLN5 gene, leading to motor deficits, mental deterioration, cognitive impairment, visual impairment, and epileptic seizures in children. A characteristic pathology in CLN5 Batten disease is the defects in lysosomes, leading to neuronal dysfunction. In this study, we aimed to investigate the lysosomal changes in CLN5-deficient human neurons. We used an induced pluripotent stem cell system, which generates pure human cortical-like glutamatergic neurons. Using CRISPRi, we inhibited the expression of CLN5 in human neurons. The CLN5-deficient human neurons showed reduced acidic organelles and reduced lysosomal enzyme activity measured by microscopy and flow cytometry. Furthermore, the CLN5-deficient human neurons also showed impaired lysosomal movement-a phenotype that has never been reported in CLN5 Batten disease. Lysosomal trafficking is key to maintain local degradation of cellular wastes, especially in long neuronal projections, and our results from the human neuronal model present a key finding to understand the underlying lysosomal pathology in neurodegenerative diseases.

A schizophrenia risk factor induces marked anatomical deficits at GABAergic-dopaminergic synapses in the rat ventral tegmental area: Essential evidence for new targeted therapies.

To develop new therapies for schizophrenia, evidence accumulated over decades highlights the essential need to investigate the GABAergic synapses that presynaptically influence midbrain dopaminergic neurons. Since current technology restricts these studies to animals, and evidence accumulated in recent decades indicates a developmental origin of schizophrenia, we investigated synaptic changes in male rat offspring exposed to maternal immune activation (MIA), a schizophrenia risk factor. Using a novel combination of lentiviruses, peroxidase-immunogold double labeling, three-dimensional serial section transmission electron microscopy and stereology, we observed clear anatomical alterations in synaptic inputs on dopaminergic neurons in the midbrain posterior ventral tegmental area (pVTA). These changes relate directly to a characteristic feature of schizophrenia: increased dopamine release. In 3-month-old and 14-month-old MIA rats, we found a marked decrease in the volume of presynaptic GABAergic terminals from the rostromedial tegmental nucleus (RMTg) and in the length of the synapses they made, when innervating pVTA dopaminergic neurons. In MIA rats in the long-term, we also discovered a decrease in the volume of the postsynaptic density (PSD) and in the maximum thickness of the PSD at the same synapses. These marked deficits were evident in conventional GABA-dopamine synapses and in synaptic triads that we discovered involving asymmetric synapses that innervated RMTg GABAergic presynaptic terminals, which in turn innervated pVTA dopaminergic neurons. In triads, the PSD thickness of asymmetric synapses was significantly decreased in MIA rats in the long-term cohort. The extensive anatomical deficits provide a potential basis for new therapies targeted at synaptic inputs on midbrain pVTA dopaminergic neurons, in contrast to current striatum-targeted antipsychotic drugs.

Lentivirus-Mediated Expression of Human Secreted Amyloid Precursor Protein-Alpha Promotes Long-Term Induction of Neuroprotective Genes and Pathways in a Mouse Model of Alzheimer's Disease.

BACKGROUND: Secreted amyloid precursor protein-alpha (sAPPα) can enhance memory and is neurotrophic and neuroprotective across a range of disease-associated insults, including amyloid-ß toxicity. In a significant step toward validating sAPPα as a therapeutic for Alzheimer's disease (AD), we demonstrated that long-term overexpression of human sAPPα (for 8 months) in a mouse model of amyloidosis (APP/PS1) could prevent the behavioral and electrophysiological deficits that develop in these mice. OBJECTIVE: To explore the underlying molecular mechanisms responsible for the significant physiological and behavioral improvements observed in sAPPα-treated APP/PS1 mice. METHODS: We assessed the long-term effects on the hippocampal transcriptome following continuous lentiviral delivery of sAPPα or empty-vector to male APP/PS1 mice and wild-type controls using Affymetrix Mouse Transcriptome Assays. Data analysis was carried out within the Affymetrix Transcriptome Analysis Console and an integrated analysis of the resulting transcriptomic data was performed with Ingenuity Pathway analysis (IPA). RESULTS: Mouse transcriptome assays revealed expected AD-associated gene expression changes in empty-vector APP/PS1 mice, providing validation of the assays used for the analysis. By contrast, there were specific sAPPα-associated gene expression profiles which included increases in key neuroprotective genes such as Decorin, betaine-GABA transporter and protocadherin beta-5, subsequently validated by qRT-PCR. An integrated biological pathways analysis highlighted regulation of GABA receptor signaling, cell survival and inflammatory responses. Furthermore, upstream gene regulatory analysis implicated sAPPα activation of Interleukin-4, which can counteract inflammatory changes in AD. CONCLUSION: This study identified key molecular processes that likely underpin the long-term neuroprotective and therapeutic effects of increasing sAPPα levels in vivo.

An altered secretome is an early marker of the pathogenesis of CLN6 Batten disease.

Neuronal ceroid lipofuscinoses (NCLs) are a group of inherited childhood neurodegenerative disorders. In addition to the accumulation of auto-fluorescent storage material in lysosomes, NCLs are largely characterised by region-specific neuroinflammation that can predict neuron loss. These phenotypes suggest alterations in the extracellular environment-making the secretome an area of significant interest. This study investigated the secretome in the CLN6 (ceroid-lipofuscinosis neuronal protein 6) variant of NCL. To investigate the CLN6 secretome, we co-cultured neurons and glia isolated from Cln6nclf or Cln6± mice, and utilised mass spectrometry to compare protein constituents of conditioned media. The significant changes noted in cathepsin enzymes, were investigated further via western blotting and enzyme activity assays. Viral-mediated gene therapy was used to try and rescue the wild-type phenotype and restore the secretome-both in vitro in co-cultures and in vivo in mouse plasma. In Cln6nclf cells, proteomics revealed a marked increase in catabolic and cytoskeletal-associated proteins-revealing new similarities between the pathogenic signatures of NCLs with other neurodegenerative disorders. These changes were, in part, corrected by gene therapy intervention, suggesting these proteins as candidate in vitro biomarkers. Importantly, these in vitro changes show promise for in vivo translation, with Cathepsin L (CTSL) activity reduced in both co-cultures and Cln6nclf plasma samples post gene-therapy. This work suggests the secretome plays a role in CLN6 pathogenesis and highlights its potential use as an in vitro model. Proteomic changes present a list of candidate biomarkers for monitoring disease and assessing potential therapeutics in future studies.

CNS Transduction Benefits of AAV-PHP.eB over AAV9 Are Dependent on Administration Route and Mouse Strain.

Adeno-associated viral (AAV) vectors are attractive tools for central nervous system (CNS) gene therapy because some vectors can cross the blood-brain barrier (BBB), allowing them to be used as minimally invasive treatments. A novel AAV vector recently evolved in vivo, AAV-PHP.eB, has been reported to cross the BBB more effectively than the existing gold standard AAV9, but not under all conditions. Here, we compared the efficacy of single-stranded AAV-PHP.eB and AAV9 in targeting mouse CNS and peripheral tissues after administration via various routes, in two different mouse strains (C57BL/6J and B6C3), and after packaging AAV-PHP.eB with a self-complementary genome. We found that AAV-PHP.eB produced higher CNS transduction than AAV9 after intravenous injection, but only in C57BL/6J and not in B6C3 mice. AAV-PHP.eB and AAV9 produced similar CNS transduction when the administration route did not require the vectors to cross the BBB. Packaging AAV-PHP.eB with a self-complementary genome increased overall CNS transduction, but at the expense of strong neuronal tropism. AAV-PHP.eB resulted in less transduction of liver tissue than AAV9 under all conditions. Taken together, these results suggest the potential for AAV-PHP.eB as a vector for CNS gene therapy applications, but consideration will be required for translation beyond mouse models.

The contribution of multicellular model organisms to neuronal ceroid lipofuscinosis research.

The NCLs (neuronal ceroid lipofuscinosis) are forms of neurodegenerative disease that affect people of all ages and ethnicities but are most prevalent in children. Commonly known as Batten disease, this debilitating neurological disorder is comprised of 13 different subtypes that are categorized based on the particular gene that is mutated (CLN1-8, CLN10-14). The pathological mechanisms underlying the NCLs are not well understood due to our poor understanding of the functions of NCL proteins. Only one specific treatment (enzyme replacement therapy) is approved, which is for the treating the brain in CLN2 disease. Hence there remains a desperate need for further research into disease-modifying treatments. In this review, we present and evaluate the genes, proteins and studies performed in the social amoeba, nematode, fruit fly, zebrafish, mouse and large animals pertinent to NCL. In particular, we highlight the use of multicellular model organisms to study NCL protein function, pathology and pathomechanisms. Their use in testing novel therapeutic approaches is also presented. With this information, we highlight how future research in these systems may be able to provide new insight into NCL protein functions in human cells and aid in the development of new therapies.

The Tripeptide RER Mimics Secreted Amyloid Precursor Protein-Alpha in Upregulating LTP.

Secreted amyloid precursor protein-alpha (sAPPα), generated by enzymatic processing of the APP, possesses a range of neurotrophic and neuroprotective properties and plays a critical role in the molecular mechanisms of memory and learning. One of the key active regions of sAPPα is the central APP domain (E2) that contains within it the tripeptide sequence, RER. This sequence is exposed on the surface of a coiled coil substructure of E2. RER has by itself displayed memory-enhancing properties, and can protect newly formed engrams from interference in a manner similar to that displayed by sAPPα itself. In order to determine whether RER mimics other properties of sAPPα, we investigated the electrophysiological effects of the N-terminal protected acetylated RER (Ac-RER) and an isoform containing a chiral switch in the first amino acid from an l- to a d-orientation (Ac-rER), on synaptic plasticity. We found that, like sAPPα, exogenous perfusion with nanomolar concentrations of Ac-RER or Ac-rER enhanced the induction and stability of long-term potentiation (LTP) in area CA1 of rat and mouse hippocampal slices, in a protein synthesis- and trafficking-dependent manner. This effect did not occur with a control Ac-AAA or Ac-IFR tripeptide, nor with a full-length sAPPα protein where RER was substituted with AAA. Ac-rER also protected LTP against amyloid-beta (Aß25 - 35)-induced LTP impairment. Our findings provide further evidence that the RER-containing region of sAPPα is functionally significant and by itself can produce effects similar to those displayed by full length sAPPα, suggesting that this tripeptide, like sAPPα, may have therapeutic potential.

Gene Therapy Corrects Brain and Behavioral Pathologies in CLN6-Batten Disease.

CLN6-Batten disease, a form of neuronal ceroid lipofuscinosis is a rare lysosomal storage disorder presenting with gradual declines in motor, visual, and cognitive abilities and early death by 12-15 years of age. We developed a self-complementary adeno-associated virus serotype 9 (scAAV9) vector expressing the human CLN6 gene under the control of a chicken ß-actin (CB) hybrid promoter. Intrathecal delivery of scAAV9.CB.hCLN6 into the cerebrospinal fluid (CSF) of the lumbar spinal cord of 4-year-old non-human primates was safe, well tolerated, and led to efficient targeting throughout the brain and spinal cord. A single intracerebroventricular (i.c.v.) injection at post-natal day 1 in Cln6 mutant mice delivered scAAV9.CB.CLN6 directly into the CSF, and it prevented or drastically reduced all of the pathological hallmarks of Batten disease. Moreover, there were significant improvements in motor performance, learning and memory deficits, and survival in treated Cln6 mutant mice, extending survival from 15 months of age (untreated) to beyond 21 months of age (treated). Additionally, many parameters were similar to wild-type counterparts throughout the lifespan of the treated mice.

A C-terminal peptide from secreted amyloid precursor protein-α enhances long-term potentiation in rats and a transgenic mouse model of Alzheimer's disease.

Processing of the amyloid precursor protein by alternative secretases results in ectodomain shedding of either secreted amyloid precursor protein-α (sAPPα) or its counterpart secreted amyloid precursor protein-ß (sAPPß). Although sAPPα contains only 16 additional amino acids at its C-terminus compared to sAPPß, it displays significantly greater potency in neuroprotection, neurotrophism and enhancement of long-term potentiation (LTP). In the current study, this 16 amino acid peptide sequence (CTα16) was characterised for its ability to replicate the synaptic plasticity-enhancing properties of sAPPα. An N-acetylated version of CTα16 produced concentration-dependent increases in the induction and persistence of LTP at Schaffer collateral/commissural synapses in area CA1 of young adult rat hippocampal slices. A scrambled peptide had no effect. CTα16 significantly enhanced de novo protein synthesis, and correspondingly its enhancement of LTP was blocked by the protein synthesis inhibitor cycloheximide, as well as by the α7-nicotinic receptor blocker α-bungarotoxin. The impaired LTP of 14-16 month old APPswe/PS1dE9 transgenic mice, a mouse model of Alzheimer's disease, was completely restored to the wild-type level by CTα16. These results indicate that the CTα16 peptide fragment of sAPPα mimics the larger protein's functionality with respect to LTP, stimulation of protein synthesis and activation of α7-nAChRs, and thus like sAPPα may have potential as a therapeutic agent against the plasticity and cognitive deficits observed in AD and other neurological disorders.

Genetic Targeting and Chemogenetic Inhibition of Newborn Neurons.

The aim of this study was to develop a method to silence a very specific set of cells in a spatially and temporally refined manner. Here, an approach is presented that combines the use of a transgenic mouse line, expressing cre recombinase under a nestin promoter, with lentiviral delivery of a floxed, ivermectin (IVM)-gated chloride channel construct to the dentate gyrus. This approach was used to express an IVM-sensitive chloride channel in newly born granule cells in adult mouse brains, and its ability to silence neuronal activity was tested by analyzing the effect on immediate early gene expression in vitro in cre-transgenic primary neuronal cultures. IVM treatment of cells expressing the chloride channel prevented gabazine-induced expression of the immediate early gene product EGR1, while cells expressing a control inactive channel or no channel retained their EGR1 response. Thus, a genetic strategy is presented for targeting a specific neurogenic niche for transgene expression in the adult mouse brain, and proof of principle is shown that it can be used in vitro as a method for silencing neuronal activity.

Transcriptome Profiling of Layer 5 Intratelencephalic Projection Neurons From the Mature Mouse Motor Cortex.

The mature cortex contains hugely diverse populations of pyramidal projection neurons (PNs), critical to normal forebrain circuits. In order to understand the healthy cortex, it is essential to characterize this neuronal complexity. We recently demonstrated different identities for Fezf2-positive (Fezf2+ve) and Fezf2-negative (Fezf2-ve) intratelencephalic-PNs (IT-PNs) from layer 5 of the motor cortex (M1). Comparatively, each IT-PN type has a distinct electrophysiological phenotype and the Fezf2+ve IT-PNs display a unique apical dendritic tuft. Here, we aimed to expand our understanding of the molecular underpinnings defining these unique IT-PN types. Using a validated Fezf2-GFP reporter mouse, retrograde labeling techniques and fluorescence activated cell sorting (FACS), combined with a novel approach for low-input RNA-sequencing, we isolated mature Fezf2+ve and Fezf2-ve IT-PNs for transcriptome profiling. Through the comparison of Fezf2+ve and Fezf2-ve IT-PN gene expression profiles, we identified significant enrichment of 81 genes in the Fezf2+ve IT-PNs and 119 genes in the Fezf2-ve IT-PNs. Term enrichment analysis of these enriched genes demonstrated significant overrepresentation of the calcium-binding EF-hand domain in Fezf2+ve IT-PNs, suggesting a greater importance for calcium handling in these neurons. Of the Fezf2-ve IT-PN enriched genes an unexpected and unique enrichment of genes, previously associated with microglia were identified. Our dataset identifies the molecular profiles of two unique IT-PN types in the mature M1, providing important targets to investigate for their maintenance in the healthy mature brain.

Longitudinal In Vivo Monitoring of the CNS Demonstrates the Efficacy of Gene Therapy in a Sheep Model of CLN5 Batten Disease.

Neuronal ceroid lipofuscinoses (NCLs; Batten disease) are neurodegenerative lysosomal storage diseases predominantly affecting children. Single administration of brain-directed lentiviral or recombinant single-stranded adeno-associated virus 9 (ssAAV9) vectors expressing ovine CLN5 into six pre-clinically affected sheep with a naturally occurring CLN5 NCL resulted in long-term disease attenuation. Treatment efficacy was demonstrated by non-invasive longitudinal in vivo monitoring developed to align with assessments used in human medicine. The treated sheep retained neurological and cognitive function, and one ssAAV9-treated animal has been retained and is now 57 months old, almost triple the lifespan of untreated CLN5-affected sheep. The onset of visual deficits was much delayed. Computed tomography and MRI showed that brain structures and volumes remained stable. Because gene therapy in humans is more likely to begin after clinical diagnosis, self-complementary AAV9-CLN5 was injected into the brain ventricles of four 7-month-old affected sheep already showing early clinical signs in a second trial. This also halted disease progression beyond their natural lifespan. These findings demonstrate the efficacy of CLN5 gene therapy, using three different vector platforms, in a large animal model and, thus, the prognosis for human translation.

Lentivirus-mediated expression of human secreted amyloid precursor protein-alpha prevents development of memory and plasticity deficits in a mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disease driven in large part by accumulated deposits in the brain of the amyloid precursor protein (APP) cleavage product amyloid-ß peptide (Aß). However, AD is also characterised by reductions in secreted amyloid precursor protein-alpha (sAPPα), an alternative cleavage product of APP. In contrast to the neurotoxicity of accumulated Αß, sAPPα has many neuroprotective and neurotrophic properties. Increasing sAPPα levels has the potential to serve as a therapeutic treatment that mitigates the effects of Aß and rescue cognitive function. Here we tested the hypothesis that lentivirus-mediated expression of a human sAPPα construct in a mouse model of AD (APPswe/PS1dE9), begun before the onset of plaque pathology, could prevent later behavioural and electrophysiological deficits. Male mice were given bilateral intra-hippocampal injections at 4 months of age and tested 8-10 months later. Transgenic mice expressing sAPPα performed significantly better than untreated littermates in all aspects of the spatial water maze task. Expression of sAPPα also resulted in partial rescue of long-term potentiation (LTP), tested in vitro. These improvements occurred in the absence of changes in amyloid pathology. Supporting these findings on LTP, lentiviral-mediated expression of sAPPα for 3 months from 10 months of age, or acute sAPPα treatment in hippocampal slices from 18 to 20 months old transgenic mice, completely reversed the deficits in LTP. Together these findings suggest that sAPPα has wide potential to act as either a preventative or restorative therapeutic treatment in AD by mitigating the effects of Aß toxicity and enhancing cognitive reserve.

RNA-Sequencing Analysis Reveals a Regulatory Role for Transcription Factor Fezf2 in the Mature Motor Cortex.

Forebrain embryonic zinc finger (Fezf2) encodes a transcription factor essential for the specification of layer 5 projection neurons (PNs) in the developing cerebral cortex. As with many developmental transcription factors, Fezf2 continues to be expressed into adulthood, suggesting it remains crucial to the maintenance of neuronal phenotypes. Despite the continued expression, a function has yet to be explored for Fezf2 in the PNs of the developed cortex. Here, we investigated the role of Fezf2 in mature neurons, using lentiviral-mediated delivery of a shRNA to conditionally knockdown the expression of Fezf2 in the mouse primary motor cortex (M1). RNA-sequencing analysis of Fezf2-reduced M1 revealed significant changes to the transcriptome, identifying a regulatory role for Fezf2 in the mature M1. Kyoto Encyclopedia Genes and Genomes (KEGG) pathway analyses of Fezf2-regulated genes indicated a role in neuronal signaling and plasticity, with significant enrichment of neuroactive ligand-receptor interaction, cell adhesion molecules and calcium signaling pathways. Gene Ontology analysis supported a functional role for Fezf2-regulated genes in neuronal transmission and additionally indicated an importance in the regulation of behavior. Using the mammalian phenotype ontology database, we identified a significant overrepresentation of Fezf2-regulated genes associated with specific behavior phenotypes, including associative learning, social interaction, locomotor activation and hyperactivity. These roles were distinct from that of Fezf2-regulated genes identified in development, indicating a dynamic transition in Fezf2 function. Together our findings demonstrate a regulatory role for Fezf2 in the mature brain, with Fezf2-regulated genes having functional roles in sustaining normal neuronal and behavioral phenotypes. These results support the hypothesis that developmental transcription factors are important for maintaining neuron transcriptomes and that disruption of their expression could contribute to the progression of disease phenotypes.

Characterisation of early changes in ovine CLN5 and CLN6 Batten disease neural cultures for the rapid screening of therapeutics.

Batten disease (neuronal ceroid lipofuscinosis) refers to a group of neurodegenerative lysosomal storage diseases predominantly affecting children. There are currently no effective treatments, and the functions of many of the associated gene products are unknown. Here we characterise fetal neural cultures from two genetically distinct sheep forms of Batten disease, with mutations in the lysosomal protein encoding gene CLN5 and endoplasmic reticulum membrane protein encoding gene CLN6, respectively. We found similar reductions in autophagy, acidic organelles and synaptic recycling in both forms compared to unaffected cells. We then developed a high-throughput screen and tested for correction of deficient cells with lentiviral-mediated CLN5 or CLN6 gene transfer and fibrate drugs, gemfibrozil and fenofibrate in CLN6 deficient neural cultures. These assays provide a simple system to rapidly screen candidate therapies or libraries of drugs prior to in vivo testing.