Cortical RORß is required for layer 4 transcriptional identity and barrel integrity.

Retinoic acid-related orphan receptor beta (RORß) is a transcription factor (TF) and marker of layer 4 (L4) neurons, which are distinctive both in transcriptional identity and the ability to form aggregates such as barrels in rodent somatosensory cortex. However, the relationship between transcriptional identity and L4 cytoarchitecture is largely unknown. We find RORß is required in the cortex for L4 aggregation into barrels and thalamocortical afferent (TCA) segregation. Interestingly, barrel organization also degrades with age in wildtype mice. Loss of RORß delays excitatory input and disrupts gene expression and chromatin accessibility, with down-regulation of L4 and up-regulation of L5 genes, suggesting a disruption in cellular specification. Expression and binding site accessibility change for many other TFs, including closure of neurodevelopmental TF binding sites and increased expression and binding capacity of activity-regulated TFs. Lastly, a putative target of RORß, Thsd7a, is down-regulated without RORß, and Thsd7a knock-out alone disrupts TCA organization in adult barrels.

Phosphorylation of tau at Y18, but not tau-fyn binding, is required for tau to modulate NMDA receptor-dependent excitotoxicity in primary neuronal culture.

BACKGROUND: Hyperexcitability of neuronal networks can lead to excessive release of the excitatory neurotransmitter glutamate, which in turn can cause neuronal damage by overactivating NMDA-type glutamate receptors and related signaling pathways. This process (excitotoxicity) has been implicated in the pathogenesis of many neurological conditions, ranging from childhood epilepsies to stroke and neurodegenerative disorders such as Alzheimer's disease (AD). Reducing neuronal levels of the microtubule-associated protein tau counteracts network hyperexcitability of diverse causes, but whether this strategy can also diminish downstream excitotoxicity is less clear. METHODS: We established a cell-based assay to quantify excitotoxicity in primary cultures of mouse hippocampal neurons and investigated the role of tau in exicitotoxicity by modulating neuronal tau expression through genetic ablation or transduction with lentiviral vectors expressing anti-tau shRNA or constructs encoding wildtype versus mutant mouse tau. RESULTS: We demonstrate that shRNA-mediated knockdown of tau reduces glutamate-induced, NMDA receptor-dependent Ca2+ influx and neurotoxicity in neurons from wildtype mice. Conversely, expression of wildtype mouse tau enhances Ca2+ influx and excitotoxicity in tau-deficient (Mapt -/-) neurons. Reconstituting tau expression in Mapt -/- neurons with mutant forms of tau reveals that the tau-related enhancement of Ca2+ influx and excitotoxicity depend on the phosphorylation of tau at tyrosine 18 (pY18), which is mediated by the tyrosine kinase Fyn. These effects are most evident at pathologically elevated concentrations of glutamate, do not involve GluN2B-containing NMDA receptors, and do not require binding of Fyn to tau's major interacting PxxP motif or of tau to microtubules. CONCLUSIONS: Although tau has been implicated in diverse neurological diseases, its most pathogenic forms remain to be defined. Our study suggests that reducing the formation or level of pY18-tau can counteract excitotoxicity by diminishing NMDA receptor-dependent Ca2+ influx.

Differentiation of V2a interneurons from human pluripotent stem cells.

The spinal cord consists of multiple neuronal cell types that are critical to motor control and arise from distinct progenitor domains in the developing neural tube. Excitatory V2a interneurons in particular are an integral component of central pattern generators that control respiration and locomotion; however, the lack of a robust source of human V2a interneurons limits the ability to molecularly profile these cells and examine their therapeutic potential to treat spinal cord injury (SCI). Here, we report the directed differentiation of CHX10+ V2a interneurons from human pluripotent stem cells (hPSCs). Signaling pathways (retinoic acid, sonic hedgehog, and Notch) that pattern the neural tube were sequentially perturbed to identify an optimized combination of small molecules that yielded ∼25% CHX10+ cells in four hPSC lines. Differentiated cultures expressed much higher levels of V2a phenotypic markers (CHX10 and SOX14) than other neural lineage markers. Over time, CHX10+ cells expressed neuronal markers [neurofilament, NeuN, and vesicular glutamate transporter 2 (VGlut2)], and cultures exhibited increased action potential frequency. Single-cell RNAseq analysis confirmed CHX10+ cells within the differentiated population, which consisted primarily of neurons with some glial and neural progenitor cells. At 2 wk after transplantation into the spinal cord of mice, hPSC-derived V2a cultures survived at the site of injection, coexpressed NeuN and VGlut2, extended neurites >5 mm, and formed putative synapses with host neurons. These results provide a description of V2a interneurons differentiated from hPSCs that may be used to model central nervous system development and serve as a potential cell therapy for SCI.

Microglial NFκB-TNFα hyperactivation induces obsessive-compulsive behavior in mouse models of progranulin-deficient frontotemporal dementia.

Frontotemporal dementia (FTD) is the second most common dementia before 65 years of age. Haploinsufficiency in the progranulin (GRN) gene accounts for 10% of all cases of familial FTD. GRN mutation carriers have an increased risk of autoimmune disorders, accompanied by elevated levels of tissue necrosis factor (TNF) α. We examined behavioral alterations related to obsessive-compulsive disorder (OCD) and the role of TNFα and related signaling pathways in FTD patients with GRN mutations and in mice lacking progranulin (PGRN). We found that patients and mice with GRN mutations displayed OCD and self-grooming (an OCD-like behavior in mice), respectively. Furthermore, medium spiny neurons in the nucleus accumbens, an area implicated in development of OCD, display hyperexcitability in PGRN knockout mice. Reducing levels of TNFα in PGRN knockout mice abolished excessive self-grooming and the associated hyperexcitability of medium spiny neurons of the nucleus accumbens. In the brain, PGRN is highly expressed in microglia, which are a major source of TNFα. We therefore deleted PGRN specifically in microglia and found that it was sufficient to induce excessive grooming. Importantly, excessive grooming in these mice was prevented by inactivating nuclear factor κB (NF-κB) in microglia/myeloid cells. Our findings suggest that PGRN deficiency leads to excessive NF-κB activation in microglia and elevated TNFα signaling, which in turn lead to hyperexcitability of medium spiny neurons and OCD-like behavior.

Expression of A152T human tau causes age-dependent neuronal dysfunction and loss in transgenic mice.

A152T-variant human tau (hTau-A152T) increases risk for tauopathies, including Alzheimer's disease. Comparing mice with regulatable expression of hTau-A152T or wild-type hTau (hTau-WT), we find age-dependent neuronal loss, cognitive impairments, and spontaneous nonconvulsive epileptiform activity primarily in hTau-A152T mice. However, overexpression of either hTau species enhances neuronal responses to electrical stimulation of synaptic inputs and to an epileptogenic chemical. hTau-A152T mice have higher hTau protein/mRNA ratios in brain, suggesting that A152T increases production or decreases clearance of hTau protein. Despite their functional abnormalities, aging hTau-A152T mice show no evidence for accumulation of insoluble tau aggregates, suggesting that their dysfunctions are caused by soluble tau. In human amyloid precursor protein (hAPP) transgenic mice, co-expression of hTau-A152T enhances risk of early death and epileptic activity, suggesting copathogenic interactions between hTau-A152T and amyloid-ß peptides or other hAPP metabolites. Thus, the A152T substitution may augment risk for neurodegenerative diseases by increasing hTau protein levels, promoting network hyperexcitability, and synergizing with the adverse effects of other pathogenic factors.

A Mammalian enhancer trap resource for discovering and manipulating neuronal cell types.

There is a continuing need for driver strains to enable cell-type-specific manipulation in the nervous system. Each cell type expresses a unique set of genes, and recapitulating expression of marker genes by BAC transgenesis or knock-in has generated useful transgenic mouse lines. However, since genes are often expressed in many cell types, many of these lines have relatively broad expression patterns. We report an alternative transgenic approach capturing distal enhancers for more focused expression. We identified an enhancer trap probe often producing restricted reporter expression and developed efficient enhancer trap screening with the PiggyBac transposon. We established more than 200 lines and found many lines that label small subsets of neurons in brain substructures, including known and novel cell types. Images and other information about each line are available online (enhancertrap.bio.brandeis.edu).

DNA repair factor BRCA1 depletion occurs in Alzheimer brains and impairs cognitive function in mice.

Maintaining DNA integrity is vital for all cells and organisms. Defective DNA repair may contribute to neurological disorders, including Alzheimer's disease (AD). We found reduced levels of BRCA1, but not of other DNA repair factors, in the brains of AD patients and human amyloid precursor protein (hAPP) transgenic mice. Amyloid-ß oligomers reduced BRCA1 levels in primary neuronal cultures. In wild-type mice, knocking down neuronal BRCA1 in the dentate gyrus caused increased DNA double-strand breaks, neuronal shrinkage, synaptic plasticity impairments, and learning and memory deficits, but not apoptosis. Low levels of hAPP/Amyloid-ß overexpression exacerbated these effects. Physiological neuronal activation increased BRCA1 levels, whereas stimulating predominantly extrasynaptic N-methyl-D-aspartate receptors promoted the proteasomal degradation of BRCA1. We conclude that BRCA1 is regulated by neuronal activity, protects the neuronal genome, and critically supports neuronal integrity and cognitive functions. Pathological accumulation of Aß depletes neuronal BRCA1, which may contribute to cognitive deficits in AD.

Pathophysiology of locus ceruleus neurons in a mouse model of Rett syndrome.

Rett syndrome (RTT) is a neurodevelopmental disorder caused by loss-of-function mutations in the Methyl-CpG-binding protein-2 (MECP2) gene and is characterized by derangements in cognition, behavior, motor control, respiration and autonomic homeostasis, as well as seizures. Deficits in norepinephrine (NE) are thought to contribute to RTT pathogenesis, but little is known about how MeCP2 regulates function of noradrenergic neurons. We therefore characterized morphological, electrical, and neurochemical properties of neurons in the locus ceruleus (LC), the major source of noradrenergic innervation to the central neuraxis, in Mecp2 mutant mice. We found that MeCP2 null LC neurons are electrically hyperexcitable, smaller in size, and express less of the NE-synthesizing enzyme tyrosine hydroxylase (TH) compared with wild-type neurons. Increased excitability of mutant neurons is associated with reductions in passive membrane conductance and the amplitude of the slow afterhyperpolarization. Studies in Mecp2 heterozygotes, which are mosaic for the null allele, demonstrated that electrical hyperexcitability and reduced neuronal size are cell-autonomous consequences of MeCP2 loss, whereas reduced TH expression appears to reflect both cell-autonomous and non-autonomous influences. Finally, we found reduced levels of TH and norepinephrine in cingulate cortex, a forebrain target of the LC. Thus, genetic loss of MeCP2 results in a somewhat paradoxical LC neuron phenotype, characterized by both electrical hyperexcitability and reduced indices of noradrenergic function. Given the importance of the LC in modulating activity in brainstem and forebrain networks, we hypothesize that dysregulation of LC function in the absence of MeCP2 plays a key role in the pathophysiology of RTT.

Comparative assessment of the effectiveness and tolerability of lornoxicam 8 mg BID and diclofenac 50 mg TID in adult indian patients with osteoarthritis of the hip or knee: A 4-week, double-blind, randomized, comparative, multicenter study.

BACKGROUND: Reports of cardiovascular adverse events (AEs) associated with the use of cyclooxygenase-2 inhibitors for the treatment of osteoarthritis (OA) have prompted the quest for a better-tolerated NSAID. OBJECTIVE: The aim of this study was to compare the effectiveness and tolerability of lornoxicam 8 mg BID and diclofenac 50 mg TID in adult Indian patients with OA of the hip or knee. METHODS: This 4-week, double-blind, randomized, comparative, multicenter study was undertaken to compare oral lornoxicam and diclofenac in patients with OA. Patients who met the selection criteria were enrolled consecutively from the outpatient clinics of each of the participating hospitals in India. Participants completed the Western Ontario and McMasters Individual Osteoarthritis Index (WOMAC-OA), WOMAC Composite Index (WOMAC-CI) (for pain, stiffness, and physical function), and a 10-cm visual analog scale (VAS) (0-10 where 0 = no pain and 10 = worst possible pain or severe or excruciating pain) at each study visit (weeks 0 [baseline], 2, and 4 [or at early termination]). Patients' and physicians' global assessments of arthritis control were measured at each study visit when laboratory and clinical AEs were also monitored. The primary end points were the WOMAC-OA, the WOMAC-CI, and VAS scores for pain among the patients who completed the study. RESULTS: Of the 273 patients (159 men, 114 women; mean [SD] age, 44.73 [10.72] years; range, 28-68 years) enrolled in the study, 13 (7 in the lornoxicam group and 6 in the diclofenac group) were lost to follow-up and their effectiveness and tolerability results were not included in the study analysis. Over the 4-week study period, both drugs provided significant (P < 0.05) sustained relief of OA symptoms compared with baseline. Compared with baseline, the mean pain score (WOMAC-CI) decreased 90.6% (13.88 [4.47] vs 1.30 [1.49]; P < 0.05) in the lornoxicam group and 88.9% (14.15 [4.56] vs 1.57 [1.49]; P < 0.05) in the diclofenac group after 4 weeks of treatment. After 4 weeks of treatment, the VAS pain score decreased from baseline 83.1% (8.04 [2.70] vs 1.36 [1.43]; P < 0.05) in the lornoxicam group and 79.3% (7.98 [2.98] vs 1.65 [1.47]; P < 0.05) in the diclofenac group. Compared with baseline, the improvement rated at 2 weeks was not significantly different between the 2 groups. Lornoxicam and diclofenac were well tolerated. The rate of mild to moderate adverse gastrointestinal events was not significantly different in the lornoxicam group compared with the diclofenac group (14.6% vs 18.4%). Similarly, overall tolerability between the 2 groups was not significantly different. None of the patients experienced cardiovascular AEs (eg, edema or increased blood pressure). CONCLUSION: The results of the present study suggest that lornoxicam was comparable to diclofenac in effectiveness and tolerability after 4 weeks of treatment in these adult Indian patients with OA of the hip or knee who completed the study.

Evaluation of the efficacy, safety and tolerability of valdecoxib gel (1%) in adult patients with painful inflammatory joint disease.

Valdecoxib, a COX-2 inhibitor, has recently been introduced as a gel formulation. The present study was conducted to evaluate the efficacy, safety and tolerability of valdecoxib gel in adult patients with painful inflammatory joint conditions. The present study was a 10-day prospective, open, multicentric (6 centres) trial. Patients with clinical and radiological diagnosis of painful inflammatory joint conditions were treated with valdecoxib gel (1%). Efficacy was assessed by visual analogue scale (VAS), patient's and physician's global assessment of pain relief. Grading of associated clinical manifestations such as stiffness, swelling, tenderness and restriction of mobility was done. Tolerability and safety was assessed by physical examination, laboratory parameters and evaluation of adverse events. There was a statistically significant decrease in the mean pain visual analogue score (p<0.05). Onset of pain relief was within 15 minutes. There was a reduction of 58.8%, 57.2%, 65.4% and 60.2% in mean scores of stiffness, swelling, tenderness and mobility respectively from the baseline which was statistically significant. The laboratory values were within normal limits. The drug was well tolerated. There was no report of any hypersensitivity reaction. This study confirms that valdecoxib gel (1%) is an effective and safe option for the management of painful inflammatory joint conditions.