Scientific Resources

General anesthetics produce a reversible coma-like state through modulation of excitatory and inhibitory synaptic transmission. Recent evidence suggests that anesthetic exposure can also lead to sustained cognitive dysfunction. However,the subcellular effects of anesthetics on the structure of established synapses are not known. We investigated effects of the widely used volatile anesthetic isoflurane on the structural stability of hippocampal dendritic spines,a postsynaptic structure critical to excitatory synaptic transmission in learning and memory. Exposure to clinical concentrations of isoflurane induced rapid and non-uniform shrinkage and loss of dendritic spines in mature cultured rat hippocampal neurons. Spine shrinkage was associated with a reduction in spine F-actin concentration. Spine loss was prevented by either jasplakinolide or cytochalasin D,drugs that prevent F-actin disassembly. Isoflurane-induced spine shrinkage and loss were reversible upon isoflurane elimination. Thus,isoflurane destabilizes spine F-actin,resulting in changes to dendritic spine morphology and number. These findings support an actin-based mechanism for isoflurane-induced alterations of synaptic structure in the hippocampus. These reversible alterations in dendritic spine structure have important implications for acute anesthetic effects on excitatory synaptic transmission and synaptic stability in the hippocampus,a locus for anesthetic-induced amnesia,and have important implications for anesthetic effects on synaptic plasticity. View Publication

The bacterial CRISPR/Cas9 system allows sequence-specific gene editing in many organisms and holds promise as a tool to generate models of human diseases,for example,in human pluripotent stem cells. CRISPR/Cas9 introduces targeted double-stranded breaks (DSBs) with high efficiency,which are typically repaired by non-homologous end-joining (NHEJ) resulting in nonspecific insertions,deletions or other mutations (indels). DSBs may also be repaired by homology-directed repair (HDR) using a DNA repair template,such as an introduced single-stranded oligo DNA nucleotide (ssODN),allowing knock-in of specific mutations. Although CRISPR/Cas9 is used extensively to engineer gene knockouts through NHEJ,editing by HDR remains inefficient and can be corrupted by additional indels,preventing its widespread use for modelling genetic disorders through introducing disease-associated mutations. Furthermore,targeted mutational knock-in at single alleles to model diseases caused by heterozygous mutations has not been reported. Here we describe a CRISPR/Cas9-based genome-editing framework that allows selective introduction of mono- and bi-allelic sequence changes with high efficiency and accuracy. We show that HDR accuracy is increased dramatically by incorporating silent CRISPR/Cas-blocking mutations along with pathogenic mutations,and establish a method termed 'CORRECT' for scarless genome editing. By characterizing and exploiting a stereotyped inverse relationship between a mutation's incorporation rate and its distance to the DSB,we achieve predictable control of zygosity. Homozygous introduction requires a guide RNA targeting close to the intended mutation,whereas heterozygous introduction can be accomplished by distance-dependent suboptimal mutation incorporation or by use of mixed repair templates. Using this approach,we generated human induced pluripotent stem cells with heterozygous and homozygous dominant early onset Alzheimer's disease-causing mutations in amyloid precursor protein (APP(Swe)) and presenilin 1 (PSEN1(M146V)) and derived cortical neurons,which displayed genotype-dependent disease-associated phenotypes. Our findings enable efficient introduction of specific sequence changes with CRISPR/Cas9,facilitating study of human disease. View Publication

A critical challenge to deciphering the pathophysiology of neurodevelopmental disease is identifying which of the myriad abnormalities that emerge during CNS maturation persist to contribute to long-term brain dysfunction. Childhood-onset dystonia caused by a loss-of-function mutation in the AAA+ protein torsinA exemplifies this challenge. Neurons lacking torsinA develop transient nuclear envelope (NE) malformations during CNS maturation,but no NE defects are described in mature torsinA null neurons. We find that during postnatal CNS maturation torsinA null neurons develop mislocalized and dysfunctional nuclear pore complexes (NPC) that lack NUP358,normally added late in NPC biogenesis. SUN1,a torsinA-related molecule implicated in interphase NPC biogenesis,also exhibits localization abnormalities. Whereas SUN1 and associated nuclear membrane abnormalities resolve in juvenile mice,NPC defects persist into adulthood. These findings support a role for torsinA function in NPC biogenesis during neuronal maturation and implicate altered NPC function in dystonia pathophysiology. View Publication

Basal forebrain cholinergic neurons (BFCNs) are believed to be one of the first cell types to be affected in all forms of AD,and their dysfunction is clinically correlated with impaired short-term memory formation and retrieval. We present an optimized in vitro protocol to generate human BFCNs from iPSCs,using cell lines from presenilin 2 (PSEN2) mutation carriers and controls. As expected,cell lines harboring the PSEN2 N141I mutation displayed an increase in the A$\beta$42/40 in iPSC-derived BFCNs. Neurons derived from PSEN2 N141I lines generated fewer maximum number of spikes in response to a square depolarizing current injection. The height of the first action potential at rheobase current injection was also significantly decreased in PSEN2 N141I BFCNs. CRISPR/Cas9 correction of the PSEN2 point mutation abolished the electrophysiological deficit,restoring both the maximal number of spikes and spike height to the levels recorded in controls. Increased A$\beta$42/40 was also normalized following CRISPR/Cas-mediated correction of the PSEN2 N141I mutation. The genome editing data confirms the robust consistency of mutation-related changes in A$\beta$42/40 ratio while also showing a PSEN2-mutation-related alteration in electrophysiology. View Publication

UNLABELLED Parkinson's disease (PD) is characterized by the accumulation of α-synuclein (α-syn) within Lewy body inclusions in the nervous system. There are currently no disease-modifying therapies capable of reducing α-syn inclusions in PD. Recent data has indicated that loss-of-function mutations in the GBA1 gene that encodes lysosomal β-glucocerebrosidase (GCase) represent an important risk factor for PD,and can lead to α-syn accumulation. Here we use a small-molecule modulator of GCase to determine whether GCase activation within lysosomes can reduce α-syn levels and ameliorate downstream toxicity. Using induced pluripotent stem cell (iPSC)-derived human midbrain dopamine (DA) neurons from synucleinopathy patients with different PD-linked mutations,we find that a non-inhibitory small molecule modulator of GCase specifically enhanced activity within lysosomal compartments. This resulted in reduction of GCase substrates and clearance of pathological α-syn,regardless of the disease causing mutations. Importantly,the reduction of α-syn was sufficient to reverse downstream cellular pathologies induced by α-syn,including perturbations in hydrolase maturation and lysosomal dysfunction. These results indicate that enhancement of a single lysosomal hydrolase,GCase,can effectively reduce α-syn and provide therapeutic benefit in human midbrain neurons. This suggests that GCase activators may prove beneficial as treatments for PD and related synucleinopathies. SIGNIFICANCE STATEMENT The presence of Lewy body inclusions comprised of fibrillar α-syn within affected regions of PD brain has been firmly documented,however no treatments exist that are capable of clearing Lewy bodies. Here,we used a mechanistic-based approach to examine the effect of GCase activation on α-syn clearance in human midbrain DA models that naturally accumulate α-syn through genetic mutations. Small molecule-mediated activation of GCase was effective at reducing α-syn inclusions in neurons,as well as associated downstream toxicity,demonstrating a therapeutic effect. Our work provides an example of how human iPSC-derived midbrain models could be used for testing potential treatments for neurodegenerative disorders,and identifies GCase as a critical therapeutic convergence point for a wide range of synucleinopathies. View Publication

Aging and oxidative stress are two prominent pathological mechanisms for Parkinson's disease (PD) that are strongly associated with the degeneration of dopamine (DA) neurons in the midbrain. DA and other catechols readily oxidize into highly reactive o-quinone species that are precursors of neuromelanin (NM) pigment and under pathological conditions can modify and damage macromolecules. The role of DA oxidation in PD pathogenesis remains unclear in part due to the lack of appropriate disease models and the absence of a simple method for the quantification of DA-derived oxidants. Here,we describe a rapid,simple,and reproducible method for the quantification of o-quinones in cells and tissues that relies on the near-infrared fluorescent properties of these species. Importantly,we demonstrate that catechol-derived oxidants can be quantified in human neuroblastoma cells and midbrain dopamine neurons derived from induced pluripotent stem cells,providing a novel model to study the downstream actions of o-quinones. This method should facilitate further study of oxidative stress and DA oxidation in PD and related diseases that affect the dopaminergic system. View Publication

Recent large-scale genomics efforts to characterize the cis-regulatory sequences that orchestrate genome-wide expression patterns have produced impressive catalogues of putative regulatory elements. Most of these sequences have not been functionally tested,and our limited understanding of the non-coding genome prevents us from predicting which sequences are bona fide cis-regulatory elements. Recently,massively parallel reporter assays (MPRAs) have been deployed to measure the activity of putative cis-regulatory sequences in several biological contexts,each with specific advantages and distinct limitations. We developed LV-MPRA,a novel lentiviral-based,massively parallel reporter gene assay,to study the function of genome-integrated regulatory elements in any mammalian cell type; thus,making it possible to apply MPRAs in more biologically relevant contexts. We measured the activity of 2,600 sequences in U87 glioblastoma cells and human neural progenitor cells (hNPCs) and explored how regulatory activity is encoded in DNA sequence. We demonstrate that LV-MPRA can be applied to estimate the effects of local DNA sequence and regional chromatin on regulatory activity. Our data reveal that primary DNA sequence features,such as GC content and dinucleotide composition,accurately distinguish sequences with high activity from sequences with low activity in a full chromosomal context,and may also function in combination with different transcription factor binding sites to determine cell type specificity. We conclude that LV-MPRA will be an important tool for identifying cis-regulatory elements and stimulating new understanding about how the non-coding genome encodes information. View Publication

Inflammatory activation precedes and correlates with accumulating τ lesions in Alzheimer's disease and tauopathies. However,the relationship between neuroinflammation and etiology of pathologic τ remains elusive. To evaluate whether inflammatory signaling may promote or accelerate neurofibrillary tangle pathology,we explored the effect of recombinant adeno-associated virus (rAAV)-mediated overexpression of a master inflammatory cytokine,IFN-γ,on τ phosphorylation. In initial studies in primary neuroglial cultures,rAAV-mediated expression of IFN-γ did not alter endogenous τ production or paired helical filament τ phosphorylation. Next,we tested the effect of rAAV-mediated expression of IFN-γ in the brains of 2 mouse models of tauopathy: JNPL3 and rTg4510. In both models,IFN-γ increased 1) signal transducer and activator of transcription 1 levels and gliosis,and 2) hyperphosphorylation and conformational alterations of soluble τ compared with control cohorts. However,sarkosyl-insoluble phosphorylated τ levels and ubiquitin staining were unaltered in the IFN-γ cohorts. Notably,IFN-γ-induced τ hyperphosphorylation was associated with release of the inhibitory effect of glycogen synthase kinase 3β function by decreasing Ser9 phosphorylation. Our data suggest that type II IFN signaling can promote τ phosphorylation by modulating cellular kinase activity,though this is insufficient in accelerating neuritic tangle pathology. View Publication

A number of genes regulate regeneration of peripheral axons,but their ability to drive axon growth and regeneration in the central nervous system (CNS) remains largely untested. To address this question we overexpressed eight transcription factors and one small GTPase alone and in pairwise combinations to test whether combinatorial overexpression would have a synergistic impact on CNS neuron neurite growth. The Jun oncogene/signal transducer and activator of transcription 6 (JUN/STAT6) combination increased neurite growth in dissociated cortical neurons and in injured cortical slices. In injured cortical slices,JUN overexpression increased axon growth to a similar extent as JUN and STAT6 together. Interestingly,JUN overexpression was not associated with increased growth associated protein 43 (GAP43) or integrin alpha 7 (ITGA7) expression,though these are predicted transcriptional targets. This study demonstrates that JUN overexpression in cortical neurons stimulates axon growth,but does so independently of changes in expression of genes thought to be critical for JUNs effects on axon growth. We conclude that JUN activity underlies this CNS axonal growth response,and that it is mechanistically distinct from peripheral regeneration responses,in which increases in JUN expression coincide with increases in GAP43 expression. View Publication

Network activity homeostatically alters synaptic efficacy to constrain neuronal output. However,it is unclear how such compensatory adaptations coexist with synaptic information storage,especially in established networks. Here,we report that in mature hippocampal neurons in vitro,network activity preferentially regulated excitatory synapses within the proximal dendrites of CA3 neurons. These homeostatic synapses exhibited morphological,functional,and molecular signatures of the specialized contacts between mossy fibers of dentate granule cells and thorny excrescences (TEs) of CA3 pyramidal neurons. In vivo TEs were also selectively and bidirectionally altered by chronic activity changes. TE formation required presynaptic synaptoporin and was suppressed by the activity-inducible kinase,Plk2. These results implicate the mossy fiber-TE synapse as an independently tunable gain control locus that permits efficacious homeostatic adjustment of mossy fiber-CA3 synapses,while preserving synaptic weights that may encode information elsewhere within the mature hippocampal circuit. View Publication

Dendritic protein synthesis plays a critical role in several forms of synaptic plasticity,including BDNF (brain-derived neurotrophic factor)-mediated long-term synaptic potentiation (LTP). Dendritic transcripts are typically transported in a repressed state as components of large ribonucleoprotein complexes,and then translated upon stimulation at,or in the vicinity,of activated synapses. Heterogeneous nuclear ribonucleoprotein A2/B1 (hnRNP A2/B1) is a trans-acting factor involved in dendritic mRNA trafficking,but how the distribution of the protein in dendrites is regulated has not been characterized. Here we found that a fraction of hnRNP A2/B1 is present at the synapse under resting conditions in cultured hippocampal neurons. Accordingly,this ribonucleoprotein was detected in free mRNP,monosomal,and polyribosomal fractions obtained from synaptoneurosomes. Neuronal activity and BDNF treatment increased hnRNP A2/B1 protein levels in the cell body and dendritic compartments,and induced the delivery of this protein to synaptic sites. The activity-dependent accumulation of hnRNP A2/B1 at the synapse required,at least in part,the activation of TrkB receptors,presumably by BDNF. This neurotrophin also upregulated the hnRNP A2/B1 mRNA in the soma but was without effect on the abundance of neuritic hnRNP A2/B1 transcripts. These results show that the distribution of hnRNP A2/B1 is regulated by BDNF and by neuronal activity,an effect that may have a role in BDNF-induced synaptic plasticity events. View Publication

The widespread application of human stem-cell-derived neurons for functional studies is impeded by complicated differentiation protocols,immaturity,and deficient optogene expression as stem cells frequently lose transgene expression over time. Here we report a simple but precise Cre-loxP-based strategy for generating conditional,and thereby stable,optogenetic human stem-cell lines. These cells can be easily and efficiently differentiated into functional neurons,and optogene expression can be triggered by administering Cre protein to the cultures. This conditional expression system may be applied to stem-cell-derived neurons whenever timed transgene expression could help to overcome silencing at the stem-cell level. View Publication