[Show abstract][Hide abstract] ABSTRACT: Primary afferent collateral sprouting is a process whereby non-injured primary afferent neurons respond to some stimulus and extend new branches from existing axons. Neurons of both the central and peripheral nervous systems undergo this process, which contributes to both adaptive and maladaptive plasticity (e.g., [1-9]). In the model used here (the "spared dermatome" model), the intact sensory neurons respond to the denervation of adjacent areas of skin by sprouting new axon branches into that adjacent denervated territory. Investigations of gene expression changes associated with collateral sprouting can provide a better understanding of the molecular mechanisms controlling this process. Consequently, it can be used to develop treatments to promote functional recovery for spinal cord injury and other similar conditions. This report includes raw gene expression data files from microarray experiments in order to study the gene regulation in spared sensory ganglia in the initiation (7 days) and maintenance (14 days) phases of the spared dermatome model relative to intact ("naïve") sensory ganglia. Data has been deposited into GEO (GSE72551).
Genomics Data 12/2015; 6:249-252. DOI:10.1016/j.gdata.2015.10.005
[Show abstract][Hide abstract] ABSTRACT: Hippocampal adult neurogenesis is thought to subserve pattern separation, the process by which similar patterns of neuronal inputs are transformed into distinct neuronal representations, permitting the discrimination of highly similar stimuli in hippocampus-dependent tasks. However, the mechanism by which immature adult-born dentate granule neurons cells (abDGCs) perform this function remains unknown. Two theories of abDGC function, one by which abDGCs modulate and sparsify activity in the dentate gyrus and one by which abDGCs act as autonomous coding units, are generally suggested to be mutually exclusive. This review suggests that these two mechanisms work in tandem to dynamically regulate memory resolution while avoiding memory interference and maintaining memory robustness.
Neurobiology of Learning and Memory 11/2015; DOI:10.1016/j.nlm.2015.10.013 · 3.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Bipolar disorder is a complex neuropsychiatric disorder that is characterized by intermittent episodes of mania and depression; without treatment, 15% of patients commit suicide. Hence, it has been ranked by the World Health Organization as a top disorder of morbidity and lost productivity. Previous neuropathological studies have revealed a series of alterations in the brains of patients with bipolar disorder or animal models, such as reduced glial cell number in the prefrontal cortex of patients, upregulated activities of the protein kinase A and C pathways and changes in neurotransmission. However, the roles and causation of these changes in bipolar disorder have been too complex to exactly determine the pathology of the disease. Furthermore, although some patients show remarkable improvement with lithium treatment for yet unknown reasons, others are refractory to lithium treatment. Therefore, developing an accurate and powerful biological model for bipolar disorder has been a challenge. The introduction of induced pluripotent stem-cell (iPSC) technology has provided a new approach. Here we have developed an iPSC model for human bipolar disorder and investigated the cellular phenotypes of hippocampal dentate gyrus-like neurons derived from iPSCs of patients with bipolar disorder. Guided by RNA sequencing expression profiling, we have detected mitochondrial abnormalities in young neurons from patients with bipolar disorder by using mitochondrial assays; in addition, using both patch-clamp recording and somatic Ca(2+) imaging, we have observed hyperactive action-potential firing. This hyperexcitability phenotype of young neurons in bipolar disorder was selectively reversed by lithium treatment only in neurons derived from patients who also responded to lithium treatment. Therefore, hyperexcitability is one early endophenotype of bipolar disorder, and our model of iPSCs in this disease might be useful in developing new therapies and drugs aimed at its clinical treatment.
[Show abstract][Hide abstract] ABSTRACT: As a group, we met to discuss the current challenges for creating meaningful patient-specific in vitro models to study brain disorders. Although the convergence of findings between laboratories and patient cohorts provided us confidence and optimism that hiPSC-based platforms will inform future drug discovery efforts, a number of critical technical challenges remain. This opinion piece outlines our collective views on the current state of hiPSC-based disease modeling and discusses what we see to be the critical objectives that must be addressed collectively as a field.
[Show abstract][Hide abstract] ABSTRACT: The brain's serotonergic system centrally regulates several physiological processes and its dysfunction has been implicated in the pathophysiology of several neuropsychiatric disorders. While in the past our understanding of serotonergic neurotransmission has come mainly from mouse models, the development of pluripotent stem cell and induced fibroblast-to-neuron (iN) transdifferentiation technologies has revolutionized our ability to generate human neurons in vitro. Utilizing these techniques and a novel lentiviral reporter for serotonergic neurons, we identified and overexpressed key transcription factors to successfully generate human serotonergic neurons. We found that overexpressing the transcription factors NKX2.2, FEV, GATA2 and LMX1B in combination with ASCL1 and NGN2 directly and efficiently generated serotonergic neurons from human fibroblasts. Induced serotonergic neurons (iSNs) showed increased expression of specific serotonergic genes that are known to be expressed in raphe nuclei. iSNs displayed spontaneous action potentials, released serotonin in vitro and functionally responded to selective serotonin reuptake inhibitors (SSRIs). Here, we demonstrate the efficient generation of functional human serotonergic neurons from human fibroblasts as a novel tool for studying human serotonergic neurotransmission in health and disease.Molecular Psychiatry advance online publication, 27 October 2015; doi:10.1038/mp.2015.161.
[Show abstract][Hide abstract] ABSTRACT: LINE-1 retrotransposons are fast-evolving mobile genetic entities that play roles in gene regulation, pathological conditions, and evolution. Here, we show that the primate LINE-1 50UTR contains a pri- mate-specific open reading frame (ORF) in the anti- sense orientation that we named ORF0. The gene product of this ORF localizes to promyelocytic leuke- mia-adjacent nuclear bodies. ORF0 is present in more than 3,000 loci across human and chimpanzee genomes and has a promoter and a conserved strong Kozak sequence that supports translation. By virtue of containing two splice donor sites, ORF0 can also form fusion proteins with proximal exons. ORF0 transcripts are readily detected in induced pluripotent stem (iPS) cells from both pri- mate species. Capped and polyadenylated ORF0 mRNAs are present in the cytoplasm, and endoge- nous ORF0 peptides are identified upon proteomic analysis. Finally, ORF0 enhances LINE-1 mobility. Taken together, these results suggest a role for ORF0 in retrotransposon-mediated diversity.
[Show abstract][Hide abstract] ABSTRACT: NMDA receptor (NMDAR)-dependent forms of synaptic plasticity are thought to underlie the assembly of developing neuronal circuits and to play a crucial role in learning and memory. It remains unclear how NMDAR might contribute to the wiring of adult-born granule cells (GCs). Here we demonstrate that nascent GCs lacking NMDARs but rescued from apoptosis by overexpressing the pro-survival protein Bcl2 were deficient in spine formation. Insufficient spinogenesis might be a general cause of cell death restricted within the NMDAR-dependent critical time window for GC survival. NMDAR loss also led to enhanced mushroom spine formation and synaptic AMPAR activity throughout the development of newborn GCs. Moreover, similar elevated synapse maturation in the absence of NMDARs was observed in neonate-generated GCs and CA1 pyramidal neurons. Together, these data suggest that NMDAR operates as a molecular monitor for controlling the activity-dependent establishment and maturation rate of synaptic connections between newborn neurons and others.
[Show abstract][Hide abstract] ABSTRACT: Aging is a major risk factor for many human diseases, and in vitro generation of human neurons is an attractive approach for modeling aging-related brain disorders. However, modeling aging in differentiated human neurons has proved challenging. We generated neurons from human donors across a broad range of ages, either by iPSC-based reprogramming and differentiation or by direct conversion into induced neurons (iNs). While iPSCs and derived neurons did not retain aging-associated gene signatures, iNs displayed age-specific transcriptional profiles and revealed age-associated decreases in the nuclear transport receptor RanBP17. We detected an age-dependent loss of nucleocytoplasmic compartmentalization (NCC) in donor fibroblasts and corresponding iNs and found that reduced RanBP17 impaired NCC in young cells, while iPSC rejuvenation restored NCC in aged cells. These results show that iNs retain important aging-related signatures, thus allowing modeling of the aging process in vitro, and they identify impaired NCC as an important factor in human aging.
[Show abstract][Hide abstract] ABSTRACT: Retroviral vectors are a powerful technology for achieving long-term genetic manipulation. This introduction provides some background on replication-deficient retroviral vectors based on Moloney murine leukemia virus and lentivirus. Details, examples, and associated protocols are provided for using these vectors to fluorescently label, genetically alter, and image both live and fixed murine brain tissue.
[Show abstract][Hide abstract] ABSTRACT: Retroviral vectors are powerful tools for genetic manipulation. This protocol discusses the production, purification, and use of replication-deficient retroviral vectors based on Moloney murine leukemia virus and lentivirus. It also describes the injection of a retroviral vector into the dentate gyrus of young adult mice to fluorescently label live murine brain tissue.
[Show abstract][Hide abstract] ABSTRACT: This protocol describes the harvesting of brain tissue from mice that have had the retroviral vector CAG-GFP injected into the dentate gyrus. Brain tissue from these mice is dissected, the tissue is fixed, and the sections are prepared. The fixed sections are imaged using fluorescent confocal microscopy, and newborn granule cells containing GFP are visualized and are characterized.
[Show abstract][Hide abstract] ABSTRACT: In this protocol, acute brain slices are prepared from mice in which newborn granule cells have been labeled using retroviral vector technology. Using a live-cell imaging stage and confocal microscopy coupled to imaging software, dendritic spines are analyzed.
[Show abstract][Hide abstract] ABSTRACT: cis-regulatory changes play a central role in mor- phological divergence, yet the regulatory principles underlying emergence of human traits remain poorly understood. Here, we use epigenomic profiling from human and chimpanzee cranial neural crest cells to systematically and quantitatively annotate diver- gence of craniofacial cis-regulatory landscapes. Epi- genomic divergence is often attributable to genetic variation within TF motifs at orthologous enhancers, with a novel motif being most predictive of activity biases. We explore properties of this cis-regulatory change, revealing the role of particular retroele- ments, uncovering broad clusters of species-biased enhancers near genes associated with human facial variation, and demonstrating that cis-regulatory divergence is linked to quantitative expression differ- ences of crucial neural crest regulators. Our work provides a wealth of candidates for future evolu- tionary studies and demonstrates the value of ‘‘cellular anthropology,’’ a strategy of using in-vitro- derived embryonic cell types to elucidate both fundamental and evolving mechanisms underlying morphological variation in higher primates
[Show abstract][Hide abstract] ABSTRACT: C9orf72 mutations are the most common cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Dipeptide repeat proteins (DPRs) produced by unconventional translation of the C9orf72 repeat expansions cause neurodegeneration in cell culture and in animal models. We performed two unbiased screens in Saccharomyces cerevisiae and identified potent modifiers of DPR toxicity, including karyopherins and effectors of Ran-mediated nucleocytoplasmic transport, providing insight into potential disease mechanisms and therapeutic targets.
[Show abstract][Hide abstract] ABSTRACT: Human cell reprogramming technologies offer access to live human neurons from patients and provide a new alternative for modeling neurological disorders in vitro. Neural electrical activity is the essence of nervous system function in vivo. Therefore, we examined neuronal activity in media widely used to culture neurons. We found that classic basal media, as well as serum, impair action potential generation and synaptic communication. To overcome this problem, we designed a new neuronal medium (BrainPhys basal + serum-free supplements) in which we adjusted the concentrations of inorganic salts, neuroactive amino acids, and energetic substrates. We then tested that this medium adequately supports neuronal activity and survival of human neurons in culture. Long-term exposure to this physiological medium also improved the proportion of neurons that were synaptically active. The medium was designed to culture human neurons but also proved adequate for rodent neurons. The improvement in BrainPhys basal medium to support neurophysiological activity is an important step toward reducing the gap between brain physiological conditions in vivo and neuronal models in vitro.
Proceedings of the National Academy of Sciences 05/2015; 112(20):201504393. DOI:10.1073/pnas.1504393112 · 9.67 Impact Factor