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To enrich spatio-temporal information on the distribution of alien, cryptogenic, and neonative species in the Mediterranean and the Black Sea, a collective effort by 173 marine scientists was made to provide unpublished records and make them open access to the scientific community. Through this effort, we collected and harmonized a dataset of 12, 649 records. It includes 247 taxa, of which 217 are Animalia, 25 Plantae and 5 Chromista, from 23 countries surrounding the Mediterranean and the Black Sea. Chordata was the most abundant taxonomic group, followed by Arthropoda, Mollusca, and Annelida. In terms of species records, Siganus luridus, Siganus rivulatus, Saurida lessepsianus, Pterois miles, Upeneus moluccensis, Charybdis (Archias) longicollis, and Caulerpa cylindracea were the most numerous. The temporal distribution of the records ranges from 1973 to 2022, with 44% of the records in 2020–2021. Lethrinus borbonicus is reported for the first time in the Mediterranean Sea, while Pomatoschistus quagga, Caulerpa cylindracea, Grateloupia turuturu, and Misophria pallida are first records for the Black Sea ; Kapraunia schneideri is recorded for the second time in the Mediterranean and for the first time in Israel ; Prionospio depauperata and Pseudonereis anomala are reported for the first time from the Sea of Marmara. Many first country records are also included, namely: Amathia verticillata (Montenegro), Ampithoe valida (Italy), Antithamnion amphigeneum (Greece), Clavelina oblonga (Tunisia and Slovenia), Dendostrea cf. folium (Syria), Epinephelus fasciatus (Tunisia), Ganonema farinosum (Montenegro), Macrorhynchia philippina (Tunisia), Marenzelleria neglecta (Romania), Paratapes textilis (Tunisia), and Botrylloides diegensis (Tunisia).

Significance We identify cellular senescence occurring in neural progenitor cells (NPCs) from primary progressive multiple sclerosis (PPMS). In this study, senescent progenitor cells were identified within demyelinated white matter lesions in progressive MS (PMS) autopsy tissue, and induced pluripotent stem-derived NPCs from patients with PPMS were found to express cellular senescence markers compared with age-matched control NPCs. Reversal of this cellular senescence phenotype, by treatment with rapamycin, restored PPMS NPC-mediated support for oligodendrocyte (OL) maturation. Proteomic and histological analyses identify senescent progenitor cells in PMS as a source of high-mobility group box-1, which limits maturation and promotes transcriptomic changes in OLs. These findings provide evidence that cellular senescence is an active process in PMS that may contribute to limited remyelination in disease., Cellular senescence is a form of adaptive cellular physiology associated with aging. Cellular senescence causes a proinflammatory cellular phenotype that impairs tissue regeneration, has been linked to stress, and is implicated in several human neurodegenerative diseases. We had previously determined that neural progenitor cells (NPCs) derived from induced pluripotent stem cell (iPSC) lines from patients with primary progressive multiple sclerosis (PPMS) failed to promote oligodendrocyte progenitor cell (OPC) maturation, whereas NPCs from age-matched control cell lines did so efficiently. Herein, we report that expression of hallmarks of cellular senescence were identified in SOX2+ progenitor cells within white matter lesions of human progressive MS (PMS) autopsy brain tissues and iPS-derived NPCs from patients with PPMS. Expression of cellular senescence genes in PPMS NPCs was found to be reversible by treatment with rapamycin, which then enhanced PPMS NPC support for oligodendrocyte (OL) differentiation. A proteomic analysis of the PPMS NPC secretome identified high-mobility group box-1 (HMGB1), which was found to be a senescence-associated inhibitor of OL differentiation. Transcriptome analysis of OPCs revealed that senescent NPCs induced expression of epigenetic regulators mediated by extracellular HMGB1. Lastly, we determined that progenitor cells are a source of elevated HMGB1 in human white matter lesions. Based on these data, we conclude that cellular senescence contributes to altered progenitor cell functions in demyelinated lesions in MS. Moreover, these data implicate cellular aging and senescence as a process that contributes to remyelination failure in PMS, which may impact how this disease is modeled and inform development of future myelin regeneration strategies.

Human induced pluripotent stem cells (iPSCs) have emerged as an invaluable resource for basic research, disease modeling, and drug discovery over recent years. Given the numerous advantages of iPSCs over alternative models-including their human origin, their ability to be differentiated into almost any cell type, and the therapeutic potential of patient-specific iPSCs in personalized medicine-many labs are now considering iPSC models for their studies. As the quality of the starting population of iPSCs is a key determinant in the success of any one of these applications, it is crucial to adhere to best practices in iPSC culture. In the following protocol, we offer a comprehensive guide to the culture, cryopreservation, and quality control methods required for the establishment and maintenance of high-quality iPSC cultures.

Microglia, the immune cells of the central nervous system (CNS), play critical roles in CNS homeostasis and disease. Mounting evidence has linked aberrant microglial functions to neurodevelopment, neuroinflammatory and neurodegenerative diseases, underlining the need for novel models to investigate human microglia biology. Here we describe a protocol for generating in vitro patient-specific microglia progenitors and microglia-like cells from induced pluripotent stem cells (iPSCs). Our protocol generates microglia progenitor cells in approximately 35 days, which then can further mature into microglia-like cells within two additional weeks. Microglia differentiation is driven by specific growth factors and cytokines in serum-free conditions, resulting in mesodermal progenitors that grow in a monolayer which releases free-floating microglia progenitors. Isolated progenitors can be used in co-culture systems with other neuronal cells, xenotransplanted to generate chimeric mouse models, or further differentiated into adherent microglia-like cells for functional studies.

The main objective of this book is to present a thorough update on stem cell research and the potential therapeutic applications of stem cells. The text is structured following a path that starts from the molecular basics and the biological properties of pluripotent, embryonic or reprogrammed stem cells, and it compares the different degrees of stemness, while describing the adult stem populations residing in the various tissues and organs of the human body. Starting from basic research, the book discusses examples of regenerative medicine that translate the experimental findings into clinical applications of cell therapy. Finally, the book reviews how stem cells represent a model to understand not only the physiological mechanisms that control their fate, but also the pathological mechanisms involved in the aberrant biology of cancer stem cells. Each chapter has been conceived by distinguished researchers in the field who provide detailed and updated contributions that distill knowledge in a very readable text. Laura Bonsi is Associate Professor of Histology at the Department of Experimental, Diagnostic and Specialty Medicine of the University of Bologna. Francesco Alviano is Assistant Professor of Histology at the Department of Experimental, Diagnostic and Specialty Medicine of the University of Bologna. Prof. Bonsi and Dr. Alviano are authors of numerous scientific papers published in international journals. They coordinate the Biotechnology Laboratory of Human Stem Cells at the University of Bologna, that is focused on the study of stem cells isolated from different sources, above all from extraembryonic tissues such as the placenta, the umbilical cord, and the fetal membranes. They are longterm members of the International Placenta Stem Cell Society (IPLASS).

Human induced pluripotent stem cells (iPSCs) have emerged as an invaluable resource for basic research, disease modeling, and drug discovery over recent years. Given the numerous advantages of iPSCs over alternative models-including their human origin, their ability to be differentiated into almost any cell type, and the therapeutic potential of patient-specific iPSCs in personalized medicine-many labs are now considering iPSC models for their studies. As the quality of the starting population of iPSCs is a key determinant in the success of any one of these applications, it is crucial to adhere to best practices in iPSC culture. In the following protocol, we offer a comprehensive guide to the culture, cryopreservation, and quality control methods required for the establishment and maintenance of high-quality iPSC cultures.

Microglia, the immune cells of the central nervous system (CNS), play critical roles in CNS homeostasis and disease. Mounting evidence has linked aberrant microglial functions to neurodevelopment, neuroinflammatory and neurodegenerative diseases, underlining the need for novel models to investigate human microglia biology. Here we describe a protocol for generating in vitro patient-specific microglia progenitors and microglia-like cells from induced pluripotent stem cells (iPSCs). Our protocol generates microglia progenitor cells in approximately 35 days, which then can further mature into microglia-like cells within two additional weeks. Microglia differentiation is driven by specific growth factors and cytokines in serum-free conditions, resulting in mesodermal progenitors that grow in a monolayer which releases free-floating microglia progenitors. Isolated progenitors can be used in co-culture systems with other neuronal cells, xenotransplanted to generate chimeric mouse models, or further differentiated into adherent microglia-like cells for functional studies.

Summary Given the critical roles of astrocytes in neuroinflammation and neurological diseases, models for studying human astrocyte biology are in increasing demand. Here, we present a protocol to isolate human astrocytes from induced pluripotent stem cell (iPSC)-based cultures, neural organoids, and primary tissue, using the surface marker CD49f. Moreover, we provide protocols for in vitro co-cultures of human iPSC-derived neurons and astrocytes, as well as for neurotoxicity assays that expose neurons to conditioned media from reactive astrocytes. For complete details on the use and execution of this protocol, please refer to Barbar et al. (2020)., Graphical Abstract, Highlights • A protocol for isolation of human CD49f+ astrocytes • Adaptations for isolation from iPSC cultures, 3D organoids, and fetal brain • Adaptable for different endpoints (e.g., co-cultures, functional studies) • An in vitro neurotoxicity assay exposing iPSC neurons to astrocyte-conditioned medium, Given the critical roles of astrocytes in neuroinflammation and neurological diseases, models for studying human astrocyte biology are in increasing demand. Here, we present a protocol to isolate human astrocytes from induced pluripotent stem cell (iPSC)-based cultures, neural organoids, and primary tissue, using the surface marker CD49f. Moreover, we provide protocols for in vitro co-cultures of human iPSC-derived neurons and astrocytes, as well as for neurotoxicity assays that expose neurons to conditioned media from reactive astrocytes.

Three major molecular subtypes of Alzheimer’s disease are identified, cross-validated, and characterized across 1543 individuals., Alzheimer’s disease (AD), the most common form of dementia, is recognized as a heterogeneous disease with diverse pathophysiologic mechanisms. In this study, we interrogate the molecular heterogeneity of AD by analyzing 1543 transcriptomes across five brain regions in two AD cohorts using an integrative network approach. We identify three major molecular subtypes of AD corresponding to different combinations of multiple dysregulated pathways, such as susceptibility to tau-mediated neurodegeneration, amyloid-β neuroinflammation, synaptic signaling, immune activity, mitochondria organization, and myelination. Multiscale network analysis reveals subtype-specific drivers such as GABRB2, LRP10, MSN, PLP1, and ATP6V1A. We further demonstrate that variations between existing AD mouse models recapitulate a certain degree of subtype heterogeneity, which may partially explain why a vast majority of drugs that succeeded in specific mouse models do not align with generalized human trials across all AD subtypes. Therefore, subtyping patients with AD is a critical step toward precision medicine for this devastating disease.

Organoid technologies provide an accessible system to examine cellular composition, interactions, and organization in the developing human brain, but previously have lacked oligodendrocytes, the myelinating glia of the central nervous system. Here we reproducibly generate oligodendrocytes and myelin in human pluripotent stem cell-derived “oligocortical spheroids”. Transcriptional, immunohistochemical, and electron microscopy analyses demonstrate molecular features consistent with maturing oligodendrocytes by 20 weeks in culture, including expression of MYRF, PLP1, and MBP proteins and initial myelin wrapping of axons, with maturation to longitudinal wrapping and compact myelin by 30 weeks. Promyelinating drugs enhance the rate and extent of oligodendrocyte generation and myelination, while oligocortical spheroids generated from patients with a genetic myelin disorder recapitulate human disease phenotypes. Oligocortical spheroids provide a versatile platform to observe and dissect the complex interactions required for myelination of the developing central nervous system and offer new opportunities for disease modeling and therapeutic development in human tissue.

Objective: Biomarkers aid diagnosis, allow inexpensive screening of therapies and guide selection of patient-specific therapeutic regimens in most internal medicine disciplines. In contrast, neurology lacks validated measurements of the physiological status, or dysfunction(s) of cells of the central nervous system (CNS). Accordingly, patients with chronic neurological diseases are often treated with a single disease-modifying therapy without understanding patient-specific drivers of disability. Therefore, using multiple sclerosis (MS) as an example of a complex polygenic neurological disease, we sought to determine if cerebrospinal fluid (CSF) biomarkers are intra-individually stable, cell type-, disease- and/or process-specific and responsive to therapeutic intervention. Methods: We used statistical learning in a modeling cohort (n=225) to develop diagnostic classifiers from DNA-aptamer-based measurements of 1128 CSF proteins. An independent validation cohort (n=85) assessed the reliability of derived classifiers. The biological interpretation resulted from in-vitro modeling of primary or stem cell-derived human CNS cells and cell lines. Results: The classifier that differentiates MS from CNS diseases that mimic MS clinically, pathophysiologically and on imaging, achieved a validated area under receiver-operator characteristic curve (AUROC) of 0.98, while the classifier that differentiates relapsing-remitting from progressive MS achieved a validated AUROC of 0.91. No classifiers could differentiate primary- from secondary-progressive MS better than random guessing. Treatment-induced changes in biomarkers greatly exceeded intra-individual- and technical variabilities of the assay. Interpretation: CNS biological processes reflected by CSF biomarkers are robust, stable, and disease- or even disease-stage specific. This opens opportunities for broad utilization of CSF biomarkers in drug development and precision medicine for CNS disorders. This article is protected by copyright. All rights reserved.

To identify the molecular mechanisms and novel therapeutic targets of late-onset Alzheimer's Disease (LOAD), we performed an integrative network analysis of multi-omics profiling of four cortical areas across 364 donors with varying cognitive and neuropathological phenotypes. Our analyses revealed thousands of molecular changes and uncovered neuronal gene subnetworks as the most dysregulated in LOAD. ATP6V1A was identified as a key regulator of a top-ranked neuronal subnetwork, and its role in disease-related processes was evaluated through CRISPR-based manipulation in human induced pluripotent stem cell-derived neurons and RNAi-based knockdown in Drosophila models. Neuronal impairment and neurodegeneration caused by ATP6V1A deficit were improved by a repositioned compound, NCH-51. This study provides not only a global landscape but also detailed signaling circuits of complex molecular interactions in key brain regions affected by LOAD, and the resulting network models will serve as a blueprint for developing next-generation therapeutic agents against LOAD.

Astrocytes play a central role in the central nervous system (CNS), maintaining brain homeostasis, providing metabolic support to neurons, regulating connectivity of neural circuits, and controlling blood flow as an integral part of the blood-brain barrier. They have been increasingly implicated in the mechanisms of neurodegenerative diseases, prompting a greater need for methods that enable their study. The advent of human induced pluripotent stem cell (iPSC) technology has made it possible to generate patient-specific astrocytes and CNS cells using protocols developed by our team and others as valuable disease models. Yet isolating astrocytes from primary specimens or from in vitro mixed cultures for downstream analyses has remained challenging. To address this need, we performed a screen for surface markers that allow FACS sorting of astrocytes. Here we demonstrate that CD49f is an effective marker for sorting functional human astrocytes. We sorted CD49f+ cells from a protocol we previously developed that generates a complex culture of oligodendrocytes, neurons and astrocytes from iPSCs. CD49f+-purified cells express all canonical astrocyte markers and perform characteristic functions, such as neuronal support and glutamate uptake. Of particular relevance to neurodegenerative diseases, CD49f+ astrocytes can be stimulated to take on an A1 neurotoxic phenotype, in which they secrete pro-inflammatory cytokines and show an impaired ability to support neuronal maturation. This study establishes a novel marker for isolating functional astrocytes from complex CNS cell populations, strengthening the use of iPSC-astrocytes for the study of their regulation and dysregulation in neurodegenerative diseases.

New methods for investigating human astrocytes are urgently needed, given their critical role in the central nervous system. Here we show that CD49f is a novel marker for human astrocytes, expressed in fetal and adult brains from healthy and diseased individuals. CD49f can be used to purify fetal astrocytes and human induced pluripotent stem cell (hiPSC)-derived astrocytes. We provide single-cell and bulk transcriptome analyses of CD49f(+) hiPSC-astrocytes, and demonstrate that they perform key astrocytic functions in vitro, including trophic support of neurons, glutamate uptake, and phagocytosis. Notably, CD49f(+) hiPSC-astrocytes respond to inflammatory stimuli, acquiring an A1-like reactive state, in which they display impaired phagocytosis and glutamate uptake and fail to support neuronal maturation. Most importantly, we show that conditioned medium from human reactive A1-like astrocytes is toxic to human and rodent neurons. CD49f(+) hiPSC-astrocytes are thus a valuable resource for investigating human astrocyte function and dysfunction in health and disease.

Multiple sclerosis is an autoimmune demyelinating disorder of the CNS, characterized by inflammatory lesions and an underlying neurodegenerative process, which is more prominent in patients with progressive disease course. It has been proposed that mitochondrial dysfunction underlies neuronal damage, the precise mechanism by which this occurs remains uncertain. To investigate potential mechanisms of neurodegeneration, we conducted a functional screening of mitochondria in neurons exposed to the CSF of multiple sclerosis patients with a relapsing remitting (n = 15) or a progressive (secondary, n = 15 or primary, n = 14) disease course. Live-imaging of CSF-treated neurons, using a fluorescent mitochondrial tracer, identified mitochondrial elongation as a unique effect induced by the CSF from progressive patients. These morphological changes were associated with decreased activity of mitochondrial complexes I, III and IV and correlated with axonal damage. The effect of CSF treatment on the morphology of mitochondria was characterized by phosphorylation of serine 637 on the dynamin-related protein DRP1, a post-translational modification responsible for unopposed mitochondrial fusion in response to low glucose conditions. The effect of neuronal treatment with CSF from progressive patients was heat stable, thereby prompting us to conduct an unbiased exploratory lipidomic study that identified specific ceramide species as differentially abundant in the CSF of progressive patients compared to relapsing remitting multiple sclerosis. Treatment of neurons with medium supplemented with ceramides, induced a time-dependent increase of the transcripts levels of specific glucose and lactate transporters, which functionally resulted in progressively increased glucose uptake from the medium. Thus ceramide levels in the CSF of patients with progressive multiple sclerosis not only impaired mitochondrial respiration but also decreased the bioavailability of glucose by increasing its uptake. Importantly the neurotoxic effect of CSF treatment could be rescued by exogenous supplementation with glucose or lactate, presumably to compensate the inefficient fuel utilization. Together these data suggest a condition of ‘virtual hypoglycosis’ induced by the CSF of progressive patients in cultured neurons and suggest a critical temporal window of intervention for the rescue of the metabolic impairment of neuronal bioenergetics underlying neurodegeneration in multiple sclerosis patients.

Background Once multiple sclerosis (MS) reaches the progressive stage, immunomodulatory treatments have limited efficacy. This suggests that processes other than activation of innate immunity may at least partially underlie disability progression during late stages of MS. Pathology identified these alternative processes as aberrant activation of astrocytes and microglia, and subsequent degeneration of oligodendrocytes and neurons. However, we mostly lack biomarkers that could measure central nervous system (CNS) cell-specific intrathecal processes in living subjects. This prevents differentiating pathogenic processes from an epiphenomenon. Therefore, we sought to develop biomarkers of CNS cell-specific processes and link them to disability progression in MS. Methods In a blinded manner, we measured over 1000 proteins in the cerebrospinal fluid (CSF) of 431 patients with neuroimmunological diseases and healthy volunteers using modified DNA-aptamers (SOMAscan®). We defined CNS cell type-enriched clusters using variable cluster analysis, combined with in vitro modeling. Differences between diagnostic categories were identified in the training cohort (n = 217) and their correlation to disability measures were assessed; results were validated in an independent validation cohort (n = 214). Results Astrocyte cluster 8 (MMP7, SERPINA3, GZMA and CLIC1) and microglial cluster 2 (DSG2 and TNFRSF25) were reproducibly elevated in MS and had a significant and reproducible correlation with MS severity suggesting their pathogenic role. In vitro studies demonstrated that proteins of astrocyte cluster 8 are noticeably released upon stimulation with proinflammatory stimuli and overlap with the phenotype of recently described neuro-toxic (A1) astrocytes. Conclusion Microglial activation and toxic astrogliosis are associated with MS disease process and may partake in CNS tissue destruction. This hypothesis should be tested in new clinical trials.

Abnormalities of brain connectivity and signal transduction are consistently observed in individuals with schizophrenias (SZ). Underlying these anomalies, convergent in vivo, post mortem, and genomic evidence suggest abnormal oligodendrocyte (OL) development and function and lower myelination in SZ. Our primary hypothesis was that there would be abnormalities in the number of induced pluripotent stem (iPS) cell-derived OLs from subjects with SZ. Our secondary hypothesis was that these in vitro abnormalities would correlate with measures of white matter (WM) integrity and myelination in the same subjects in vivo, estimated from magnetic resonance imaging. Six healthy control (HC) and six SZ iPS cell lines, derived from skin fibroblasts from well-characterized subjects, were differentiated into OLs. FACS analysis of the oligodendrocyte-specific surface, glycoprotein O4, was performed at three time points of development (days 65, 75, and 85) to quantify the number of late oligodendrocyte progenitor cells (OPCs) and OLs in each line. Significantly fewer O4-positive cells developed from SZ versus HC lines (95% CI 1.0: 8.6, F1,10 = 8.06, p = 0.02). The difference was greater when corrected for age (95% CI 5.4:10.4, F1,8 = 53.6, p 1,9 = 4.3, p = 0.07), reaching significance for mature OLs at day 85 in culture (r = 0.70, p

Alexander disease (AxD) is a leukodystrophy that primarily affects astrocytes and is caused by mutations in the astrocytic filament gene GFAP. While astrocytes are thought to have important roles in controlling myelination, AxD animal models do not recapitulate critical myelination phenotypes and it is therefore not clear how AxD astrocytes contribute to leukodystrophy. Here, we show that AxD patient iPSC-derived astrocytes recapitulate key features of AxD pathology such as GFAP aggregation. Moreover, AxD astrocytes inhibit proliferation of human iPSC-derived oligodendrocyte progenitor cells (OPCs) in co-culture and reduce their myelination potential. CRISPR/Cas9-based correction of GFAP mutations reversed these phenotypes. Transcriptomic analyses of AxD astrocytes and postmortem brains identified CHI3L1 as a key mediator of AxD astrocyte-induced inhibition of OPC activity. Thus, this iPSC-based model of AxD not only recapitulates patient phenotypes not observed in animal models, but also reveals mechanisms underlying disease pathology and provides a platform for assessing therapeutic interventions.

In the CNS, oligodendrocytes act as the myelinating cells. Oligodendrocytes have been identified to be key players in several neurodegenerative disorders. This protocol describes a robust, fast and reproducible differentiation protocol to generate human oligodendrocytes from pluripotent stem cells (PSCs) using a chemically defined, growth factor-rich medium. Within 8 d, PSCs differentiate into paired box 6-positive (PAX6(+)) neural stem cells, which give rise to OLIG2(+) progenitors by day 12. Oligodendrocyte lineage transcription factor 2-positive (OLIG2(+)) cells begin to express the transcription factor NKX2.2 around day 18, followed by SRY-box 10 (SOX10) around day 40. Oligodendrocyte progenitor cells (OPCs) that are positive for the cell surface antigen recognized by the O4 antibody (O4(+)) appear around day 50 and reach, on average, 43% of the cell population after 75 d of differentiation. O4(+) OPCs can be isolated by cell sorting for myelination studies, or they can be terminally differentiated to myelin basic protein-positive (MBP(+)) oligodendrocytes. This protocol also describes an alternative strategy for markedly reducing the length and the costs of the differentiation and generating ∼30% O4(+) cells after only 55 d of culture.

Background: Schizophrenia (SZ) is a severe mental disorder with heritability estimated at ~80%. Genetic variants in contactin-associated protein-like 2 (CNTNAP2) have been reported in SZ. This gene is critically involved in normal neuronal synchronization and myelin production. Deletions in this gene would therefore be expected to impact white matter (WM) integrity. Compromised WM integrity has been implicated in SZ and may also be a heritable biomarker. In order to help characterize the genetic components of WM changes in SZ, we examined 2 carriers of a large heterozygous deletion in CNTNAP2 with discordant clinical phenotypes. Methods: A 59-year-old female proband who met DSM-IV criteria for a diagnosis of schizoaffective disorder (depressed subtype), her clinically unaffected 90-year-old father, and 4 unrelated nonpsychiatric controls completed a diffusion kurtosis imaging protocol on a Siemens 3T system. Human-induced pluripotent stem cell (hiPSC) lines from skin biopsies of both carriers were generated and differentiated in vitro to oligodendrocytes. Results: The fractional anisotropy (FA) and radial kurtosis (RK) were reduced, and the radial diffusivity (RD) was increased in the corona radiata and the genu of the corpus callosum (CC) in the proband compared with the father and controls. The clinically unaffected father closely resembled the controls in the genu of CC but differed from them in the uncinate fasciculus and internal capsule. In the whole-brain WM analysis, the FA and RK were reduced, and the RD was increased, in both the proband and the father compared with the controls, more substantially in the proband than in the father. Preliminary results from the in vitro differentiation suggest defective differentiation of patient-derived hiPSCs to oligodendrocyte precursor cells in the proband only. Conclusion: These preliminary data suggest that WM integrity is compromised in both carriers, possibly due to a demyelinating process that may be associated with this specific mutation. More severe and widespread demyelination is present in the clinically affected proband than in the unaffected carrier father, suggesting that additional WM changes may be associated with SZ, possibly independent of this mutation. These findings complement the molecular and cellular phenotypes of the hiPSC neural cells derived from these carriers and support the role of brain imaging in helping to elucidate objectively measurable neuroanatomic phenotypic consequences of genetic variant susceptibility. This is one of the first studies to combine neuroimaging and hiPSC-based observations in carriers of the same mutation with discordant phenotypes, demonstrating the utility of both approaches in understanding pleiotropic clinical effects.

Summary Multiple sclerosis (MS) is a chronic demyelinating disease of unknown etiology that affects the CNS. While current therapies are primarily directed against the immune system, the new challenge is to address progressive MS with remyelinating and neuroprotective strategies. Here, we develop a highly reproducible protocol to efficiently derive oligodendrocyte progenitor cells (OPCs) and mature oligodendrocytes from induced pluripotent stem cells (iPSCs). Key elements of our protocol include adherent cultures, dual SMAD inhibition, and addition of retinoids from the beginning of differentiation, which lead to increased yields of OLIG2 progenitors and high numbers of OPCs within 75 days. Furthermore, we show the generation of viral and integration-free iPSCs from primary progressive MS (PPMS) patients and their efficient differentiation to oligodendrocytes. PPMS OPCs are functional, as demonstrated by in vivo myelination in the shiverer mouse. These results provide encouraging advances toward the development of autologous cell therapies using iPSCs., Graphical Abstract, Highlights • Development of a rapid, highly efficient, and robust protocol to produce O4+ hOPCs • Generation of iPSCs from primary progressive MS patients • Differentiation of PPMS iPSCs to mature oligodendrocytes in vitro • Successful in vivo myelination from PPMS-iPSC-derived OPCs, In this article, Fossati and colleagues describe an efficient and highly reproducible differentiation protocol to generate oligodendrocyte progenitor cells (OPCs) from induced pluripotent stem cells. Using this protocol, they show that OPCs from primary progressive multiple sclerosis (MS) patients are able to myelinate neurons in the shiverer mouse model, providing the premise for the development of future autologous cell transplantation therapies in MS.

Biomarkers aid diagnosis, allow inexpensive screening of therapies, and guide selection of patient-specific therapeutic regimens in most internal medicine disciplines. In contrast, neurology lacks validated measurements of the physiological status, or dysfunction(s) of cells of the central nervous system (CNS). Accordingly, patients with chronic neurological diseases are often treated with a single disease-modifying therapy without understanding patient-specific drivers of disability. Therefore, using multiple sclerosis (MS) as an example of a complex polygenic neurological disease, we sought to determine whether cerebrospinal fluid (CSF) biomarkers are intraindividually stable, cell type-, disease- and/or process-specific, and responsive to therapeutic intervention.We used statistical learning in a modeling cohort (n = 225) to develop diagnostic classifiers from DNA-aptamer-based measurements of 1,128 CSF proteins. An independent validation cohort (n = 85) assessed the reliability of derived classifiers. The biological interpretation resulted from in vitro modeling of primary or stem cell-derived human CNS cells and cell lines.The classifier that differentiates MS from CNS diseases that mimic MS clinically, pathophysiologically, and on imaging achieved a validated area under the receiver operating characteristic curve (AUROC) of 0.98, whereas the classifier that differentiates relapsing-remitting from progressive MS achieved a validated AUROC of 0.91. No classifiers could differentiate primary progressive from secondary progressive MS better than random guessing. Treatment-induced changes in biomarkers greatly exceeded intraindividual and technical variabilities of the assay.CNS biological processes reflected by CSF biomarkers are robust, stable, disease specific, or even disease stage specific. This opens opportunities for broad utilization of CSF biomarkers in drug development and precision medicine for CNS disorders. Ann Neurol 2017;82:795-812.

Mitochondria, the organelles that function as the powerhouse of the cell, have been increasingly linked to the pathogenesis of many neurological disorders, including multiple sclerosis (MS). MS is a chronic inflammatory demyelinating disease of the central nervous system (CNS) and a leading cause of neurological disability in young adults in the western world. Its etiology remains unknown, and while the inflammatory component of MS has been heavily investigated and targeted for therapeutic intervention, the failure of remyelination and the process of axonal degeneration are still poorly understood. Recent studies suggest a role of mitochondrial dysfunction in the neurodegenerative aspects of MS. This review is focused on mitochondrial functions under physiological conditions and the consequences of mitochondrial alterations in various CNS disorders. Moreover, we summarize recent findings linking mitochondrial dysfunction to MS and discuss novel therapeutic strategies targeting mitochondria-related pathways as well as emerging experimental approaches for modeling mitochondrial disease.

Induced pluripotent stem cells (iPSCs) are being generated using various reprogramming methods and from different cell sources. Hence, a lot of effort has been devoted to evaluating the differences among iPSC lines, in particular with respect to their differentiation capacity. While line-to-line variability should mainly reflect the genetic diversity within the human population, here we review some studies that have brought attention to additional variation caused by genomic and epigenomic alterations. We discuss strategies to evaluate aberrant changes and to minimize technical and culture-induced noise, in order to generate safe cells for clinical applications. We focus on the findings from a recent study, which compared the differentiation capacity of several iPSC lines committed to the hematopoietic lineage and correlated the differential maturation capacity with aberrant DNA methylations. Although iPSC variation represents a challenge for the field, we embrace the authors’ perspective that iPSC variations should be used to our advantage for predicting and selecting the best performing iPSC lines, depending on the desired application.

A fundamental impediment to understanding the brain is the availability of inexpensive and robust methods for targeting and manipulating specific neuronal populations. The need to overcome this barrier is pressing because there are considerable anatomical, physiological, cognitive and behavioral differences between mice and higher mammalian species in which it is difficult to specifically target and manipulate genetically defined functional cell types. In particular, it is unclear the degree to which insights from mouse models can shed light on the neural mechanisms that mediate cognitive functions in higher species, including humans. Here we describe a novel recombinant adeno-associated virus that restricts gene expression to GABAergic interneurons within the telencephalon. We demonstrate that the viral expression is specific and robust, allowing for morphological visualization, activity monitoring and functional manipulation of interneurons in both mice and non-genetically tractable species, thus opening the possibility to study GABAergic function in virtually any vertebrate species.

Pluripotent stem cells provide an invaluable tool for generating human, disease-relevant cells. Multiple sclerosis is an inflammatory demyelinating disease of the central nervous system, characterized by myelin damage. Oligodendrocytes are the myelinating cells of the central nervous system (CNS); they differentiate from progenitor cells, and their membranes ensheath axons, providing trophic support and allowing fast conduction velocity. The current understanding of oligodendrocyte biology was founded by rodent studies, where the establishment of repressive epigenetic marks on histone proteins, followed by activation of myelin genes, leads to lineage progression. To assess whether this epigenetic regulation is conserved across species, we differentiated human embryonic and induced pluripotent stem cells to oligodendrocytes and asked whether similar histone marks and relative enzymatic activities could be detected. The transcriptional levels of enzymes responsible for methylation and acetylation of histone marks were analyzed during oligodendrocyte differentiation, and the post-translational modifications on histones were detected using immunofluorescence. These studies showed that also in human cells, differentiation along the oligodendrocyte lineage is characterized by the acquisition of multiple repressive histone marks, including deacetylation of lysine residues on histone H3 and trimethylation of residues K9 and K27. These data suggest that the epigenetic modulation of oligodendrocyte identity is highly conserved across species.

Neurodevelopmental disorders, such as autism spectrum disorders and schizophrenia, are complex disorders with a high degree of heritability. Genetic studies have identified several candidate genes associated with these disorders, including contactin-associated protein-like 2 (CNTNAP2). Traditionally, in animal models or in vitro, CNTNAP2 has been studied by genetic deletion or transcriptional knockdown, which reduces the expression of the entire gene; however, it remains unclear whether the mutations identified in clinical settings are sufficient to alter CNTNAP2 expression in human neurons. Here, using human induced pluripotent stem cells (hiPSCs) derived from two individuals with a large (289 kb) heterozygous deletion in CNTNAP2 (affecting exons 14–15) and discordant clinical outcomes, we have characterized CNTNAP2 expression patterns in hiPSC neural progenitor cells, two independent populations of hiPSC-derived neurons and hiPSC-derived oligodendrocyte precursor cells. First, we observed exon-specific changes in CNTNAP2 expression in both carriers; although the expression of exons 14–15 is significantly decreased, the expression of other exons is upregulated. Second, we observed significant differences in patterns of allele-specific expression in CNTNAP2 carriers that were consistent with the clinical outcome. Third, we observed a robust neural migration phenotype that correlated with diagnosis and exon- and allele-specific CNTNAP2 expression patterns, but not with genotype. In all, our data highlight the importance of considering the nature, location, and regulation of mutated alleles when attempting to connect genome wide association studies to gene function.

The New York Stem Cell Foundation's "Sixth Annual Translational Stem Cell Research Conference" convened on October 11-12, 2011 at the Rockefeller University in New York City. Over 450 scientists, patient advocates, and stem cell research supporters from 14 countries registered for the conference. In addition to poster and platform presentations, the conference featured panels entitled "Road to the Clinic" and "The Future of Regenerative Medicine."

The New York Stem Cell Foundation's "Fifth Annual Translational Stem Cell Research Conference" convened on October 12-13, 2010 at the Rockefeller University in New York City. The conference attracted over 400 scientists, patient advocates, and stem cell research supporters from 16 countries. In addition to poster and platform presentations, the conference featured panels entitled "Road to the Clinic" and "Regulatory Roadblocks."

B cells, the Ab-producing cells of the immune system, develop from hematopoietic stem cells (HSCs) through well-defined stages during which Ig genes are rearranged to generate a clonal BCR. Signaling through the BCR plays a role in the subsequent cell fate decisions leading to the generation of three distinct types of B cells: B1, marginal zone, and follicular B cells. Common lymphoid progenitors (CLPs) are descended from HSCs, and although recent observations suggest that CLPs may not be physiological T cell precursors, it is generally accepted that CLPs are obligate progenitors for B cells. In addition, a CLP-like progenitor of unknown significance that lacks expression of c-kit (kit−CLP) was recently identified in the mouse model. In this study, we show that CLPs, kit−CLPs and a population within the lin−Sca1+kit+flt3− HSC compartment generate mature B cell types in different proportions: CLPs and kit−CLPs show a stronger marginal zone /follicular ratio than lin−Sca1+kit+flt3− cells, whereas kit−CLPs show a stronger B1 bias than any other progenitor population. Furthermore, expression of Sca1 on B cells depends on their progenitor origin as B cells derived from CLPs and kit−CLPs express more Sca1 than those derived from lin−Sca1+kit+flt3− cells. These observations indicate a role for progenitor origin in B cell fate choices and suggest the existence of CLP-independent B cell development.

The significance of a population in mouse bone marrow of lineage-negative (Lin(-)), Sca1-positive, c-kit-negative (LSK(-)) cells, which is reported to be devoid of long-term repopulation capacity or myeloid potential, is unknown. In this study, we show that the LSK(-) population is composed of several subsets defined by the expression of flt3, CD25, and IL-7Ralpha. The first subset was CD25(-) and more than 90% expressed either flt3, IL-7Ralpha, or both. The CD25(-)LSK(-) population had T cell, B cell, and NK cell potential in vivo, and most of this activity was localized in the flt3(+) subset, irrespective of the expression of IL-7Ralpha. Although lymphoid potential of flt3(+)LSK(-) cells in vivo was 3-fold lower than that of lin(-)Sca1(low)kit(low)IL7Ralpha(+) common lymphoid progenitors (CLPs), their cloning efficiency in vitro was 10-fold lower than that of CLPs. Furthermore, although the myeloid potential of flt3(+)LSK(-) cells was 10-fold lower than that of CLPs in the absence of M-CSF, the relative myeloid potential of both populations was similar in its presence. These observations suggest differential growth factor requirements of both populations. The second subset of LSK(-) cells was homogeneously CD25(+)flt3(-)IL7Ralpha(+) and could be generated from both CD25(-)LSK(-) cells and from CLPs, but did not engraft in immunodeficient Rag1(-/-) or Rag1(-/-)gamma(c)(-/-) hosts. This population, of which the significance is unclear, was increased in Rag1(-/-) mice and in old mice. Thus, the LSK(-) population is phenotypically and functionally heterogeneous and contains early lymphoid-committed precursors. Our findings imply that the early stages of lymphoid commitment are more complex than was thus far assumed.

Achieving gender equality in science will require devising and implementing strategies to overcome the political, administrative, financial, and cultural challenges that exist in the current environment. In this forum, we propose an initial shortlist of recommendations to promote gender equality in science and stimulate future efforts to level the field.

Nat. Neurosci. 19, 1743–1749 (2016); published online 31 October 2016; corrected after print 29 November 2016 In the version of this article initially published, authors Joshua S. Grimley, Anne-Rachel Krostag and Ajamete Kaykas were missing. These authors have been inserted into the author list after Jianhua Chu; they are at the Allen Institute for Brain Science, Seattle, Washington, USA, and performed experiments related to hESCs.

A fundamental impediment to understanding the brain is the availability of inexpensive and robust methods for targeting and manipulating specific neuronal populations. The need to overcome this barrier is pressing because there are considerable anatomical, physiological, cognitive, and behavioral differences between mice and higher mammalian species in which it is difficult to specifically target and manipulate genetically defined functional cell-types. In particular, it is unclear the degree to which insights from mouse models can shed light on the neural mechanisms that mediate cognitive functions in higher species including humans. Here we describe a novel recombinant adeno-associated virus (rAAV) that restricts gene expression to GABAergic interneurons within the telencephalon. We demonstrate that the viral expression is specific and robust, allowing for morphological visualization, activity monitoring and functional manipulation of interneurons in both mice and non-genetically tractable species, thus opening the possibility to study GABA-ergic function in virtually any vertebrate species.

Since monumental studies from scientists like His, Ramon y Cajal, Lorente de No and many others have put down roots for modern neuroscience, the scientific community has spent a considerable amount of time, and money, investigating any possible aspect of the evolution, development and function of neurons. Today, the complexity and diversity of myriads of neuronal populations, and their progenitors, is still focus of extensive studies in hundreds of laboratories around the world. However, our prevalent neuron-centric perspective has dampened the efforts in understanding glial cells, even though their active participation in the brain physiology and pathophysiology has been increasingly recognized over the years. Among all glial cells of the central nervous system (CNS), oligodendrocytes (OLs) are a particularly specialized type of cells that provide fundamental support to neuronal activity by producing the myelin sheath. Despite their functional relevance, the developmental mechanisms regulating the generation of OLs are still poorly understood. In particular, it is still not known whether these cells share the same degree of heterogeneity of their neuronal companions and whether multiple subtypes exist within the lineage. Here, we will review and discuss current knowledge about OL development and function in the brain and spinal cord. We will try to address some specific questions: do multiple OL subtypes exist in the CNS? What is the evidence for their existence and those against them? What are the functional features that define an oligodendrocyte? We will end our journey by reviewing recent advances in human pluripotent stem cell differentiation towards OLs. This exciting field is still at its earliest days, but it is quickly evolving with improved protocols to generate functional OLs from different spatial origins. As stem cells constitute now an unprecedented source of human OLs, we believe that they will become an increasingly valuable tool for deciphering the complexity of human OL identity.