Modeling disrupted synapse formation in wolfram syndrome using hESCs-derived neural cells and cerebral organoids identifies Riluzole as a therapeutic molecule.

Dysregulated neurite outgrowth and synapse formation underlie many psychiatric disorders, which are also manifested by wolfram syndrome (WS). Whether and how the causative gene WFS1 deficiency affects synapse formation remain elusive. By mirroring human brain development with cerebral organoids, WFS1-deficient cerebral organoids not only recapitulate the neuronal loss in WS patients, but also exhibit significantly impaired synapse formation and function associated with reduced astrocytes. WFS1 deficiency in neurons autonomously delays neuronal differentiation with altered expressions of genes associated with psychiatric disorders, and impairs neurite outgrowth and synapse formation with elevated cytosolic calcium. Intriguingly, WFS1 deficiency in astrocytes decreases the expression of glutamate transporter EAAT2 by NF-κB activation and induces excessive glutamate. When co-cultured with wildtype neurons, WFS1-deficient astrocytes lead to impaired neurite outgrowth and increased cytosolic calcium in neurons. Importantly, disrupted synapse formation and function in WFS1-deficient cerebral organoids and impaired neurite outgrowth affected by WFS1-deficient astrocytes are efficiently reversed with Riluzole treatment, by restoring EAAT2 expression in astrocytes. Furthermore, Riluzole rescues the depressive-like behavior in the forced swimming test and the impaired recognition and spatial memory in the novel object test and water maze test in Wfs1 conditional knockout mice. Altogether, our study provides novel insights into how WFS1 deficiency affects synapse formation and function, and offers a strategy to treat this disease.

LncRNA SOX1-OT V1 acts as a decoy of HDAC10 to promote SOX1-dependent hESC neuronal differentiation.

Long noncoding RNAs (lncRNAs) are abundantly expressed in the nervous system, but their regulatory roles in neuronal differentiation are poorly understood. Using a human embryonic stem cell (hESC)-based 2D neural differentiation approach and a 3D cerebral organoid system, we show that SOX1-OT variant 1 (SOX1-OT V1), a SOX1 overlapping noncoding RNA, plays essential roles in both dorsal cortical neuron differentiation and ventral GABAergic neuron differentiation by facilitating SOX1 expression. SOX1-OT V1 physically interacts with HDAC10 through its 5' region, acts as a decoy to block HDAC10 binding to the SOX1 promoter, and thus maintains histone acetylation levels at the SOX1 promoter. SOX1 in turn activates ASCL1 expression and promotes neuronal differentiation. Taken together, we identify a SOX1-OT V1/HDAC10-SOX1-ASCL1 axis, which promotes neurogenesis, highlighting a role for lncRNAs in hESC neuronal differentiation.

RGCC balances self-renewal and neuronal differentiation of neural stem cells in the developing mammalian neocortex.

During neocortical development, neural stem cells (NSCs) divide symmetrically to self-renew at the early stage and then divide asymmetrically to generate post-mitotic neurons. The molecular mechanisms regulating the balance between NSC self-renewal and neurogenesis are not fully understood. Using mouse in utero electroporation (IUE) technique and in vitro human NSC differentiation models including cerebral organoids (hCOs), we show here that regulator of cell cycle (RGCC) modulates NSC self-renewal and neuronal differentiation by affecting cell cycle regulation and spindle orientation. RGCC deficiency hampers normal cell cycle process and dysregulates the mitotic spindle, thus driving more cells to divide asymmetrically. These modulations diminish the NSC population and cause NSC pre-differentiation that eventually leads to brain developmental malformation in hCOs. We further show that RGCC might regulate NSC spindle orientation by affecting the organization of centrosome and microtubules. Our results demonstrate that RGCC is essential to maintain the NSC pool during cortical development and suggest that RGCC defects could have etiological roles in human brain malformations.

PAUPAR and PAX6 sequentially regulate human embryonic stem cell cortical differentiation.

Long noncoding RNAs (lncRNAs) play a wide range of roles in the epigenetic regulation of crucial biological processes, but the functions of lncRNAs in cortical development are poorly understood. Using human embryonic stem cell (hESC)-based 2D neural differentiation approach and 3D cerebral organoid system, we identified that the lncRNA PAUPAR, which is adjacent to PAX6, plays essential roles in cortical differentiation by interacting with PAX6 to regulate the expression of a large number of neural genes. Mechanistic studies showed that PAUPAR confers PAX6 proper binding sites on the target neural genes by directly binding the genomic regions of these genes. Moreover, PAX6 recruits the histone methyltransferase NSD1 through its C-terminal PST enrichment domain, then regulate H3K36 methylation and the expression of target genes. Collectively, our data reveal that the PAUPAR/PAX6/NSD1 complex plays a critical role in the epigenetic regulation of hESC cortical differentiation and highlight the importance of PAUPAR as an intrinsic regulator of cortical differentiation.

Self-organized developmental patterning and differentiation in cerebral organoids.

Cerebral organoids recapitulate human brain development at a considerable level of detail, even in the absence of externally added signaling factors. The patterning events driving this self-organization are currently unknown. Here, we examine the developmental and differentiative capacity of cerebral organoids. Focusing on forebrain regions, we demonstrate the presence of a variety of discrete ventral and dorsal regions. Clearing and subsequent 3D reconstruction of entire organoids reveal that many of these regions are interconnected, suggesting that the entire range of dorso-ventral identities can be generated within continuous neuroepithelia. Consistent with this, we demonstrate the presence of forebrain organizing centers that express secreted growth factors, which may be involved in dorso-ventral patterning within organoids. Furthermore, we demonstrate the timed generation of neurons with mature morphologies, as well as the subsequent generation of astrocytes and oligodendrocytes. Our work provides the methodology and quality criteria for phenotypic analysis of brain organoids and shows that the spatial and temporal patterning events governing human brain development can be recapitulated in vitro.

Genetically engineered cerebral organoids model brain tumor formation.

Brain tumors are among the most lethal and devastating cancers. Their study is limited by genetic heterogeneity and the incompleteness of available laboratory models. Three-dimensional organoid culture models offer innovative possibilities for the modeling of human disease. Here we establish a 3D in vitro model called a neoplastic cerebral organoid (neoCOR), in which we recapitulate brain tumorigenesis by introducing oncogenic mutations in cerebral organoids via transposon- and CRISPR-Cas9-mediated mutagenesis. By screening clinically relevant mutations identified in cancer genome projects, we defined mutation combinations that result in glioblastoma-like and central nervous system primitive neuroectodermal tumor (CNS-PNET)-like neoplasms. We demonstrate that neoCORs are suitable for use in investigations of aspects of tumor biology such as invasiveness, and for evaluation of drug effects in the context of specific DNA aberrations. NeoCORs will provide a valuable complement to the current basic and preclinical models used to study brain tumor biology.

Author Correction: Genetically engineered cerebral organoids model brain tumor formation.

In the originally published paper, the "before" image for the afatinib condition in Fig. 6c was incorrect. Instead of an image displaying a GBM-3 neoplastic organoid before afatinib treatment, this panel showed an image from the GBM-2 control (DMSO) group before treatment. This error has now been corrected in the HTML and PDF versions of the article; the "before, afatinib" panel in Fig. 6c now shows a representative image from the indicated experiment. The color of all error bars in Fig. 6 has also been changed to black, for consistency. All statistical analysis and all conclusions presented in the article are unaffected by this error. Nevertheless, we apologize for the mistake.

Fused cerebral organoids model interactions between brain regions.

Human brain development involves complex interactions between different regions, including long-distance neuronal migration or formation of major axonal tracts. Different brain regions can be cultured in vitro within 3D cerebral organoids, but the random arrangement of regional identities limits the reliable analysis of complex phenotypes. Here, we describe a coculture method combining brain regions of choice within one organoid tissue. By fusing organoids of dorsal and ventral forebrain identities, we generate a dorsal-ventral axis. Using fluorescent reporters, we demonstrate CXCR4-dependent GABAergic interneuron migration from ventral to dorsal forebrain and describe methodology for time-lapse imaging of human interneuron migration. Our results demonstrate that cerebral organoid fusion cultures can model complex interactions between different brain regions. Combined with reprogramming technology, fusions should offer researchers the possibility to analyze complex neurodevelopmental defects using cells from neurological disease patients and to test potential therapeutic compounds.

Stem cell modeling of nervous system tumors.

Nervous system tumors, particularly brain tumors, represent the most common tumors in children and one of the most lethal tumors in adults. Despite decades of research, there are few effective therapies for these cancers. Although human nervous system tumor cells and genetically engineered mouse models have served as excellent platforms for drug discovery and preclinical testing, they have limitations with respect to accurately recapitulating important aspects of the pathobiology of spontaneously arising human tumors. For this reason, attention has turned to the deployment of human stem cell engineering involving human embryonic or induced pluripotent stem cells, in which genetic alterations associated with nervous system cancers can be introduced. These stem cells can be used to create self-assembling three-dimensional cerebral organoids that preserve key features of the developing human brain. Moreover, stem cell-engineered lines are amenable to xenotransplantation into mice as a platform to investigate the tumor cell of origin, discover cancer evolutionary trajectories and identify therapeutic vulnerabilities. In this article, we review the current state of human stem cell models of nervous system tumors, discuss their advantages and disadvantages, and provide consensus recommendations for future research.

Dermatan sulfotransferase Chst14/D4st1, but not chondroitin sulfotransferase Chst11/C4st1, regulates proliferation and neurogenesis of neural progenitor cells.

Chondroitin sulfates (CSs) and dermatan sulfates (DSs) are enriched in the microenvironment of neural stem cells (NSCs) during development and in the adult neurogenic niche, and have been implicated in mechanisms governing neural precursor migration, proliferation and differentiation. In contrast to previous studies, in which a chondroitinaseABC-dependent unselective deglycosylation of both CSs and DSs was performed, we used chondroitin 4-O-sulfotransferase-1 (Chst11/C4st1)- and dermatan 4-O-sulfotransferase-1 (Chst14/D4st1)-deficient NSCs specific for CSs and DSs, respectively, to investigate the involvement of specific sulfation profiles of CS and DS chains, and thus the potentially distinct roles of CSs and DSs in NSC biology. In comparison to wild-type controls, deficiency for Chst14 resulted in decreased neurogenesis and diminished proliferation of NSCs accompanied by increased expression of GLAST and decreased expression of Mash-1, and an upregulation of the expression of the receptors for fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF). By contrast, deficiency in Chst11 did not influence NSC proliferation, migration or differentiation. These observations indicate for the first time that CSs and DSs play distinct roles in the self-renewal and differentiation of NSCs.

In the mouse cortex, oligodendrocytes regain a plastic capacity, transforming into astrocytes after acute injury.

Acute brain injuries evoke various response cascades directing the formation of the glial scar. Here, we report that acute lesions associated with hemorrhagic injuries trigger a re-programming of oligodendrocytes. Single-cell RNA sequencing highlighted a subpopulation of oligodendrocytes activating astroglial genes after acute brain injuries. By using PLP-DsRed1/GFAP-EGFP and PLP-EGFPmem/GFAP-mRFP1 transgenic mice, we visualized this population of oligodendrocytes that we termed AO cells based on their concomitant activity of astro- and oligodendroglial genes. By fate mapping using PLP- and GFAP-split Cre complementation and repeated chronic in vivo imaging with two-photon laser-scanning microscopy, we observed the conversion of oligodendrocytes into astrocytes via the AO cell stage. Such conversion was promoted by local injection of IL-6 and was diminished by IL-6 receptor-neutralizing antibody as well as by inhibiting microglial activation with minocycline. In summary, our findings highlight the plastic potential of oligodendrocytes in acute brain trauma due to microglia-derived IL-6.

A whole-genome scan for Artemisinin cytotoxicity reveals a novel therapy for human brain tumors.

The natural compound Artemisinin is the most widely used antimalarial drug worldwide. Based on its cytotoxicity, it is also used for anticancer therapy. Artemisinin and its derivates are endoperoxides that damage proteins in eukaryotic cells; their definite mechanism of action and host cell targets, however, have remained largely elusive. Using yeast and haploid stem cell screening, we demonstrate that a single cellular pathway, namely porphyrin (heme) biosynthesis, is required for the cytotoxicity of Artemisinins. Genetic or pharmacological modulation of porphyrin production is sufficient to alter its cytotoxicity in eukaryotic cells. Using multiple model systems of human brain tumor development, such as cerebral glioblastoma organoids, and patient-derived tumor spheroids, we sensitize cancer cells to dihydroartemisinin using the clinically approved porphyrin enhancer and surgical fluorescence marker 5-aminolevulinic acid, 5-ALA. A combination treatment of Artemisinins and 5-ALA markedly and specifically killed brain tumor cells in all model systems tested, including orthotopic patient-derived xenografts in vivo. These data uncover the critical molecular pathway for Artemisinin cytotoxicity and a sensitization strategy to treat different brain tumors, including drug-resistant human glioblastomas.

Reversion of MRAP2 Protein Sequence Generates a Functional Novel Pharmacological Modulator for MC4R Signaling.

As a member of the melanocortin receptor family, melanocortin 4 receptor (MC4R) plays a critical role in regulating energy homeostasis and feeding behavior, and has been proven as a promising therapeutic target for treating severe obesity syndrome. Numerous studies have demonstrated that central MC4R signaling is significantly affected by melanocortin receptor accessory protein 2 (MRAP2) in humans, mice and zebrafish. MRAP2 proteins exist as parallel or antiparallel dimers on the plasma membrane, but the structural insight of dual orientations with the pharmacological profiles has not yet been fully studied. Investigation and optimization of the conformational topology of MRAP2 are critical for the development of transmembrane allosteric modulators to treat MC4R-associated disorders. In this study, we synthesized a brand new single transmembrane protein by reversing wild-type mouse and zebrafish MRAP2 sequences and examined their dimerization, interaction and pharmacological activities on mouse and zebrafish MC4R signaling. We showed that the reversed zebrafish MRAPa exhibited an opposite function on modulating zMC4R signaling and the reversed mouse MRAP2 lost the capability for regulating MC4R trafficking but exhibited a novel function for cAMP cascades, despite proper expression and folding. Taken together, our results provided new biochemical insights on the oligomeric states and membrane orientations of MRAP2 proteins, as well as its pharmacological assistance for modulating MC4R signaling.

Determination of the Interaction and Pharmacological Modulation of MCHR1 Signaling by the C-Terminus of MRAP2 Protein.

Melanin concentrating hormone (MCH), an orexigenic neuropeptide, is primarily secreted by the hypothalamus and acts on its receptor, the melanin-concentrating hormone receptor 1 (MCHR1), to regulate appetite and energy homeostasis. The Melanocortin Receptor Accessory Protein 2 (MRAP2), a small single transmembrane protein broadly expressed in multiple tissues, has been defined as a vital endocrine modulator of five melanocortin receptors (MC1R-MC5R) and several other GPCRs in the regulation of central neuronal activities and peripheral energy balance. Here, we demonstrated the interaction between MRAP2 and MCHR1 by immunoprecipitation and bimolecular fluorescent assay and found that MRAP2 could inhibit MCHR1 signaling in vitro. A series of functional truncations of different regions further identified that the C-terminal domains of MRAP2 protein were required for the pharmacological modulation of intracellular Ca2+ coupled cascades and membrane transport. These findings elucidated the broad regulatory profile of MRAP2 protein in the central nervous system and may provide implications for the modulation of central MCHR1 function in vivo.

Functional role of the interaction between polysialic acid and extracellular histone H1.

Polysialic acid (PSA) is a large and highly negatively charged glycan that plays crucial roles in nervous system development and function in the adult. It has been suggested to facilitate cell migration, neurite outgrowth, and synaptic plasticity because its hydration volume could enhance flexibility of cell interactions. Evidence for receptors of PSA has so far been elusive. We now identified histone H1 as binding partner of PSA via a single-chain variable fragment antibody using an anti-idiotypic approach. Histone H1 directly binds to PSA as shown by ELISA. Surface biotinylation of cultured cerebellar neurons indicated an extracellular localization of histone H1. Immunostaining of live cerebellar neurons and Schwann cells confirmed that an extracellular pool of histone H1 colocalizes with PSA at the cell surface. Histone H1 was also detected in detergent-insoluble synaptosomal membrane subfractions and postsynaptic densities. When applied in vitro, histone H1 stimulated neuritogenesis, process formation and proliferation of Schwann cells, and migration of neural precursor cells via a PSA-dependent mechanism, further indicating that histone H1 is active extracellularly. These in vitro observations suggested an important functional role for the interaction between histone H1 and PSA not only for nervous system development but also for regeneration in the adult. Indeed, histone H1 improved functional recovery, axon regrowth, and precision of reinnervation of the motor branch in adult mice with femoral nerve injury. Our findings encourage investigations on the therapeutic potential of histone H1 in humans.

Maternal sevoflurane exposure induces temporary defects in interkinetic nuclear migration of radial glial progenitors in the fetal cerebral cortex through the Notch signalling pathway.

OBJECTIVES: The effects of general anaesthetics on fetal brain development remain elusive. Radial glial progenitors (RGPs) generate the majority of neurons in developing brains. Here, we evaluated the acute alterations in RGPs after maternal sevoflurane exposure. METHODS: Pregnant mice were exposed to 2.5% sevoflurane for 6 hours on gestational day 14.5. Interkinetic nuclear migration (INM) of RGPs in the ventricular zone (VZ) of the fetal brain was evaluated by thymidine analogues labelling. Cell fate of RGP progeny was determined by immunostaining using various neural markers. The Morris water maze (MWM) was used to assess the neurocognitive behaviours of the offspring. RNA sequencing (RNA-Seq) was performed for the potential mechanism, and the potential mechanism validated by quantitative real-time PCR (qPCR), Western blot and rescue experiments. Furthermore, INM was examined in human embryonic stem cell (hESC)-derived 3D cerebral organoids. RESULTS: Maternal sevoflurane exposure induced temporary abnormities in INM, and disturbed the cell cycle progression of RGPs in both rodents and cerebral organoids without cell fate alternation. RNA-Seq analysis, qPCR and Western blot showed that the Notch signalling pathway was a potential downstream target. Reactivation of Notch by Jag1 and NICD overexpression rescued the defects in INM. Young adult offspring showed no obvious cognitive impairments in MWM. CONCLUSIONS: Maternal sevoflurane exposure during neurogenic period temporarily induced abnormal INM of RGPs by targeting the Notch signalling pathway without inducing long-term effects on RGP progeny cell fate or offspring cognitive behaviours. More importantly, the defects of INM in hESC-derived cerebral organoids provide a novel insight into the effects of general anaesthesia on human brain development.

Polysialic acid glycomimetics promote myelination and functional recovery after peripheral nerve injury in mice.

alpha2,8 Polysialic acid (PSA) is a carbohydrate attached to the glycoprotein backbone of the neural cell adhesion molecule (NCAM) and implicated in nervous system development and repair. Here, we investigated whether PSA can improve functional recovery after peripheral nerve lesion in adult mice. We applied a functional PSA mimicking peptide or a control peptide in a polyethylene cuff used to surgically reconnect the severed stumps of the femoral nerve before it bifurcates into the motor and sensory branches. Using video-based motion analysis to monitor motor recovery over a 3 month postoperative period, we observed a better functional outcome in the PSA mimetic-treated than in control mice receiving a control peptide or phosphate buffered saline. Retrograde tracing of regenerated motoneurons and morphometric analyses showed that motoneuron survival, motoneuron soma size and axonal diameters were not affected by treatment with the PSA mimetic. However, remyelination of regenerated axons distal to the injury site was considerably improved by the PSA mimetic indicating that effects on Schwann cells in the denervated nerve may underlie the functional effects seen in motor recovery. In line with this notion was the observation that the PSA mimetic enhanced the elongation of Schwann cell processes and Schwann cell proliferation in vitro, when compared with the control peptide. Moreover, Schwann cell proliferation in vivo was enhanced in both motor and sensory branches of the femoral nerve by application of the PSA mimetic. These effects were likely mediated by NCAM through its interaction with the fibroblast growth factor receptor (FGFR), since they were not observed when the PSA mimetic was applied to NCAM-deficient Schwann cells, and since application of two different FGFR inhibitors reduced process elongation from Schwann cells in vitro. Our results indicate the potential of PSA mimetics as therapeutic agents promoting motor recovery and myelination after peripheral nerve injury.

Application of Fused Organoid Models to Study Human Brain Development and Neural Disorders.

Human brain organoids cultured from human pluripotent stem cells provide a promising platform to recapitulate histological features of the human brain and model neural disorders. However, unlike animal models, brain organoids lack a reproducible topographic organization, which limits their application in modeling intricate biology, such as the interaction between different brain regions. To overcome these drawbacks, brain organoids have been pre-patterned into specific brain regions and fused to form an assembloid that represents reproducible models recapitulating more complex biological processes of human brain development and neurological diseases. This approach has been applied to model interneuron migration, neuronal projections, tumor invasion, oligodendrogenesis, forebrain axis establishment, and brain vascularization. In this review article, we will summarize the usage of this technology to understand the fundamental biology underpinning human brain development and disorders.