Capturing the biology of disease severity in a PSC-based model of familial dysautonomia

Advances and challenges in modeling inherited peripheral neuropathies using iPSCs

Inherited peripheral neuropathies (IPNs) are a group of diseases associated with mutations in various genes with fundamental roles in the development and function of peripheral nerves. Over the past 10 years, significant advances in identifying molecular disease mechanisms underlying axonal and myelin degeneration, acquired from cellular biology studies and transgenic fly and rodent models, have facilitated the development of promising treatment strategies. However, no clinical treatment has emerged to date. This lack of treatment highlights the urgent need for more biologically and clinically relevant models recapitulating IPNs. For both neurodevelopmental and neurodegenerative diseases, patient-specific induced pluripotent stem cells (iPSCs) are a particularly powerful platform for disease modeling and preclinical studies. In this review, we provide an update on different in vitro human cellular IPN models, including traditional two-dimensional monoculture iPSC derivatives, and recent advances in more complex human iPSC-based systems using microfluidic chips, organoids, and assembloids.

Molecular and cellular neurocardiology in heart disease

This paper updates and builds on a previous White Paper in this journal that some of us contributed to concerning the molecular and cellular basis of cardiac neurobiology of heart disease. Here we focus on recent findings that underpin cardiac autonomic development, novel intracellular pathways and neuroplasticity. Throughout we highlight unanswered questions and areas of controversy. Whilst some neurochemical pathways are already demonstrating prognostic viability in patients with heart failure, we also discuss the opportunity to better understand sympathetic impairment by using patient specific stem cells that provides pathophysiological contextualization to study 'disease in a dish'. Novel imaging techniques and spatial transcriptomics are also facilitating a road map for target discovery of molecular pathways that may form a therapeutic opportunity to treat cardiac dysautonomia.

Parasympathetic neurons derived from human pluripotent stem cells model human diseases and development

Autonomic parasympathetic neurons (parasymNs) control unconscious body responses, including "rest-and-digest." ParasymN innervation is important for organ development, and parasymN dysfunction is a hallmark of autonomic neuropathy. However, parasymN function and dysfunction in humans are vastly understudied due to the lack of a model system. Human pluripotent stem cell (hPSC)-derived neurons can fill this void as a versatile platform. Here, we developed a differentiation paradigm detailing the derivation of functional human parasymNs from Schwann cell progenitors. We employ these neurons (1) to assess human autonomic nervous system (ANS) development, (2) to model neuropathy in the genetic disorder familial dysautonomia (FD), (3) to show parasymN dysfunction during SARS-CoV-2 infection, (4) to model the autoimmune disease Sjögren's syndrome (SS), and (5) to show that parasymNs innervate white adipocytes (WATs) during development and promote WAT maturation. Our model system could become instrumental for future disease modeling and drug discovery studies, as well as for human developmental studies.

Isogenic hiPSC models of Turner syndrome development reveal shared roles of inactive X and Y in the human cranial neural crest network

Modeling the developmental etiology of viable human aneuploidy can be challenging in rodents due to syntenic boundaries, or primate-specific biology. In humans, monosomy-X (45,X) causes Turner syndrome (TS), altering craniofacial, skeletal, endocrine, and cardiovascular development, which in contrast remain unaffected in 39,X-mice. To learn how human monosomy-X may impact early embryonic development, we turned to human 45,X and isogenic euploid induced pluripotent stem cells (hiPSCs) from male and female mosaic donors. Because neural crest (NC) derived cell types are hypothesized to underpin craniofacial and cardiovascular changes in TS, we performed a highly-powered differential expression study on hiPSC-derived anterior neural crest cells (NCCs). Across three independent isogenic panels, 45,X NCCs show impaired acquisition of PAX7+SOX10+ markers, and disrupted expression of other NCC-specific genes, relative to their isogenic euploid controls. In particular, 45,X NCCs increase cholesterol biosynthesis genes while reducing transcripts that feature 5' terminal oligopyrimidine (TOP) motifs, including those of ribosomal protein and nuclear-encoded mitochondrial genes. Such metabolic pathways are also over-represented in weighted co-expression gene modules that are preserved in monogenic neurocristopathy. Importantly, these gene modules are also significantly enriched in 28% of all TS-associated terms of the human phenotype ontology. Our analysis identifies specific sex-linked genes that are expressed from two copies in euploid males and females alike and qualify as candidate haploinsufficient drivers of TS phenotypes in NC-derived lineages. This study demonstrates that isogenic hiPSC-derived NCC panels representing monosomy-X can serve as a powerful model of early NC development in TS and inform new hypotheses towards its etiology.

Generation of Functional and Mature Sympathetic Neurons from Human Pluripotent Stem Cells via a Neuroepithelial Route

The sympathetic nervous system (SNS) is a crucial branch of the autonomic nervous system (ANS) that is responsible for regulating visceral function and various physiological processes. Dysfunction of the SNS can lead to various diseases, such as hypertension and metabolic disorders. However, obtaining sympathetic neurons from human tissues for research is challenging. The current research aimed at recapitulating the process of human sympathetic neuron development and achieved the successful establishment of a stepwise, highly efficient in vitro differentiation protocol. This protocol facilitated the generation of functional and mature sympathetic neurons from human pluripotent stem cells (hPSCs) using a chemical-defined induction medium. Initially, each differentiation stage was refined to derive sympathoadrenal progenitors (SAPs) from hPSCs through neural epithelial cells (NECs) and trunk neural crest stem cells (NCSCs). hPSC-derived SAPs could be expanded in vitro for at least 12 passages while maintaining the expression of SAP-specific transcription factors and neuronal differentiation potency. SAPs readily generated functional sympathetic neurons (SymNs) when cultured in the neuronal maturation medium for 3-4 weeks. These SymNs expressed sympathetic markers, exhibited electrophysiological properties, and secreted sympathetic neurotransmitters. More importantly, we further demonstrated that hPSC-derived SymNs can efficiently regulate the adipogenesis of human adipose-derived stem cells (ADSCs) and lipid metabolism in vitro. In conclusion, our study provided a simple and robust protocol for generating functional sympathetic neurons from hPSCs, which may be an invaluable tool in unraveling the mechanisms of SNS-related diseases.

Low glucose induced Alzheimer's disease-like biochemical changes in human induced pluripotent stem cell-derived neurons is due to dysregulated O-GlcNAcylation

INTRODUCTION

Sporadic Alzheimer's disease (sAD) is the leading type of dementia. Brain glucose hypometabolism, along with decreased O-GlcNAcylation levels, occurs before the onset of symptoms and correlates with pathogenesis. Heretofore, the mechanisms involved and the roles of O-GlcNAcylation in sAD pathology largely remain unknown due to a lack of human models of sAD.

METHODS

Human cortical neurons were generated from pluripotent stem cells (PSCs) and treated with glucose reduction media.

RESULTS

We found a narrow window of glucose concentration that induces sAD-like phenotypes in PSC-derived neurons. With our model, we reveal that dysregulated O-GlcNAc, in part through mitochondrial dysfunction, causes the onset of sAD-like changes. We demonstrate the therapeutic potential of inhibiting O-GlcNAcase in alleviating AD-like biochemical changes.

DISCUSSION

Our results suggest that dysregulated O-GlcNAc might be a direct molecular link between hypometabolism and sAD-like alternations. Moreover, this model can be exploited to explore molecular processes and for drug development.

HIGHLIGHTS

Lowering glucose to a critical level causes AD-like changes in cortical neurons. Defective neuronal structure and function were also recapitulated in current model. Dysregulated O-GlcNAcylation links impaired glucose metabolism to AD-like changes. Mitochondrial abnormalities correlate with O-GlcNAcylation and precede AD-like phenotype. Our model provides a platform to study sAD as a metabolic disease in human neurons.

Isolation of human pluripotent stem cell-derived sensory neuron subtypes by immunopanning

Sensory neurons (SNs) detect a wide range of information from the body and the environment that is critical for homeostasis. There are three main subtypes of SNs: nociceptors, mechanoreceptors, and proprioceptors, which express different membrane proteins, such as TRKA, TRKB, or TRKC, respectively. Human pluripotent stem cell technology provides an ideal platform to study development and diseases of SNs, however there is not a viable method to isolate individual SN subtype for downstream analysis available. Here, we employ the method immunopanning to isolate each SN subtype. This method is very gentle and allows proper survival after the isolation. We use antibodies against TRKA, TRKB, and TRKC to isolate nociceptors, mechanoreceptors, and proprioceptors, respectively. We show that our cultures are enriched for each subtype and express their respective subtype markers. Furthermore, we show that the immunopanned SNs are electrically active and respond to specific stimuli. Thus, our method can be used to purify viable neuronal subtypes using respective membrane proteins for downstream studies.

Genipin Crosslinks the Extracellular Matrix to Rescue Developmental and Degenerative Defects, and Accelerates Regeneration of Peripheral Neurons

The peripheral nervous system (PNS) is essential for proper body function. A high percentage of the population suffer nerve degeneration or peripheral damage. For example, over 40% of patients with diabetes or undergoing chemotherapy develop peripheral neuropathies. Despite this, there are major gaps in the knowledge of human PNS development and therefore, there are no available treatments. Familial Dysautonomia (FD) is a devastating disorder that specifically affects the PNS making it an ideal model to study PNS dysfunction. FD is caused by a homozygous point mutation in ELP1 leading to developmental and degenerative defects in the sensory and autonomic lineages. We previously employed human pluripotent stem cells (hPSCs) to show that peripheral sensory neurons (SNs) are not generated efficiently and degenerate over time in FD. Here, we conducted a chemical screen to identify compounds able to rescue this SN differentiation inefficiency. We identified that genipin, a compound prescribed in Traditional Chinese Medicine for neurodegenerative disorders, restores neural crest and SN development in FD, both in the hPSC model and in a FD mouse model. Additionally, genipin prevented FD neuronal degeneration, suggesting that it could be offered to patients suffering from PNS neurodegenerative disorders. We found that genipin crosslinks the extracellular matrix, increases the stiffness of the ECM, reorganizes the actin cytoskeleton, and promotes transcription of YAP-dependent genes. Finally, we show that genipin enhances axon regeneration in an in vitro axotomy model in healthy sensory and sympathetic neurons (part of the PNS) and in prefrontal cortical neurons (part of the central nervous system, CNS). Our results suggest genipin can be used as a promising drug candidate for treatment of neurodevelopmental and neurodegenerative diseases, and as a enhancer of neuronal regeneration.

Development of an oral treatment that rescues gait ataxia and retinal degeneration in a phenotypic mouse model of familial dysautonomia

Familial dysautonomia (FD) is a rare neurodegenerative disease caused by a splicing mutation in elongator acetyltransferase complex subunit 1 (ELP1). This mutation leads to the skipping of exon 20 and a tissue-specific reduction of ELP1, mainly in the central and peripheral nervous systems. FD is a complex neurological disorder accompanied by severe gait ataxia and retinal degeneration. There is currently no effective treatment to restore ELP1 production in individuals with FD, and the disease is ultimately fatal. After identifying kinetin as a small molecule able to correct the ELP1 splicing defect, we worked on its optimization to generate novel splicing modulator compounds (SMCs) that can be used in individuals with FD. Here, we optimize the potency, efficacy, and bio-distribution of second-generation kinetin derivatives to develop an oral treatment for FD that can efficiently pass the blood-brain barrier and correct the ELP1 splicing defect in the nervous system. We demonstrate that the novel compound PTC258 efficiently restores correct ELP1 splicing in mouse tissues, including brain, and most importantly, prevents the progressive neuronal degeneration that is characteristic of FD. Postnatal oral administration of PTC258 to the phenotypic mouse model TgFD9;Elp1Δ20/flox increases full-length ELP1 transcript in a dose-dependent manner and leads to a 2-fold increase in functional ELP1 in the brain. Remarkably, PTC258 treatment improves survival, gait ataxia, and retinal degeneration in the phenotypic FD mice. Our findings highlight the great therapeutic potential of this novel class of small molecules as an oral treatment for FD.

Emergence of nociceptive functionality and opioid signaling in human induced pluripotent stem cell-derived sensory neurons

ABSTRACT

Induced pluripotent stem cells (iPSCs) have enabled the generation of various difficult-to-access cell types such as human nociceptors. A key challenge associated with human iPSC-derived nociceptors (hiPSCdNs) is their prolonged functional maturation. While numerous studies have addressed the expression of classic neuronal markers and ion channels in hiPSCdNs, the temporal development of key signaling cascades regulating nociceptor activity has remained largely unexplored. In this study, we used an immunocytochemical high-content imaging approach alongside electrophysiological staging to assess metabotropic and ionotropic signaling of large scale-generated hiPSCdNs across 70 days of in vitro differentiation. During this period, the resting membrane potential became more hyperpolarized, while rheobase, action potential peak amplitude, and membrane capacitance increased. After 70 days, hiPSCdNs exhibited robust physiological responses induced by GABA, pH shift, ATP, and capsaicin. Direct activation of protein kinase A type II (PKA-II) through adenylyl cyclase stimulation with forskolin resulted in PKA-II activation at all time points. Depolarization-induced activation of PKA-II emerged after 35 days of differentiation. However, effective inhibition of forskolin-induced PKA-II activation by opioid receptor agonists required 70 days of in vitro differentiation. Our results identify a pronounced time difference between early expression of functionally important ion channels and emergence of regulatory metabotropic sensitizing and desensitizing signaling only at advanced stages of in vitro cultivation, suggesting an independent regulation of ionotropic and metabotropic signaling. These data are relevant for devising future studies into the development and regulation of human nociceptor function and for defining time windows suitable for hiPSCdN-based drug discovery.

Modeling incomplete penetrance in arrhythmogenic cardiomyopathy by human induced pluripotent stem cell derived cardiomyocytes

Human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs) are commonly used to model arrhythmogenic cardiomyopathy (ACM), a heritable cardiac disease characterized by severe ventricular arrhythmias, fibrofatty myocardial replacement and progressive ventricular dysfunction. Although ACM is inherited as an autosomal dominant disease, incomplete penetrance and variable expressivity are extremely common, resulting in different clinical manifestations. Here, we propose hiPSC-CMs as a powerful in vitro model to study incomplete penetrance in ACM. Six hiPSC lines were generated from blood samples of three ACM patients carrying a heterozygous deletion of exon 4 in the PKP2 gene, two asymptomatic (ASY) carriers of the same mutation and one healthy control (CTR), all belonging to the same family. Whole exome sequencing was performed in all family members and hiPSC-CMs were examined by ddPCR, western blot, Wes™ immunoassay system, patch clamp, immunofluorescence and RNASeq. Our results show molecular and functional differences between ACM and ASY hiPSC-CMs, including a higher amount of mutated PKP2 mRNA, a lower expression of the connexin-43 protein, a lower overall density of sodium current, a higher intracellular lipid accumulation and sarcomere disorganization in ACM compared to ASY hiPSC-CMs. Differentially expressed genes were also found, supporting a predisposition for a fatty phenotype in ACM hiPSC-CMs. These data indicate that hiPSC-CMs are a suitable model to study incomplete penetrance in ACM.

Norepinephrine transporter defects lead to sympathetic hyperactivity in Familial Dysautonomia models

Familial dysautonomia (FD), a rare neurodevelopmental and neurodegenerative disorder affects the sympathetic and sensory nervous system. Although almost all patients harbor a mutation in ELP1, it remains unresolved exactly how function of sympathetic neurons (symNs) is affected; knowledge critical for understanding debilitating disease hallmarks, including cardiovascular instability or dysautonomic crises, that result from dysregulated sympathetic activity. Here, we employ the human pluripotent stem cell (hPSC) system to understand symN disease mechanisms and test candidate drugs. FD symNs are intrinsically hyperactive in vitro, in cardiomyocyte co-cultures, and in animal models. We report reduced norepinephrine transporter expression, decreased intracellular norepinephrine (NE), decreased NE re-uptake, and excessive extracellular NE in FD symNs. SymN hyperactivity is not a direct ELP1 mutation result, but may connect to NET via RAB proteins. We found that candidate drugs lowered hyperactivity independent of ELP1 modulation. Our findings may have implications for other symN disorders and may allow future drug testing and discovery.

Stem Cell-Based Models for Studying the Effects of Cancer and Cancer Therapies on the Peripheral Nervous System

In recent years, the complexity of cancer and cancer therapies and their interactions with the peripheral nervous system have come into focus, but limitations in experimental models have remained a significant challenge in the field. As evidence, there are currently no therapies approved that target cancer-peripheral nervous system or cancer therapy-peripheral nervous system interactions as an anti-neoplastic or anti-neurotoxic agent, respectively. Human pluripotent stem cells offer an appealing model system that, unlike rodent models, is compatible with high throughput, high content applications; techniques that reflect modern drug discovery methodologies. Thus, utilizing the key advantages of stem cell-based models in tandem with the strengths of traditional animal models offers a complementary and interdisciplinary strategy to advance cancer and cancer therapy-peripheral nervous system research and drug discovery. In this review, the current status of the cancer-peripheral nervous system and cancer therapy-peripheral nervous system research is discussed, examples where stem cell-based models have been implemented are described, and avenues where stem cell-based models may further advance the field are proposed.

Developmental regulation of neuronal gene expression by Elongator complex protein 1 dosage

Familial dysautonomia (FD), a hereditary sensory and autonomic neuropathy, is caused by a mutation in the Elongator complex protein 1 (ELP1) gene that leads to a tissue-specific reduction of ELP1 protein. Our work to generate a phenotypic mouse model for FD headed to the discovery that homozygous deletion of the mouse Elp1 gene leads to embryonic lethality prior to mid-gestation. Given that FD is caused by a reduction, not loss, of ELP1, we generated two new mouse models by introducing different copy numbers of the human FD ELP1 transgene into the Elp1 knockout mouse (Elp1-/-) and observed that human ELP1 expression rescues embryonic development in a dose-dependent manner. We then conducted a comprehensive transcriptome analysis in mouse embryos to identify genes and pathways whose expression correlates with the amount of ELP1. We found that ELP1 is essential for the expression of genes responsible for nervous system development. Further, gene length analysis of the differentially expressed genes showed that the loss of Elp1 mainly impacts the expression of long genes and that by gradually restoring Elongator, their expression is progressively rescued. Finally, through evaluation of co-expression modules, we identified gene sets with unique expression patterns that depended on ELP1 expression.

Selective retinal ganglion cell loss and optic neuropathy in a humanized mouse model of familial dysautonomia

Familial dysautonomia (FD) is an autosomal recessive neurodegenerative disease caused by a splicing mutation in the gene encoding Elongator complex protein 1 (ELP1, also known as IKBKAP). This mutation results in tissue-specific skipping of exon 20 with a corresponding reduction of ELP1 protein, predominantly in the central and peripheral nervous system. Although FD patients have a complex neurological phenotype caused by continuous depletion of sensory and autonomic neurons, progressive visual decline leading to blindness is one of the most problematic aspects of the disease, as it severely affects their quality of life. To better understand the disease mechanism as well as to test the in vivo efficacy of targeted therapies for FD, we have recently generated a novel phenotypic mouse model, TgFD9; IkbkapΔ20/flox. This mouse exhibits most of the clinical features of the disease and accurately recapitulates the tissue-specific splicing defect observed in FD patients. Driven by the dire need to develop therapies targeting retinal degeneration in FD, herein, we comprehensively characterized the progression of the retinal phenotype in this mouse, and we demonstrated that it is possible to correct ELP1 splicing defect in the retina using the splicing modulator compound (SMC) BPN-15477.

Towards bridging the translational gap by improved modeling of human nociception in health and disease

Despite numerous studies which have explored the pathogenesis of pain disorders in preclinical models, there is a pronounced translational gap, which is at least partially caused by differences between the human and rodent nociceptive system. An elegant way to bridge this divide is the exploitation of human-induced pluripotent stem cell (iPSC) reprogramming into human iPSC-derived nociceptors (iDNs). Several protocols were developed and optimized to model nociceptive processes in health and disease. Here we provide an overview of the different approaches and summarize the knowledge obtained from such models on pain pathologies associated with monogenetic sensory disorders so far. In addition, novel perspectives offered by increasing the complexity of the model systems further to better reflect the natural environment of nociceptive neurons by involving other cell types in 3D model systems are described.

A protocol to differentiate nociceptors, mechanoreceptors, and proprioceptors from human pluripotent stem cells

Human pluripotent stem cells (hPSCs) show promise for studying diseases affecting cell populations that are not easily available, including sensory neurons (SNs). Here, we present a differentiation protocol in chemically defined conditions to generate peripheral SNs from hPSCs. We describe four main steps: expansion of hPSCs, neural crest cell (NCC) differentiation, NCC dissociation and replating, and sensory neuron (SN) differentiation. This protocol enables generation of a mechanoreceptor-enriched culture or a population containing all three SN subtypes (nociceptors, mechanoreceptors, and proprioceptors).

For complete details on the use and execution of this protocol, please refer to Saito-Diaz et al. (2021).

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Protocol for differentiation of hPSCs into different types of SNs from one culture

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Step-by-step protocol for in vitro differentiation of NCCs

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In vitro differentiation into mechanoreceptor-enriched culture

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Differentiation of three main SN subtypes that mimic in vivo composition

A dual SHOX2:GFP; MYH6:mCherry knockin hESC reporter line for derivation of human SAN-like cells

The sinoatrial node (SAN) is the primary pacemaker of the heart. The human SAN is poorly understood due to limited primary tissue access and limitations in robust in vitro derivation methods. We developed a dual SHOX2:GFP; MYH6:mCherry knockin human embryonic stem cell (hESC) reporter line, which allows the identification and purification of SAN-like cells. Using this line, we performed several rounds of chemical screens and developed an efficient strategy to generate and purify hESC-derived SAN-like cells (hESC-SAN). The derived hESC-SAN cells display molecular and electrophysiological characteristics of bona fide nodal cells, which allowed exploration of their transcriptional profile at single-cell level. In sum, our dual reporter system facilitated an effective strategy for deriving human SAN-like cells, which can potentially be used for future disease modeling and drug discovery.

A metastasis-on-a-chip approach to explore the sympathetic modulation of breast cancer bone metastasis

Organ-on-a-chip models have emerged as a powerful tool to model cancer metastasis and to decipher specific crosstalk between cancer cells and relevant regulators of this particular niche. Recently, the sympathetic nervous system (SNS) was proposed as an important modulator of breast cancer bone metastasis. However, epidemiological studies concerning the benefits of the SNS targeting drugs on breast cancer survival and recurrence remain controversial. Thus, the role of SNS signaling over bone metastatic cancer cellular processes still requires further clarification. Herein, we present a novel humanized organ-on-a-chip model recapitulating neuro-breast cancer crosstalk in a bone metastatic context. We developed and validated an innovative three-dimensional printing based multi-compartment microfluidic platform, allowing both selective and dynamic multicellular paracrine signaling between sympathetic neurons, bone tropic breast cancer cells and osteoclasts. The selective multicellular crosstalk in combination with biochemical, microscopic and proteomic profiling show that synergistic paracrine signaling from sympathetic neurons and osteoclasts increase breast cancer aggressiveness demonstrated by augmented levels of pro-inflammatory cytokines (e.g. interleukin-6 and macrophage inflammatory protein 1α). Overall, this work introduced a novel and versatile platform that could potentially be used to unravel new mechanisms involved in intracellular communication at the bone metastatic niche.

The crucial role of model systems in understanding the complexity of cell signaling in human neurocristopathies

Animal models are useful to study the molecular, cellular, and morphogenetic mechanisms underlying normal and pathological development. Cell-based study models have emerged as an alternative approach to study many aspects of human embryonic development and disease. The neural crest (NC) is a transient, multipotent, and migratory embryonic cell population that generates a diverse group of cell types that arises during vertebrate development. The abnormal formation or development of the NC results in neurocristopathies (NCPs), which are characterized by a broad spectrum of functional and morphological alterations. The impaired molecular mechanisms that give rise to these multiphenotypic diseases are not entirely clear yet. This fact, added to the high incidence of these disorders in the newborn population, has led to the development of systematic approaches for their understanding. In this article, we have systematically reviewed the ways in which experimentation with different animal and cell model systems has improved our knowledge of NCPs, and how these advances might contribute to the development of better diagnostic and therapeutic tools for the treatment of these pathologies. This article is categorized under: Congenital Diseases > Genetics/Genomics/Epigenetics Congenital Diseases > Stem Cells and Development Congenital Diseases > Molecular and Cellular Physiology Neurological Diseases > Genetics/Genomics/Epigenetics.

Bone biomechanical properties and tissue-scale bone quality in a genetic mouse model of familial dysautonomia

PURPOSE

Familial dysautonomia (FD) is associated with a high prevalence of bone fractures, but the impacts of the disease on bone mass and quality are unclear. The purpose of this study was to evaluate tissue through whole-bone scale bone quality in a mouse model of FD.

METHODS

Femurs from mature adult Tuba1a-Cre; Elp1^LoxP/LoxP conditional knockouts (CKO) (F = 7, M = 4) and controls (F = 5, M = 6) were evaluated for whole-bone flexural material properties, trabecular microarchitecture and cortical geometry, and areal bone mineral density (BMD). Adjacent maps spanning the thickness of femur midshaft cortical bone assessed tissue-scale modulus (nanoindentation), bone mineralization, mineral maturity, and collagen secondary structure (Raman spectroscopy).

RESULTS

Consistent with prior studies on this mouse model, the Elp1 CKO mouse model recapitulated several key hallmarks of human FD, with one difference being the male mice tended to have a more severe phenotype than females. Deletion of Elp1 in neurons (using the neuronal-specific Tuba1a-cre) led to a significantly reduced whole-bone toughness but not strength or modulus. Elp1 CKO female mice had reduced trabecular microarchitecture (BV/TV, Tb.Th, Conn.D.) but not cortical geometry. The mutant mice also had a small but significant reduction in cortical bone nanoindentation modulus. While bone tissue mineralization and mineral maturity were not impaired, FD mice may have altered collagen secondary structure. Changes in collagen secondary structure were inversely correlated with bone toughness. BMD from dual-energy x-ray absorptiometry (DXA) was unchanged with FD.

CONCLUSION

The deletion of Elp1 in neurons is sufficient to generate a mouse line which demonstrates loss of whole-bone toughness, consistent with the poor bone quality suspected in the clinical setting. The Elp1 CKO model, as with human FD, impacts the nervous system, gut, kidney function, mobility, gait, and posture. The bone quality phenotype of Elp1 CKO mice, which includes altered microarchitecture and tissue-scale material properties, is complex and likely influenced by these multisystemic changes. This mouse model may provide a useful platform to not only investigate the mechanisms responsible for bone fragility in FD, but also a powerful model system with which to evaluate potential therapeutic interventions for bone fragility in FD patients.

The sympathetic nervous system in development and disease

The sympathetic nervous system prepares the body for 'fight or flight' responses and maintains homeostasis during daily activities such as exercise, eating a meal or regulation of body temperature. Sympathetic regulation of bodily functions requires the establishment and refinement of anatomically and functionally precise connections between postganglionic sympathetic neurons and peripheral organs distributed widely throughout the body. Mechanistic studies of key events in the formation of postganglionic sympathetic neurons during embryonic and early postnatal life, including axon growth, target innervation, neuron survival, and dendrite growth and synapse formation, have advanced the understanding of how neuronal development is shaped by interactions with peripheral tissues and organs. Recent progress has also been made in identifying how the cellular and molecular diversity of sympathetic neurons is established to meet the functional demands of peripheral organs. In this Review, we summarize current knowledge of signalling pathways underlying the development of the sympathetic nervous system. These findings have implications for unravelling the contribution of sympathetic dysfunction stemming, in part, from developmental perturbations to the pathophysiology of peripheral neuropathies and cardiovascular and metabolic disorders.

Differentiation of Human Pluripotent Stem Cells Into Specific Neural Lineages

Human pluripotent stem cells (hPSCs) are sources of several somatic cell types for human developmental studies, in vitro disease modeling, and cell transplantation therapy. Improving strategies of derivation of high-purity specific neural and glial lineages from hPSCs is critical for application to the study and therapy of the nervous system. Here, we will focus on the principles behind establishment of neuron and glia differentiation methods according to developmental studies. We will also highlight the limitations and challenges associated with the differentiation of several “difficult” neural lineages and delay in neuronal maturation and functional integration. To overcome these challenges, we will introduce strategies and novel technologies aimed at improving the differentiation of various neural lineages to expand the application potential of hPSCs to the study of the nervous system.

Profiling of Human Neural Crest Chemoattractant Activity as a Replacement of Fetal Bovine Serum for In Vitro Chemotaxis Assays

Fetal bovine serum (FBS) is the only known stimulus for the migration of human neural crest cells (NCCs). Non-animal chemoattractants are desirable for the optimization of chemotaxis as-says to be incorporated in a test battery for reproductive and developmental toxicity. We con-firmed here in an optimized transwell assay that FBS triggers directed migration along a con-centration gradient. The responsible factor was found to be a protein in the 30–100 kDa size range. In a targeted approach, we tested a large panel of serum constituents known to be chem-otactic for NCCs in animal models (e.g., VEGF, PDGF, FGF, SDF-1/CXCL12, ephrins, endothelin, Wnt, BMPs). None of the corresponding human proteins showed any effect in our chemotaxis assays based on human NCCs. We then examined, whether human cells would produce any fac-tor able to trigger NCC migration in a broad screening approach. We found that HepG2 hepa-toma cells produced chemotaxis-triggering activity (CTA). Using chromatographic methods and by employing the NCC chemotaxis test as bioassay, the responsible protein was enriched by up to 5000-fold. We also explored human serum and platelets as a direct source, independent of any cell culture manipulations. A CTA was enriched from platelet lysates several thousand-fold. Its temperature and protease sensitivity suggested also a protein component. The capacity of this factor to trigger chemotaxis was confirmed by single-cell video-tracking analysis of migrating NCCs. The human CTA characterized here may be employed in the future for the setup of assays testing for the disturbance of directed NCC migration by toxicants.

Therapeutic manipulation of IKBKAP mis-splicing with a small molecule to cure familial dysautonomia

Approximately half of genetic disease-associated mutations cause aberrant splicing. However, a widely applicable therapeutic strategy to splicing diseases is yet to be developed. Here, we analyze the mechanism whereby IKBKAP-familial dysautonomia (FD) exon 20 inclusion is specifically promoted by a small molecule splice modulator, RECTAS, even though IKBKAP-FD exon 20 has a suboptimal 5' splice site due to the IVS20 + 6 T > C mutation. Knockdown experiments reveal that exon 20 inclusion is suppressed in the absence of serine/arginine-rich splicing factor 6 (SRSF6) binding to an intronic splicing enhancer in intron 20. We show that RECTAS directly interacts with CDC-like kinases (CLKs) and enhances SRSF6 phosphorylation. Consistently, exon 20 splicing is bidirectionally manipulated by targeting cellular CLK activity with RECTAS versus CLK inhibitors. The therapeutic potential of RECTAS is validated in multiple FD disease models. Our study indicates that small synthetic molecules affecting phosphorylation state of SRSFs is available as a new therapeutic modality for mechanism-oriented precision medicine of splicing diseases.

Human stem cell models to study host-virus interactions in the central nervous system

Advancements in human pluripotent stem cell technology offer a unique opportunity for the neuroimmunology field to study host-virus interactions directly in disease-relevant cells of the human central nervous system (CNS). Viral encephalitis is most commonly caused by herpesviruses, arboviruses and enteroviruses targeting distinct CNS cell types and often leading to severe neurological damage with poor clinical outcomes. Furthermore, different neurotropic viruses will affect the CNS at distinct developmental stages, from early prenatal brain development to the aged brain. With the unique flexibility and scalability of human pluripotent stem cell technology, it is now possible to examine the molecular mechanisms underlying acute infection and latency, determine which CNS subpopulations are specifically infected, study temporal aspects of viral susceptibility, perform high-throughput chemical or genetic screens for viral restriction factors and explore complex cell-non-autonomous disease mechanisms. Therefore, human pluripotent stem cell technology has the potential to address key unanswered questions about antiviral immunity in the CNS, including emerging questions on the potential CNS tropism of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Reverse Engineering of Ewing Sarcoma Regulatory Network Uncovers PAX7 and RUNX3 as Master Regulators Associated with Good Prognosis

Ewing Sarcoma (ES) is a rare malignant tumor occurring most frequently in adolescents and young adults. The ES hallmark is a chromosomal translocation between the chromosomes 11 and 22 that results in an aberrant transcription factor (TF) through the fusion of genes from the FET and ETS families, commonly EWSR1 and FLI1. The regulatory mechanisms behind the ES transcriptional alterations remain poorly understood. Here, we reconstruct the ES regulatory network using public available transcriptional data. Seven TFs were identified as potential MRs and clustered into two groups: one composed by PAX7 and RUNX3, and another composed by ARNT2, CREB3L1, GLI3, MEF2C, and PBX3. The MRs within each cluster act as reciprocal agonists regarding the regulation of shared genes, regulon activity, and implications in clinical outcome, while the clusters counteract each other. The regulons of all the seven MRs were differentially methylated. PAX7 and RUNX3 regulon activity were associated with good prognosis while ARNT2, CREB3L1, GLI3, and PBX3 were associated with bad prognosis. PAX7 and RUNX3 appear as highly expressed in ES biopsies and ES cell lines. This work contributes to the understanding of the ES regulome, identifying candidate MRs, analyzing their methilome and pointing to potential prognostic factors.

Derivation of Peripheral Nociceptive, Mechanoreceptive, and Proprioceptive Sensory Neurons from the same Culture of Human Pluripotent Stem Cells

The three peripheral sensory neuron (SN) subtypes, nociceptors, mechanoreceptors, and proprioceptors, localize to dorsal root ganglia and convey sensations such as pain, temperature, pressure, and limb movement/position. Despite previous reports, to date no protocol is available allowing the generation of all three SN subtypes at high efficiency and purity from human pluripotent stem cells (hPSCs). We describe a chemically defined differentiation protocol that generates all three SN subtypes from the same starting population, as well as methods to enrich for each individual subtype. The protocol yields high efficiency and purity cultures that are electrically active and respond to specific stimuli. We describe their molecular character and maturity stage and provide evidence for their use as an axotomy model; we show disease phenotypes in hPSCs derived from patients with familial dysautonomia. Our protocol will allow the modeling of human disorders affecting SNs, the search for treatments, and the study of human development.

Human iPSC-Based Modeling of Central Nerve System Disorders for Drug Discovery

A high-throughput drug screen identifies potentially promising therapeutics for clinical trials. However, limitations that persist in current disease modeling with limited physiological relevancy of human patients skew drug responses, hamper translation of clinical efficacy, and contribute to high clinical attritions. The emergence of induced pluripotent stem cell (iPSC) technology revolutionizes the paradigm of drug discovery. In particular, iPSC-based three-dimensional (3D) tissue engineering that appears as a promising vehicle of in vitro disease modeling provides more sophisticated tissue architectures and micro-environmental cues than a traditional two-dimensional (2D) culture. Here we discuss 3D based organoids/spheroids that construct the advanced modeling with evolved structural complexity, which propels drug discovery by exhibiting more human specific and diverse pathologies that are not perceived in 2D or animal models. We will then focus on various central nerve system (CNS) disease modeling using human iPSCs, leading to uncovering disease pathogenesis that guides the development of therapeutic strategies. Finally, we will address new opportunities of iPSC-assisted drug discovery with multi-disciplinary approaches from bioengineering to Omics technology. Despite technological challenges, iPSC-derived cytoarchitectures through interactions of diverse cell types mimic patients' CNS and serve as a platform for therapeutic development and personalized precision medicine.

Research Advances on Therapeutic Approaches to Congenital Central Hypoventilation Syndrome (CCHS)

Congenital central hypoventilation syndrome (CCHS) is a genetic disorder of neurodevelopment, with an autosomal dominant transmission, caused by heterozygous mutations in the PHOX2B gene. CCHS is a rare disorder characterized by hypoventilation due to the failure of autonomic control of breathing. Until now no curative treatment has been found. PHOX2B is a transcription factor that plays a crucial role in the development (and maintenance) of the autonomic nervous system, and in particular the neuronal structures involved in respiratory reflexes. The underlying pathogenetic mechanism is still unclear, although studies in vivo and in CCHS patients indicate that some neuronal structures may be damaged. Moreover, in vitro experimental data suggest that transcriptional dysregulation and protein misfolding may be key pathogenic mechanisms. This review summarizes latest researches that improved the comprehension of the molecular pathogenetic mechanisms responsible for CCHS and discusses the search for therapeutic intervention in light of the current knowledge about PHOX2B function.

Human sensory neurons derived from pluripotent stem cells for disease modelling and personalized medicine

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New techniques emerge to study peripheral sensory neurons in iPS-cell derived models.

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Genetic pain syndromes, e.g. gain- and loss-of-function mutations in Nav-channels are helpful.

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Individualized treatment for neuropathic pain can be identified with iPS-cell derived nociceptors.

In this concise Mini-Review we will summarize ongoing developments of new techniques to study physiology and pathophysiology of the peripheral sensory nervous system in human stem cell derived models. We will focus on recent developments of reprogramming somatic cells into induced pluripotent stem cells, neural differentiation towards neuronal progenitors and human sensory neurons.

We will sum up the high potential of this new technique for disease modelling of human neuropathies with a focus on genetic pain syndromes, such as gain- and loss-of-function mutations in voltage-gated sodium channels. The stem cell derived human sensory neurons are used for drug testing and we will summarize their usefulness for individualized treatment identification in patients with neuropathic pain. The review will give an outlook on potential application of this technique as companion diagnostics and for personalized medicine.

Induced Pluripotent Stem Cell (iPSC)-Based Neurodegenerative Disease Models for Phenotype Recapitulation and Drug Screening

Neurodegenerative diseases represent a significant unmet medical need in our aging society. There are no effective treatments for most of these diseases, and we know comparatively little regarding pathogenic mechanisms. Among the challenges faced by those involved in developing therapeutic drugs for neurodegenerative diseases, the syndromes are often complex, and small animal models do not fully recapitulate the unique features of the human nervous system. Human induced pluripotent stem cells (iPSCs) are a novel technology that ideally would permit us to generate neuronal cells from individual patients, thereby eliminating the problem of species-specificity inherent when using animal models. Specific phenotypes of iPSC-derived cells may permit researchers to identify sub-types and to distinguish among unique clusters and groups. Recently, iPSCs were used for drug screening and testing for neurologic disorders including Alzheimer’s disease (AD), amyotrophic lateral sclerosis (ALS), spinocerebellar atrophy (SCA), and Zika virus infection. However, there remain many challenges still ahead, including how one might effectively recapitulate sporadic disease phenotypes and the selection of ideal phenotypes and for large-scale drug screening. Fortunately, quite a few novel strategies have been developed that might be combined with an iPSC-based model to solve these challenges, including organoid technology, single-cell RNA sequencing, genome editing, and deep learning artificial intelligence. Here, we will review current applications and potential future directions for iPSC-based neurodegenerative disease models for critical drug screening.

The plant hormone kinetin in disease therapy and healthy aging

It has been more than 60 years since the discovery of kinetin, the first known member of a group of plant hormones called cytokinins. In this review we summarize the health-promoting activity of kinetin in animal systems, ranging from cells cultured in vitro through invertebrates to mammals. Kinetin has been shown to modulate aging, to delay age-related physiological decline and to protect against some neurodegenerative diseases. We also review studies on its mechanism of action, as well as point out gaps in our current knowledge.

Overview of Methods to Differentiate Sympathetic Neurons from Human Pluripotent Stem Cells

Sympathetic neurons are crucial for maintenance of body homeostasis and regulation of all organs. Diseases can arise from malfunction of sympathetic neurons, including malignancies, hypertension, and genetic disorders. Human pluripotent stem cells (hPSCs) allow modeling of human diseases and the in-depth study of pathologies of specific cell types associated with such disorders. Advances in the ability to differentiate hPSCs in vitro has allowed the generation of specific cell types such as sympathetic neurons, which provides the novel opportunity to study diseases affecting the sympathetic nervous system in the human context. Here, we compare selected recent publications that have achieved the goal of generating sympathetic neurons from hPSCs. We discuss strengths and weaknesses of each approach and debate future improvements and the next steps for using these neurons to better our understanding of sympathetic neuron disorders and their treatments. © 2019 by John Wiley & Sons, Inc.

Antisense oligonucleotides correct the familial dysautonomia splicing defect in IKBKAP transgenic mice

Familial dysautonomia (FD) is a rare inherited neurodegenerative disorder caused by a point mutation in the IKBKAP gene that results in defective splicing of its pre-mRNA. The mutation weakens the 5′ splice site of exon 20, causing this exon to be skipped, thereby introducing a premature termination codon. Though detailed FD pathogenesis mechanisms are not yet clear, correcting the splicing defect in the relevant tissue(s), thus restoring normal expression levels of the full-length IKAP protein, could be therapeutic. Splice-switching antisense oligonucleotides (ASOs) can be effective targeted therapeutics for neurodegenerative diseases, such as nusinersen (Spinraza), an approved drug for spinal muscular atrophy. Using a two-step screen with ASOs targeting IKBKAP exon 20 or the adjoining intronic regions, we identified a lead ASO that fully restored exon 20 splicing in FD patient fibroblasts. We also characterized the corresponding cis-acting regulatory sequences that control exon 20 splicing. When administered into a transgenic FD mouse model, the lead ASO promoted expression of full-length human IKBKAP mRNA and IKAP protein levels in several tissues tested, including the central nervous system. These findings provide insights into the mechanisms of IKBKAP exon 20 recognition, and pre-clinical proof of concept for an ASO-based targeted therapy for FD.

ELP1 Splicing Correction Reverses Proprioceptive Sensory Loss in Familial Dysautonomia

Familial dysautonomia (FD) is a recessive neurodegenerative disease caused by a splice mutation in Elongator complex protein 1 (ELP1, also known as IKBKAP); this mutation leads to variable skipping of exon 20 and to a drastic reduction of ELP1 in the nervous system. Clinically, many of the debilitating aspects of the disease are related to a progressive loss of proprioception; this loss leads to severe gait ataxia, spinal deformities, and respiratory insufficiency due to neuromuscular incoordination. There is currently no effective treatment for FD, and the disease is ultimately fatal. The development of a drug that targets the underlying molecular defect provides hope that the drastic peripheral neurodegeneration characteristic of FD can be halted. We demonstrate herein that the FD mouse TgFD9;Ikbkap^Δ20/flox recapitulates the proprioceptive impairment observed in individuals with FD, and we provide the in vivo evidence that postnatal correction, promoted by the small molecule kinetin, of the mutant ELP1 splicing can rescue neurological phenotypes in FD. Daily administration of kinetin starting at birth improves sensory-motor coordination and prevents the onset of spinal abnormalities by stopping the loss of proprioceptive neurons. These phenotypic improvements correlate with increased amounts of full-length ELP1 mRNA and protein in multiple tissues, including in the peripheral nervous system (PNS). Our results show that postnatal correction of the underlying ELP1 splicing defect can rescue devastating disease phenotypes and is therefore a viable therapeutic approach for persons with FD.

The diverse neural crest: from embryology to human pathology

We review here some of the historical highlights in exploratory studies of the vertebrate embryonic structure known as the neural crest. The study of the molecular properties of the cells that it produces, their migratory capacities and plasticity, and the still-growing list of tissues that depend on their presence for form and function, continue to enrich our understanding of congenital malformations, paediatric cancers and evolutionary biology. Developmental biology has been key to our understanding of the neural crest, starting with the early days of experimental embryology and through to today, when increasingly powerful technologies contribute to further insight into this fascinating vertebrate cell population.

Autonomic Neurons with Sympathetic Character Derived From Human Pluripotent Stem Cells

We describe an in vitro differentiation protocol to derive autonomic neurons of the peripheral nervous system with the character of postganglionic sympathetic neurons from human pluripotent stem cells. This protocol has been used to generate autonomic neurons from healthy embryonic stem cells as well as from patient-derived induced pluripotent stem cells, which were previously used to model familial dysautonomia, a genetic childhood disorder affecting the autonomic nervous system. Here, we describe each step in detail that is necessary to successfully derive these cells. First, we generate neural crest cells, which are purified using fluorescence-activated cell sorting. This is followed by intermediate culture as neural crest spheroids, where the cells can be expanded, and lastly long-term differentiation into neurons. The cells have morphological and molecular characteristics of autonomic neurons and thus can be employed to study diseases affecting the autonomic nervous system. © 2019 by John Wiley & Sons, Inc.

Induced pluripotent stem cells for disease modeling, cell therapy and drug discovery in genetic autonomic disorders: a review

The autonomic nervous system (ANS) regulates all organs in the body independent of consciousness, and is thus essential for maintaining homeostasis of the entire organism. Diseases of the ANS can arise due to environmental insults such as injury, toxins/drugs and infections or due to genetic lesions. Human studies and animal models have been instrumental to understanding connectivity and regulation of the ANS and its disorders. However, research into cellular pathologies and molecular mechanisms of ANS disorders has been hampered by the difficulties in accessing human patient-derived ANS cells in large numbers to conduct meaningful research, mainly because patient neurons cannot be easily biopsied and primary human neuronal cultures cannot be expanded.Human-induced pluripotent stem cell (hiPSC) technology can elegantly bridge these issues, allowing unlimited access of patient-derived ANS cell types for cellular, molecular and biochemical analysis, facilitating the discovery of novel therapeutic targets, and eventually leading to drug discovery. Additionally, such cells may provide a source for cell replacement therapy to replenish lost or injured ANS tissue in patients.Here, we first review the anatomy and embryonic development of the ANS, as this knowledge is crucial for understanding disease modeling approaches. We then review the current advances in human stem cell technology for modeling diseases of the ANS, recent strides toward cell replacement therapy and drug discovery initiatives.

Efficient derivation of sympathetic neurons from human pluripotent stem cells with a defined condition

Sympathetic neurons (SNs) are an essential component of the autonomic nervous system. They control vital bodily functions and are responsible for various autonomic disorders. However, obtaining SNs from living humans for in vitro study has not been accomplished. Although human pluripotent stem cell (hPSC)-derived SNs could be useful for elucidating the pathophysiology of human autonomic neurons, the differentiation efficiency remains low and reporter-based cell sorting is usually required for the subsequent pathophysiological analysis. To improve the efficiency, we refined each differentiation stage using PHOX2B::eGFP reporter hPSC lines to establish a robust and efficient protocol to derive functional SNs via neuromesodermal progenitor-like cells and trunk neural crest cells. Sympathetic neuronal progenitors could be expanded and stocked during differentiation. Our protocol can selectively enrich sympathetic lineage-committed cells at high-purity (≈80%) from reporter-free hPSC lines. Our system provides a platform for diverse applications, such as developmental studies and the modeling of SN-associated diseases.

CRISPR Gene Editing in the Kidney

CRISPR is a nuclease guidance system that enables rapid and efficient gene editing of specific DNA sequences within genomes. We review applications of CRISPR for the study and treatment of kidney disease. CRISPR enables functional experiments in cell lines and model organisms to validate candidate genes arising from genetic studies. CRISPR has furthermore been used to establish the first models of genetic disease in human kidney organoids derived from pluripotent stem cells. These gene-edited organoids are providing new insight into the cellular mechanisms of polycystic kidney disease and nephrotic syndrome. CRISPR-engineered cell therapies are currently in clinical trials for cancers and immunologic syndromes, an approach that may be applicable to inflammatory conditions such as lupus nephritis. Use of CRISPR in large domestic species such as pigs raises the possibility of farming kidneys for transplantation to alleviate the shortage of donor organs. However, significant challenges remain, including how to effectively deliver CRISPR to kidneys and how to control gene editing events within the genome. Thorough testing of CRISPR in preclinical models will be critical to the safe and efficacious translation of this powerful young technology into therapies.

Neurocristopathies: New insights 150 years after the neural crest discovery

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

Differentiation of Mouse Embryonic Stem Cells into Cortical Interneuron Precursors

GABAergic cortical interneurons are a heterogeneous population of cells that play critical roles in regulating the output of excitatory pyramidal neurons as well as synchronizing the outputs of pyramidal neuron ensembles. Deficits in interneuron function have been implicated in a variety of neuropsychiatric disorders, including schizophrenia, autism, and epilepsy. The derivation of cortical interneurons from embryonic stem cells not only allows for the study of their development and function, but provides insight into the molecular mechanisms underlying the pathogenesis of cortical interneuron-related disorders. Interneurons also have the remarkable capacity to survive, migrate, and integrate into host cortical circuitry post-transplantation, making them ideal candidates for use in cell-based therapies. Here, we present a scalable, highly efficient, modified embryoid body-to-monolayer method for the derivation of Nkx2.1-expressing interneuron progenitors and their progeny from mouse embryonic stem cells (mESCs). Using a Nkx2.1::mCherry:Lhx6::GFP dual reporter mESC line, Nkx2.1 progenitors or their Lhx6-expressing post-mitotic progeny can be isolated via fluorescence-activated cell sorting (FACS) and subsequently used in a number of downstream applications. We also provide methods to enrich for parvalbumin (PV) or somatostatin (SST) interneuron subgroups, which may be helpful for studying aspects of fate determination or for use in therapeutic applications that would benefit from interneuron subgroup-enriched transplantations.

Evidence linking microRNA suppression of essential prosurvival genes with hippocampal cell death after traumatic brain injury

The underlying molecular mechanisms of how dysregulated microRNAs (miRNAs) cause neurodegeneration after traumatic brain injury (TBI) remain elusive. Here we analyzed the biological roles of approximately 600 genes - we previously found these dysregulated in dying and surviving rat hippocampal neurons - that are targeted by ten TBI-altered miRNAs. Bioinformatic analysis suggests that neurodegeneration results from a global miRNA-mediated suppression of genes essential for maintaining proteostasis; many are hub genes - involved in RNA processing, cytoskeletal metabolism, intracellular trafficking, cell cycle progression, repair/maintenance, bioenergetics and cell-cell signaling - whose disrupted expression is linked to human disease. Notably, dysregulation of these essential genes would significantly impair synaptic function and functional brain connectivity. In surviving neurons, upregulated miRNA target genes are co-regulated members of prosurvival pathways associated with cellular regeneration, neural plasticity, and development. This study captures the diversity of miRNA-regulated genes that may be essential for cell repair and survival responses after TBI.

Animal and cellular models of familial dysautonomia

Since Riley and Day first described the clinical phenotype of patients with familial dysautonomia (FD) over 60 years ago, the field has made considerable progress clinically, scientifically, and translationally in treating and understanding the etiology of FD. FD is classified as a hereditary sensory and autonomic neuropathy (HSAN type III) and is both a developmental and a progressive neurodegenerative condition that results from an autosomal recessive mutation in the gene IKBKAP, also known as ELP1. FD primarily impacts the peripheral nervous system but also manifests in central nervous system disruption, especially in the retina and optic nerve. While the disease is rare, the rapid progress being made in elucidating the molecular and cellular mechanisms mediating the demise of neurons in FD should provide insight into degenerative pathways common to many neurological disorders. Interestingly, the protein encoded by IKBKAP/ELP1, IKAP or ELP1, is a key scaffolding subunit of the six-subunit Elongator complex, and variants in other Elongator genes are associated with amyotrophic lateral sclerosis (ALS), intellectual disability, and Rolandic epilepsy. Here we review the recent model systems that are revealing the molecular and cellular pathophysiological mechanisms mediating FD. These powerful model systems can now be used to test targeted therapeutics for mitigating neuronal loss in FD and potentially other disorders.

Proteasome inhibitors to alleviate aberrant IKBKAP mRNA splicing and low IKAP/hELP1 synthesis in familial dysautonomia

FD is a rare neurodegenerative disorder caused by a mutation of the IKBKAP gene, which induces low expression levels of the Elongator subunit IKAP/hELP1 protein. A rational strategy for FD treatment could be to identify drugs increasing IKAP/hELP1 expression levels by blocking protein degradation pathways such as the 26S proteasome. Proteasome inhibitors are promising molecules emerging in cancer treatment and could thus constitute an enticing pharmaceutical strategy for FD treatment. Therefore, we tested three proteasome inhibitors on FD human olfactory ecto-mesenchymal stem cells (hOE-MSCs): two approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA), bortezomib and carfilzomib, as well as epoxomicin. Although all 3 inhibitors demonstrated activity in correcting IKBKAP mRNA aberrant splicing, carfilzomib was superior in enhancing IKAP/hELP1 quantity. Moreover, we observed a synergistic effect of suboptimal doses of carfilzomib on kinetin in improving IKBKAP isoforms ratio and IKAP/hELP1 expression levels allowing to counterbalance carfilzomib toxicity. Finally, we identified several dysregulated miRNAs after carfilzomib treatment that target proteasome-associated mRNAs and determined that IKAP/hELP1 deficiency in FD pathology is correlated to an overactivity of the 26S proteasome. Altogether, these results reinforce the rationale for using chemical compounds inhibiting the 26S proteasome as an innovative option for FD and a promising therapeutic pathway for many other neurodegenerative diseases.