Utility of Induced Pluripotent Stem Cells for the Study and Treatment of Genetic Diseases: Focus on Childhood Neurological Disorders

Mining human clinical waste as a rich source of stem cells for neural regeneration

Neural diseases are challenging to treat and are regarded as one of the major causes of disability and morbidity in the world. Stem cells can provide a solution, by offering a mechanism to replace damaged circuitry. However, obtaining sufficient cell sources for neural regeneration remains a significant challenge. In recent years, waste-derived stem(-like) cells (WDS-lCs) extracted from both prenatal and adult clinical waste tissues/products, have gained increasing attention for application in neural tissue repair and remodeling. This often-overlooked pool of cells possesses favorable characteristics; including self-renewal, neural differentiation, secretion of neurogenic factors, cost-effectiveness, and low ethical concerns. Here, we offer a perspective regarding the biological properties, extraction protocols, and preclinical and clinical treatments where prenatal and adult WDS-lCs have been utilized for cell replacement therapy in neural applications, and the challenges involved in optimizing these approaches toward patient led therapies.

Single-cell RNA-seq data analysis reveals functionally relevant biomarkers of early brain development and their regulatory footprints in human embryonic stem cells (hESCs)

The complicated process of neuronal development is initiated early in life, with the genetic mechanisms governing this process yet to be fully elucidated. Single-cell RNA sequencing (scRNA-seq) is a potent instrument for pinpointing biomarkers that exhibit differential expression across various cell types and developmental stages. By employing scRNA-seq on human embryonic stem cells, we aim to identify differentially expressed genes (DEGs) crucial for early-stage neuronal development. Our focus extends beyond simply identifying DEGs. We strive to investigate the functional roles of these genes through enrichment analysis and construct gene regulatory networks to understand their interactions. Ultimately, this comprehensive approach aspires to illuminate the molecular mechanisms and transcriptional dynamics governing early human brain development. By uncovering potential links between these DEGs and intelligence, mental disorders, and neurodevelopmental disorders, we hope to shed light on human neurological health and disease. In this study, we have used scRNA-seq to identify DEGs involved in early-stage neuronal development in hESCs. The scRNA-seq data, collected on days 26 (D26) and 54 (D54), of the in vitro differentiation of hESCs to neurons were analyzed. Our analysis identified 539 DEGs between D26 and D54. Functional enrichment of those DEG biomarkers indicated that the up-regulated DEGs participated in neurogenesis, while the down-regulated DEGs were linked to synapse regulation. The Reactome pathway analysis revealed that down-regulated DEGs were involved in the interactions between proteins located in synapse pathways. We also discovered interactions between DEGs and miRNA, transcriptional factors (TFs) and DEGs, and between TF and miRNA. Our study identified 20 significant transcription factors, shedding light on early brain development genetics. The identified DEGs and gene regulatory networks are valuable resources for future research into human brain development and neurodevelopmental disorders.

Advances in iPSC Technology in Neural Disease Modeling, Drug Screening, and Therapy

Neurodegenerative disorders (NDs) including Alzheimer's Disease, Parkinson's Disease, Amyotrophic Lateral Sclerosis (ALS), and Huntington's disease are all incurable and can only be managed with drugs for the associated symptoms. Animal models of human illnesses help to advance our understanding of the pathogenic processes of diseases. Understanding the pathogenesis as well as drug screening using appropriate disease models of neurodegenerative diseases (NDs) are vital for identifying novel therapies. Human-derived induced pluripotent stem cell (iPSC) models can be an efficient model to create disease in a dish and thereby can proceed with drug screening and identifying appropriate drugs. This technology has many benefits, including efficient reprogramming and regeneration potential, multidirectional differentiation, and the lack of ethical concerns, which open up new avenues for studying neurological illnesses in greater depth. The review mainly focuses on the use of iPSC technology in neuronal disease modeling, drug screening, and cell therapy.

A Functional Single-Nucleotide Polymorphism Upstream of the Collagen Type III Gene Is Associated with Catastrophic Fracture Risk in Thoroughbred Horses

Fractures caused by bone overloading are a leading cause of euthanasia in Thoroughbred racehorses. The risk of fatal fracture has been shown to be influenced by both environmental and genetic factors but, to date, no specific genetic mechanisms underpinning fractures have been identified. In this study, we utilised a genome-wide polygenic risk score to establish an in vitro cell system to study bone gene regulation in horses at high and low genetic risk of fracture. Candidate gene expression analysis revealed differential expression of COL3A1 and STAT1 genes in osteoblasts derived from high- and low-risk horses. Whole-genome sequencing of two fracture cases and two control horses revealed a single-nucleotide polymorphism (SNP) upstream of COL3A1 that was confirmed in a larger cohort to be significantly associated with fractures. Bioinformatics tools predicted that this SNP may impact the binding of the transcription factor SOX11. Gene modulation demonstrated SOX11 is upstream of COL3A1, and the region binds to nuclear proteins. Furthermore, luciferase assays demonstrated that the region containing the SNP has promoter activity. However, the specific effect of the SNP depends on the broader genetic background of the cells and suggests other factors may also be involved in regulating COL3A1 expression. In conclusion, we have identified a novel SNP that is significantly associated with fracture risk and provide new insights into the regulation of the COL3A1 gene.

Potential use of iPSCs for disease modeling, drug screening, and cell-based therapy for Alzheimer's disease

Alzheimer's disease (AD) is a chronic illness marked by increasing cognitive decline and nervous system deterioration. At this time, there is no known medication that will stop the course of Alzheimer's disease; instead, most symptoms are treated. Clinical trial failure rates for new drugs remain high, highlighting the urgent need for improved AD modeling for improving understanding of the underlying pathophysiology of disease and improving drug development. The development of induced pluripotent stem cells (iPSCs) has made it possible to model neurological diseases like AD, giving access to an infinite number of patient-derived cells capable of differentiating neuronal fates. This advance will accelerate Alzheimer's disease research and provide an opportunity to create more accurate patient-specific models of Alzheimer's disease to support pathophysiological research, drug development, and the potential application of stem cell-based therapeutics. This review article provides a complete summary of research done to date on the potential use of iPSCs from AD patients for disease modeling, drug discovery, and cell-based therapeutics. Current technological developments in AD research including 3D modeling, genome editing, gene therapy for AD, and research on familial (FAD) and sporadic (SAD) forms of the disease are discussed. Finally, we outline the issues that need to be elucidated and future directions for iPSC modeling in AD.

Automated high-content imaging in iPSC-derived neuronal progenitors

Induced pluripotent stem cells (iPSCs) have great potential as physiological disease models for human disorders where access to primary cells is difficult, such as neurons. In recent years, many protocols have been developed for the generation of iPSCs and the differentiation into specialised cell subtypes of interest. More recently, these models have been modified to allow large-scale phenotyping and high-content screening of small molecule compounds in iPSC-derived neuronal cells. Here, we describe the automated seeding of day 11 ventral midbrain progenitor cells into 96-well plates, administration of compounds, automated staining for immunofluorescence, the acquisition of images on a high-content screening platform and workflows for image analysis.

Cerebral Organoids and Antisense Oligonucleotide Therapeutics: Challenges and Opportunities

The advent of stem cell-derived cerebral organoids has already advanced our understanding of disease mechanisms in neurological diseases. Despite this, many remain without effective treatments, resulting in significant personal and societal health burden. Antisense oligonucleotides (ASOs) are one of the most widely used approaches for targeting RNA and modifying gene expression, with significant advancements in clinical trials for epilepsy, neuromuscular disorders and other neurological conditions. ASOs have further potential to address the unmet need in other neurological diseases for novel therapies which directly target the causative genes, allowing precision treatment. Induced pluripotent stem cell (iPSC) derived cerebral organoids represent an ideal platform in which to evaluate novel ASO therapies. In patient-derived organoids, disease-causing mutations can be studied in the native genetic milieu, opening the door to test personalized ASO therapies and n-of-1 approaches. In addition, CRISPR-Cas9 can be used to generate isogenic iPSCs to assess the effects of ASOs, by either creating disease-specific mutations or correcting available disease iPSC lines. Currently, ASO therapies face a number of challenges to wider translation, including insufficient uptake by distinct and preferential cell types in central nervous system and inability to cross the blood brain barrier necessitating intrathecal administration. Cerebral organoids provide a practical model to address and improve these limitations. In this review we will address the current use of organoids to test ASO therapies, opportunities for future applications and challenges including those inherent to cerebral organoids, issues with organoid transfection and choice of appropriate read-outs.

Purine nucleoside phosphorylase deficiency induces p53-mediated intrinsic apoptosis in human induced pluripotent stem cell-derived neurons

Purine nucleoside phosphorylase (PNP) is an important enzyme in the purine degradation and salvage pathway. PNP deficiency results in marked T lineage lymphopenia and severe immunodeficiency. Additionally, PNP-deficient patients and mice suffer from diverse non-infectious neurological abnormalities of unknown etiology. To further investigate the cause for these neurologic abnormalities, induced pluripotent stem cells (iPSC) from two PNP-deficient patients were differentiated into neurons. The iPSC-derived PNP-deficient neurons had significantly reduced soma and nuclei volumes. The PNP-deficient neurons demonstrated increased spontaneous and staurosporine-induced apoptosis, measured by cleaved caspase-3 expression, together with decreased mitochondrial membrane potential and increased cleaved caspase-9 expression, indicative of enhanced intrinsic apoptosis. Greater expression of tumor protein p53 was also observed in these neurons, and inhibition of p53 using pifithrin-α prevented the apoptosis. Importantly, treatment of the iPSC-derived PNP-deficient neurons with exogenous PNP enzyme alleviated the apoptosis. Inhibition of ribonucleotide reductase (RNR) in iPSC derived from PNP-proficient neurons with hydroxyurea or with nicotinamide and trichostatin A increased the intrinsic neuronal apoptosis, implicating RNR dysfunction as the potential mechanism for the damage caused by PNP deficiency. The findings presented here establish a potential mechanism for the neurological defects observed in PNP-deficient patients and reinforce the critical role that PNP has for neuronal viability.

Biofidelic dynamic compression of human cortical spheroids reproduces neurotrauma phenotypes

Fundamental questions about patient heterogeneity and human-specific pathophysiology currently obstruct progress towards a therapy for traumatic brain injury (TBI). Human in vitro models have the potential to address these questions. 3D spheroidal cell culture protocols for human-origin neural cells have several important advantages over their 2D monolayer counterparts. Three dimensional spheroidal cultures may mature more quickly, develop more biofidelic electrophysiological activity and/or reproduce some aspects of brain architecture. Here, we present the first human in vitro model of non-penetrating TBI employing 3D spheroidal cultures. We used a custom-built device to traumatize these spheroids in a quantifiable, repeatable and biofidelic manner and correlated the heterogeneous, mechanical strain field with the injury phenotype. Trauma reduced cell viability, mitochondrial membrane potential and spontaneous, synchronous, electrophysiological activity in the spheroids. Electrophysiological deficits emerged at lower injury severities than changes in cell viability. Also, traumatized spheroids secreted lactate dehydrogenase, a marker of cell damage, and neurofilament light chain, a promising clinical biomarker of neurotrauma. These results demonstrate that 3D human in vitro models can reproduce important phenotypes of neurotrauma in vitro.

Genome Editing in iPSC-Based Neural Systems: From Disease Models to Future Therapeutic Strategies

Therapeutic advances for neurological disorders are challenging due to limited accessibility of the human central nervous system and incomplete understanding of disease mechanisms. Many neurological diseases lack precision treatments, leading to significant disease burden and poor outcome for affected patients. Induced pluripotent stem cell (iPSC) technology provides human neuronal cells that facilitate disease modeling and development of therapies. The use of genome editing, in particular CRISPR-Cas9 technology, has extended the potential of iPSCs, generating new models for a number of disorders, including Alzheimers and Parkinson Disease. Editing of iPSCs, in particular with CRISPR-Cas9, allows generation of isogenic pairs, which differ only in the disease-causing mutation and share the same genetic background, for assessment of phenotypic differences and downstream effects. Moreover, genome-wide CRISPR screens allow high-throughput interrogation for genetic modifiers in neuronal phenotypes, leading to discovery of novel pathways, and identification of new therapeutic targets. CRISPR-Cas9 has now evolved beyond altering gene expression. Indeed, fusion of a defective Cas9 (dCas9) nuclease with transcriptional repressors or activation domains allows down-regulation or activation of gene expression (CRISPR interference, CRISPRi; CRISPR activation, CRISPRa). These new tools will improve disease modeling and facilitate CRISPR and cell-based therapies, as seen for epilepsy and Duchenne muscular dystrophy. Genome engineering holds huge promise for the future understanding and treatment of neurological disorders, but there are numerous barriers to overcome. The synergy of iPSC-based model systems and gene editing will play a vital role in the route to precision medicine and the clinical translation of genome editing-based therapies.

Potential for Stem Cell-Based Therapy in the Road of Treatment for Neurological Disorders Secondary to COVID-19

Abstract

The severe acute respiratory syndrome coronavirus 2 has led to the worldwide pandemic named coronavirus disease 2019 (COVID-19). It has caused a significant increase in the number of cases and mortalities since its first diagnosis in December 2019. Although COVID-19 primarily affects the respiratory system, neurological involvement of the central and peripheral nervous system has been also reported. Herein, the higher risk of neurodegenerative diseases in COVID-19 patients in future is also imaginable. Neurological complications of COVID-19 infection are more commonly seen in severely ill individuals; but, earlier diagnosis and treatment can lead to better long-lasting results. In this respect, stem cell biotechnologies with considerable self-renewal and differentiation capacities have experienced great progress in the field of neurological disorders whether in finding out their underlying processes or proving them promising therapeutic approaches. Herein, many neurological disorders have been found to benefit from stem cell medicine strategies. Accordingly, in the present review, the authors are trying to discuss stem cell-based biotechnologies as promising therapeutic options for neurological disorders secondary to COVID-19 infection through reviewing neurological manifestations of COVID-19 and current stem cell-based biotechnologies for neurological disorders.

Lay Summary

Due to the substantial burden of neurological disorders in the health, economic, and social system of society, the emergence of neurological manifestations following COVID-19 (as a life-threatening pandemic) creates the need to use efficient and modern methods of treatment. Since stem cell-based methods have been efficient for a large number of neurological diseases, it seems that the use of mentioned methods is also effective in the process of improving neurological disorders caused by COVID-19. Hereupon, the current review aims to address stem cell-based approaches as treatments showing promise to neurological disorders related to COVID-19.

The role of manganese dysregulation in neurological disease: emerging evidence

Manganese is an essential trace metal. The dysregulation of manganese seen in a broad spectrum of neurological disorders reflects its importance in brain development and key neurophysiological processes. Historically, the observation of acquired manganism in miners and people who misuse drugs provided early evidence of brain toxicity related to manganese exposure. The identification of inherited manganese transportopathies, which cause neurodevelopmental and neurodegenerative syndromes, further corroborates the neurotoxic potential of this element. Moreover, manganese dyshomoeostasis is also implicated in Parkinson's disease and other neurodegenerative conditions, such as Alzheimer's disease and Huntington's disease. Ongoing and future research will facilitate the development of better targeted therapeutical strategies than are currently available for manganese-associated neurological disorders.

N-Cadherin Nanoantagonist Driven Mesenchymal-to-Epithelial Transition in Fibroblasts for Improving Reprogramming Efficiency

Induced pluripotent stem cells (iPSCs) hold promise in revolutionizing medicine; however, their application potential is limited because of low reprogramming efficiency. Mesenchymal-to-epithelial transition (MET) has been proved to involve reprogramming of somatic cells into iPSCs, making it a promising target for enhancing generation of iPSCs. Here, we nanoengineered N-cadherin-blocking peptide ADH-1 with gold nanoparticles, generating a multivalent N-cadherin antagonist (ADH-AuNPs), for improving reprogramming efficiency through driving cell MET. ADH-AuNPs exhibited good biocompatibility and showed higher N-cadherin inhibitory activity than ADH-1 due to multivalency, thereby enhancing cell-state reprogramming toward epithelial lineages. Particularly, ADH-AuNPs improved reprogramming efficiency by more than 7-fold after introduction of four Yamanaka factors. Importantly, ADH-AuNPs generated iPSCs displayed high stemness and pluripotency in vitro and in vivo. Therefore, we provide a cooperative strategy for promoting the iPSC generation efficacy.

Resolving cell state in iPSC-derived human neural samples with multiplexed fluorescence imaging

Human induced pluripotent stem cell-derived (iPSC) neural cultures offer clinically relevant models of human diseases, including Amyotrophic Lateral Sclerosis, Alzheimer’s, and Autism Spectrum Disorder. In situ characterization of the spatial-temporal evolution of cell state in 3D culture and subsequent 2D dissociated culture models based on protein expression levels and localizations is essential to understanding neural cell differentiation, disease state phenotypes, and sample-to-sample variability. Here, we apply PRobe-based Imaging for Sequential Multiplexing (PRISM) to facilitate multiplexed imaging with facile, rapid exchange of imaging probes to analyze iPSC-derived cortical and motor neuron cultures that are relevant to psychiatric and neurodegenerative disease models, using over ten protein targets. Our approach permits analysis of cell differentiation, cell composition, and functional marker expression in complex stem-cell derived neural cultures. Furthermore, our approach is amenable to automation, offering in principle the ability to scale-up to dozens of protein targets and samples.

Tomov et al. utilize DNA-PRISM to allow for multiplexed imaging of cultured cells using antibodies modified with oligonucleotide probes. The differentiation of iPSCs to cortical and motor neurons is characterized in model cultures, relevant for use in disease research and drug screening.

Targeting Poison Exons to Treat Developmental and Epileptic Encephalopathy

Developmental and epileptic encephalopathies (DEEs) describe a subset of neurodevelopmental disorders categorized by refractory epilepsy that is often associated with intellectual disability and autism spectrum disorder. The majority of DEEs are now known to have a genetic basis with de novo coding variants accounting for the majority of cases. More recently, a small number of individuals have been identified with intronic SCN1A variants that result in alternative splicing events that lead to ectopic inclusion of poison exons (PEs). PEs are short highly conserved exons that contain a premature truncation codon, and when spliced into the transcript, lead to premature truncation and subsequent degradation by nonsense-mediated decay. The reason for the inclusion/exclusion of these PEs is not entirely clear, but research suggests an autoregulatory role in gene expression and protein abundance. This is seen in proteins such as RNA-binding proteins and serine/arginine-rich proteins. Recent studies have focused on targeting these PEs as a method for therapeutic intervention. Targeting PEs using antisense oligonucleotides (ASOs) has shown to be effective in modulating alternative splicing events by decreasing the amount of transcripts harboring PEs, thus increasing the abundance of full-length transcripts and thereby the amount of protein in haploinsufficient genes implicated in DEE. In the age of personalized medicine, cellular and animal models of the genetic epilepsies have become essential in developing and testing novel precision therapeutics, including PE-targeting ASOs in a subset of DEEs.

An Update on the Phenotype, Genotype and Neurobiology of ADCY5-Related Disease

Adenylyl cyclase 5 (ADCY5)-related phenotypes comprise an expanding disease continuum, but much remains to be understood about the underlying pathogenic mechanisms of the disease. ADCY5-related disease comprises a spectrum of hyperkinetic disorders involving chorea, myoclonus, and/or dystonia, often with paroxysmal exacerbations. Hypotonia, developmental delay, and intellectual disability may be present. The causative gene encodes adenylyl cyclase, the enzyme responsible for the conversion of adenosine triphosphate (ATP) to cyclic adenosine-3',5'-monophosphate (cAMP). cAMP is a second messenger that exerts a wide variety of effects via several intracellular signaling pathways. ADCY5 is the most commonly expressed isoform of adenylyl cyclase in medium spiny neurons (MSNs) of the striatum, and it integrates and controls dopaminergic signaling. Through cAMP pathway, ADCY5 is a key regulator of the cortical and thalamic signaling that control initiation of voluntary movements and prevention of involuntary movements. Gain-of-function mutations in ADCY5 have been recently linked to a rare genetic disorder called ADCY5-related dyskinesia, where dysregulation of the cAMP pathway leads to reduced inhibitory activity and involuntary hyperkinetic movements. Here, we present an update on the neurobiology of ADCY5, together with a detailed overview of the reported clinical phenotypes and genotypes. Although a range of therapeutic approaches has been trialed, there are currently no disease-modifying treatments. Improved in vitro and in vivo laboratory models will no doubt increase our understanding of the pathogenesis of this rare genetic movement disorder, which will improve diagnosis, and also facilitate the development of precision medicine approaches for this, and other forms of hyperkinesia. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Establishment of a human induced pluripotent stem cell (iPSC) line (JUCTCi010-A) from a healthy Jordanian female skin dermal fibroblasts

Human integration-free induced pluripotent pluripotent stem cells (hiPSCs) were generated from skin fibroblasts obtained from a 27-year-old healthy Jordanian female. The resulting iPSCs expressed the most common pluripotency stem cell markers, they retained the normal karyotype similar to the original fibroblasts and showed the potential to differentiate into three germ layers in vitro. This iPSC line could serve as a wild-type control that can be used in hereditary disease modeling studies and in optimization of different differentiation protocols.

Tunable and Reversible Substrate Stiffness Reveals a Dynamic Mechanosensitivity of Cardiomyocytes

New directions in material applications have allowed for the fresh insight into the coordination of biophysical cues and regulators. Although the role of the mechanical microenvironment on cell responses and mechanics is often studied, most analyses only consider static environments and behavior, however, cells and tissues are themselves dynamic materials that adapt in myriad ways to alterations in their environment. Here, we introduce an approach, through the addition of magnetic inclusions into a soft poly(dimethylsiloxane) elastomer, to fabricate a substrate that can be stiffened nearly instantaneously in the presence of cells through the use of a magnetic gradient to investigate short-term cellular responses to dynamic stiffening or softening. This substrate allows us to observe time-dependent changes, such as spreading, stress fiber formation, Yes-associated protein translocation, and sarcomere organization. The identification of temporal dynamic changes on a short time scale suggests that this technology can be more broadly applied to study targeted mechanisms of diverse biologic processes, including cell division, differentiation, tissue repair, pathological adaptations, and cell-death pathways. Our method provides a unique in vitro platform for studying the dynamic cell behavior by better mimicking more complex and realistic microenvironments. This platform will be amenable to future studies aimed at elucidating the mechanisms underlying mechanical sensing and signaling that influence cellular behaviors and interactions.

Impaired mitochondrial dynamics underlie axonal defects in hereditary spastic paraplegias

Mechanisms by which long corticospinal axons degenerate in hereditary spastic paraplegia (HSP) are largely unknown. Here, we have generated induced pluripotent stem cells (iPSCs) from patients with two autosomal recessive forms of HSP, SPG15 and SPG48, which are caused by mutations in the ZFYVE26 and AP5Z1 genes encoding proteins in the same complex, the spastizin and AP5Z1 proteins, respectively. In patient iPSC-derived telencephalic glutamatergic and midbrain dopaminergic neurons, neurite number, length and branching are significantly reduced, recapitulating disease-specific phenotypes. We analyzed mitochondrial morphology and noted a significant reduction in both mitochondrial length and their densities within axons of these HSP neurons. Mitochondrial membrane potential was also decreased, confirming functional mitochondrial defects. Notably, mdivi-1, an inhibitor of the mitochondrial fission GTPase DRP1, rescues mitochondrial morphology defects and suppresses the impairment in neurite outgrowth and late-onset apoptosis in HSP neurons. Furthermore, knockdown of these HSP genes causes similar axonal defects, also mitigated by treatment with mdivi-1. Finally, neurite outgrowth defects in SPG15 and SPG48 cortical neurons can be rescued by knocking down DRP1 directly. Thus, abnormal mitochondrial morphology caused by an imbalance of mitochondrial fission and fusion underlies specific axonal defects and serves as a potential therapeutic target for SPG15 and SPG48.

Using stem cell-derived neurons in drug screening for neurological diseases

Induced pluripotent stem cells and their derivatives have become an important tool for researching disease mechanisms. It is hoped that they could be used to discover new therapies by providing the most reliable and relevant human in vitro disease models for drug discovery. This review will summarize recent efforts to use stem cell-derived neurons for drug screening. We also explain the current hurdles to using these cells for high-throughput pharmaceutical screening and developments that may help overcome these hurdles. Finally, we critically discuss whether induced pluripotent stem cell-derived neurons will come to fruition as a model that is regularly used to screen for drugs to treat neurological diseases.

Identifying Extrinsic versus Intrinsic Drivers of Variation in Cell Behavior in Human iPSC Lines from Healthy Donors

Large cohorts of human induced pluripotent stem cells (iPSCs) from healthy donors are a potentially powerful tool for investigating the relationship between genetic variants and cellular behavior. Here, we integrate high content imaging of cell shape, proliferation, and other phenotypes with gene expression and DNA sequence datasets from over 100 human iPSC lines. By applying a dimensionality reduction approach, Probabilistic Estimation of Expression Residuals (PEER), we extracted factors that captured the effects of intrinsic (genetic concordance between different cell lines from the same donor) and extrinsic (cell responses to different fibronectin concentrations) conditions. We identify genes that correlate in expression with intrinsic and extrinsic PEER factors and associate outlier cell behavior with genes containing rare deleterious non-synonymous SNVs. Our study, thus, establishes a strategy for examining the genetic basis of inter-individual variability in cell behavior.

Organs to Cells and Cells to Organoids: The Evolution of in vitro Central Nervous System Modelling

With 100 billion neurons and 100 trillion synapses, the human brain is not just the most complex organ in the human body, but has also been described as "the most complex thing in the universe." The limited availability of human living brain tissue for the study of neurogenesis, neural processes and neurological disorders has resulted in more than a century-long strive from researchers worldwide to model the central nervous system (CNS) and dissect both its striking physiology and enigmatic pathophysiology. The invaluable knowledge gained with the use of animal models and post mortem human tissue remains limited to cross-species similarities and structural features, respectively. The advent of human induced pluripotent stem cell (hiPSC) and 3-D organoid technologies has revolutionised the approach to the study of human brain and CNS in vitro, presenting great potential for disease modelling and translational adoption in drug screening and regenerative medicine, also contributing beneficially to clinical research. We have surveyed more than 100 years of research in CNS modelling and provide in this review an historical excursus of its evolution, from early neural tissue explants and organotypic cultures, to 2-D patient-derived cell monolayers, to the latest development of 3-D cerebral organoids. We have generated a comprehensive summary of CNS modelling techniques and approaches, protocol refinements throughout the course of decades and developments in the study of specific neuropathologies. Current limitations and caveats such as clonal variation, developmental stage, validation of pluripotency and chromosomal stability, functional assessment, reproducibility, accuracy and scalability of these models are also discussed.

Big Lessons from Tiny Flies: Drosophila melanogaster as a Model to Explore Dysfunction of Dopaminergic and Serotonergic Neurotransmitter Systems

The brain of Drosophila melanogaster is comprised of some 100,000 neurons, 127 and 80 of which are dopaminergic and serotonergic, respectively. Their activity regulates behavioral functions equivalent to those in mammals, e.g., motor activity, reward and aversion, memory formation, feeding, sexual appetite, etc. Mammalian dopaminergic and serotonergic neurons are known to be heterogeneous. They differ in their projections and in their gene expression profile. A sophisticated genetic tool box is available, which allows for targeting virtually any gene with amazing precision in Drosophila melanogaster. Similarly, Drosophila genes can be replaced by their human orthologs including disease-associated alleles. Finally, genetic manipulation can be restricted to single fly neurons. This has allowed for addressing the role of individual neurons in circuits, which determine attraction and aversion, sleep and arousal, odor preference, etc. Flies harboring mutated human orthologs provide models which can be interrogated to understand the effect of the mutant protein on cell fate and neuronal connectivity. These models are also useful for proof-of-concept studies to examine the corrective action of therapeutic strategies. Finally, experiments in Drosophila can be readily scaled up to an extent, which allows for drug screening with reasonably high throughput.

Use of induced pluripotent stem cells to investigate the effects of purine nucleoside phosphorylase deficiency on neuronal development

Background: Inherited defects in the function of the purine nucleoside phosphorylase (PNP) enzyme can cause severe T cell immune deficiency and early death from infection, autoimmunity, or malignancy. In addition, more than 50% of patients suffer diverse non-infectious neurological complications. However the cause for the neurological abnormalities are not known.

Objectives: Differentiate induced pluripotent stem cells (iPSC) from PNP-deficient patients into neuronal cells to better understand the effects of impaired purine metabolism on neuronal development.

Methods: Sendai virus was used to generate pluripotent stem cells from PNP-deficient and healthy control lymphoblastoid cells. Cells were differentiated into neuronal cells through the formation of embryoid bodies.

Results: After demonstration of pluripotency, normal karyotype, and retention of the PNP deficiency state, iPSC were differentiated into neuronal cells. PNP-deficient neuronal cells had reduced soma and nuclei size in comparison to cells derived from healthy controls. Spontaneous apoptosis, determined by Caspase-3 expression, was increased in PNP-deficient cells.

Conclusions: iPSC from PNP-deficient patients can be differentiated into neuronal cells, thereby providing an important tool to study the effects of impaired purine metabolism on neuronal development and potential treatments.

Statement of novelty: We report here the first generation and use of neuronal cells derived from induced pluripotent stem cells to model human PNP deficiency, thereby providing an important tool for better understanding and management of this condition.

Ion Channels in Genetic Epilepsy: From Genes and Mechanisms to Disease-Targeted Therapies

Epilepsy is a common and serious neurologic disease with a strong genetic component. Genetic studies have identified an increasing collection of disease-causing genes. The impact of these genetic discoveries is wide reaching-from precise diagnosis and classification of syndromes to the discovery and validation of new drug targets and the development of disease-targeted therapeutic strategies. About 25% of genes identified in epilepsy encode ion channels. Much of our understanding of disease mechanisms comes from work focused on this class of protein. In this study, we review the genetic, molecular, and physiologic evidence supporting the pathogenic role of a number of different voltage- and ligand-activated ion channels in genetic epilepsy. We also review proposed disease mechanisms for each ion channel and highlight targeted therapeutic strategies.

Luteolin attenuates interleukin-6-mediated astrogliosis in human iPSC-derived neural aggregates: A candidate preventive substance for maternal immune activation-induced abnormalities

Maternal infection during pregnancy increases the risk of neurodevelopmental conditions such as autism spectrum disorders and schizophrenia in offspring. Several previous animal studies have indicated that maternal immune activation (MIA), rather than a specific pathogen, alters fetal brain development. Among them, prenatal exposure to interleukin-6 (IL-6) has been associated with behavioral and neuropathological abnormalities, though such findings remain to be elucidated in humans. We developed a human cell-based model of MIA by exposing human induced pluripotent stem cells (hiPSCs)-derived neural aggregates to IL-6 and investigated whether luteolin-a naturally occurring flavonoid found in edible plants-could prevent MIA-induced abnormalities. We generated neural aggregates from hiPSCs using the serum-free floating culture of embryoid body-like aggregates with quick reaggregation (SFEBq) method, following which aggregates were cultured in suspension. We then exposed the aggregates to IL-6 (100ng/ml) for 24h at day 51. Transient IL-6 exposure significantly increased the area ratio of astrocytes (GFAP-positive area ratio) and decreased the area ratio of early-born neurons (TBR1-positive or CTIP2-positive area ratio) relative to controls. In addition, western blot analysis revealed that levels of phosphorylated STAT3 were significantly elevated in IL-6-exposed neural aggregates. Luteolin treatment inhibited STAT3 phosphorylation and counteracted IL-6-mediated increases of GFAP-positive cells and reductions of TBR1-positive and CTIP2-positive cells. Our observations suggest that the flavonoid luteolin may attenuate or prevent MIA-induced neural abnormalities. As we observed increased apoptosis at high concentrations of luteolin, further studies are required to determine the optimal intake dosage and duration for pregnant women.

Clinical potential of human-induced pluripotent stem cells : Perspectives of induced pluripotent stem cells

The recent establishment of induced pluripotent stem (iPS) cells promises the development of autologous cell therapies for degenerative diseases, without the ethical concerns associated with human embryonic stem (ES) cells. Initially, iPS cells were generated by retroviral transduction of somatic cells with core reprogramming genes. To avoid potential genotoxic effects associated with retroviral transfection, more recently, alternative non-viral gene transfer approaches were developed. Before a potential clinical application of iPS cell-derived therapies can be planned, it must be ensured that the reprogramming to pluripotency is not associated with genome mutagenesis or epigenetic aberrations. This may include direct effects of the reprogramming method or "off-target" effects associated with the reprogramming or the culture conditions. Thus, a rigorous safety testing of iPS or iPS-derived cells is imperative, including long-term studies in model animals. This will include not only rodents but also larger mammalian model species to allow for assessing long-term stability of the transplanted cells, functional integration into the host tissue, and freedom from undifferentiated iPS cells. Determination of the necessary cell dose is also critical; it is assumed that a minimum of 1 billion transplantable cells is required to achieve a therapeutic effect. This will request medium to long-term in vitro cultivation and dozens of cell divisions, bearing the risk of accumulating replication errors. Here, we review the clinical potential of human iPS cells and evaluate which are the most suitable approaches to overcome or minimize risks associated with the application of iPS cell-derived cell therapies.

Geroscience: Addressing the mismatch between its exciting research opportunities, its economic imperative and its current funding crisis

There is at present a huge disconnect between levels of funding for basic research on fundamental mechanisms of biological aging and, given demographic projections, the anticipated enormous social and economic impacts of a litany of chronic diseases for which aging is by far the major risk factor: One valuable approach, recently instigated by Felipe Sierra & colleagues at the US National Institute on Aging, is the development of a Geroscience Interest Group among virtually all of the NIH institutes. A complementary approach would be to seek major escalations of private funding. The American Federation for Aging Research, the Paul Glenn Foundation and the Ellison Medical Foundation pioneered efforts by the private sector to provide substantial supplements to public sources of funding. It is time for our community to organize efforts towards the enhancements of such crucial contributions, especially in support of the emerging generation of young investigators, many of whom are leaving our ranks to seek alternative employment. To do so, we must provide potential donors with strong economic, humanitarian and scientific rationales. An initial approach to such efforts is briefly outlined in this manuscript as a basis for wider discussions within our community.