WNT/NOTCH Pathway Is Essential for the Maintenance and Expansion of Human MGE Progenitors

Local Thyroid Hormone Action in Brain Development

Proper brain development essentially depends on the timed availability of sufficient amounts of thyroid hormone (TH). This, in turn, necessitates a tightly regulated expression of TH signaling components such as TH transporters, deiodinases, and TH receptors in a brain region- and cell-specific manner from early developmental stages onwards. Abnormal TH levels during critical stages, as well as mutations in TH signaling components that alter the global and/or local thyroidal state, result in detrimental consequences for brain development and neurological functions that involve alterations in central neurotransmitter systems. Thus, the question as to how TH signaling is implicated in the development and maturation of different neurotransmitter and neuromodulator systems has gained increasing attention. In this review, we first summarize the current knowledge on the regulation of TH signaling components during brain development. We then present recent advances in our understanding on how altered TH signaling compromises the development of cortical glutamatergic neurons, inhibitory GABAergic interneurons, cholinergic and dopaminergic neurons. Thereby, we highlight novel mechanistic insights and point out open questions in this evolving research field.

Alpha terpineol directs bone marrow mesenchymal stem cells toward neuronal lineage through regulation of wnt signaling pathway

Central nervous system anomalies give rise to neuropathological consequences with immense damage to the neuronal tissues. Cell based therapeutics have the potential to manage several neuropathologies whereby the differentiated cells are explored for neuronal regeneration. The current study analyzes the effect of a bioactive compound, alpha terpineol (AT) on the differentiation of rat bone marrow derived mesenchymal stem cells (BM-MSCs) toward neuronal lineage, and explores regulation of differentiation process through the study of Wnt pathway mediators. BM-MSCs were cultured and characterized based on their surface markers and tri-lineage differentiation. Safe dose of AT as optimized by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium bromide assay, was used for the treatment of MSCs. Treated cells were analyzed for the neuronal, astroglial and germ layer transition markers at the gene and protein levels, by quantitative polymerase chain reaction and immunocytochemistry, respectively. Temporal expression of Wnt pathway genes was assessed during the course of neuronal differentiation. AT treated group showed significant upregulation of neuron specific (NSE, MAP2, Tau, Nestin, and NefL) and astroglial (GFAP) genes with positive expression of late neuronal markers. Germ layer transition analysis showed the overexpression of ectodermal markers (NCAM, Nestin, and Pax6), whereas endodermal (AFP, MixL1, and Sox17), and mesodermal (Mesp1 and T Brachyury) markers were also found to be upregulated. Wnt signaling pathway was activated during the initial phase (30 min) of differentiation, which later was downregulated at 1, 3, and 5 h. AT efficiently induces neuronal differentiation of BM-MSCs by regulating Wnt signaling. Overexpression of both early and late neuronal markers indicate their neuro-progenitor state and thus can be utilized as a promising approach in cellular therapeutics to treat various neurodegenerative ailments. In addition, exploration of the molecular pathways may be helpful to understand the mechanism of cell-based neuronal regeneration.

Hypoimmunogenic human pluripotent stem cells are valid cell sources for cell therapeutics with normal self-renewal and multilineage differentiation capacity

Hypoimmunogenic human pluripotent stem cells (hPSCs) are expected to serve as an unlimited cell source for generating universally compatible "off-the-shelf" cell grafts. However, whether the engineered hypoimmunogenic hPSCs still preserve their advantages of unlimited self-renewal and multilineage differentiation to yield functional tissue cells remains unclear. Here, we systematically studied the self-renewal and differentiation potency of three types of hypoimmunogenic hPSCs, established through the biallelic lesion of B2M gene to remove all surface expression of classical and nonclassical HLA class I molecules (B2Mnull), biallelic homologous recombination of nonclassical HLA-G1 to the B2M loci to knockout B2M while expressing membrane-bound β2m-HLA-G1 fusion proteins (B2MmHLAG), and ectopic expression of soluble and secreted β2m-HLA-G5 fusion proteins in B2MmHLAG hPSCs (B2Mm/sHLAG) in the most widely used WA09 human embryonic stem cells. Our results showed that hypoimmunogenic hPSCs with variable expression patterns of HLA molecules and immune compromising spectrums retained their normal self-renewal capacity and three-germ-layer differentiation potency. More importantly, as exemplified by neurons, cardiomyocytes and hepatocytes, hypoimmunogenic hPSC-derived tissue cells were fully functional as of their morphology, electrophysiological properties, macromolecule transportation and metabolic regulation. Our findings thus indicate that engineered hypoimmunogenic hPSCs hold great promise of serving as an unlimited universal cell source for cell therapeutics.

Application of Medial Ganglionic Eminence Cell Transplantation in Diseases Associated With Interneuron Disorders

Excitatory projection neurons and inhibitory interneurons primarily accomplish the neural activity of the cerebral cortex, and an imbalance of excitatory-inhibitory neural networks may lead to neuropsychiatric diseases. Gamma-aminobutyric acid (GABA)ergic interneurons mediate inhibition, and the embryonic medial ganglionic eminence (MGE) is a source of GABAergic interneurons. After transplantation, MGE cells migrate to different brain regions, differentiate into multiple subtypes of GABAergic interneurons, integrate into host neural circuits, enhance synaptic inhibition, and have tremendous application value in diseases associated with interneuron disorders. In the current review, we describe the fate of MGE cells derived into specific interneurons and the related diseases caused by interneuron loss or dysfunction and explore the potential of MGE cell transplantation as a cell-based therapy for a variety of interneuron disorder-related diseases, such as epilepsy, schizophrenia, autism spectrum disorder, and Alzheimer’s disease.

Fate of hematopoietic stem cells determined by Notch1 signaling (Review)

Regulation of the fate of hematopoietic stem cells (HSCs), including silencing, self-renewal or differentiation into blood line cells, is crucial to maintain the homeostasis of the human blood system and prevent leukemia. Notch1, a key receptor in the Notch signaling pathway, plays an important regulatory role in these properties of HSCs, particularly in the maintenance of the stemness of HSCs. In recent decades, the ubiquitination modification of Notch1 has been gradually revealed, and also demonstrated to affect the proliferation and differentiation of HSCs. Therefore, a detailed elucidation of Notch1 and its ubiquitination modification may help to improve understanding of the maintenance of HSC properties and the pathogenesis of leukemia. In addition, it may aid in identifying potential therapeutic targets for specific leukemias and provide potential prognostic indicators for HSC transplantation (HSCT). In the present review, the association between Notch1 and HSCs and the link between the ubiquitination modification of Notch1 and HSCs were described. In addition, the association between abnormal HSCs mediated by Notch1 or ubiquitinated Notch1and T-cell acute lymphoblastic leukemia (T-ALL) was also examined, which provides a promising direction for clinical application.

Identification of TGFβ signaling as a regulator of interneuron neurogenesis in a human pluripotent stem cell model

Cortical interneurons are GABAergic inhibitory cells that connect locally in the neocortex and play a pivotal role in shaping cortical network activities. Dysfunction of these cells is believed to lead to runaway excitation underlying seizure-based diseases, such as epilepsy, autism and schizophrenia. There is a growing interest in using cortical interneurons derived from human pluripotent stem cells for understanding their complex development and for modeling neuropsychiatric diseases. Here, we report the identification of a novel role of transforming growth factor β (TGFβ) signaling in modulating interneuron progenitor maintenance and neuronal differentiation. TGFβ signaling inhibition suppresses terminal differentiation of interneuron progenitors, while exogenous TGFβ3 accelerates the transition of progenitors into postmitotic neurons. We provide evidence that TGFb signaling exerts this function via regulating cell cycle length of the NKX2.1+ neural progenitors. Together, the present study represents a useful platform for studying human interneuron development and interneuron-associated neurological diseases with human pluripotent stem cells.

Developmental programming and lineage branching of early human telencephalon

The dorsal and ventral human telencephalons contain different neuronal subtypes, including glutamatergic, GABAergic, and cholinergic neurons, and how these neurons are generated during early development is not well understood. Using scRNA-seq and stringent validations, we reveal here a developmental roadmap for human telencephalic neurons. Both dorsal and ventral telencephalic radial glial cells (RGs) differentiate into neurons via dividing intermediate progenitor cells (IPCs_div) and early postmitotic neuroblasts (eNBs). The transcription factor ASCL1 plays a key role in promoting fate transition from RGs to IPCs_div in both regions. RGs from the regionalized neuroectoderm show heterogeneity, with restricted glutamatergic, GABAergic, and cholinergic differentiation potencies. During neurogenesis, IPCs_div gradually exit the cell cycle and branch into sister eNBs to generate distinct neuronal subtypes. Our findings highlight a general RGs-IPCs_div-eNBs developmental scheme for human telencephalic progenitors and support that the major neuronal fates of human telencephalon are predetermined during dorsoventral regionalization with neuronal diversity being further shaped during neurogenesis and neural circuit integration.

Epigenetic Regulation of the Wnt/β-Catenin Signaling Pathway in Cancer

Studies over the past four decades have elucidated the role of Wnt/β-catenin mediated regulation in cell proliferation, differentiation and migration. These processes are fundamental to embryonic development, regeneration potential of tissues, as well as cancer initiation and progression. In this review, we focus on the epigenetic players which influence the Wnt/β-catenin pathway via modulation of its components and coordinated regulation of the Wnt target genes. The role played by crosstalk with other signaling pathways mediating tumorigenesis is also elaborated. The Hippo/YAP pathway is particularly emphasized due to its extensive crosstalk via the Wnt destruction complex. Further, we highlight the recent advances in developing potential therapeutic interventions targeting the epigenetic machinery based on the characterization of these regulatory networks for effective treatment of various cancers and also for regenerative therapies.

β-Catenin Deletion in Regional Neural Progenitors Leads to Congenital Hydrocephalus in Mice

Congenital hydrocephalus is a major neurological disorder with high rates of morbidity and mortality; however, the underlying cellular and molecular mechanisms remain largely unknown. Reproducible animal models mirroring both embryonic and postnatal hydrocephalus are also limited. Here, we describe a new mouse model of congenital hydrocephalus through knockout of β-catenin in Nkx2.1-expressing regional neural progenitors. Progressive ventriculomegaly and an enlarged brain were consistently observed in knockout mice from embryonic day 12.5 through to adulthood. Transcriptome profiling revealed severe dysfunctions in progenitor maintenance in the ventricular zone and therefore in cilium biogenesis after β-catenin knockout. Histological analyses also revealed an aberrant neuronal layout in both the ventral and dorsal telencephalon in hydrocephalic mice at both embryonic and postnatal stages. Thus, knockout of β-catenin in regional neural progenitors leads to congenital hydrocephalus and provides a reproducible animal model for studying pathological changes and developing therapeutic interventions for this devastating disease.

Systems Toxicology Approach for Assessing Developmental Neurotoxicity in Larval Zebrafish

Adverse outcomes that result from chemical toxicity are rarely caused by dysregulation of individual proteins; rather, they are often caused by system-level perturbations in networks of molecular events. To fully understand the mechanisms of toxicity, it is necessary to recognize the interactions of molecules, pathways, and biological processes within these networks. The developing brain is a prime example of an extremely complex network, which makes developmental neurotoxicity one of the most challenging areas in toxicology. We have developed a systems toxicology method that uses a computable biological network to represent molecular interactions in the developing brain of zebrafish larvae. The network is curated from scientific literature and describes interactions between biological processes, signaling pathways, and adverse outcomes associated with neurotoxicity. This allows us to identify important signaling hubs, pathway interactions, and emergent adverse outcomes, providing a more complete understanding of neurotoxicity. Here, we describe the construction of a zebrafish developmental neurotoxicity network and its validation by integration with publicly available neurotoxicity-related transcriptomic datasets. Our network analysis identified consistent regulation of tumor suppressors p53 and retinoblastoma 1 (Rb1) as well as the oncogene Krüppel-like factor (Klf8) in response to chemically induced developmental neurotoxicity. The developed network can be used to interpret transcriptomic data in a neurotoxicological context.

Protocol for genome-scale CRISPR screening in engineered lineage reporter hPSCs to study cell fate determination

PAX6 is a key determinant of human neuroectoderm cell fate. Here, we describe a protocol for genome-scale CRISPR screening for use in genetically engineered human pluripotent stem cells (hPSCs). Using the germ layer reporter PAX6 and an inducible CRISPR/Cas9 knockout system, we describe how to identify lineage-specific preventing genes. This protocol can be applied for use with other reporter genes to study cell fate determination in hPSCs.

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

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Generation of PAX6 lineage reporter hPSCs

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Detailed protocol for genome-scale CRISPR screening in hPSCs

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Combining PAX6 hPSCs and CRISPR screening to study cell fate determination

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Protocol allows identification of lineage specification preventing genes

Comprehending the crosstalk between Notch, Wnt and Hedgehog signaling pathways in oral squamous cell carcinoma - clinical implications

BACKGROUND

Oral squamous cell carcinoma (OSCC) is a malignant oral cavity neoplasm that affects many people, especially in developing countries. Despite several advances that have been made in diagnosis and treatment, the morbidity and mortality rates due to OSCC remain high. Accumulating evidence indicates that aberrant activation of cellular signaling pathways, such as the Notch, Wnt and Hedgehog pathways, occurs during the development and metastasis of OSCC. In this review, we have articulated the roles of the Notch, Wnt and Hedgehog signaling pathways in OSCC and their crosstalk during tumor development and progression. We have also examined possible interactions and associations between these pathways and treatment regimens that could be employed to effectively tackle OSCC and/or prevent its recurrence.

CONCLUSIONS

Activation of the Notch signaling pathway upregulates the expression of several genes, including c-Myc, β-catenin, NF-κB and Shh. Associations between the Notch signaling pathway and other pathways have been shown to enhance OSCC tumor aggressiveness. Crosstalk between these pathways supports the maintenance of cancer stem cells (CSCs) and regulates OSCC cell motility. Thus, application of compounds that block these pathways may be a valid strategy to treat OSCC. Such compounds have already been employed in other types of cancer and could be repurposed for OSCC.

RUES2 hESCs exhibit MGE-biased neuronal differentiation and muHTT-dependent defective specification hinting at SP1

RUES2 cell lines represent the first collection of isogenic human embryonic stem cells (hESCs) carrying different pathological CAG lengths in the HTT gene. However, their neuronal differentiation potential has yet to be thoroughly evaluated. Here, we report that RUES2 during ventral telencephalic differentiation is biased towards medial ganglionic eminence (MGE). We also show that HD-RUES2 cells exhibit an altered MGE transcriptional signature in addition to recapitulating known HD phenotypes, with reduced expression of the neurodevelopmental regulators NEUROD1 and BDNF and increased cleavage of synaptically enriched N-cadherin. Finally, we identified the transcription factor SP1 as a common potential detrimental co-partner of muHTT by de novo motif discovery analysis on the LGE, MGE, and cortical genes differentially expressed in HD human pluripotent stem cells in our and additional datasets. Taken together, these observations suggest a broad deleterious effect of muHTT in the early phases of neuronal development that may unfold through its altered interaction with SP1.

Deregulation of Neuro-Developmental Genes and Primary Cilium Cytoskeleton Anomalies in iPSC Retinal Sheets from Human Syndromic Ciliopathies

Ciliopathies are heterogeneous genetic diseases affecting primary cilium structure and function. Meckel-Gruber (MKS) and Bardet-Biedl (BBS) syndromes are severe ciliopathies characterized by skeletal and neurodevelopment anomalies, including polydactyly, cognitive impairment, and retinal degeneration. We describe the generation and molecular characterization of human induced pluripotent stem cell (iPSC)-derived retinal sheets (RSs) from controls, and MKS (TMEM67) and BBS (BBS10) cases. MKS and BBS RSs displayed significant common alterations in the expression of hundreds of developmental genes and members of the WNT and BMP pathways. Induction of crystallin molecular chaperones was prominent in MKS and BBS RSs suggesting a stress response to misfolded proteins. Unique to MKS photoreceptors was the presence of supernumerary centrioles and cilia, and aggregation of ciliary proteins. Unique to BBS photoreceptors was the accumulation of DNA damage and activation of the mitotic spindle checkpoint. This study reveals how combining cell reprogramming, organogenesis, and next-generation sequencing enables the elucidation of mechanisms involved in human ciliopathies.

Wnt-Notch Signaling Interactions During Neural and Astroglial Patterning of Human Stem Cells

The human brain formation involves complicated processing, which is regulated by a gene regulatory network influenced by different signaling pathways. The cross-regulatory interactions between elements of different pathways affect the process of cell fate assignment during neural and astroglial tissue patterning. In this study, the interactions between Wnt and Notch pathways, the two major pathways that influence neural and astroglial differentiation of human induced pluripotent stem cells (hiPSCs) individually, were investigated. In particular, the synergistic effects of Wnt-Notch pathway on the neural patterning processes along the anterior-posterior or dorsal-ventral axis of hiPSC-derived cortical spheroids were explored. The human cortical spheroids derived from hiPSCs were treated with Wnt activator CHIR99021 (CHIR), Wnt inhibitor IWP4, and Notch inhibitor (N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester [DAPT]) individually, or in combinations (CHIR + DAPT, IWP4 + DAPT). The results suggest that CHIR + DAPT can promote Notch signaling, similar or higher than CHIR alone, whereas IWP4 + DAPT reduces Notch activity compared to IWP4 alone. Also, CHIR + DAPT promoted hindbrain marker HOXB4 expression more consistently than CHIR alone, while IWP4 + DAPT promoted Olig2 expression, indicating the synergistic effects distinctly different from that of the individual small molecule. In addition, IWP4 simultaneously promoted dorsal and ventral identity. The patterned neural spheroids can be switched for astroglial differentiation using bone morphogenetic protein 4. This study should advance the derivations of neurons, astroglial cells, and brain region-specific organoids from hiPSCs for disease modeling, drug screening, as well as for hiPSC-based therapies. Impact Statement Wnt signaling plays a central role in neural patterning of human pluripotent stem cells. It can interact with Notch signaling in defining dorsal-ventral and rostral-caudal (or anterior-posterior) axis of brain organoids. This study investigates novel Wnt and Notch interactions (i.e., Wntch) in neural patterning of dorsal forebrain spheroids or organoids derived from human induced pluripotent stem cells. The synergistic effects of Wnt activator or inhibitor with Notch inhibitor were observed. This study should advance the derivations of neurons, astroglial cells, and brain region-specific organoids from human stem cells for disease modeling and drug screening, as well as for stem cell-based therapies. The results can be used to establish better in vitro culture methods for efficiently mimicking in vivo structure of central nervous system.

Precision medicine for human cancers with Notch signaling dysregulation (Review)

NOTCH1, NOTCH2, NOTCH3 and NOTCH4 are transmembrane receptors that transduce juxtacrine signals of the delta-like canonical Notch ligand (DLL)1, DLL3, DLL4, jagged canonical Notch ligand (JAG)1 and JAG2. Canonical Notch signaling activates the transcription of BMI1 proto-oncogene polycomb ring finger, cyclin D1, CD44, cyclin dependent kinase inhibitor 1A, hes family bHLH transcription factor 1, hes related family bHLH transcription factor with YRPW motif 1, MYC, NOTCH3, RE1 silencing transcription factor and transcription factor 7 in a cellular context-dependent manner, while non-canonical Notch signaling activates NF-κB and Rac family small GTPase 1. Notch signaling is aberrantly activated in breast cancer, non-small-cell lung cancer and hematological malignancies, such as T-cell acute lymphoblastic leukemia and diffuse large B-cell lymphoma. However, Notch signaling is inactivated in small-cell lung cancer and squamous cell carcinomas. Loss-of-function NOTCH1 mutations are early events during esophageal tumorigenesis, whereas gain-of-function NOTCH1 mutations are late events during T-cell leukemogenesis and B-cell lymphomagenesis. Notch signaling cascades crosstalk with fibroblast growth factor and WNT signaling cascades in the tumor microenvironment to maintain cancer stem cells and remodel the tumor microenvironment. The Notch signaling network exerts oncogenic and tumor-suppressive effects in a cancer stage- or (sub)type-dependent manner. Small-molecule γ-secretase inhibitors (AL101, MRK-560, nirogacestat and others) and antibody-based biologics targeting Notch ligands or receptors [ABT-165, AMG 119, rovalpituzumab tesirine (Rova-T) and others] have been developed as investigational drugs. The DLL3-targeting antibody-drug conjugate (ADC) Rova-T, and DLL3-targeting chimeric antigen receptor-modified T cells (CAR-Ts), AMG 119, are promising anti-cancer therapeutics, as are other ADCs or CAR-Ts targeting tumor necrosis factor receptor superfamily member 17, CD19, CD22, CD30, CD79B, CD205, Claudin 18.2, fibroblast growth factor receptor (FGFR)2, FGFR3, receptor-type tyrosine-protein kinase FLT3, HER2, hepatocyte growth factor receptor, NECTIN4, inactive tyrosine-protein kinase 7, inactive tyrosine-protein kinase transmembrane receptor ROR1 and tumor-associated calcium signal transducer 2. ADCs and CAR-Ts could alter the therapeutic framework for refractory cancers, especially diffuse-type gastric cancer, ovarian cancer and pancreatic cancer with peritoneal dissemination. Phase III clinical trials of Rova-T for patients with small-cell lung cancer and a phase III clinical trial of nirogacestat for patients with desmoid tumors are ongoing. Integration of human intelligence, cognitive computing and explainable artificial intelligence is necessary to construct a Notch-related knowledge-base and optimize Notch-targeted therapy for patients with cancer.

Cancer stem cells in esophageal squamous cell cancer

Cancer stem cells (CSCs) are hypothesized to govern the origin, progression, drug resistance, recurrence and metastasis of human cancer. CSCs have been identified in nearly all types of human cancer, including esophageal squamous cell cancer (ESCC). Four major methods are typically used to isolate or enrich CSCs, including: i) fluorescence-activated cell sorting or magnetic-activated cell sorting using cell-specific surface markers; ii) stem cell markers, including aldehyde dehydrogenase 1 family member A1; iii) side population cell phenotype markers; and iv) microsphere culture methods. ESCC stem cells have been identified using a number of these methods. An increasing number of stem cell signatures and pathways have been identified, which have assisted in the clarification of molecular mechanisms that regulate the stemness of ESCC stem cells. Certain viruses, such as human papillomavirus and hepatitis B virus, are also considered to be important in the formation of CSCs, and there is a crosstalk between stemness and viruses-associated genes/pathways, which may suggest a potential therapeutic strategy for the eradication of CSCs. In the present review, findings are summarized along these lines of inquiry.