Highly efficient generation of glutamatergic/cholinergic NT2-derived postmitotic human neurons by short-term treatment with the nucleoside analogue cytosine β-D-arabinofuranoside

PLCβ1 by-passes early growth response -1 to induce the differentiation of neuronal cells

The Gαq/phospholipase C-β (PLCβ) signaling system mediates calcium responses to a variety of hormones and neurotransmitters. Recent studies suggest that PLCβ1 expression plays a role in the differentiation of two types of cultured neuronal cells (PC12 and SK-N-SH) through a mechanism independent of Gαq. Here, we show that, similar to that observed in PC12 and SK-N-SH cells, PLCβ1 expression increases when human NT2 cells are induced to differentiate either through cytosine-β-D-arabinofuranoside or retinoic acid. Preventing this increase, abolishes differentiation, and down-regulating PLCβ1 in rat primary astrocytes causes cells to adapt an undifferentiated morphology. Surprisingly, transfecting PLCβ1 into undifferentiated PC12 or NT2 cells induces differentiation without the need for differentiating agents. Studies to uncover the underlying mechanism focused on the transcription factor early growth response 1 (Egr-1) which mediates PLCβ1 expression early in differentiation. Over-expressing PLCβ1 in HEK293 cells enhances Egr-1 expression and induces morphological changes. We show that increased levels of cytosolic PLCβ1 in undifferentiated PC12 cells disrupts the association between Egr-1 and its cytosolic binding partner (Tar RNA binding protein), promoting relocalization of Egr-1 to the nucleus, which promotes transcription of proteins needed for differentiation. These studies show a novel mechanism through which differentiation can be modulated.

AraC-induced neuron-like differentiation of human NTERA2/D1 cells and quantification of endogenous pre-mir-106b and 19b levels

MicroRNAs (miRNAs) are approximately 22 nucleotide-long non-coding RNAs that are encoded in the genome. miRNAs form base pairs with target mRNAs in the RNA-induced silencing complex and repress their expression through a mechanism called RNA silencing. Expression profiles of miRNAs differ between cells and tissues. In this study, we performed cytosine β-D-arabinofuranoside (AraC)-induced neuron-like differentiation of human NTERA2/D1 (NT2) cells and quantified endogenous miRNA levels using quantitative RT-PCR. In conclusion, pre-mir-106b and pre-mir-19b levels were decreased after AraC-induced neuron-like differentiation of NT2 cells, indicating the functional relevance of miRNAs in the differentiation of mammalian cells.

The cellular model for Alzheimer's disease research: PC12 cells

Alzheimer's disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive decline and irreversible memory impairment. Currently, several studies have failed to fully elucidate AD's cellular and molecular mechanisms. For this purpose, research on related cellular models may propose potential predictive models for the drug development of AD. Therefore, many cells characterized by neuronal properties are widely used to mimic the pathological process of AD, such as PC12, SH-SY5Y, and N2a, especially the PC12 pheochromocytoma cell line. Thus, this review covers the most systematic essay that used PC12 cells to study AD. We depict the cellular source, culture condition, differentiation methods, transfection methods, drugs inducing AD, general approaches (evaluation methods and metrics), and in vitro cellular models used in parallel with PC12 cells.

Paracetamol perturbs neuronal arborization and disrupts the cytoskeletal proteins SPTBN1 and TUBB3 in both human and chicken in vitro models

Epidemiological studies have linked long-term/high-dose usage of paracetamol (N-acetyl-para-aminophenol, APAP) during pregnancy to adverse neuropsychiatric outcomes, primarily attention-deficit hyperactive disorder (ADHD), in the offspring. Though variable, ADHD has been associated with phenotypic alterations characterized by reductions in grey matter densities and aberrations in structural connectivity, effects which are thought to originate in neurodevelopment. We used embryonic chicken cerebellar granule neurons (CGNs) and neuronally differentiating human NTERA2 cells (NT2Ns) to investigate the in vitro effects of APAP on cell viability, migration, neuritogenesis, and the intracellular levels of various proteins involved in neurodevelopment as well as in the maintenance of the structure and function of neurites. Exposure to APAP ranging from 100 to 1600 μM yielded concentration- and time-dependent reductions in cell viability and levels of neurite arborization, as well as reductions in the levels of the cytoskeletal protein β2-spectrin, with the highest APAP concentration resulting in between 50 and 75% reductions in the aforementioned metrics over the course of 72 h. Exposure to APAP also reduced migration in the NT2Ns but not CGNs. Moreover, we found concentration- and time-dependent increases in punctate aggregation of the cytoskeletal protein β3-tubulin following exposure to APAP in both cell model systems, with the highest APAP concentration approximately doubling the number of aggregates over 72-120 h. Our findings demonstrate that APAP negatively perturbs neurite arborization degree, with concurrent reductions in the protein levels of β2-spectrin and disruption of the integrity of β3-tubulin, both proteins of which play important roles in neuronal structure and function.

Discovery of a CNS penetrant small molecule SMN2 splicing modulator with improved tolerability for spinal muscular atrophy

Spinal muscular atrophy (SMA) is a motor neuron disease, typically resulting from loss-of-function mutations in the survival motor neuron 1 (SMN1) gene. Nusinersen/SPINRAZA, a splice-switching oligonucleotide that modulates SMN2 (a paralog of SMN1) splicing and consequently increases SMN protein levels, has a therapeutic effect for SMA. Previously reported small-molecule SMN2 splicing modulators such as risdiplam/EVRYSDI and its analog SMN-C3 modulate not only the splicing of SMN2 but also that of secondary splice targets, including forkhead box protein M1 (FOXM1). Through screening SMA patient-derived fibroblasts, a novel small molecule, designated TEC-1, was identified that selectively modulates SMN2 splicing over three secondary splice targets. TEC-1 did not strongly affect the splicing of FOXM1, and unlike risdiplam, did not induce micronucleus formation. In addition, TEC-1 showed higher selectively on galactosylceramidase and huntingtin gene expression compared to previously reported compounds (e.g., SMN-C3) due to off-target effects on cryptic exon inclusion and nonsense-mediated mRNA decay. Moreover, TEC-1 significantly ameliorated the disease phenotype in an SMA murine model in vivo. Thus, TEC-1 may have promising therapeutic potential for SMA, and our study demonstrates the feasibility of RNA-targeting small-molecule drug development with an improved tolerability profile.

Rewiring of the Human Mitochondrial Interactome during Neuronal Reprogramming Reveals Regulators of the Respirasome and Neurogenesis

Mitochondrial protein (MP) assemblies undergo alterations during neurogenesis, a complex process vital in brain homeostasis and disease. Yet which MP assemblies remodel during differentiation remains unclear. Here, using mass spectrometry-based co-fractionation profiles and phosphoproteomics, we generated mitochondrial interaction maps of human pluripotent embryonal carcinoma stem cells and differentiated neuronal-like cells, which presented as two discrete cell populations by single-cell RNA sequencing. The resulting networks, encompassing 6,442 high-quality associations among 600 MPs, revealed widespread changes in mitochondrial interactions and site-specific phosphorylation during neuronal differentiation. By leveraging the networks, we show the orphan C20orf24 as a respirasome assembly factor whose disruption markedly reduces respiratory chain activity in patients deficient in complex IV. We also find that a heme-containing neurotrophic factor, neuron-derived neurotrophic factor [NENF], couples with Parkinson disease-related proteins to promote neurotrophic activity. Our results provide insights into the dynamic reorganization of mitochondrial networks during neuronal differentiation and highlights mechanisms for MPs in respirasome, neuronal function, and mitochondrial diseases.

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Rewiring of mitochondrial (mt) protein interaction network in distinct cell states

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Dramatic changes in site-specific phosphorylation during neuronal differentiation

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C20orf24 is a respirasome assembly factor depleted in patients deficient in CIV

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NENF binding with DJ-1/PINK1 promotes neurotrophic activity and neuronal survival

Induced pluripotent stem cells (iPSCs) as model to study inherited defects of neurotransmission in inborn errors of metabolism

The ability to reprogram somatic cells to induced pluripotent stem cells (iPSCs) has revolutionized the way of modeling human disease. Especially for the modeling of rare human monogenetic diseases with limited numbers of patients available worldwide and limited access to the mostly affected tissues, iPSCs have become an invaluable tool. To study rare diseases affecting neurotransmitter biosynthesis and neurotransmission, stem cell models carrying patient-specific mutations have become highly important as most of the cell types present in the human brain and the central nervous system (CNS), including motoneurons, neurons, oligodendrocytes, astrocytes, and microglia, can be differentiated from iPSCs following distinct developmental programs. Differentiation can be performed using classical 2D differentiation protocols, thereby generating specific subtypes of neurons or glial cells in a dish. On the other side, 3D differentiation into "organoids" opened new ways to study misregulated developmental processes associated with rare neurological and neurometabolic diseases. For the analysis of defects in neurotransmission associated with rare neurometabolic diseases, different types of brain organoids have been made available during the last years including forebrain, midbrain and cerebral organoids. In this review, we illustrate reprogramming of somatic cells to iPSCs, differentiation in 2D and 3D, as well as already available disease-specific iPSC models, and discuss current and future applications of these techniques.

Analysis of regeneration- and myelination-associated proteins in human neuroma in continuity and discontinuity

BACKGROUND

Neuromas are pathologic nerve distensions caused by a nerve's response to trauma, resulting in a dysfunctional to non-functional nerve. Depending on the severance of the affected nerve, the resulting neuroma can be differentiated into continuous and stump neuroma. While neuroma formation has been investigated in animal models with enormous regenerative capacity, the search for differences in human response to nerve trauma on a molecular level ultimately seeks to identify reasons for functionally successful versus unsuccessful regeneration after peripheral nerve trauma in man.

METHODS

In the present study, the regenerative potential of axons and the capability of Schwann cells (SC) to remyelinate regenerating axons was quantitatively and segmentally analyzed and compared within human neuroma in-continuity and discontinuity.

RESULTS

For the stump neuroma and the neuroma in-continuity, there was a significant reduction of the total number of axons (86% stump neuroma and 91% neuroma in-continuity) from the proximal to the distal part of the neuroma, while the amount of fibrotic tissue increased, respectively. Labeling the myelin sheath of regenerating axons revealed a remyelination of regenerating axons by SCs in both neuroma types. The segmented analysis showed no distinct alterations in the number and spatial distribution of regenerating, mature, and myelinated axons between continuous and discontinuous neuroma.

CONCLUSIONS

The quantitative and segmented analysis showed no distinct alterations in the number and spatial distribution of regenerating, mature, and myelinated axons between continuous and discontinuous neuroma, while the extensive expression of Gap43 in up to 55% of the human neuroma axons underlines their regenerative capacity independent of whether the neuroma is in continuity or discontinuity. Remyelination of Gap43-positive axons suggests that the capability of SCs to remyelinate regenerating axons is preserved in neuroma tissue.

Data for the morphometric characterization of NT2-derived postmitotic neurons

NTERA2/D1 human teratocarcinoma progenitors induced to differentiate into postmitotic neurons by either long-term treatment with retinoic acid or short-term treatment with the nucleoside analog cytosine β-D-arabinofuranoside were subjected to morphometric analysis and compared. Our data provide a methodological and conceptual framework for future investigations aiming at distinguishing neuronal phenotypes on the basis of morphometric analysis. Data presented here are related to research concurrently published in “Highly Efficient Generation of Glutamatergic/Cholinergic NT2-Derived Postmitotic Human Neurons by Short-Term treatment with the Nucleoside Analogue Cytosine β-D-Arabinofuranoside” [1].