PAX3 inhibits β-Tubulin-III expression and neuronal differentiation of neural stem cell

PRMT5 Maintains Tumor Stem Cells to Promote Pediatric High-Grade Glioma Tumorigenesis

Pediatric high-grade gliomas (PHGG) are aggressive, undifferentiated central nervous system tumors with poor outcomes, for which no standard-of-care drug therapy currently exists. Through a knockdown (KD) screen for epigenetic regulators, we identified PRMT5 as essential for PHGG cell growth. We hypothesized that, similar to its effect in normal cells, PRMT5 promotes self-renewal of stem-like PHGG tumor-initiating cells essential for tumor growth. We conducted in vitro analyses, including limiting dilution studies of self-renewal, to determine the phenotypic effects of PRMT5 KD. We performed chromatin immunoprecipitation sequencing (ChIP-Seq) to identify PRMT5-mediated epigenetic changes and performed gene set enrichment analysis to identify pathways that PRMT5 regulates. Using an orthotopic xenograft model of PHGG, we tracked survival and histologic characteristics resulting from PRMT5 KD or administration of a PRMT5 inhibitor ± radiation therapy. In vitro, PRMT5 KD slowed cell-cycle progression, tumor growth and self-renewal, and altered chromatin occupancy at genes associated with differentiation, tumor formation, and growth. In vivo, PRMT5 KD increased survival and reduced tumor aggressiveness; however, pharmacologic inhibition of PRMT5 with or without radiation therapy did not improve survival. PRMT5 KD epigenetically reduced tumor-initiating cells' self-renewal, leading to increased survival in preclinical models. Pharmacologic inhibition of PRMT5 enzymatic activity may have failed in vivo due to insufficient reduction of PRMT5 activity by chemical inhibition, or this failure may suggest that nonenzymatic activities of PRMT5 are more relevant. Implications: PRMT5 maintains and promotes the growth of stem-like cells that initiate and drive tumorigenesis in PHGG.

A novel model of autologous tooth transplantation for the study of nerve recruitment

BACKGROUND

Limited treatment options exist for damaged nerves and despite impressive advances in tissue engineering, scientists and clinicians have yet to fully replicate nerve development and recruitment. Innervation is a critical feature for normal organ function. While most organs are innervated prior to birth, a rare example of postnatal nerve recruitment occurs in the natural development of secondary teeth during adolescence. Many animals undergo postnatal shedding of deciduous teeth with development and eruption of secondary teeth, a process requiring recruitment of nerve and vasculature to each tooth pulp for viability. Here, the investigators created a novel model for the study of postnatal innervation by exploiting the natural phenomenon of tooth-driven nerve recruitment.

METHODS

The investigators theorized that developing teeth possess a special capacity to induce innervation which could be harnessed in a clinical setting for nerve regeneration, and hyptothesized that a transplant model could be created to capture this phenomenon. In this descriptive study, a rat model of autologous tooth transplantation and de novo nerve recruitment was developed by surgically transferring whole developing molars to the autologous tibia.

RESULTS

Downstream histological analysis performed 6 to 14 weeks after surgery demonstrated integration of molar into tibia in 81% of postoperative rats, with progressive pulpal expression of nerve marker ß-tubulin III suggestive of neuronal recruitment.

CONCLUSIONS

These findings provide a novel model for the study of organ transplantation and support the theory that developing dental tissues may retain nerve-inductive properties postnatally.

Single-cell RNA sequencing of aging neural progenitors reveals loss of excitatory neuron potential and a population with transcriptional immune response

In the adult murine brain, neural stem cells (NSCs) can be found in two main niches: the dentate gyrus (DG) and the subventricular zone (SVZ). In the DG, NSCs produce intermediate progenitors (IPs) that differentiate into excitatory neurons, while progenitors in the SVZ migrate to the olfactory bulb (OB), where they mainly differentiate into inhibitory interneurons. Neurogenesis, the process of generating new neurons, persists throughout life but decreases dramatically with aging, concomitantly with increased inflammation. Although many cell types, including microglia, undergo significant transcriptional changes, few such changes have been detected in neural progenitors. Furthermore, transcriptional profiles in progenitors from different neurogenic regions have not been compared on a single-cell level, and little is known about how they are affected by aging-related inflammation. We have generated a single cell RNA sequencing dataset enriched for IPs, which revealed that most aged neural progenitors only acquire minor transcriptional changes. However, progenitors set to become excitatory neurons decrease faster than others. In addition, a population in the aged SVZ, not detected in the OB, acquired major transcriptional activation related to immune responses. This suggests that differences in age related neurogenic decline between regions is not due to tissue differences but rather cell type specific intrinsic transcriptional programs, and that subset of neuroblasts in the SVZ react strongly to age related inflammatory cues.

NOTCH3 promotes docetaxel resistance of prostate cancer cells through regulating TUBB3 and MAPK signaling pathway

Docetaxel is the preferred chemotherapeutic agent in patients with castrate-resistant prostate cancer (CRPC). However, patients eventually develop docetaxel resistance and in the absence of effective treatment options. Consequently, it is essential to investigate the mechanisms generating docetaxel resistance and develop novel alternative therapeutic targets. RNA sequencing was undertaken on docetaxel-sensitive and docetaxel-resistant prostate cancer (PCa) cells. Subsequently, chemoresistance, cancer stemness, and lipid metabolism were investigated. To obtain insight into the precise activities and action mechanisms of NOTCH3 in docetaxel-resistant PCa, immunoprecipitation, mass spectrometry, ChIP, luciferase reporter assay, cell metabolism, and animal experiments were performed. Through RNA sequencing analysis, we found that NOTCH3 expression was markedly higher in docetaxel-resistant cells relative to parental cells, and that this trend was continued in docetaxel-resistant PCa tissues. Experiments in vitro and in vivo revealed that NOTCH3 enhanced stemness, lipid metabolism, and docetaxel resistance in PCa. Mechanistically, NOTCH3 is bound to TUBB3 and activates the MAPK signaling pathway. Moreover, NOTCH3 was directly regulated by MEF2A in docetaxel-resistant cells. Notably, targeting NOTCH3 and the MEF2A/TUBB3 signaling axis was related to docetaxel chemoresistance in PCa. Overall, these results demonstrated that NOTCH3 fostered stemness, lipid metabolism, and docetaxel resistance in PCa via the TUBB3 and MAPK signaling pathways. Therefore, NOTCH3 may be employed as a prognostic biomarker in PCa patients. NOTCH3 could be a therapeutic target for PCa patients, particularly those who have developed docetaxel resistance.

Effect of Fetal Bovine Serum or Basic Fibroblast Growth Factor on Cell Survival and the Proliferation of Neural Stem Cells: The Influence of Homocysteine Treatment

In vitro cell culture is a routinely used method which is also applied for in vitro modeling of various neurological diseases. On the other hand, media used for cell culture are often not strictly standardized between laboratories, which hinders the comparison of the obtained results. Here, we compared the effects of homocysteine (Hcy), a molecule involved in neurodegeneration, on immature cells of the nervous system cultivated in basal medium or media supplemented by either fetal bovine serum or basic fibroblast growth factor. The number of cells in basal media supplemented with basic fibroblast growth factor (bFGF) was 2.5 times higher in comparison to the number of cells in basal media supplemented with fetal bovine serum (FBS). We also found that the neuron-specific β-3-tubulin protein expression dose dependently decreased with increasing Hcy exposure. Interestingly, bFGF exerts a protective effect on β-3-tubulin protein expression at a concentration of 1000 µM Hcy compared to FBS-treated neural stem cells on Day 7. Supplementation with bFGF increased SOX2 protein expression two-fold compared to FBS supplementation. GFAP protein expression increased five-fold on Day 3 in FBS-treated neural stem cells, whereas on Day 7, bFGF increased GFAP expression two-fold compared to FBS-treated neural stem cells. Here, we have clearly shown that the selection of culturing media significantly influences various cellular parameters, which, in turn, can lead to different conclusions in experiments based on in vitro models of pathological conditions.

Gene expression and locomotor recovery in adult rats with spinal cord injury and plasma-synthesized polypyrrole/iodine application combined with a mixed rehabilitation scheme

Introduction

Spinal cord injury (SCI) can cause paralysis, for which effective therapeutic strategies have not been developed yet. The only accepted strategy for patients is rehabilitation (RB), although this does not allow complete recovery of lost functions, which makes it necessary to combine it with strategies such as plasma-synthesized polypyrrole/iodine (PPy/I), a biopolymer with different physicochemical properties than PPy synthesized by conventional methods. After SCI in rats, PPy/I promotes functional recovery. Therefore, the purpose of this study was to increase the beneficial effects of both strategies and identify which genes activate PPy/I when applied alone or in combination with a mixed scheme of RB by swimming and enriched environment (SW/EE) in rats with SCI.

Methods

Microarray analysis was performed to identify mechanisms of action underlying the effects of PPy/I and PPy/I+SW/EE on motor function recovery as evaluated by the BBB scale.

Results

Results showed robust upregulation by PPy/I in genes related to the developmental process, biogenesis, synapse, and synaptic vesicle trafficking. In addition, PPy/I+SW/EE increased the expression of genes related to proliferation, biogenesis, cell development, morphogenesis, cell differentiation, neurogenesis, neuron development, and synapse formation processes. Immunofluorescence analysis showed the expression of β-III tubulin in all groups, a decreased expression of caspase-3 in the PPy/I group and GFAP in the PPy/I+SW/EE group (p < 0.05). Better preservation of nerve tissue was observed in PPy/I and PPy/SW/EE groups (p < 0.05). In the BBB scale, the control group scored 1.72 ± 0.41, animals with PPy/I treatment scored 4.23 ± 0.33, and those with PPy/I+SW/EE scored 9.13 ± 0.43 1 month after follow-up.

Conclusion

Thus, PPy/I+SW/EE could represent a therapeutic alternative for motor function recovery after SCI.

Histone acetyltransferase KAT2A modulates neural stem cell differentiation and proliferation by inducing degradation of the transcription factor PAX6

Neural stem cells (NSCs) proliferation and differentiation rely on proper expression and post-translational modification of transcription factors involved in the determination of cell fate. Further characterization is needed to connect modifying enzymes with their transcription factor substrates in the regulation of these processes. Here, we demonstrated that the inhibition of KAT2A, a histone acetyltransferase, leads to a phenotype of small eyes in the developing embryo of zebrafish, which is associated with enhanced proliferation and apoptosis of NSCs in zebrafish eyes. We confirmed that this phenotype is mediated by the evaluated level of PAX6 protein. We further verified that KAT2A negatively regulates PAX6 at the protein level in cultured neural stem cells of rat cerebral cortex. We revealed that PAX6 is a novel acetylation substrate of KAT2A, and the acetylation of PAX6 promotes its ubiquitination mediated by the E3 ligase RNF8 that facilitated PAX6 degradation. Our study proposes that KAT2A inhibition results in accelerated proliferation, delayed differentiation, or apoptosis, depending on the context of PAX6 dosage. Thus, the KAT2A/PAX6 axis plays an essential role to keep a balance between the self-renewal and differentiation of NSCs.

Restoration of functional PAX3 transcriptional factor enhanced neuronal differentiation in PAX3b isoform-depleted neuroblastoma cells

Reexpressed PAX3 transcription factor is believed to be responsible for the differentiation defects observed in neuroblastoma. Although the importance of PAX3 in neuronal differentiation is documented how it is involved in the defective differentiation remains unexplored particularly with its isoforms. Here, first we have analyzed PAX3 expression, its functional status, and its correlation with the neuronal marker expression in SH-SY5Y and its parental SK-N-SH cells. We have found that SH-SY5Y cells which expressed more PAX3 showed increased expression of neuronal marker genes (TUBB, MAP2, NEFL, NEUROG2, SYP) and reported PAX3 target genes (MET, TGFA, and NCAM1) than the SK-N-SH cells that had low PAX3 level. Retinoic acid treatment is unable to induce neuronal differentiation in cells (SK-N-SH) with low PAX3 level/activity. Moreover, ectopic expression of PAX3 in SK-N-SH cells neither induces neuronal marker genes nor its target genes. PAX3 isoform expression analysis revealed the expression of PAX3b isoform that contains only paired domain in SK-N-SH cells, whereas in SH-SY5Y cells, we could also observe PAX3c isoform that contains all functional domains. Further, PAX3b depletion in SK-N-SH cells is not induced PAX3 target genes, and the cells remain poorly differentiated. Interestingly, ectopic PAX3 expression in PAX3b-depleted SK-N-SH cells enhanced neuronal outgrowth along with neuronal marker gene induction. Collectively, these results showed that the PAX3b isoform may be responsible for the differentiation defect observed in SK-N-SH cells and restoration of functional PAX3 in the absence of PAX3b can induce neurogenesis in these cells.

Depletion of SASH1, an astrocyte differentiation-related gene, contributes to functional recovery in spinal cord injury

AIMS

This study aimed to evaluate the effects of the depletion of SAM and SH3 domain-containing protein 1 (SASH1) on functional recovery after spinal cord injury (SCI) and to investigate the possible mechanism of SASH1 knockdown in astrocytes facilitating axonal growth.

METHODS

SCI model was established in adult rats. SASH1 small interfering RNA (siSASH1) was used to investigate its function. Hindlimb motor function was evaluated by the Basso-Bresnahan-Beattie (BBB) assay. The gene expressions were evaluated by the methods of qRT-PCR, Western-blotting, ELISA, and immunohistochemistry.

RESULTS

SASH1 knockdown improved the BBB scores after SCI and significantly reduced GFAP expression. In cultured spinal astrocytes, siSASH1 treatment decreased interferon-γ release and increased brain-derived neurotrophic factor (BDNF) release. When cocultured with SASH1-knockdown astrocytes, axonal growth increased. The neuronal tropomyosin receptor kinase B (BDNF receptor) expression increased, especially in the axonal tips. SASH1 expression increased while NSCs differentiated into glial cells, instead of neurons. After SASH1 depletion, differentiated NSCs maintained a higher level of Nestin protein and an increase in BDNF release.

CONCLUSIONS

These results indicate that SASH1 acts as an astrocytic differentiation-maintaining protein, and SASH1 downregulation limits glial activation and contributes toward functional recovery after SCI.

GCN5/KAT2A contributes to axon growth and neurogenesis

Posttranslational modification (PTM) of tubulin proteins is involved in microtubule dynamics. Acetylation, an important alpha-tubulin PTM, which is regarded as a hallmark event of stable microtubules, often occurs in neurogenesis and axon outgrowth. GCN5/KAT2A is a well-known histone acetyltransferase and has also been reported to hold the activity of nonhistone acetyltransferases, such as acetylated tubulin (Ace-tubulin). In this study, we investigated the role of GCN5/KAT2A in axon growth and neurogenesis. E18 cortical neurons obtained from day 18 embryos of pregnant Sprague-Dawley (SD) rats were cultured and transfected with GCN5 siRNA or treated with the GCN5 inhibitor MB-3. Neural stem cells (NSCs) derived from the cerebral cortexes of E14 SD rats were cultured and differentiated. During differentiation, MB-3 was applied to investigate the effect of GCN5 dysfunction on neurogenesis. The axonal length and the ratio and distribution of acetylated and tyrosinated tubulin (Tyr-tubulin) were evaluated by immunostaining assay. The expression levels of Nestin, Tuj1, acetylated tubulin, and tyrosinated tubulin proteins were analyzed by Western blotting assays. In primary neurons, both GCN5 siRNA and MB-3 treatment reduced acetylated tubulin protein, changed the ratio of acetylated and tyrosinated tubulin, and decreased axonal length. During NSC differentiation, MB-3 application reduced axon outgrowth, decreased acetylated tubulin and altered the distribution of acetylated tubulin and tyrosinated tubulin. This study revealed for the first time that the acetyltransferase GCN5/KAT2A could contribute to axon outgrowth by altering the ratio and distribution of acetylated tubulin.

βIII-Tubulin Gene Regulation in Health and Disease

Microtubule proteins form a dynamic component of the cytoskeleton, and play key roles in cellular processes, such as vesicular transport, cell motility and mitosis. Expression of microtubule proteins are often dysregulated in cancer. In particular, the microtubule protein βIII-tubulin, encoded by the TUBB3 gene, is aberrantly expressed in a range of epithelial tumours and is associated with drug resistance and aggressive disease. In normal cells, TUBB3 expression is tightly restricted, and is found almost exclusively in neuronal and testicular tissues. Understanding the mechanisms that control TUBB3 expression, both in cancer, mature and developing tissues will help to unravel the basic biology of the protein, its role in cancer, and may ultimately lead to the development of new therapeutic approaches to target this protein. This review is devoted to the transcriptional and posttranscriptional regulation of TUBB3 in normal and cancerous tissue.

BET inhibition increases βIII-tubulin expression and sensitizes metastatic breast cancer in the brain to vinorelbine

Metastases from primary breast cancer result in poor survival. βIII-tubulin (TUBB3) has been established as a therapeutic target for breast cancer metastases specifically to the brain. In this study, we conducted a systematic analysis to determine the regulation of TUBB3 expression in breast cancer metastases to the brain and strategically target these metastases using vinorelbine (VRB), a drug approved by the U.S. Food and Drug Administration (FDA). We found that human epidermal growth factor receptor 2 (HER2) signaling regulates TUBB3 expression in both trastuzumab-sensitive and trastuzumab-resistant neoplastic cells. We further discovered that bromodomain and extra-terminal domain (BET) inhibition increases TUBB3 expression, rendering neoplastic cells more susceptible to apoptosis by VRB. Orthotopic xenograft assays using two different breast cancer cell models revealed a reduction in tumor volume with BET inhibition and VRB treatment. In addition, in vivo studies using a model of multiple brain metastasis (BM) showed improved survival with the combination of radiation + BET inhibitor (iBET-762) + VRB (75% long-term survivors, P < 0.05). Using in silico analysis and BET inhibition, we found that the transcription factor myeloid zinc finger-1 (MZF-1) protein binds to the TUBB3 promoter. BET inhibition decreases MZF-1 expression and subsequently increases TUBB3 expression. Overexpression of MZF-1 decreases TUBB3 expression and reduces BM in vivo, whereas its knockdown increases TUBB3 expression in breast cancer cells. In summary, this study demonstrates a regulatory mechanism of TUBB3 and provides support for an application of BET inhibition to sensitize breast cancer metastases to VRB-mediated therapy.

miR-299-3p suppresses cell progression and induces apoptosis by downregulating PAX3 in gastric cancer

Gastric cancer (GC) is ranked the fourth leading cause of cancer-related death, with an over 75% mortality rate worldwide. In recent years, miR-299-3p has been identified as a biomarker in multiple cancers, such as acute promyelocytic leukemia, thyroid cancer, and lung cancer. However, the regulatory mechanism of miR-299-3p in GC cell progression is still largely unclear. Cell viability and apoptosis tests were performed by CCK8 and flow cytometry assay, respectively. Transwell assay was recruited to examine cell invasion ability. The interaction between miR-299-3p and PAX3 was determined by the luciferase reporter system. PAX3 protein level was evaluated by western blot assay. The expression of miR-299-3p was downregulated in GC tissues and cell lines (MKN-45, AGS, and MGC-803) compared with the normal tissues and cells. Besides, overexpression of miR-299-3p significantly suppressed proliferation and invasion and promoted apoptosis in GC. Next, we clarified that PAX3 expression was regulated by miR-299-3p using a luciferase reporter system, qRT-PCR, and western blot assay. Additionally, downregulation of PAX3 repressed GC cell progression. The rescue experiments indicated that restoration of PAX3 inversed miR-299-3p-mediated inhibition on cell proliferation and invasion. miR-299-3p suppresses cell proliferation and invasion as well as induces apoptosis by regulating PAX3 expression in GC, representing desirable biomarkers for GC diagnosis and therapy.

Altered Secretome and ROS Production in Olfactory Mucosa Stem Cells Derived from Friedreich's Ataxia Patients

Friedreich’s ataxia is the most common hereditary ataxia for which there is no cure or approved treatment at present. However, therapeutic developments based on the understanding of pathological mechanisms underlying the disease have advanced considerably, with the implementation of cellular models that mimic the disease playing a crucial role. Human olfactory ecto-mesenchymal stem cells represent a novel model that could prove useful due to their accessibility and neurogenic capacity. Here, we isolated and cultured these stem cells from Friedreich´s ataxia patients and healthy donors, characterizing their phenotype and describing disease-specific features such as reduced cell viability, impaired aconitase activity, increased ROS production and the release of cytokines involved in neuroinflammation. Importantly, we observed a positive effect on patient-derived cells, when frataxin levels were restored, confirming the utility of this in vitro model to study the disease. This model will improve our understanding of Friedreich´s ataxia pathogenesis and will help in developing rationally designed therapeutic strategies.

The Synthetic Cannabinoids THJ-2201 and 5F-PB22 Enhance In Vitro CB1 Receptor-Mediated Neuronal Differentiation at Biologically Relevant Concentrations

Recreational use of synthetic cannabinoids (SCs) before and during pregnancy poses a major public health risk, due to the potential onset of neurodevelopmental disorders in the offspring. Herein, we report the assessment of the neurotoxic potential of two commonly abused SCs, THJ-2201 and 5F-PB22, particularly focusing on how they affect neuronal differentiation in vitro. Differentiation ratios, total neurite length, and neuronal marker expression were assessed in NG108-15 neuroblastoma x glioma cells exposed to the SCs at non-toxic, biologically relevant concentrations (≤1 μM), either in acute or repeated exposure settings. Both SCs enhanced differentiation ratios and total neurite length of NG108-15 cells near two-fold compared to vehicle-treated cells, in a CB1R activation-dependent way, as the CB1R blockade with a specific antagonist (SR141718) abrogated SC-induced effects. Interestingly, repeated 5F-PB22 exposure was required to reach effects similar to a single THJ-2201 dose. Cell viability and proliferation, mitochondrial membrane potential, and intracellular ATP levels were also determined. The tested SCs increased mitochondrial tetramethyl rhodamine ethyl ester (TMRE) accumulation after 24 h at biologically relevant concentrations but did not affect any of the other toxicological parameters. Overall, we report firsthand the CB1R-mediated enhancement of neurodifferentiation by 5F-PB22 and THJ-2201 at biologically relevant concentrations.

The regulation of survival and differentiation of neural stem cells by miR-124 via modulating PAX3

MicroRNAs (miRNAs) have crucial functions in the regulation of proliferation and differentiation of neural stem cells (NSCs). MiR-124 has been reported to be implicated in neurogenesis. However, the precise function and mechanism of miR-124 still need further verification. In this study, we identified paired box 3 (PAX3) as a potential target of miR-124 using bioinformatics approaches. Next, we found PAX3 had reversed expression pattern with miR-124 as well as TUBB3 and GFAP. Dual-luciferase assay showed that miR-124 could bind to the 3'-UTR of PAX3 mRNA and restrain its expression. It was demonstrated that overexpression and knocking down of miR-124 in NSCs could promote the survival and suppress the apoptosis of NSCs. Meanwhile, miR-124 enhanced the expression of TUBB3 and GFAP via impairing PAX3 expression. Mechanistic study revealed that augmented Akt-GSK3β signaling pathway was the driving-force for the regulatory functions of miR-124 in NSCs. In summary, this study for the first time uncovered that miR-124 could suppress PAX3 expression, which in turn regulated the differentiation of NSCs.