DNA topoisomerase IIβ as a molecular switch in neural differentiation of mesenchymal stem cells

Deep Sc-RNA sequencing decoding the molecular dynamic architecture of the human retina

The human retina serves as a light detector and signals transmission tissue. Advanced insights into retinal disease mechanisms and therapeutic strategies require a deep understanding of healthy retina molecular events. Here, we sequenced the mRNA of over 0.6 million single cells from human retinas across six regions at nine different ages. Sixty cell sub-types have been identified from the human mature retinas with unique markers. We revealed regional and age differences of gene expression profiles within the human retina. Cell-cell interaction analysis indicated a rich synaptic connection within the retinal cells. Gene expression regulon analysis revealed the specific expression of transcription factors and their regulated genes in human retina cell types. Some of the gene's expression, such as DKK3, are elevated in aged retinas. A further functional investigation suggested that over expression of DKK3 could impact mitochondrial stability. Overall, decoding the molecular dynamic architecture of the human retina improves our understanding of the vision system.

TOP2B Is Required to Maintain the Adrenergic Neural Phenotype and for ATRA-Induced Differentiation of SH-SY5Y Neuroblastoma Cells

The neuroblastoma cell line SH-SY5Y is widely used to study retinoic acid (RA)-induced gene expression and differentiation and as a tool to study neurodegenerative disorders. SH-SY5Y cells predominantly exhibit adrenergic neuronal properties, but they can also exist in an epigenetically interconvertible alternative state with more mesenchymal characteristics; as a result, these cells can be used to study gene regulation circuitry controlling neuroblastoma phenotype. Using a combination of pharmacological inhibition and targeted gene inactivation, we have probed the requirement for DNA topoisomerase IIB (TOP2B) in RA-induced gene expression and differentiation and in the balance between adrenergic neuronal versus mesenchymal transcription programmes. We found that expression of many, but not all genes that are rapidly induced by ATRA in SH-SY5Y cells was significantly reduced in the TOP2B null cells; these genes include BCL2, CYP26A1, CRABP2, and NTRK2. Comparing gene expression profiles in wild-type versus TOP2B null cells, we found that long genes and genes expressed at a high level in WT SH-SY5Y cells were disproportionately dependent on TOP2B. Notably, TOP2B null SH-SY5Y cells upregulated mesenchymal markers vimentin (VIM) and fibronectin (FN1) and components of the NOTCH signalling pathway. Enrichment analysis and comparison with the transcription profiles of other neuroblastoma-derived cell lines supported the conclusion that TOP2B is required to fully maintain the adrenergic neural-like transcriptional signature of SH-SY5Y cells and to suppress the alternative mesenchymal epithelial-like epigenetic state.

Oncogenetic Function and Prognostic Value of DNA Topoisomerase II Alpha in Human Malignances: A Pan-Cancer Analysis

Increasing studies have revealed significant associations between TOP2A with oncogenesis and prognosis of human cancers; however, pan-cancer analysis has not been reported. Here, we explored the potential carcinogenic function and the association with clinical outcomes of TOP2A in 33 different human cancers. The results showed that TOP2A was amplified in 31 investigated cancers; TOP2A expression was significantly associated with metastasis of six different cancers and significantly associated with the survival of patients in ten different cancers; TOP2A-encoded protein was obviously upregulated in five available cancers; phosphorylated TOP2A protein at S1106 was significantly upregulated in all six available cancers. Moreover, TOP2A expression was found to be associated with the cancer-associated immune cell infiltration, including fibroblasts, Tregs, and macrophages. In addition, the Kyoto encyclopedia of genes and genomes (KEGG) pathway and Gene Ontology (GO) enrichment analyses revealed a most significant association between TOP2A with the Wnt signaling pathway and DNA conformation change. This work provides a comprehensive knowledge of TOP2A in different cancers, including carcinogenic function, prognostic values for metastasis, and clinical outcomes.

Anthraquinone: a promising scaffold for the discovery and development of therapeutic agents in cancer therapy

Cancer, characterized by uncontrolled malignant neoplasm, is a leading cause of death in both advanced and emerging countries. Although, ample drugs are accessible in the market to intervene with tumor progression, none are totally effective and safe. Natural anthraquinone (AQ) equivalents such as emodin, aloe-emodin, alchemix and many synthetic analogs extend their antitumor activity on different targets including telomerase, topoisomerases, kinases, matrix metalloproteinases, DNA and different phases of cell lines. Nano drug delivery strategies are advanced tools which deliver drugs into tumor cells with minimum drug leakage to normal cells. This review delineates the way AQ derivatives are binding on these targets by abolishing tumor cells to produce anticancer activity and purview of nanoformulations related to AQ analogs.

A de novo TOP2B variant associated with global developmental delay and autism spectrum disorder

Background

TOP2B encodes type II topoisomerase beta, which controls topological changes during DNA transcription. TOP2B is expressed in the developing nervous system and is involved in brain development and neural differentiation. Recently, a de novo missense TOP2B variant (c.187C>T) has been identified in an individual with neurodevelopmental disorder (NDD). However, the association between TOP2B variants and NDDs remains uncertain.

Methods

Trio‐based whole‐exome sequencing was performed on a 7‐year‐old girl, presenting muscle hypotonia, stereotypic hand movements, epilepsy, global developmental delay, and autism spectrum disorder. Brain magnetic resonance images were normal. She was unable to walk independently and spoke no meaningful words.

Results

We found a de novo variant in TOP2B (NM_001330700.1:c.187C>T, p.(His63Tyr)), which is identical to the previous case. The clinical features of the two individuals with the c.187C>T variant overlapped.

Conclusion

Our study supports the finding that TOP2B variants may cause NDDs.

Mutations in TOP2B cause autosomal-dominant hereditary hearing loss via inhibition of the PI3K-Akt signalling pathway

Hereditary hearing impairment is a clinically and genetically heterogeneous disease. Whole-exome sequencing was performed on seven affected and six unaffected members in a large Chinese family with autosomal-dominant nonsyndromic hearing loss. The pathogenic variant of the gene encoding human topoisomerase IIβ TOP2B (c.G4837C:p.D1613H) was cosegregated with hearing loss in this pedigree and another two variants of TOP2B were detected in 66 sporadic patients with hearing loss. top2b knockdown led to significant defects in zebrafish inner ears and caused downregulation of akt which resulted in inactivation of PI3K-Akt signalling. As a result, supporting cell and hair cell numbers were reduced through inhibition of the PI3K-Akt pathway. Therefore, we hypothesized that mutations in TOP2B can cause autosomal-dominant nonsyndromic hearing impairment through inhibition of the PI3K-Akt signalling pathway. DATABASE: The whole-exome sequence data in the study are available at the Sequence Read Archive database (NCBI) under the accession numbers SRR9050868, SRR9050867, SRR90508676, SRR90508675, SRR90508674, SRR90508673, SRR90508672, SRR90508671, SRR90508679, SRR90508670, SRR9050859. SRR9050858 and SRR9050857, respectively.

The role of E2F1-topoIIβ signaling in regulation of cell cycle exit and neuronal differentiation of human SH-SY5Y cells

This study aims to test the role of E2F1-topoIIβ signaling in neuronal differentiation of SH-SY5Y cells. With retinoic acid (RA) induction, a high percentage of cells were found to be arrested at the G₀/G₁ phase, with decreased levels of cyclinD1, CDK4, phosphorylation status of pRb and E2F1, in addition to an elevated level of p27. The cells were shown to differentiate into neuronal phenotypes characterized by highly expressed neuronal markers, MAP2 and enriched topoIIβ, and remarkable neurite outgrowth. Exogenously forced E2F1 expression with a specific E2F1 plasmid led to suppression of topoIIβ expression and disruption of the neuronal differentiation of SH-SY5Y cells. On further examination using the ChIP assay, we found that E2F1 bound directly to the promoter region of topoIIβ, and its binding ability was inversely correlated with topoIIβ expression in response to RA induction. Thus, our findings suggest that E2F1-topoIIβ signaling may play a role in regulation of cell cycle exit and neuronal differentiation.

The Roles of DNA Topoisomerase IIβ in Transcription

Type IIA topoisomerases allow DNA double helical strands to pass through each other by generating transient DNA double strand breaks βDSBs), and in so doing, resolve torsional strain that accumulates during transcription, DNA replication, chromosome condensation, chromosome segregation and recombination. Whereas most eukaryotes possess a single type IIA enzyme, vertebrates possess two distinct type IIA topoisomerases, Topo IIα and Topo IIβ. Although the roles of Topo IIα, especially in the context of chromosome condensation and segregation, have been well-studied, the roles of Topo IIβ are only beginning to be illuminated. This review begins with a summary of the initial studies surrounding the discovery and characterization of Topo IIβ and then focuses on the insights gained from more recent studies that have elaborated important functions for Topo IIβ in transcriptional regulation.

DNA topoisomerase IIβ stimulates neurite outgrowth in neural differentiated human mesenchymal stem cells through regulation of Rho-GTPases (RhoA/Rock2 pathway) and Nurr1 expression

Background

DNA topoisomerase IIβ (topo IIβ) is known to regulate neural differentiation by inducing the neuronal genes responsible for critical neural differentiation events such as neurite outgrowth and axon guidance. However, the pathways of axon growth controlled by topo IIβ have not been clarified yet. Microarray results of our previous study have shown that topo IIβ silencing in neural differentiated primary human mesenchymal stem cells (hMSCs) significantly alters the expression pattern of genes involved in neural polarity, axonal growth, and guidance, including Rho-GTPases. This study aims to further analyze the regulatory role of topo IIβ on the process of axon growth via regulation of Rho-GTPases.

Methods and results

For this purpose, topo IIβ was silenced in neurally differentiated hMSCs. Cells lost their morphology because of topo IIβ deficiency, becoming enlarged and flattened. Additionally, a reduction in both neural differentiation efficiency and neurite length, upregulation in RhoA and Rock2, downregulation in Cdc42 gene expression were detected. On the other hand, cells were transfected with topo IIβ gene to elucidate the possible neuroprotective effect of topo IIβ overexpression on neural-induced hMSCs. Topo IIβ overexpression prompted all the cells to exhibit neural cell morphology as characterized by longer neurites. RhoA and Rock2 expressions were downregulated, whereas Cdc42 expression was upregulated. Nurr1 expression level correlated with topo IIβ in both topo IIβ-overexpressed and -silenced cells. Furthermore, differential translocation of Rho-GTPases was detected by immunostaining in response to topo IIβ.

Conclusion

Our results suggest that topo IIβ deficiency could give rise to neurodegeneration through dysregulation of Rho-GTPases. However, further in-vivo research is needed to demonstrate if re-regulation of Rho GTPases by topo IIβ overexpression could be a neuroprotective treatment in the case of neurodegenerative diseases.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0859-4) contains supplementary material, which is available to authorized users.

Topoisomerase IIβ and its role in different biological contexts

Topoisomerase IIβ is a type II DNA topoisomerase that was reported to be expressed in all mammalian cells but abundantly expressed in cells that have undergone terminal differentiation to attain a post mitotic state. Enzymatically it catalyzes ATP-dependent topological changes of double stranded DNA, while as a protein it was reported to be associated with several factors in promoting cell growth, migration, DNA repair and transcription regulation. The cellular roles of topoisomerase IIβ are very less understood compared to its counterpart topoisomerase IIα. This review discusses origin of Topoisomerase II beta, its structure, activities reported in vitro and in vivo along with implications in cellular processes namely transcription, DNA repair, neuronal development, aging, HIV-infection and cancer.

A panel of four decreased serum microRNAs as a novel biomarker for early Parkinson's disease

CONTEXT

Sensitive, non-invasive biomarkers that facilitate Parkinson's disease (PD) detection and stage assignment are currently unavailable.

OBJECTIVE

The objective of this study is to investigate the potential of circulating microRNAs (miRNAs) as novel biomarkers for PD.

MATERIALS AND METHODS

Solexa sequencing technology and quantitative real-time PCR were applied to screen and verify altered serum miRNAs in PD patients.

RESULTS

Serum miR-141, miR-214, miR-146b-5p, and miR-193a-3p were decreased significantly in PD patients compared with controls. Furthermore, the 4-miRNA panel enabled the differentiation of HY stage 1 and 2 PD patients from controls.

DISCUSSION AND CONCLUSION

The four serum miRNAs may represent novel biomarkers for the early detection of PD.

Tetramethylpyrazine induces SH-SY5Y cell differentiation toward the neuronal phenotype through activation of the PI3K/Akt/Sp1/TopoIIβ pathway

Tetramethylpyrazine (TMP) is an active compound extracted from the traditional Chinese medicinal herb Chuanxiong. Previously, we have shown that TMP induces human SH-SY5Y neuroblastoma cell differentiation toward the neuronal phenotype by targeting topoisomeraseIIβ (TopoIIβ), a protein implicated in neural development. In the present study, we aimed to elucidate whether the transcriptional factors specificity protein 1 (Sp1) and nuclear factor Y (NF-Y), in addition to the upstream signaling pathways ERK1/2 and PI3K/Akt, are involved in modulating TopoIIβ expression in the neuronal differentiation process. We demonstrated that SH-SY5Y cells treated with TMP (80μM) terminally differentiated into neurons, characterized by increased neuronal markers, tubulin βIII and microtubule associated protein 2 (MAP2), and increased neurite outgrowth, with no negative effect on cell survival. TMP also increased the expression of TopoIIβ, which was accompanied by increased expression of Sp1 in the differentiated neuron-like cells, whereas NF-Y protein levels remained unchanged following the differentiation progression. We also found that the phosphorylation level of Akt, but not ERK1/2, was significantly increased as a result of TMP stimulation. Furthermore, as established by chromatin immunoprecipitation (ChIP) assay, activation of the PI3K/Akt pathway increased Sp1 binding to the promoter of the TopoIIβ gene. Blockage of PI3K/Akt was shown to lead to subsequent inhibition of TopoIIβ expression and neuronal differentiation. Collectively, the results indicate that the PI3K/Akt/Sp1/TopoIIβ signaling pathway is necessary for TMP-induced neuronal differentiation. Our findings offer mechanistic insights into understanding the upstream regulation of TopoIIβ in neuronal differentiation, and suggest potential applications of TMP both in neuroscience research and clinical practice to treat relevant diseases of the nervous system.

Distinct expression patterns for type II topoisomerases IIA and IIB in the early foetal human telencephalon

TOP2A and TOP2B are type II topoisomerase enzymes that have important but distinct roles in DNA replication and RNA transcription. Recently, TOP2B has been implicated in the transcription of long genes in particular that play crucial roles in neural development and are susceptible to mutations contributing to neurodevelopmental conditions such as autism and schizophrenia. This study maps their expression in the early foetal human telencephalon between 9 and 12 post‐conceptional weeks. TOP2A immunoreactivity was restricted to cell nuclei of the proliferative layers of the cortex and ganglionic eminences (GE), including the ventricular zone and subventricular zone (SVZ) closely matching expression of the proliferation marker KI67. Comparison with sections immunolabelled for NKX2.1, a medial GE (MGE) marker, and PAX6, a cortical progenitor cell and lateral GE (LGE) marker, revealed that TOP2A‐expressing cells were more abundant in MGE than the LGE. In the cortex, TOP2B is expressed in cell nuclei in both proliferative (SVZ) and post‐mitotic compartments (intermediate zone and cortical plate) as revealed by comparison with immunostaining for PAX6 and the post‐mitotic neuron marker TBR1. However, co‐expression with KI67 was rare. In the GE, TOP2B was also expressed by proliferative and post‐mitotic compartments. In situ hybridisation studies confirmed these patterns of expression, except that TOP2A mRNA is restricted to cells in the G2/M phase of division. Thus, during early development, TOP2A is likely to have a role in cell proliferation, whereas TOP2B is expressed in post‐mitotic cells and may be important in controlling expression of long genes even at this early stage.

The potential use of mesenchymal stem cells in stroke therapy--From bench to bedside

Stroke is the second main cause of morbidity and mortality worldwide. The rationale for the use of mesenchymal stem cells (MSCs) in stroke is based on the capacity of MSCs to secrete a large variety of bioactive molecules such as growth factors, cytokines and chemokines leading to reduction of inflammation, increased neurogenesis from the germinative niches of central nervous system, increased angiogenesis, effects on astrocytes, oligodendrocytes and axons. This review presents the data derived from experimental studies and the evidence available from clinical trials about the use of MSCs in stroke therapy.