DNA Damage Response and Cell Cycle Regulation in Pluripotent Stem Cells

Non-clinical safety assessment of Annona atemoya leaf extract: evaluation of genotoxicity

The leaves, stems, and fruits of Annona atemoya (A. atemoya; AA), a fruit-bearing plant of the family Annonaceae, exhibit anti-angiogenic, anti-oxidative, anti-inflammatory, and neuroprotective activities. However, the safety of AA has not been comprehensively elucidated. In this study, we evaluated the potential genotoxicity of an AA leaf (AAL) ethanol extract using a standard three-test battery constituting in vitro mammalian chromosomal aberration, in vivo micronucleus, and bacterial reverse mutation (also known as the Ames test) tests, as recommended by the Ministry of Food and Drug Safety of Korea. In vitro chromosomal aberration assay revealed that AAL extract did not induce structural or numerical aberrations, with or without metabolic activation (S9). In vivo micronucleus assay revealed that the number of micronucleated polychromatic erythrocytes (PCEs) and the PCE/normochromatic erythrocyte ratio after AAL extract treatment were not substantially different from those in the negative control. Changes in body weight and mortality were not observed. However, AAL extract partially induced mutagenic activity in all three bacterial strains in the bacterial reverse mutation assay, indicating that it could potentially aid in determining the genotoxic safety of AAL. QuantSeq 3' mRNA sequencing analysis to elucidate the genotoxicity mechanisms of AAL extract using TK6 cells revealed that the genotoxic effects of AAL may be associated with cellular morphology-associated (cell development and keratinization), nucleotide metabolism, and electron transport chain functions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-024-00241-4.

The role of DNA damage in neural stem cells ageing

Neural stem cells (NSCs) are pluripotent stem cells with the potential to differentiate into a variety of nerve cells. NSCs are susceptible to both intracellular and extracellular insults, thus causing DNA damage. Extracellular insults include ultraviolet, ionizing radiation, base analogs, modifiers, alkyl agents and others, while intracellular factors include Reactive oxygen species (ROS) radicals produced by mitochondria, mismatches that occur during DNA replication, deamination of bases, loss of bases, and more. When encountered with DNA damage, cells typically employ three coping strategies: DNA repair, damage tolerance, and apoptosis. NSCs, like many other stem cells, have the ability to divide, differentiate, and repair DNA damage to prevent mutations from being passed down to the next generation. However, when DNA damage accumulates over time, it will lead to a series of alterations in the metabolism of cells, which will cause cellular ageing. The ageing and exhaustion of neural stem cell will have serious effects on the body, such as neurodegenerative diseases. The purpose of this review is to examine the processes by which DNA damage leads to NSCs ageing and the mechanisms of DNA repair in NSCs.

Long Non-Coding RNA-Cardiac-Inducing RNA 6 Mediates Repair of Infarcted Hearts by Inducing Mesenchymal Stem Cell Differentiation into Cardiogenic Cells through Cyclin-Dependent Kinase 1

This study aims to investigate the induction effect of LncRNA-CIR6 on MSC differentiation into cardiogenic cells in vitro and in vivo. In addition to pretreatment with Ro-3306 (a CDK1 inhibitor), LncRNA-CIR6 was transfected into BMSCs and hUCMSCs using jetPRIME. LncRNA-CIR6 was further transfected into the hearts of C57BL/6 mice via 100 μL of AAV9-cTnT-LncRNA-CIR6-ZsGreen intravenous injection. After three weeks of transfection followed by AMI surgery, hUCMSCs (5 × 105/100 μL) were injected intravenously one week later. Cardiac function was evaluated using VEVO 2100 and electric mapping nine days after cell injection. Immunofluorescence, Evans blue-TTC, Masson staining, FACS, and Western blotting were employed to determine relevant indicators. LncRNA-CIR6 induced a significant percentage of differentiation in BMSCs (83.00 ± 0.58)% and hUCMSCs (95.43 ± 2.13)% into cardiogenic cells, as determined by the expression of cTnT using immunofluorescence and FACS. High cTNT expression was observed in MSCs after transfection with LncRNA-CIR6 by Western blotting. Compared with the MI group, cardiac contraction and conduction function in MI hearts treated with LncRNA-CIR6 or combined with MSCs injection groups were significantly increased, and the areas of MI and fibrosis were significantly lower. The transcriptional expression region of LncRNA-CIR6 was on Chr17 from 80209290 to 80209536. The functional region of LncRNA-CIR6 was located at nucleotides 0-50/190-255 in the sequence. CDK1, a protein found to be related to the proliferation and differentiation of cardiomyocytes, was located in the functional region of the LncRNA-CIR6 secondary structure (from 0 to 17). Ro-3306 impeded the differentiation of MSCs into cardiogenic cells, while MSCs transfected with LncRNA-CIR6 showed a high expression of CDK1. LncRNA-CIR6 mediates the repair of infarcted hearts by inducing MSC differentiation into cardiogenic cells through CDK1.

CBX8 Promotes Epithelial-mesenchymal Transition, Migration, and Invasion of Lung Cancer through Wnt/β-catenin Signaling Pathway

BACKGROUND

Lung cancer (LC) is primarily responsible for cancer-related deaths worldwide. Epithelial-mesenchymal transition (EMT) is a process in which epithelial cells acquire mesenchymal features and is associated with the development of tumors. CBX8, a member of the PcG protein family, plays a critical role in various cancers, containing LC. However, specific regulatory mechanisms of CBX8 in LC progression are not fully understood. This study aimed to investigate the regulatory role of CBX8 in LC progression.

METHODS

Bioinformatics was used to analyze the relationship between CBX8 level and tumor and the enrichment pathway of CBX8 enrichment. qRT-PCR was used to detect the differential expression of CBX8 in LC cells and normal lung epithelial cells. The effects of knockdown or overexpression of CBX8 on the proliferation, migration and invasion of LC cells were evaluated by CCK- -8 assay and Transwell assay, and the levels of proteins associated with the EMT pathway and Wnt/ β-catenin signaling pathway were detected by western blot.

RESULTS

Bioinformatics analysis revealed that CBX8 was highly expressed in LC and enriched on the Wnt/β-catenin signaling pathway. The expression level of CBX8 was significantly elevated in LC cells. Knockdown of CBX8 significantly inhibited cell proliferation, migration and invasion, and decreased the expression levels of EMT-related proteins and Wnt/β-catenin pathway-related proteins. Conversely, overexpression of CBX8 promoted cell proliferation, migration and invasion, and increased the expression levels of EMT-related proteins and Wnt/β-catenin pathway-related proteins. The Wnt inhibitor IWP-4 alleviated the effects produced by overexpression of CBX8.

CONCLUSION

Collectively, these data demonstrated that CBX8 induced EMT through Wnt/β-- catenin signaling, driving migration and invasion of LC cells.

G1 Dynamics at the Crossroads of Pluripotency and Cancer

G1 cell cycle phase dynamics are regulated by intricate networks involving cyclins, cyclin-dependent kinases (CDKs), and CDK inhibitors, which control G1 progression and ensure proper cell cycle transitions. Moreover, adequate origin licensing in G1 phase, the first committed step of DNA replication in the subsequent S phase, is essential to maintain genome integrity. In this review, we highlight the intriguing parallels and disparities in G1 dynamics between stem cells and cancer cells, focusing on their regulatory mechanisms and functional outcomes. Notably, SOX2, OCT4, KLF4, and the pluripotency reprogramming facilitator c-MYC, known for their role in establishing and maintaining stem cell pluripotency, are also aberrantly expressed in certain cancer cells. In this review, we discuss recent advances in understanding the regulatory role of these pluripotency factors in G1 dynamics in the context of stem cells and cancer cells, which may offer new insights into the interconnections between pluripotency and tumorigenesis.

Editorial for the 'Reciprocal Links between RNA Metabolism and DNA Damage' Special Issue: July 2023

Two central parts of molecular biology are the control of genome integrity and genome expression [...].

Gene editing with 'pencil' rather than 'scissors' in human pluripotent stem cells

Owing to the advances in genome editing technologies, research on human pluripotent stem cells (hPSCs) have recently undergone breakthroughs that enable precise alteration of desired nucleotide bases in hPSCs for the creation of isogenic disease models or for autologous ex vivo cell therapy. As pathogenic variants largely consist of point mutations, precise substitution of mutated bases in hPSCs allows researchers study disease mechanisms with "disease-in-a-dish" and provide functionally repaired cells to patients for cell therapy. To this end, in addition to utilizing the conventional homologous directed repair system in the knock-in strategy based on endonuclease activity of Cas9 (i.e., 'scissors' like gene editing), diverse toolkits for editing the desirable bases (i.e., 'pencils' like gene editing) that avoid the accidental insertion and deletion (indel) mutations as well as large harmful deletions have been developed. In this review, we summarize the recent progress in genome editing methodologies and employment of hPSCs for future translational applications.

Stemness of Normal and Cancer Cells: The Influence of Methionine Needs and SIRT1/PGC-1α/PPAR-α Players

Stem cells are a population of undifferentiated cells with self-renewal and differentiation capacities. Normal and cancer stem cells share similar characteristics in relation to their stemness properties. One-carbon metabolism (OCM), a network of interconnected reactions, plays an important role in this dependence through its role in the endogenous synthesis of methionine and S-adenosylmethionine (SAM), the universal donor of methyl groups in eukaryotic cells. OCM genes are differentially expressed in stem cells, compared to their differentiated counterparts. Furthermore, cultivating stem cells in methionine-restricted conditions hinders their stemness capacities through decreased SAM levels with a subsequent decrease in histone methylation, notably H3K4me3, with a decrease in stem cell markers. Stem cells' reliance on methionine is linked to several mechanisms, including high methionine flux or low endogenous methionine biosynthesis. In this review, we provide an overview of the recent discoveries concerning this metabolic dependence and we discuss the mechanisms behind them. We highlight the influence of SIRT1 on SAM synthesis and suggest a role of PGC-1α/PPAR-α in impaired stemness produced by methionine deprivation. In addition, we discuss the potential interest of methionine restriction in regenerative medicine and cancer treatment.

Alterations in hepatic mitotic and cell cycle transcriptional networks during the metabolic switch in broiler chicks

During embryonic life, chicks mainly derive energy from hepatic oxidation of yolk lipids. After hatch, chicks must rely on carbohydrate-rich feed to obtain energy. This requires an abrupt and intensive switch of metabolic processes, particularly in the liver. We recently identified a number of transcriptional and post-transcriptional regulatory networks that work concordantly to tune metabolic processes during the metabolic switch. Here, we used delayed feeding post-hatch (48 h) to impede the metabolic switch in broilers. We used RNA-seq to identify hepatic transcriptome differences between late stage embryos (E18) and two-day-old chicks (D2), which were either fed-from-hatch (FED) or not fed (DLY). Between FED and E18, 2,430 genes were differentially expressed (fold-change≥ 2; FDR p-value 0.05), of these 1,237 were downregulated in FED birds and 1,193 were upregulated. Between DLY and E18, 1979 genes were differentially expressed, of these 1,043 were downregulated and 936 were upregulated in DLY birds. Between DLY and FED, 880 genes were differentially expressed, of these 543 were downregulated and 337 were upregulated in DLY birds. We found that in addition to disturbances in a number of metabolic pathways, unfed chicks had a widespread suppression of gene networks associated with cell proliferation, cell cycle progression and mitosis. Expression patterns suggest that hepatocytes of delayed-fed birds have abnormal mitosis and increased polyploidization. This suggests that post-hatch feed consumption maintains the rate and integrity of liver growth immediately, which in turn, likely helps facilitate the appropriate programming of hepatic metabolic networks.

The Role of E3 Ligase Pirh2 in Disease

The p53-dependent ubiquitin ligase Pirh2 regulates a number of proteins involved in different cancer-associated processes. Targeting the p53 family proteins, Chk2, p27Kip1, Twist1 and others, Pirh2 participates in such cellular processes as proliferation, cell cycle regulation, apoptosis and cellular migration. Thus, it is not surprising that Pirh2 takes part in the initiation and progression of different diseases and pathologies including but not limited to cancer. In this review, we aimed to summarize the available data on Pirh2 regulation, its protein targets and its role in various diseases and pathological processes, thus making the Pirh2 protein a promising therapeutic target.