Megakaryocytes and hepatocytes are unique cells in mammals that undergo polyploidization through endomitosis in terminal differentiation. Many polyploidization regulators and underlying mechanisms have been reported, most of which are tightly coupled with development, organogenesis, and cell differentiation. However, the nature of endomitosis, which involves successful entry into and exit from mitosis without complete cytokinesis, has not yet been fully elucidated. We highlight that endomitosis is a new cell fate in the cell cycle, and tetraploidy is a critical stage at the bifurcation of cell fate decision. This review summarizes the recent research progress in this area and provides novel insights into how cells manipulate mitosis toward endomitosis. Endomitotic cells can evade the tetraploidy restrictions and proceed to multiple rounds of the cell cycle. This knowledge not only deepens our understanding of endomitosis as a fundamental biological process but also offers new perspectives on the physiological and pathophysiological implications of polyploidization.
Hepatocytes/physiology* ; Megakaryocytes/physiology* ; Humans ; Polyploidy ; Animals ; Cell Cycle/physiology* ; Cell Differentiation ; Mitosis/physiology*

<i>Ni>⁶-methyladenosine (m⁶A) modification plays a critical role in cell cycle regulation, while the mechanism of m⁶A in regulating mitosis remains underexplored. Here, we found that the total m⁶A modification level in cells increased during mitosis by the liquid chromatography-mass spectrometry/mass spectrometry and m⁶A dot blot assays. Silencing methyltransferase-like 3 (METTL3) or METTL14 results in delayed mitosis, abnormal spindle assembly, and chromosome segregation defects by the immunofluorescence. By analyzing transcriptome-wide m⁶A targets in HeLa cells, we identified <i>polo-like kinase 1i> (<i>PLK1i>) as a key gene modified by m⁶A in regulating mitosis. Specifically, through immunoblotting and RNA pulldown, m⁶A modification inhibits PLK1 translation <i>viai> YTH <i>Ni>⁶-methyladenosine RNA binding protein 1, thus mediating cell cycle homeostasis. Demethylation of <i>PLK1i> mRNA leads to significant mitotic abnormalities. These findings highlight the critical role of m⁶A in regulating mitosis and the potential of m⁶A as a therapeutic target in proliferative diseases such as cancer.
Humans ; Polo-Like Kinase 1 ; Cell Cycle Proteins/metabolism* ; Proto-Oncogene Proteins/metabolism* ; Protein Serine-Threonine Kinases/metabolism* ; Mitosis/physiology* ; HeLa Cells ; Adenosine/genetics* ; Methyltransferases/metabolism* ; RNA, Messenger/metabolism* ; RNA-Binding Proteins/metabolism*

Infertility has become one of the most serious diseases worldwide, and 50% of this disease can be attributed to male-related factors. Spermatogenesis, by definition, is a complex process by which spermatogonial stem cells (SSCs) self-renew to maintain stem cell population within the testes and differentiate into mature spermatids. It is of great significance to uncover gene regulation and signaling pathways that are involved in the fate determinations of SSCs with aims to better understand molecular mechanisms underlying human spermatogenesis and identify novel targets for gene therapy of male infertility. Significant achievement has recently been made in demonstrating the signaling molecules and pathways mediating the fate decisions of mammalian SSCs. In this review, we address key gene regulation and crucial signaling transduction pathways in controlling the self-renewal, differentiation, and apoptosis of SSCs, and we illustrate the networks of genes and signaling pathways in SSC fate determinations. We also highlight perspectives and future directions in SSC regulation by genes and their signaling pathways. This review could provide novel insights into the genetic regulation of normal and abnormal spermatogenesis and offer molecular targets to develop new approaches for gene therapy of male infertility.
Humans ; Male ; Signal Transduction/physiology* ; Apoptosis/physiology* ; Spermatogenesis/physiology* ; Cell Differentiation ; Adult Germline Stem Cells/physiology* ; Spermatogonia/cytology* ; Gene Expression Regulation ; Animals ; Infertility, Male/genetics* ; Cell Self Renewal/genetics*

Nonobstructive azoospermia (NOA), one of the most severe types of male infertility, etiology often remains unclear in most cases. Therefore, this study aimed to detect four biallelic detrimental variants (0.5%) in the minichromosome maintenance domain containing 2 ( MCMDC2 ) genes in 768 NOA patients by whole-exome sequencing (WES). Hematoxylin and eosin (H&E) demonstrated that MCMDC2 deleterious variants caused meiotic arrest in three patients (c.1360G>T, c.1956G>T, and c.685C>T) and hypospermatogenesis in one patient (c.94G>T), as further confirmed through immunofluorescence (IF) staining. The single-cell RNA sequencing data indicated that MCMDC2 was substantially expressed during spermatogenesis. The variants were confirmed as deleterious and responsible for patient infertility through bioinformatics and in vitro experimental analyses. The results revealed four MCMDC2 variants related to NOA, which contributes to the current perception of the function of MCMDC2 in male fertility and presents new perspectives on the genetic etiology of NOA.
Humans ; Male ; Azoospermia/genetics* ; Meiosis/genetics* ; Spermatogenesis/genetics* ; Adult ; Exome Sequencing ; Microtubule-Associated Proteins/genetics* ; Alleles ; Infertility, Male/genetics*

The maintenance of hematopoietic stem cells (HSCs) is a complex process involving numerous cell-extrinsic and -intrinsic regulators. The first member of the cyclin-dependent kinase family of inhibitors to be identified, p21, has been reported to perform a wide range of critical biological functions, including cell cycle regulation, transcription, differentiation, and so on. Given the previous inconsistent results regarding the functions of p21 in HSCs in a p21-knockout mouse model, we employed p21-tdTomato (tdT) mice to further elucidate its role in HSCs during homeostasis. The results showed that p21-tdT+ HSCs exhibited increased self-renewal capacity compared to p21-tdT- HSCs. Zbtb18, a transcriptional repressor, was upregulated in p21-tdT+ HSCs, and its knockdown significantly impaired the reconstitution capability of HSCs. Furthermore, p21 interacted with ZBTB18 to co-repress the expression of cKit in HSCs and thus regulated the self-renewal of HSCs. Our data provide novel insights into the physiological role and mechanisms of p21 in HSCs during homeostasis independent of its conventional role as a cell cycle inhibitor.
Animals ; Hematopoietic Stem Cells/cytology* ; Cyclin-Dependent Kinase Inhibitor p21/genetics* ; Mice ; Cell Self Renewal ; Repressor Proteins/genetics* ; Mice, Inbred C57BL ; Mice, Knockout ; Humans ; Gene Expression Regulation

OBJECTIVE: To investigate the fate and underlying mechanisms of G2 phase arrest in cancer cells elicited by ionizing radiation (IR). METHODS: Human melanoma A375 and 92-1 cells were treated with X-rays radiation or Aurora A inhibitor MLN8237 (MLN) and/or p21 depletion by small interfering RNA (siRNA). Cell cycle distribution was determined using flow cytometry and a fluorescent ubiquitin-based cell cycle indicator (FUCCI) system combined with histone H3 phosphorylation at Ser10 (pS10 H3) detection. Senescence was assessed using senescence-associated-β-galactosidase (SA-β-Gal), Ki67, and γH2AX staining. Protein expression levels were determined using western blotting. RESULTS: Tumor cells suffered severe DNA damage and underwent G2 arrest after IR treatment. The damaged cells did not successfully enter M phase nor were they stably blocked at G2 phase but underwent mitotic skipping and entered G1 phase as tetraploid cells, ultimately leading to senescence in G1. During this process, the p53/p21 pathway is hyperactivated. Accompanying p21 accumulation, Aurora A kinase levels declined sharply. MLN treatment confirmed that Aurora A kinase activity is essential for mitosis skipping and senescence induction. CONCLUSION Persistent p21 activation during IR-induced G2 phase blockade drives Aurora A kinase degradation, leading to senescence <i>viai> mitotic skipping.
Humans ; Aurora Kinase A/metabolism* ; Cell Line, Tumor ; Mitosis ; Cell Cycle ; Radiation, Ionizing ; RNA, Small Interfering/metabolism* ; Cyclin-Dependent Kinase Inhibitor p21/metabolism*

Meiotic initiation is a critical step in gametogenesis. Recently, some genes required for meiotic initiation have been identified. However, meiosis-initiating factors and the underlying mechanisms are far from being fully understood. We have established a long-term culture system of spermatogonial stem cells (SSCs) and an <i>in vitroi> model of meiotic initiation using mouse SSCs. Our previous study revealed that the RNA-binding protein RBFOX2 may regulate meiotic initiation, but the role and the mechanism need to be further elucidated. In this study, we constructed RBFOX2 knockdown SSC lines by using lentivirus-mediated gene delivery method, and found that the knockdown SSCs underwent normal self-renewal, mitosis and differentiation. However, they were unable to initiate meiosis when treated with retinoic acid, and they underwent apoptosis. These results indicate that RBFOX2 plays an essential role in meiotic initiation of spermatogonia. This work provides new clues for understanding the functions of RNA-binding proteins in meiotic initiation.
Mice ; Male ; Animals ; Spermatogonia/metabolism* ; Meiosis/genetics* ; Cell Differentiation ; Tretinoin/pharmacology* ; Mitosis ; Testis/metabolism*

OBJECTIVE: To investigate the mechanism of nucleolin (NCL) involved in lymphoma proliferation by regulating thymidine kinase 1 (TK1). METHODS: Twenty-three patients with diffuse large B-cell lymphoma (DLBCL) were selected and divided into initial treatment group (14 cases) and relapsed/refractory group (9 cases). Serum TK1 and C23 protein in peripheral blood mononuclear cells were detected. Cell models of CA46-NCL-KD (CA46-NCL-knockdown) and CA46-NCL-KNC (CA46-NCL-knockdown negative control) were established by lentivirus vector mediated transfection in Burkitt lymphoma cell line CA46. The half maximal inhibitory concentration (IC₅₀) of CA46-NCL-KD, CA46-NCL-KNC, and CA46 to adriamycin were detected by cell proliferation assay (MTS). The expression of NCL mRNA and protein in CA46-NCL-KD and CA46-NCL-KNC cells were dectected by Q-PCR and Western blot, respectively. The cell cycle of CA46-NCL-KD, CA46-NCL-KNC, and CA46 cells were detected by flow cytometry. The expression of TK1 protein in CA46-NCL-KD and CA46-NCL-KNC cells was detected by an enhanced chemiluminescence (ECL) dot blot assay. RESULTS: The level of serum TK1 in the initial treatment group was 0.43(0-30-1.01) pmol/L, which was lower than 10.56(2.19-14.99) pmol/L in the relapsed/refractory group (<i>Pi><0-01), and the relative expression level of NCL protein in peripheral blood was also significantly lower. The IC₅₀ of CA46-C23-KD cells to adriamycin was (0.147±0.02) μg/ml, which was significantly lower than (0.301±0.04) μg/ml of CA46-C23-KNC cells and (0.338±0.05) μg/ml of CA46 cells (<i>Pi><0.05). Compared with CA46-NCL-KNC cells, the expression of NCL mRNA and protein, TK1 protein decreased in CA46-NCL-KD cells, and the proportion of S phase and G₂/M phase also decreased, while G0/G1 phase increased in cell cycle. CONCLUSION The increased expression of NCL in DLBCL and CA46 cells indicates low sensitivity to drug. NCL may participate in regulation of lymphoma proliferation by affecting TK1 expression, thereby affecting the drug sensitivity.
Humans ; Leukocytes, Mononuclear/metabolism* ; Apoptosis ; Cell Line, Tumor ; Lymphoma ; Thymidine Kinase/pharmacology* ; Doxorubicin/pharmacology* ; Cell Division ; RNA, Messenger/genetics*

OBJECTIVE: To investigate the biological function of miR-203a-5p and the underlying mechanism in multiple myeloma (MM). METHODS: Three miRNA expression profiles (GSE16558, GSE24371 and GSE17498) were downloaded from the GEO database. The three miRNA expression profiles contained 131 MM samples and 17 normal plasmacyte samples. The robust rank aggregation (RRA) method was used to identify the differentially expressed miRNAs between MM and normal plasmacytes. In order to carry out cytological experiments, MM cell line with stable over-expression of miR-203a-5p was constructed with lentivirus. Expression levels of miR-203a-5p in MM cells were quantified by qRT-PCR. The effects of miR-203a-5p on MM cells were investigated using assays of cell viability and cell cycle. Cell proliferation was measured using the Cell Counting kit (CCK)8 assay. The percentage of cells in each cell cycle was measured with a FACSCalibur system. Xenograft tumor models were established to evaluate the role of miR-203a-5p in tumorigenesis <i>in vivoi> . To elucidate the underlying molecular mechanisms of miR-203a-5p in mediating cell proliferation inhibition and cell cycle arrest in MM, we used TargetScan and miRanda to predict the candidate targets of miR-203a-5p. The potential target of miR-203a-5p in MM cells was explored using the luciferase reporter assay, qRT-PCR, and Western blot. RESULTS: An integrated analysis of three MM miRNA expression datasets showed that the levels of miR-203a-5p in MM were notably downregulated compared with those in normal plasmacytes. Accordingly, the relative expression levels of miR-203a-5p were decreased in MM cell lines. In addition, overexpression of miR-203a-5p inhibited the proliferation and cell cycle progression of RPMI8226 and U266 cells. <i>In vivoi> experiments demonstrated that upregulation of miR-203a-5p expression could significantly inhibit the tumorigenesis of subcutaneous myeloma xenografts in nude mice. Mechanistic investigation led to the identification of Jagged 1 (<i>JAG1i>) as a novel and direct downstream target of miR-203a-5p. Interestingly, the reintroduction of <i>JAG1i> abrogated miR-203a-5p-induced MM cell growth inhibition and cell cycle arrest. CONCLUSION Our data demonstrate that miR-203a-5p inhibits cell proliferation and cell cycle progression in MM cells by targeting <i>JAG1i>, supporting the utility of miR-203a-5p as a novel and potential therapeutic agent for miRNA-based MM therapy.
Animals ; Mice ; Humans ; Multiple Myeloma/pathology* ; Cell Line, Tumor ; Mice, Nude ; MicroRNAs/metabolism* ; Cell Division ; Cell Proliferation ; Disease Models, Animal ; Carcinogenesis/genetics* ; Gene Expression Regulation, Neoplastic ; Jagged-1 Protein/metabolism*

OBJECTIVE: To investigate the effect of <i>Zuogui Jiangtang Jieyui> Decoction (ZJJ) on Shh signaling and self-renewal of neural stem cells in the hippocampal dentate gyrus of diabetic rats with depression. METHODS: Diabetic rat models with depression were randomly divided into model group, positive drug (metformin + fluoxetine) group, and low-, medium-, and high-dose ZJJ groups (<i>ni>=16), with normal SD rats as the control group. The positive drugs and ZJJ were administered by gavage, and the rats in the control and model groups were given distilled water. After the treatment, blood glucose level was detected using test strips, and behavioral changes of the rats were assessed by forced swimming test and water maze test. ELISA was used to examine the serum level of leptin; The expressions of nestin and Brdu proteins in the dentate gyrus of the rats were detected using immunofluorescence assay, and the expressions of self-renewal marker proteins and Shh signaling proteins were detected using Western blotting. RESULTS: The diabetic rats with depression showed significantly increased levels of blood glucose and leptin (<i>Pi> < 0.01) and prolonged immobility time in forced swimming test (<i>Pi> < 0.01) and increased stage climbing time with reduced stage seeking time and stage crossings in water maze test (<i>Pi> < 0.01). The expressions of nestin and Brdu in the dentate gyrus, the expressions of cyclin D1, SOX2, Shh, Ptch1, Smo in the hippocampus and the nuclear expression of Gli-1 were decreased (<i>Pi> < 0.01) while hippocampal Gli-3 expression was increased significantly (<i>Pi> < 0.01) in the rat models. Treatment of rat models with high-dose ZJJ significantly reduced the blood glucose (<i>Pi> < 0.01) and leptin level (<i>Pi> < 0.05) and improved their performance in behavioral tests (<i>Pi> < 0.01). The treatment also obviously increased the expressions of nestin, Brdu, cyclin D1, SOX2, Shh, Ptch1, and Smo and the nuclear expression of Gli-1 in the dentate gyrus (<i>Pi> < 0.01) and reduced hippocampal expression of Gli-3 (<i>Pi> < 0.05) in the rat models. CONCLUSION ZJJ can significantly improve the self-renewal ability of neural stem cells and activate Shh signaling in dentate gyrus of diabetic rats with depression.
Animals ; Rats ; Blood Glucose ; Bromodeoxyuridine ; Cell Self Renewal ; Cyclin D1 ; Dentate Gyrus ; Depression ; Diabetes Mellitus, Experimental ; Hippocampus ; Leptin ; Nestin ; Rats, Sprague-Dawley