Search Results (39)

Microtubule minus-end binding proteins (−TIPs) are critical regulators of microtubule dynamics and stability, whose dysfunctions are increasingly associated with tumorigenesis and cancer progression. This review systematically consolidates current research advances on the molecular characteristics, oncogenic mechanisms, and therapeutic potential of −TIPs in cancer. By integrating preclinical studies, multi-omics data, and clinical evidence, it was found that calmodulin-regulated spectrin-associated proteins (CAMSAPs) and abnormal spindle microtubule assembly (ASPM) primarily exhibit oncogenic properties, whereas CAMSAP3 acts as a tumor suppressor by negatively regulating tumor cell migration. Studies also demonstrate that pharmacological inhibition of the γ-tubulin ring complex (γ-TuRC) effectively attenuates the centrosomal hyper-clustering capacity of malignant cells, thereby suppressing invasive phenotypes. This result underscores the therapeutic value of targeting −TIPs. In summary, −TIPs play critical and complex roles in cancer progression and hold significant potential as prognostic biomarkers and therapeutic targets. Intervention strategies focusing on specific −TIPs, such as γ-TuRC, offer promising strategies for precision cancer therapy; however, the context-dependent functions of these proteins require further investigation to facilitate clinical translation. Full article

46,XY gonadal dysgenesis, characterised by absent or defective testicular development in individuals with a 46,XY karyotype, results from disruptions in the genetic programme governing testis determination and differentiation during embryogenesis. While monogenic causes explain approximately 50% of cases, emerging evidence suggests an oligogenic basis in some patients. However, many cases remain without a definitive molecular diagnosis. In this study, we investigated a patient with 46,XY gonadal dysgenesis to explore the underlying genetic aetiology. Whole-exome sequencing in the patient did not reveal any pathogenic variants in genes previously associated with this condition. Instead, it detected rare variants in STARD9 and CDK5RAP2, which encode centrosomal proteins known to interact with each other. Gene expression analysis of embryonic gonads revealed that STARD9 is sexually dimorphic, with the highest expression in testis-specific Sertoli cells, while CDK5RAP2 is ubiquitously expressed, including in Sertoli cells. These findings suggest a role for both genes in Sertoli cell development, implicating them in the pathogenesis of 46,XY gonadal dysgenesis. To evaluate the functional relevance of the identified variants, we performed molecular dynamics simulations, which suggest that these variants may impair the individual and/or combined functions of STARD9 and CDK5RAP2 proteins. This study is the first to propose a role for STARD9 and CDK5RAP2 genes in human Sertoli cell development and highlights their potential contribution to 46,XY gonadal dysgenesis. Full article

Background: Spermatogenesis depends on precise cytoskeletal regulation, particularly the microtubule system; however, the mechanisms governing tubulin homeostasis during meiosis are poorly defined. While the E3 ubiquitin ligase Hyd (Hyperplastic discs), the Drosophila homolog of UBR5 (Ubiquitin Protein Ligase E3 Component N-Recognin 5), plays roles in diverse cellular processes, its precise role in male meiosis is unknown. This study aims to define the function and expression dynamics of Hyd during Drosophila spermatogenesis and elucidate whether it acts independently of its canonical ligase activity. Methods: Using Drosophila genetics, immunofluorescence, CRISPR/Cas9-mediated tagging, and mosaic clonal analysis, we characterized Hyd expression and function in the testis. Hyd knockdown and rescue experiments were performed with wild-type and catalytically inactive transgenes. β2-tubulin expression and microtubule organization were assessed in hyd mutant clones. Results: Hyd exhibits a dynamic, stage-specific expression pattern, localizing to nuclear and meiotic structures. Hyd loss led to meiotic arrest, disrupted spindle formation, aberrant centrosome behavior, and failure of spermatid elongation. Genetic rescue demonstrated that both wild-type and catalytically inactive Hyd partially restored spermatid elongation, indicating a catalysis-independent role. Furthermore, Hyd deficiency resulted in β2-tubulin overexpression, disrupted microtubule organization, and abnormal spermatocyte morphology. Conclusions: Hyd ensures meiotic fidelity in Drosophila by fine-tuning β2-tubulin expression independently of its E3 ubiquitin ligase activity. These findings reveal a non-proteolytic function for UBR5/Hyd in cytoskeletal regulation during male gametogenesis, providing new insights into tubulin homeostasis in meiosis. Full article

The Never-in-Mitosis A-Related Kinase (NEK) family is an important, yet largely understudied, family of protein kinases involved in the regulation of a variety of critical cellular processes. Consequently, dysregulation of NEK function has been linked to the etiology and progression of several disorders, including cancer, ciliopathies, neurodegenerative disorders, inflammatory disorders, and other pervasive diseases. In this review, we have summarized recent findings to provide an overview of the NEK family and their diverse functions within various cellular contexts. In parallel, we have highlighted the emerging roles of NEK family members in human health, identifying potential therapeutic targets within the NEK family and exploring their potential for future clinical applications. Finally, we have addressed ongoing challenges and emerging research directions in this rapidly evolving field, aiming to pave the way for future discoveries and innovations. Full article

Background: Centrosome amplification, a hallmark of cell cycle dysregulation, drives carcinogenesis through aneuploidy induction and invasive phenotype acquisition. In pancreatic adenocarcinoma—a malignancy characterized by profound genomic instability—the molecular circuitry of centrosome amplification remains enigmatic. Critical gaps persist in understanding its spatiotemporal dynamics in tumor microenvironment remodeling and therapy resistance. Methods: This study integrated centrosome amplification-related genes from TCGA and Genecards, established a prognostic risk model through univariate Cox regression–LASSO penalized Cox regression–multivariate Cox regression analyses, and validated it using GEO datasets. Single-cell sequencing analyses dissected transcriptional heterogeneity and intercellular communication networks, while spatially resolved transcriptomics unveiled spatiotemporal expression patterns and molecular regulatory mechanisms of core genes. With further experimental validation via PCR analysis of patient-derived tissue samples confirming key gene expression patterns. Results: This study identified 23 centrosome amplification-related prognostic genes in pancreatic adenocarcinoma, establishing IFI27, KIF20A, KLK10, SPINK7, and TOP2A as highly specific diagnostic and prognostic biomarkers. The constructed signature was established as an independent prognostic indicator correlating with aggressive clinicopathological characteristics and chemoresistance. Mechanistically linked to enhanced DNA repair capacity and accelerated cell cycle progression, also synergizes with KRAS mutational profiles. Tumor microenvironment analysis revealed significant associations with immunosuppressive. Single-cell resolution demonstrated cellular specificity of IFI27/KLK10 in ductal epithelial cells and fibroblasts, with intercellular communication networks exhibiting multidimensional regulatory features. Spatially resolved transcriptomics delineated tumor-region-specific expression patterns of core genes. While PCR validation on matched tumor/normal tissues confirmed significant differential expression of IFI27, KIF20A, KLK10, and TOP2A. Conclusions: This study deciphers the multidimensional clinic–molecular network orchestrated by centrosome amplification in PDAC, revealing its dual-pathogenic mechanism in fueling tumor aggressiveness through coordinated induction of genomic instability and immunosuppressive microenvironment reprogramming. These findings establish a translational framework for developing centrosome dynamics-based prognostic stratification and molecularly targeted therapeutic strategies. Full article

Centrioles are remarkably stable organelles that play a main role in the assembly of centrosomes and ciliary structures. However, there are several differentiated tissues that must eliminate their centrioles to avoid centrosome formation and improper cell proliferation. Therefore, centriole elimination represents an important process in many organisms to ensure successful cell differentiation and maintenance of tissue homeostasis. In this review, we analyzed centriole inactivation and elimination in various Drosophila cell types in relation to the dynamics of the pericentriolar material. Full article

The genome is dynamically reorganized, partitioned, and divided during mitosis. Despite their role in organizing interphase chromatin, transcription factors were largely believed to be mitotic spectators evicted from chromatin during mitosis, only able to reestablish their position on DNA upon entry into G₁. However, a panoply of evidence now contradicts this early belief. Numerous transcription factors are now known to remain active during mitosis to achieve diverse purposes, including chromosome condensation, regulation of the centromere/kinetochore function, and control of centrosome homeostasis. Inactivation of transcription factors during mitosis results in chromosome segregation errors, key features of cancer. Moreover, active transcription and the production of centromere-derived transcripts during mitosis are also known to play key roles in maintaining chromosomal stability. Finally, many transcription factors are associated with chromosomal instability through poorly defined mechanisms. Herein, we will review the emerging roles of transcription factors and transcription during mitosis with a focus on their role in promoting the faithful segregation of sister chromatids. Full article

In the last decades, the study of many nuclear envelope components in Dictyostelium amoebae has revealed conserved mechanisms of nuclear envelope dynamics that root back unexpectedly deep into the eukaryotic tree of life. In this review, we describe the state of the art in nuclear envelope research in this organism starting from early work on nuclear pore complexes to characterization of the first true lamin in a non-metazoan organism and its associated nuclear envelope transmembrane proteins, such as the HeH-family protein Src1 and the LINC complex protein Sun1. We also describe the dynamic processes during semi-closed mitosis, including centrosome insertion into the nuclear envelope, and processes involved in the restoration of nuclear envelope permeability around mitotic exit and compare them to the situation in cells with open or fully closed mitosis. Full article

Dendritic spine formation/maintenance is highly dependent on actin cytoskeletal dynamics, which is regulated by small GTPases Rac1 and Cdc42 through their downstream p21-activated kinase/LIM-kinase-I/cofilin pathway. ARHGEF7, also known as ß-PIX, is a guanine nucleotide exchange factor for Rac1 and Cdc42, thereby activating Rac1/Cdc42 and the downstream pathway, leading to the upregulation of spine formation/maintenance. We found that STIL, one of the primary microcephaly gene products, is associated with ARHGEF7 in dendritic spines and that knockdown of Stil resulted in a significant reduction in dendritic spines in neurons both in vitro and in vivo. Rescue experiments indicated that the STIL requirement for spine formation/maintenance depended on its coiled coil domain that mediates the association with ARHGEF7. The overexpression of Rac1/Cdc42 compensated for the spine reduction caused by STIL knockdown. FRET experiments showed that Rac activation is impaired in STIL knockdown neurons. Chemical long-term potentiation, which triggers Rac activation, promoted STIL accumulation in the spine and its association with ARHGEF7. The dynamics of these proteins further supported their coordinated involvement in spine formation/maintenance. Based on these findings, we concluded that the centrosomal protein STIL is a novel regulatory factor essential for spine formation/maintenance by activating Rac and its downstream pathway, possibly through the association with ARHGEF7. Full article

The centrosome of the amoebozoan model Dictyostelium discoideum provides the best-established model for an acentriolar centrosome outside the Opisthokonta. Dictyostelium exhibits an unusual centrosome cycle, in which duplication is initiated only at the G2/M transition and occurs entirely during the M phase. Little is known about the role of conserved centrosomal kinases in this process. Therefore, we have generated knock-in strains for Aurora (AurK), CDK1, cyclin B, Nek2, and Plk, replacing the endogenous genes with constructs expressing the respective green fluorescent Neon fusion proteins, driven by the endogenous promoters, and studied their behavior in living cells. Our results show that CDK1 and cyclin B arrive at the centrosome first, already during G2, followed by Plk, Nek2, and AurK. Furthermore, CDK1/cyclin B and AurK were dynamically localized at kinetochores, and AurK in addition at nucleoli. The putative roles of all four kinases in centrosome duplication, mitosis, cytokinesis, and nucleolar dynamics are discussed. Full article

Centrosomal Protein 55 (CEP55) exhibits various oncogenic activities; it regulates the PI3K-Akt-pathway, midbody abscission, and chromosomal instability (CIN) in cancer cells. Here, we analyzed the mechanism of how CEP55 controls CIN in ovarian and breast cancer (OvCa) cells. Down-regulation of CEP55 reduced CIN in all cell lines analyzed, and CEP55 depletion decreased spindle microtubule (MT)-stability in OvCa cells. Moreover, recombinant CEP55 accelerated MT-polymerization and attenuated cold-induced MT-depolymerization. To analyze a potential relationship between CEP55-controlled CIN and its impact on MT-stability, we identified the CEP55 MT-binding peptides inside the CEP55 protein. Thereafter, a mutant with deficient MT-binding activity was re-expressed in CEP55-depleted OvCa cells and we could show that this mutant did not restore reduced CIN in CEP55-depleted cells. This finding strongly indicates that CEP55 regulates CIN by controlling MT dynamics. Full article

Silkworm ovary-derived BmN4 cells rely on chromatin-induced spindle assembly to form microtubule-based square mitotic spindles that ensure accurate segregation of holocentric chromosomes during cell division. The chromosome passenger protein Aurora B regulates chromosomal condensation and segregation, spindle assembly checkpoint activation, and cytokinesis; however, its role in holocentric organisms needs further clarification. This study examined the architecture and dynamics of spindle microtubules during prophase and metaphase in BmN4 cells and those with siRNA-mediated BmAurora B knockdown using immunofluorescence labeling. Anti-α-tubulin and anti-γ-tubulin antibodies revealed faint γ-tubulin signals colocalized with α-tubulin in early prophase during nuclear membrane rupture, which intensified as prophase progressed. At this stage, bright regions of α-tubulin around and on the nuclear membrane surrounding the chromatin suggested the start of microtubules assembling in the microtubule-organizing centers (MTOCs). In metaphase, fewer but larger γ-tubulin foci were detected on both sides of the chromosomes. This resulted in a distinctive multipolar square spindle with holocentric chromosomes aligned at the metaphase plate. siRNA-mediated BmAurora B knockdown significantly reduced the γ-tubulin foci during prophase, impacting microtubule nucleation and spindle structure in metaphase. Spatiotemporal BmAurora B expression analysis provided new insights into the regulation of this mitotic kinase in silkworm larval gonads during gametogenesis. Our results suggest that BmAurora B is crucial for the formation of multipolar square spindles in holocentric insects, possibly through the activation of γ-tubulin ring complexes in multiple centrosome-like MTOCs. Full article

Neospora caninum is an apicomplexan protozoan parasite responsible for causing neosporosis in a range of animal species. It results in substantial economic losses in the livestock industry and poses significant health risks to companion and wild animals. Central to its survival and pathogenicity is the process of cell division, which remains poorly understood in this parasite. In this study, we explored the cell division of Neospora caninum using a combination of modern and classic imaging tools, emphasizing its pivotal role in perpetuating the parasite’s life cycle and contributing to its ability to persist within host organisms. We described the intricacies of endodyogeny in Neospora caninum, detailing the dynamics of the cell assembly and the nuclear division by ultrastructure expansion microscopy and regular confocal microscopy. Furthermore, we explored the centrosome dynamics, the centrioles and the apicoplast through the advancement of the cell cycle. Our analysis described with unprecedented detail, the endodyogeny in this parasite. By advancing our understanding of these molecular mechanisms, we aimed to inspire innovative strategies for disease management and control, with the ultimate goal of mitigating the devastating impact of neosporosis on animal health and welfare. Full article

The cyclin-dependent kinase 1 (Cdk1)–cyclin B (CycB) complex plays critical roles in cell-cycle regulation. Before Drosophila male meiosis, CycB is exported from the nucleus to the cytoplasm via the nuclear porin 62kD (Nup62) subcomplex of the nuclear pore complex. When this export is inhibited, Cdk1 is not activated, and meiosis does not initiate. We investigated the mechanism that controls the cellular localization and activation of Cdk1. Cdk1–CycB continuously shuttled into and out of the nucleus before meiosis. Overexpression of CycB, but not that of CycB with nuclear localization signal sequences, rescued reduced cytoplasmic CycB and inhibition of meiosis in Nup62-silenced cells. Full-scale Cdk1 activation occurred in the nucleus shortly after its rapid nuclear entry. Cdk1-dependent centrosome separation did not occur in Nup62-silenced cells, whereas Cdk1 interacted with Cdk-activating kinase and Twine/Cdc25C in the nuclei of Nup62-silenced cells, suggesting the involvement of another suppression mechanism. Silencing of roughex rescued Cdk1 inhibition and initiated meiosis. Nuclear export of Cdk1 ensured its escape from inhibition by a cyclin-dependent kinase inhibitor. The complex re-entered the nucleus via importin β at the onset of meiosis. We propose a model regarding the dynamics and activation mechanism of Cdk1–CycB to initiate male meiosis. Full article

This review summarizes information about the specific features that are characteristic of the centrosome and its relationship with the cell function of highly specialized cells, such as endotheliocytes. It is based on data from other researchers and our own long-term experience. The participation of the centrosome in the functional activity of these cells, including its involvement in the performance of the main barrier function of the endothelium, is discussed. According to modern concepts, the centrosome is a multifunctional complex and an integral element of a living cell; the functions of which are not limited only to the ability to polymerize microtubules. The location of the centrosome near the center of the interphase cell, the concentration of various regulatory proteins in it, the organization of the centrosome radial system of microtubules through which intracellular transport is carried out by motor proteins and the involvement of the centrosome in the process of the perception of the external signals and their transmission make this cellular structure a universal regulatory and distribution center, controlling the entire dynamic morphology of an animal cell. Drawing from modern data on the tissue-specific features of the centrosome’s structure, we discuss the direct involvement of the centrosome in the performance of functions by specialized cells. Full article