Life without geminin

Varying outcomes of triple-negative breast cancer in different age groups-prognostic value of clinical features and proliferation

PURPOSE

Triple-negative breast cancer (TNBC) is an aggressive disease lacking specific biomarkers to guide treatment decisions. We evaluated the combined prognostic impact of clinical features and novel biomarkers of cell cycle-progression in age-dependent subgroups of TNBC patients.

METHODS

One hundred forty seven TNBC patients with complete clinical data and up to 18 year follow-up were collected from Turku University Hospital, Finland. Eight biomarkers for cell division were immunohistochemically detected to evaluate their clinical applicability in relation to patient and tumor characteristics.

RESULTS

Age at diagnosis was the decisive factor predicting disease-specific mortality in TNBC (p = 0.002). The established prognostic features, nodal status and Ki-67, predicted survival only when combined with age. The outcome and prognostic features differed significantly between age groups, middle-aged patients showing the most favorable outcome. Among young patients, only lack of basal differentiation predicted disease outcome, indicating 4.5-fold mortality risk (p = 0.03). Among patients aged > 57, the established prognostic features predicted disease outcome with up to 3.0-fold mortality risk for tumor size ≥ 2 cm (p = 0.001). Concerning cell proliferation, Ki-67 alone was a significant prognosticator among patients aged > 57 years (p = 0.009). Among the studied cell cycle-specific biomarkers, only geminin predicted disease outcome, indicating up to 6.2-fold increased risk of mortality for tumor size < 2 cm (p = 0.03).

CONCLUSION

Traditional clinical features do not provide optimal prognostic characterization for all TNBC patients. Young age should be considered as an additional adverse prognostic feature in therapeutic considerations. Increased proliferation, as evaluated using Ki-67 or geminin immunohistochemistry, showed potential in detecting survival differences in subgroups of TNBC.

DNA Replication Inhibitor Geminin and Retinoic Acid Signaling Participate in Complex Interactions Associated With Pluripotency

BACKGROUND/AIM

Several links between DNA replication, pluripotency and development have been recently identified. The involvement of miRNA in the regulation of cell cycle events and pluripotency factors has also gained attention.

MATERIALS AND METHODS

In the present study, we used the g:Profiler platform to analyze transcription factor binding sites, miRNA networks and protein-protein interactions to identify novel links among the aforementioned processes.

RESULTS AND CONCLUSION

A complex circuitry between retinoic acid signaling, SWI/SNF components, pluripotency factors including Oct4, Sox2 and Nanog and cell cycle regulators was identified. It is suggested that the DNA replication inhibitor geminin plays a central role in this circuitry.

Overexpression of UHRF1 promoted the proliferation of vascular smooth cells via the regulation of Geminin protein levels

Geminin is an inhibitor of DNA replication licensing and cell cycle. Our previous study demonstrates that Geminin plays an important role in regulating phenotypic diversity and growth of vascular smooth cells (VSMCs). Ubiquitin-like with PHD and RING Finger domains 1 (UHRF1) is an epigenetic coordinator, whose RING domain confers intrinsic E3 ligase activity, mediating the ubiquitination of several proteins and the protein-protein interaction. Aberrant expression of UHRF1 was related to aggressiveness of multiple human malignancies, where knockdown of UHRF1 led to decreased proliferation of cancer cells. However, it is unclear whether proper UHRF1 function is involved in aberrant proliferation and phenotypic switching of VSMCs via altering Geminin protein levels. In present study, in UHRF1-overexpressing A10 cells, 3H-thymidine and 5-ethynyl-20-deoxyuridine (EdU) and CCK8 were used to examine the proliferation of VSMCs. RT-PCR and Western blot analyses were performed to investigate whether UHRF1-mediated effects were achieved by altering Geminin expression in VSMCs. RNA-seq analysis was performed to dissect related mechanisms or signaling pathways of these effects. The results of in vitro experiments suggested that UHRF1 prompted proliferation and cell cycle of VSMCs via the down-regulation of Geminin protein levels with no change in Geminin mRNA expression. Besides, PI3K-Akt signaling pathway was increased upon UHRF1 up-regulation. Our study demonstrated that overexpressing UHRF1 was involved in VSMCs proliferation through reducing inhibitory Geminin protein levels to promote cell cycle as well as activating PI3K-Akt signaling. This may provide key knowledge for the development of better strategies to prevent diseases related to VSMCs abnormal proliferation.

Regulation of geminin by neuropeptide Y in vascular smooth muscle cell proliferation : A current review

Geminin, a key regulator of DNA replication licensing in the cell cycle, plays an essential role in determining the fate of cells via suppression of cell proliferation and cellular differentiation. Neuropeptide Y (NPY) intensifies the proliferation of vascular smooth muscle cells (VSMCs) directly by binding with Y1 receptors. In vitro experiments have shown that stimulation of NPY on VSMCs via regulation of geminin is a double-edged sword. Given that the proliferation and the phenotypic transformation of VSMCs increase the risk for progression of atherosclerosis, we focus on the role of geminin interference in determining the fate of VSMCs. Furthermore, we discuss the therapeutic potential of peripheral neurotransmitter interference, thus pointing toward future research directions in the treatment of atherosclerosis.

Controlling centriole numbers: Geminin family members as master regulators of centriole amplification and multiciliogenesis

To ensure that the genetic material is accurately passed down to daughter cells during mitosis, dividing cells must duplicate their chromosomes and centrosomes once and only once per cell cycle. The same key steps-licensing, duplication, and segregation-control both the chromosome and the centrosome cycle, which must occur in concert to safeguard genome integrity. Aberrations in genome content or centrosome numbers lead to genomic instability and are linked to tumorigenesis. Such aberrations, however, can also be part of the normal life cycle of specific cell types. Multiciliated cells best exemplify the deviation from a normal centrosome cycle. They are post-mitotic cells which massively amplify their centrioles, bypassing the rule for once-per-cell-cycle centriole duplication. Hundreds of centrioles dock to the apical cell surface and generate motile cilia, whose concerted movement ensures fluid flow across epithelia. The early steps that control the generation of multiciliated cells have lately started to be elucidated. Geminin and the vertebrate-specific GemC1 and McIdas are distantly related coiled-coil proteins, initially identified as cell cycle regulators associated with the chromosome cycle. Geminin is required to ensure once-per-cell-cycle genome replication, while McIdas and GemC1 bind to Geminin and are implicated in DNA replication control. Recent findings highlight Geminin family members as early regulators of multiciliogenesis. GemC1 and McIdas specify the multiciliate cell fate by forming complexes with the E2F4/5 transcription factors to switch on a gene expression program leading to centriole amplification and cilia formation. Positive and negative interactions among Geminin family members may link cell cycle control to centriole amplification and multiciliogenesis, acting close to the point of transition from proliferation to differentiation. We review key steps of centrosome duplication and amplification, present the role of Geminin family members in the centrosome and chromosome cycle, and discuss links with disease.

Geminin Participates in Differentiation Decisions of Adult Neural Stem Cells Transplanted in the Hemiparkinsonian Mouse Brain

Neural stem cells have been considered as a source of stem cells that can be used for cell replacement therapies in neurodegenerative diseases, as they can be isolated and expanded in vitro and can be used for autologous grafting. However, due to low percentages of survival and varying patterns of differentiation, strategies that will enhance the efficacy of transplantation are under scrutiny. In this article, we have examined whether alterations in Geminin's expression, a protein that coordinates the balance between self-renewal and differentiation, can improve the properties of stem cells transplanted in 6-OHDA hemiparkinsonian mouse model. Our results indicate that, in the absence of Geminin, grafted cells differentiating into dopaminergic neurons were decreased, while an increased number of oligodendrocytes were detected. The number of proliferating multipotent cells was not modified by the absence of Geminin. These findings encourage research related to the impact of Geminin on transplantations for neurodegenerative disorders, as an important molecule in influencing differentiation decisions of the cells composing the graft.

Different effects of neuropeptide Y on proliferation of vascular smooth muscle cells via regulation of Geminin

The proliferation-promoting effect of neuropeptide Y (NPY) always functions in low-serum-cultured vascular smooth muscle cells (VSMCs), and the phenotypic switch of VSMCs is regulated by concentrations of serum. Whether the property of the NPY proliferative effect in VSMCs relies on phenotype of VSMCs is unclear. We aimed to explore the role of NPY on proliferation of different VSMC phenotypes in the pathogenesis of atherosclerosis. By stimulating A10 cells with 200 nM NPY in 0.5 or 10% serum, 3H-thymidine and 5-ethynyl-2'-deoxyuridine (EdU) and CCK8 measurements were used to detect VSMC proliferation. RT-PCR and Flow cytometry were performed to detect the factors involved in different properties of the NPY proliferative effect in VSMCs. Instead of facilitating proliferation, NPY had no significant effect on the growth of VSMCs when cultured in 10% serum (VSMCs stayed at synthetic states). The underlying mechanism may be involved in down-regulation of Y1 receptor (P < 0.05 vs. Vehicle) and up-regulation of Geminin (P < 0.05 vs. Vehicle) in 10% serum-cultured VSMCs co-incubated with 200 nM NPY. Besides, modulation of Geminin was effectively blocked by the Y1 receptor antagonist. The stimulation of NPY on proliferation of VSMCs could be a double-edged sword in the development of atherosclerosis and thus provides new knowledge for therapy of atherosclerosis.

Geminin a multi task protein involved in cancer pathophysiology and developmental process: A review

DNA replicates in a timely manner with each cell division. Multiple proteins and factors are involved in the initiation of DNA replication including a dynamic interaction between Cdc10-dependent transcript (Cdt1) and Geminin (GMNN). A conformational change between GMNN-Cdt1 heterotrimer and heterohexamer complex is responsible for licensing or inhibition of the DNA replication. This molecular switch ensures a faithful DNA replication during each S phase of cell cycle. GMNN inhibits Cdt1-mediated minichromosome maintenance helicases (MCM) loading onto the chromatin-bound origin recognition complex (ORC) which results in the inhibition of pre-replication complex assembly. GMNN modulates DNA replication by direct binding to Cdt1, and thereby alters its stability and activity. GMNN is involved in various stages of development such as pre-implantation, germ layer formation, cell commitment and specification, maintenance of genome integrity at mid blastula transition, epithelial to mesenchymal transition during gastrulation, neural development, organogenesis and axis patterning. GMNN interacts with different proteins resulting in enhanced hematopoietic stem cell activity thereby activating the development-associated genes' transcription. GMNN expression is also associated with cancer pathophysiology and development. In this review we discussed the structure and function of GMNN in detail. Inhibitors of GMNN and their role in DNA replication, repair, cell cycle and apoptosis are reviewed. Further, we also discussed the role of GMNN in virus infected host cells.

Inactivation of Geminin in neural crest cells affects the generation and maintenance of enteric progenitor cells, leading to enteric aganglionosis

Neural crest cells comprise a multipotent, migratory cell population that generates a diverse array of cell and tissue types, during vertebrate development. Enteric Nervous System controls the function of the gastrointestinal tract and is mainly derived from the vagal and sacral neural crest cells. Deregulation on self-renewal and differentiation of the enteric neural crest cells is evident in enteric nervous system disorders, such as Hirschsprung disease, characterized by the absence of ganglia in a variable length of the distal bowel. Here we show that Geminin is essential for Enteric Nervous System generation as mice that lacked Geminin expression specifically in neural crest cells revealed decreased generation of vagal neural crest cells, and enteric neural crest cells (ENCCs). Geminin-deficient ENCCs showed increased apoptosis and decreased cell proliferation during the early stages of gut colonization. Furthermore, decreased number of committed ENCCs in vivo and the decreased self-renewal capacity of enteric progenitor cells in vitro, resulted in almost total aganglionosis resembling a severe case of Hirschsprung disease. Our results suggest that Geminin is an important regulator of self-renewal and survival of enteric nervous system progenitor cells.

Geminin deletion increases the number of fetal hematopoietic stem cells by affecting the expression of key transcription factors

Balancing stem cell self-renewal and initiation of lineage specification programs is essential for the development and homeostasis of the hematopoietic system. We have specifically ablated geminin in the developing murine hematopoietic system and observed profound defects in the generation of mature blood cells, leading to embryonic lethality. Hematopoietic stem cells (HSCs) accumulated in the fetal liver following geminin ablation, while committed progenitors were reduced. Genome-wide transcriptome analysis identified key HSC transcription factors as being upregulated upon geminin deletion, revealing a gene network linked with geminin that controls fetal hematopoiesis. In order to obtain mechanistic insight into the ability of geminin to regulate transcription, we examined Hoxa9 as an example of a key gene in definitive hematopoiesis. We demonstrate that in human K562 cells geminin is associated with HOXA9 regulatory elements and its absence increases HOXA9 transcription similarly to that observed in vivo. Moreover, silencing geminin reduced recruitment of the PRC2 component SUZ12 to the HOXA9 locus and resulted in an increase in RNA polymerase II recruitment and H3K4 trimethylation (H3K4me3), whereas the repressive marks H3K9me3 and H3K27me3 were reduced. The chromatin landscape was also modified at the regulatory regions of HOXA10 and GATA1. K562 cells showed a reduced ability to differentiate to erythrocytes and megakaryocytes upon geminin silencing. Our data suggest that geminin is indispensable for fetal hematopoiesis and regulates the generation of a physiological pool of stem and progenitor cells in the fetal hematopoietic system.

Licensing of DNA replication, cancer, pluripotency and differentiation: an interlinked world?

Recent findings provide evidence for a functional interplay between DNA replication and the seemingly distinct areas of cancer, development and pluripotency. Protein complexes participating in DNA replication origin licensing are now known to have roles in development, while their deregulation can lead to cancer. Moreover, transcription factors implicated in the maintenance of or reversal to the pluripotent state have links to the pre-replicative machinery. Several studies have shown that overexpression of these factors is associated to cancer.

The Geminin and Idas coiled coils preferentially form a heterodimer that inhibits Geminin function in DNA replication licensing

Geminin is an important regulator of proliferation and differentiation in metazoans, which predominantly inhibits the DNA replication licensing factor Cdt1, preventing genome over-replication. We show that Geminin preferentially forms stable coiled-coil heterodimers with its homologue, Idas. In contrast to Idas-Geminin heterodimers, Idas homodimers are thermodynamically unstable and are unlikely to exist as a stable macromolecule under physiological conditions. The crystal structure of the homology regions of Idas in complex with Geminin showed a tight head-to-head heterodimeric coiled-coil. This Idas-Geminin heterodimer binds Cdt1 less strongly than Geminin-Geminin, still with high affinity (∼30 nm), but with notably different thermodynamic properties. Consistently, in Xenopus egg extracts, Idas-Geminin is less active in licensing inhibition compared with a Geminin-Geminin homodimer. In human cultured cells, ectopic expression of Idas leads to limited over-replication, which is counteracted by Geminin co-expression. The properties of the Idas-Geminin complex suggest it as the functional form of Idas and provide a possible mechanism to modulate Geminin activity.

Contrast-enhanced intraoperative ultrasonography for vascular imaging of hepatocellular carcinoma: clinical and biological significance

Abnormal tumor vascularity is one of the typical features of hepatocellular carcinoma (HCC). In this study, the significance of contrast-enhanced intraoperative ultrasonography (CEIOUS) images of HCC vasculature was evaluated by clinicopathological and gene expression analyses. We enrolled 82 patients who underwent curative hepatic resection for HCC with CEIOUS. Clinicopathological and gene expression analyses were performed according to CEIOUS vasculature patterns. CEIOUS images of HCC vasculatures were classified as reticular HCC or thunderbolt HCC. Thunderbolt HCC was significantly correlated with higher alpha-fetoprotein levels, tumor size, histological differentiation, portal vein invasion, and tumor-node-metastasis stage, and these patients demonstrated a significantly poorer prognosis for both recurrence-free survival (P = 0.0193) and overall survival (P = 0.0362) compared with patients who had reticular HCC. Gene expression analysis revealed that a rereplication inhibitor geminin was significantly overexpressed in thunderbolt HCCs (P = 0.00326). In vitro knockdown of geminin gene reduced significantly the proliferation of human HCC cells. Immunohistochemical analysis confirmed overexpression of geminin protein in thunderbolt HCC (P < 0.0001). Multivariate analysis revealed geminin expression to be an independent factor in predicting poor survival in HCC patients (P = 0.0170).

CONCLUSION

CEIOUS vascular patterns were distinctly identifiable by gene expression profiling associated with cellular proliferation of HCC and were significantly related to HCC progression and poor prognosis. These findings might be clinically useful as a determinant factor in the postoperative treatment of HCC.

Geminin regulates cortical progenitor proliferation and differentiation

During cortical development, coordination of proliferation and differentiation ensures the timely generation of different neural progenitor lineages that will give rise to mature neurons and glia. Geminin is an inhibitor of DNA replication and it has been proposed to regulate cell proliferation and fate determination during neurogenesis via interactions with transcription factors and chromatin remodeling complexes. To investigate the in vivo role of Geminin in the maintenance and differentiation of cortical neural progenitors, we have generated mice that lack Geminin expression in the developing cortex. Our results show that loss of Geminin leads to the expansion of neural progenitor cells located at the ventricular and subventricular zones of the developing cortex. Early cortical progenitors lacking Geminin exhibit a longer S-phase and a reduced ability to generate early born neurons, consistent with a preference on self-renewing divisions. Overexpression of Geminin in progenitor cells of the cortex reduces the number of neural progenitor cells, promotes cell cycle exit and subsequent neuronal differentiation. Our study suggests that Geminin has an important role during cortical development in regulating progenitor number and ultimately neuron generation.