Table of Contents

Volume 10, Issue 11

  June 1, 2011

  Pages 1703 - 1874

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 Issue Catalogue (MARC XML)

EDITORIALS: CELL CYCLE FEATURES

Open Access Article

Rescuing stalled replication forks: MMS22L-TONSL, a novel complex for DNA replication fork repair in human cells

Wojciech Piwko, Raymond Buser and Matthias Peter
Pages 1703 - 1705
http://dx.doi.org/10.4161/cc.10.11.15557
Abstract | PDF

Comment on: Piwko W, et al. EMBO J 2010; 29:4210-22, Duro E, et al. Mol Cell 2010; 40:632–44, O’Connell BC, et al. Mol Cell 2010; 40:645–57 and O’Donnell L, et al. Mol Cell 2010; 40:619–31.


Open Access Article

Remote control of mRNA cleavage by a small RNA

Julie-Anna M. Benjamin, Karine Prévost and Eric Massé
Pages 1706 - 1707
http://dx.doi.org/10.4161/cc.10.11.15558
Abstract | PDF

Comment on: Prévost K, et al. Genes Dev 2011; 25:385-96.

Open Access Article

Nutrient amino acids signal to mTOR via inositol polyphosphate multikinase

Seyun Kim and Solomon H. Snyder
Pages 1708 - 1710
http://dx.doi.org/10.4161/cc.10.11.15559
Abstract | PDF

Comment on: Kim S, et al. Cell Metab 2011; 13:215-21.

Open Access Article

Self-propagation and transmission of misfolded mutant SOD1: Prion or prion-like phenomenon?

Christian Münch and Anne Bertolotti
Page 1711
http://dx.doi.org/10.4161/cc.10.11.15560
Abstract | PDF

Comment on: Münch C, et al. Proc Natl Acad Sci USA 2011; 108:3548-53.

Open Access Article

O-GlcNAc transferase: A sweet new cancer target

Thomas P. Lynch and Mauricio J. Reginato
Pages 1712 - 1713
http://dx.doi.org/10.4161/cc.10.11.15561
Abstract | PDF

Comment on: Caldwell SA, et al. Oncogene 2010; 29:2831-42.




CELL CYCLE NEWS & VIEWS

Open Access Article

Variation in DNA damage response pathway activity: Focus on intermediate phenotype instead of genetic polymorphisms

Diana van Heemst
Pages 1714 - 1718
http://dx.doi.org/10.4161/cc.10.11.15592
Abstract | PDF

Comment on: Kabacik S, et al. Cell Cycle 2011; 10:1152-61.

Open Access Article

Under stress: p53 controls EMT and stemness in pancreatic epithelial cells

Tobias Keck and Thomas Brabletz

http://dx.doi.org/10.4161/cc.10.11.15645
Abstract | PDF

Comment on: Pinho AV, et al. Cell Cycle 2011; 10:1312-21.

Open Access Article

A new role for E2F1 in DNA repair: All for the greater good

James DeGregori

http://dx.doi.org/10.4161/cc.10.11.15649
Abstract | PDF

Comment on: Chen J, et al. Cell Cycle 2011; 10:1287-94.

Open Access Article

p53: Guardian of pancreatic epithelial identity

Bidyut Ghosh and Steven D. Leach

http://dx.doi.org/10.4161/cc.10.11.15686
Abstract | PDF

Comment on: Andreia V. Pinho, et al. Cell Cycle 2011; 10: In press.


Open Access Article

E2F1: A new role in the DNA damage response

W. Douglas Cress

http://dx.doi.org/10.4161/cc.10.11.15687
Abstract | PDF

Comment on: Jie Chen, et al. Cell Cycle 2011; 10:1287-94.




EXTRA VIEWS

Open Access Article

Autophagy in the pathogenesis of myelodysplastic syndrome and acute myeloid leukemia

Alexander Scarth Watson, Monika Mortensen and Anna Katharina Simon
Pages 1719 - 1725
http://dx.doi.org/10.4161/cc.10.11.15673
Abstract | PDF

Autophagy is a conserved cellular pathway responsible for the sequestration of spent organelles and protein aggregates from the cytoplasm and their delivery into lysosomes for degradation. Autophagy plays an important role in adaptation to starvation, in cell survival, immunity, development and cancer. Recent evidence in mice suggests that autophagic defects in hematopoietic stem cells (HSCs) may be implicated in leukemia. Indeed, mice lacking Atg7 in HSCs develop an atypical myeloproliferation resembling human myelodysplastic syndrome (MDS) progressing to acute myeloid leukemia (AML). Studies suggest that accumulation of damaged mitochondria and reactive oxygen species result in cell death of the majority of progenitor cells and, possibly, concomitant transformation of some surviving ones. Interestingly, bone marrow cells from MDS patients are characterized by mitochondrial abnormalities and increased cell death. A role for autophagy in the transformation to cancer has been proposed in other cancer types. This review focuses on autophagy in human MDS development and progression to AML within the context of the role of mitochondria, apoptosis and reactive oxygen species (ROS) in its pathogenesis.

Open Access Article

TRIP6 and LPP, but not Zyxin, are present at a subset of telomeres in human cells

Samantha A. Sheppard, Tatiana Savinova and Diego Loayza
Pages 1726 - 1730
http://dx.doi.org/10.4161/cc.10.11.15676
Abstract | PDF

The protection of chromosome ends requires the inhibition of DNA damage responses at telomeres. This inhibition is exerted in great part by the shelterin complex, known to prevent inappropriate ATM and ATR activation. The molecular mechanisms by which shelterin protects telomeres are incompletely understood. Recently, we have implicated for the first time a class of molecules, LIM domain proteins, in telomere protection. This protection occurred through interaction with shelterin, possibly through POT1, and required the pair of LIM proteins TRIP6 and LPP, themselves part of the Zyxin family. The domain similarity between TRIP6, LPP and Zyxin led us to ask whether the latter also interacted with telomeres. Here, we show that there is specificity in the association of LIM proteins with telomeres: Zyxin, despite a high degree of similarity with TRIP6 and LPP, was not detected at telomeres, nor found in a complex with shelterin. TRIP6 and LPP, however, were detected by immunofluorescence at a small subset of telomeres, perhaps those that are critically short. We speculate that specific LIM proteins are part of complex events occurring in the context of the telomere dysfunction response, and possibly at play during the induction of senescence.

Open Access Article

Pluripotency and lineages in the mammalian blastocyst: An evolutionary view

Susana Cañon, Beatriz Fernandez-Tresguerres and Miguel Manzanares
Pages 1731 - 1738
http://dx.doi.org/10.4161/cc.10.11.15816
Abstract | PDF

Early mammalian development is characterized by a highly specific stage, the blastocyst, by which embryonic and extraembryonic lineages have been determined, but pattern formation has not yet begun. The blastocyst is also of interest because cell precursors of the embryo proper retain for a certain time the capability to generate all the cell types of the adult animal. This embryonic pluripotency is established and maintained by a regulatory network under the control of a small set of transcription factors, comprising Oct4, Sox2 and Nanog. This network is largely conserved in eutherian mammals, but there is scarce information about how it arose in vertebrates. We have analysed the conservation of gene regulatory networks controlling blastocyst lineages and pluripotency in the mouse by comparison with the chick. We found that few of elements of the network are novel to mammals; rather, most of them were present before the separation of the mammalian lineage from other amniotes, but acquired novel expression domains during early mammalian development. Our results strongly support the hypothesis that mammalian blastocyst regulatory networks evolved through rewiring of pre-existing components, involving the co-option and duplication of existing genes and the establishment of new regulatory interactions among them.

Open Access Article

Genetic control of susceptibility to carcinogen-induced colorectal cancer in mice: The Ccs3 and Ccs5 loci regulate different aspects of tumorigenesis

Charles Meunier, Tony Kwan, Claire Turbide, Nicole Beauchemin and Philippe Gros
Pages 1739 - 1749
http://dx.doi.org/10.4161/cc.10.11.15817
Abstract | PDF

Colorectal cancer (CRC) is a multistep disease that involves a two-way interaction between a complex genetic pre-disposition component, and a set of poorly understood extrinsic environmental factors. In mice, CRC can be induced by treatment with azoxymethane (AOM). Using a set of AcB/BcA recombinant congenic strains derived from CRC-susceptible A/J and CRC-resistant C57Bl/6J (B6) progenitors, we previously detected the Ccs3 locus (colon cancer susceptibility locus 3) as a major regulator of CRC susceptibility. Phenotyping of additional AcB/BcA strains for susceptibility to AOM-induced CRC has refined the Ccs3 interval to a 6.7 Mb segment on chromosome 3. In addition, the presence of intermediate susceptibility phenotypes in individual AcB/BcA strains suggested additional gene effects regulating CRC susceptibility in A/J and B6 strains. Those were investigated by linkage analysis and whole genome scanning in a set of 208 informative (B6 x A/J)F2 progeny, using tumor multiplicity as a quantitative measure of susceptibility. This analysis validated the important role of Ccs3 in regulating this trait, and additionally detected contribution from a second locus on the distal portion of chromosome 9 (LOD = 3.76), that was given the temporary designation of Ccs5. Ccs5 modulates tumor multiplicity in F2 animals bearing at least one A/J-derived susceptibility allele at Ccs3, with A/J-derived Ccs5 susceptibility alleles being inherited in a recessive manner. There is a strong additive effect of Ccs3 and Ccs5 on tumor multiplicity in F2 mice: mice doubly homozygotes for A/J or B6 alleles at Ccs3 and Ccs5 show tumor numbers similar to those of parental A/J and B6, respectively. Interestingly, the Ccs5 region overlaps several quantitative trait loci previously reported to regulate intestinal homeostasis and susceptibility to intestinal colitis in mice and humans. Our findings identify a novel two-locus system regulating CRC susceptibility in mice, of which the relevance to human CRC can now be tested experimentally.

Open Access Article

The insulin receptor substrate (IRS) proteins: At the intersection of metabolism and cancer

Leslie M. Shaw
Pages 1750 - 1756
http://dx.doi.org/10.4161/cc.10.11.15824
Abstract | PDF

Increasing evidence supports a connection between cancer and metabolism and emphasizes the need to understand how tumors respond to the metabolic microenvironment and how tumor cell metabolism is regulated. The insulin receptor (IR) and its close family member the insulin-like growth factor-1 receptor (IGF-1R) mediate the cellular response to insulin in normal cells and their function is tightly regulated to maintain metabolic homeostasis. These receptors are also expressed on tumor cells and their expression correlates with tumor progression and poor prognosis. Understanding how the IR/IGF-1R pathway functions in tumors is increasing in importance as the efficacy of drugs that target metabolic pathways, such as metformin, are investigated in prospective clinical trials. This review will focus on key signaling intermediates of the IR and IGF-1R, the Insulin Receptor Substrate (IRS) proteins, with an emphasis on IRS-2, and discuss how these adaptor proteins play a pivotal role at the intersection of metabolism and cancer.




PERSPECTIVE

Open Access Article

FANCP/SLX4: A Swiss army knife of DNA interstrand crosslink repair

Kelly E. Cybulski and Niall G. Howlett
Pages 1757 - 1763
http://dx.doi.org/10.4161/cc.10.11.15818
Abstract | PDF

Fanconi anemia (FA) is a rare genetic disease characterized by congenital abnormalities, bone marrow failure and heightened cancer susceptibility. The FA proteins are known to function in the cellular defense against DNA interstrand crosslinks (ICLs), a process that remains poorly understood. A recent spate of discoveries has led to the identification of one new FA gene, FANCP/SLX4, and two strong candidate FA genes, FAN1 and RAD51C. In this perspective we describe the discovery of FANCP/SLX4 and discuss how these new findings collectively refine our understanding of DNA ICL repair.




REVIEW

Open Access Article

Hepatic stellate cells and astrocytes: Stars of scar formation and tissue repair

Christian Schachtrup, Natacha Le Moan, Melissa A. Passino and Katerina Akassoglou
Pages 1764 - 1771
http://dx.doi.org/10.4161/cc.10.11.15828
Abstract | PDF

Scar formation inhibits tissue repair and regeneration in the liver and central nervous system. Activation of hepatic stellate cells (HSCs) after liver injury or of astrocytes after nervous system damage is considered to drive scar formation. HSCs are the fibrotic cells of the liver, as they undergo activation and acquire fibrogenic properties after liver injury. HSC activation has been compared to reactive gliosis of astrocytes, which acquire a reactive phenotype and contribute to scar formation after nervous system injury, much like HSCs after liver injury. It is intriguing that a wide range of neuroglia-related molecules are expressed by HSCs. We identified an unexpected role for the p75 neurotrophin receptor in regulating HSC activation and liver repair. Here we discuss the molecular mechanisms that regulate HSC activation and reactive gliosis and their contributions to scar formation and tissue repair. Juxtaposing key mechanistic and functional similarities in HSC and astrocyte activation might provide novel insight into liver regeneration and nervous system repair.




REPORTS

Open Access Article

Evidence for a stromal-epithelial “lactate shuttle” in human tumors: MCT4 is a marker of oxidative stress in cancer-associated fibroblasts

Diana Whitaker-Menezes, Ubaldo E. Martinez-Outschoorn, Zhao Lin, Adam Ertel, Neal Flomenberg, Agnieszka K. Witkiewicz, Ruth Birbe, Anthony Howell, Stephanos Pavlides, Ricardo Gandara, Richard G. Pestell, Federica Sotgia, Nancy J. Philp and Michael P. Lisanti
Pages 1772 - 1783
http://dx.doi.org/10.4161/cc.10.11.15659
Abstract | PDF

Recently, we proposed a new mechanism for understanding the Warburg effect in cancer metabolism. In this new paradigm, cancer-associated fibroblasts undergo aerobic glycolysis, and extrude lactate to “feed” adjacent cancer cells, which then drives mitochondrial biogenesis and oxidative mitochondrial metabolism in cancer cells. Thus, there is vectorial transport of energy-rich substrates from the fibroblastic tumor stroma to anabolic cancer cells. A prediction of this hypothesis is that cancer-associated fibroblasts should express MCT4, a mono-carboxylate transporter that has been implicated in lactate efflux from glycolytic muscle fibers and astrocytes in the brain. To address this issue, we co-cultured MCF7 breast cancer cells with normal fibroblasts. Interestingly, our results directly show that breast cancer cells specifically induce the expression of MCT4 in cancer-associated fibroblasts; MCF7 cells alone and fibroblasts alone, both failed to express MCT4. We also show that the expression of MCT4 in cancer-associated fibroblasts is due to oxidative stress, and can be prevented by pre-treatment with the anti-oxidant N-acetyl-cysteine. In contrast to our results with MCT4, we see that MCT1, a transporter involved in lactate uptake, is specifically upregulated in MCF7 breast cancer cells when co-cultured with fibroblasts. Virtually identical results were also obtained with primary human breast cancer samples. In human breast cancers, MCT4 selectively labels the tumor stroma, e.g., the cancer-associated fibroblast compartment. Conversely, MCT1 was selectively expressed in the epithelial cancer cells within the same tumors. Functionally, we show that overexpression of MCT4 in fibroblasts protects both MCF7 cancer cells and fibroblasts against cell death, under co-culture conditions. Thus, we provide the first evidence for the existence of a stromal-epithelial lactate shuttle in human tumors, analogous to the lactate shuttles that are essential for the normal physiological function of muscle tissue and brain. These data are consistent with the “reverse Warburg effect,” which states that cancer-associated fibroblasts undergo aerobic glycolysis, thereby producing lactate, which is utilized as a metabolic substrate by adjacent cancer cells. In this model, “energy transfer” or “metabolic-coupling” between the tumor stroma and epithelial cancer cells “fuels” tumor growth and metastasis, via oxidative mitochondrial metabolism in anabolic cancer cells. Most importantly, our current findings provide a new rationale and novel strategy for anti-cancer therapies, by employing MCT inhibitors.

Open Access Article

Cytokine production and inflammation drive autophagy in the tumor microenvironment: Role of stromal caveolin-1 as a key regulator

Ubaldo E. Martinez-Outschoorn, Diana Whitaker-Menezes, Zhao Lin, Neal Flomenberg, Anthony Howell, Richard G. Pestell, Michael P. Lisanti and Federica Sotgia
Pages 1784 - 1793
http://dx.doi.org/10.4161/cc.10.11.15674
Abstract | PDF

Recently, we proposed a new paradigm for understanding the role of the tumor microenvironment in breast cancer onset and progression. In this model, cancer cells induce oxidative stress in adjacent fibroblasts. This, in turn, results in the onset of stromal autophagy, which produces recycled nutrients to “feed” anabolic cancer cells. However, it remains unknown how autophagy in the tumor microenvironment relates to inflammation, another key driver of tumorigenesis. To address this issue, here we employed a well-characterized co-culture system in which cancer cells induce autophagy in adjacent fibroblasts via oxidative stress and NFκB-activation. We show, using this co-culture system, that the same experimental conditions that result in an autophagic microenvironment, also drive in the production of numerous inflammatory mediators (including IL-6, IL-8, IL-10, MIP1a, IFNg, RANTES (CCL5) and GMCSF). Furthermore, we demonstrate that most of these inflammatory mediators are individually sufficient to directly induce the onset of autophagy in fibroblasts. To further validate the in vivo relevance of these findings, we assessed the inflammatory status of Cav-1 (-/-) null mammary fat pads, which are a model of a bonafide autophagic microenvironment. Notably, we show that Cav-1 (-/-) mammary fat pads undergo infiltration with numerous inflammatory cell types, including lymphocytes, T-cells, macrophages and mast cells. Taken together, our results suggest that cytokine production and inflammation are key drivers of autophagy in the tumor microenvironment. These results may explain why a loss of stromal Cav-1 is a powerful predictor of poor clinical outcome in breast cancer patients, as it is a marker of both (1) autophagy and (2) inflammation in the tumor microenvironment. Lastly, hypoxia in fibroblasts was not sufficient to induce the full-blown inflammatory response that we observed during the co-culture of fibroblasts with cancer cells, indicating that key reciprocal interactions between cancer cells and fibroblasts may be required.

Open Access Article

Molecular profiling of a lethal tumor microenvironment, as defined by stromal caveolin-1 status in breast cancers

Agnieszka K. Witkiewicz, Jessica Kline, Maria Queenan, Jonathan R. Brody, Aristotelis Tsirigos, Erhan Bilal, Stephanos Pavlides, Adam Ertel, Federica Sotgia and Michael P. Lisanti
Pages 1794 - 1809
http://dx.doi.org/10.4161/cc.10.11.15675
Abstract | PDF

Breast cancer progression and metastasis are driven by complex and reciprocal interactions, between epithelial cancer cells and their surrounding stromal microenvironment. We have previously shown that a loss of stromal Cav-1 expression is associated with an increased risk of early tumor recurrence, metastasis and decreased overall survival. To identify and characterize the signaling pathways that are activated in Cav-1 negative tumor stroma, we performed gene expression profiling using laser microdissected breast cancer-associated stroma. Tumor stroma was laser capture microdissected from 4 cases showing high stromal Cav-1 expression and 7 cases with loss of stromal Cav-1. Briefly, we identified 238 gene transcripts that were upregulated and 232 gene transcripts that were downregulated in the stroma of tumors showing a loss of Cav-1 expression (p ≤ 0.01 and fold-change ≥1.5). Gene set enrichment analysis (GSEA) revealed “stemness,” inflammation, DNA damage, aging, oxidative stress, hypoxia, autophagy and mitochondrial dysfunction in the tumor stroma of patients lacking stromal Cav-1. Our findings are consistent with the recently proposed “Reverse Warburg Effect” and the “Autophagic Tumor Stroma Model of Cancer Metabolism.” In these two complementary models, cancer cells induce oxidative stress in adjacent stromal cells, which then forces these stromal fibroblasts to undergo autophagy/mitophagy and aerobic glycolysis. This, in turn, produces recycled nutrients (lactate, ketones and glutamine) to feed anabolic cancer cells, which are undergoing oxidative mitochondrial metabolism. Our results are also consistent with previous biomarker studies showing that the increased expression of known autophagy markers (such as ATG16L and the cathepsins) in the tumor stroma is specifically associated with metastatic tumor progression and/or poor clinical outcome.

Open Access Article

Vitamin K does not prevent soft tissue mineralization in a mouse model of pseudoxanthoma elasticum

Christopher Brampton, Yukiko Yamaguchi, Olivier Vanakker, Lut Van Laer, Li-Hsieh Chen, Manoj Thakore, Anne De Paepe, Viola Pomozi, Pál T. Szabó, Ludovic Martin, András Váradi and Olivier Le Saux
Pages 1810 - 1820
http://dx.doi.org/10.4161/cc.10.11.15681
Abstract | PDF

Pseudoxanthoma elasticum (PXE) is a heritable disease characterized by calcified elastic fibers in cutaneous, ocular, and vascular tissues. PXE is caused by mutations in ABCC6, which encodes a protein of the ATP-driven organic anion transporter family. The inability of this transporter to secrete its substrate into the circulation is the likely cause of PXE. Vitamin K plays a role in the regulation of mineralization processes as a co-factor in the carboxylation of calcification inhibitors such as Matrix Gla Protein (MGP). Vitamin K precursor or a conjugated form has been proposed as potential substrate(s) for ABCC6. We investigated whether an enriched diet of vitamin K1 or vitamin K2 (MK4) could stop or slow the disease progression in Abcc6^-/- mice. Abcc6^-/- mice were placed on a diet of either vitamin K1 or MK4 at 5 or 100 mg/kg at prenatal, 3 weeks or 3 months of age. Disease progression was quantified by measuring the calcium content of one side of the mouse muzzle skin and histological staining for calcium of the opposing side. Raising the vitamin K1 or MK4 content of the diet increased the concentration of circulating MK4 in the serum. However, this increase did not significantly affect the MGP carboxylation status or reduce its abnormal abundance, the total calcium content or the pathologic calcification in the whiskers of the 3 treatment groups compared to controls. Our findings showed that raising the dietary intake of vitamin K1 or MK4 was not beneficial in the treatment of PXE and suggested that the availability of vitamin K may not be a limiting factor in this pathology.

Open Access Article

SAYP interacts with DHR3 nuclear receptor and participates in ecdysone-dependent transcription regulation

Nadezhda E. Vorobyeva, Julia V. Nikolenko, Alexey N. Krasnov, Julia L. Kuzmina, Vladislav V. Panov, Elena N. Nabirochkina, Sofia G. Georgieva and Yulii V. Shidlovskii
Pages 1821 - 1827
http://dx.doi.org/10.4161/cc.10.11.15727
Abstract | PDF

The role of metazoan coactivator SAYP in nuclear receptor-driven gene activation in the ecdysone cascade of Drosophila is considered. SAYP interacts with DHR3 nuclear receptor and activates the corresponding genes by recruiting the BTFly (Brahma and TFIID) coactivator supercomplex. The knockdown of SAYP leads to a decrease in the level of DHR3-activated transcription. DHR3 and SAYP interact during development and have multiple common targets across the genome.

Open Access Article

A role for GPN-loop GTPase yGPN1 in sister chromatid cohesion

Béatrice Alonso, Guylaine Chaussinand, Jean Armengaud and Christian Godon
Pages 1828 - 1837
http://dx.doi.org/10.4161/cc.10.11.15763
Abstract | PDF

Sister chromatid cohesion and separation, involving the cohesin complex, are crucial for accurate inheritance of genetic information. This complex is also fundamental for efficient post-replicative repair of DNA double-strand breaks and has a key role in the mechanisms of gene transcription control. Cohesin is subjected to many post-translational modifications but the regulators implicated in the control of its activity have been poorly described. Here, we show that the conserved and essential GPN loop GTPase yGPN1 in Saccharomyces cerevisiae is involved in sister chromatid cohesion mechanisms. Based on a sister chromatid cohesion assay, we found that over-expression of the yGPN1 gene promotes sister chromatid separation during anaphase. The sharp slowdown in progression of the S phase observed in cells where yGPN1 expression is down-regulated strongly suggests that yGPN1 is necessary for DNA replication. Moreover, analysis of yGPN1 protein-protein interaction network highlights the yGPN1 links with DNA replication, sister chromatid cohesion/separation and the gene expression process.

Open Access Article

Tensin2 is a novel mediator in thrombopoietin (TPO)-induced cellular proliferation by promoting Akt signaling

Andre Scott Jung, Alexis Kaushansky, Gavin MacBeath and Kenneth Kaushansky
Pages 1838 - 1844
http://dx.doi.org/10.4161/cc.10.11.15776
Abstract | PDF

Thrombopoietin (TPO) and its receptor c-Mpl are essential in the regulation of the hematopoietic stem and progenitors cells as well as for the differentiation of megakaryocytes into mature platelets. Once TPO binds to its receptor, an intracellular signaling process is initiated through Janus kinase (JAK-2)-induced phosphorylation of the c-Mpl intracellular domain. Although some protein mediators that transmit the effects of TPO have been identified, many remain undiscovered. Using an unbiased approach with peptide microarrays that contained virtually every Src Homology (SH)2 and Phosphotyrosine Binding (PTB) domains in the human genome, we discovered a previously unreported interaction between c-Mpl at phospho-Tyrosine631 (pY₆₃₁) and Tensin2, a protein for which limited information is available. Confirming the findings of the microarrays, we discovered that Tensin2 co-precipitates with a pY₆₃₁ bearing peptide. Furthermore, we found that Tensin2 becomes phosphorylated in a TPO dependent manner. The functional consequence of Tensin2 was tested via knockdown of Tensin2, which dramatically decreased TPO-dependent cellular proliferation of UT7-TPO cell line as well as their activation of Akt signaling. These studies affirm the use of these arrays as an unbiased screening tool of protein-protein interactions. We conclude that Tensin2 is an important new mediator in TPO/c-Mpl pathway and has a positive affect on cellular growth, at least in part through its effect on the PI3K/Akt signaling.

Open Access Article

MicroRNA signatures differentiate melanoma subtypes

Elcie Chan, Rajeshvari Patel, Sunitha Nallur, Elena Ratner, Antonella Bacchiocchi, Kathleen Hoyt, Sebastian Szpakowski, Sirie Godshalk, Stephan Ariyan, Mario Sznol, Ruth Halaban, Michael Krauthammer, David Tuck, Frank J. Slack and Joanne Barnes Weidhaas
Pages 1845 - 1852
http://dx.doi.org/10.4161/cc.10.11.15777
Abstract | PDF

Melanoma is an aggressive cancer that is highly resistance to therapies once metastasized. We studied microRNA (miRNA) expression in clinical melanoma subtypes and evaluated different miRNA signatures in the background of gain of function somatic and inherited mutations associated with melanoma. Total RNA from 42 patient derived primary melanoma cell lines and three independent normal primary melanocyte cell cultures was evaluated by miRNA array. MiRNA expression was then analyzed comparing subtypes and additional clinicopathologic criteria including somatic mutations. The prevalence and association of an inherited variant in a miRNA binding site in the 3’UTR of the KRAS oncogene, referred to as the KRAS-variant, was also evaluated. We show that seven miRNAs, miR-142-3p, miR-486, miR-214, miR-218, miR-362, miR-650 and miR-31, were significantly correlated with acral as compared to non-acral melanomas (p < 0.04). In addition, we discovered that the KRAS-variant was enriched in non-acral melanoma (25%), and that miR-137 under expression was significantly associated with melanomas with the KRAS-variant. Our findings indicate that miRNAs are differentially expressed in melanoma subtypes and that their misregulation can be impacted by inherited gene variants, supporting the hypothesis that miRNA misregulation reflects biological differences in melanoma.

Open Access Article

WAVE2 regulates meiotic spindle stability, peripheral positioning and polar body emission in mouse oocytes

Shao-Chen Sun, Yong-Nan Xu, Ying-Hua Li, Seung-Eun Lee, Yong-Xun Jin, Xiang-Shun Cui and Nam-Hyung Kim
Pages 1853 - 1860
http://dx.doi.org/10.4161/cc.10.11.15796
Abstract | PDF

During oocyte meiotic maturation, meiotic spindles form in the central cytoplasm and then migrate to the cortex to extrude a small polar body, forming a highly polarized cell through a process involving actin and actin-related molecules. The mechanisms underlying oocyte polarization are still unclear. The Arp2/3 complex regulates oocyte polarization but it is not known whether the WASP family of proteins, a known regulator of the Arp2/3 complex, is involved in this context. In the present study, the role of WASP family member WAVE2 in mouse oocyte asymmetric division was investigated. (1) WAVE2 mRNA and protein were detected during mouse oocyte meiosis. (2) siRNA-mediated and antibody-mediated disruption of WAVE2 resulted in the failure of chromosome congression, spindle formation, spindle positioning and polar body extrusion. (3) WAVE2 regulated actin-driven chromosome migration since chromosomes were arrested in the central cytoplasm by WAVE2 RNAi in the absence of microtubules. (4) Localization of γ-tubulin and MAPK was disrupted after RNAi, confirming the effect of WAVE2 on spindle formation. (5) Actin cap and cortical granule-free domain (CGFD) formation was also disrupted, further confirming the failure of oocyte polarization. Our data suggest that WAVE2 regulates oocyte polarization by regulating meiotic spindle, peripheral positioning, probably via an actin-mediated pathway, and is involved in polar body emission during mouse oocyte meiotic maturation.

Open Access Article

GM130, a cis-Golgi protein, regulates meiotic spindle assembly and asymmetric division in mouse oocyte

Chun-Hui Zhang, Zhen-Bo Wang, Song Quan, Xin Huang, Jing-Shan Tong, Jun-Yu Ma, Lei Guo, Yanchang Wei, Ying-Chun Ouyang, Yi Hou, Fu-Qi Xing and Qing-Yuan Sun
Pages 1861 - 1870
http://dx.doi.org/10.4161/cc.10.11.15797
Abstract | PDF

GM130, a cis-Golgi protein, plays key roles in various mitotic events, but its function in mammalian oocyte meiosis remains unknown. In this study, we found that GM130 was localized to the spindle poles at both metaphase I and metaphase II stages and associated with the midbody at telophase I stage. The association of GM130 with spindle poles was further confirmed by its colocalization with the centrosome-associated proteins, MEK1/2. By nocodazole treatment, we clarified that GM130 localization was consistently dependent on spindle assembly. Then we investigated the possible function of GM130 by specific morpholino microinjection. This treatment caused abnormal spindle formation, and decreased first polar body extrusion. Our results showed that knockdown of GM130 impaired the localization of MTOCs proteins γ-tubulin and Plk1. Using live cell imaging we observed that depletion of GM130 affected spindle migration and resulted in elongated spindle and large polar body extrusion. We further found that depletion of GM130 blocked p-MEK1/2 accumulation at the spindle poles. And, it was shown that GM130 detached from the spindle poles in oocytes treated with MEK specific inhibitor U0126. Taken together, our results suggested that GM130 regulates microtubule organization and might cooperate with the MAPK pathway to play roles in spindle organization, migration and asymmetric division during mouse oocyte maturation.




LETTERS TO THE EDITOR

Open Access Article

Defect of development of ocular vasculature in Glut1/SLC2A1 knockdown in vivo

Ping-Pin Zheng, Edwin Romme, Peter J. van der Spek, Clemens M.F. Dirven, Rob Willemsen and Johan M. Kros
Pages 1871 - 1872
http://dx.doi.org/10.4161/cc.10.11.15754
Abstract | PDF




Open Access Article

Tumor cell embryonality and the ploidy number 32n: Is it a developmental checkpoint?

Jekaterina Erenpreisa, Mark S. Cragg, Alim P. Anisimov and Timothy M. Illidge
Pages 1873 - 1874
http://dx.doi.org/10.4161/cc.10.11.15755
Abstract | PDF