Blood supply is essential for development and growth of tumors and angiogenesis is the fundamental process of new blood vessel formation from preexisting ones. Angiogenesis is a prognostic indicator for a variety of tumors, and it coincides with increased shedding of neoplastic cells into the circulation and metastasis. Several molecules such as cell surface receptors, growth factors, and enzymes are involved in this process. While antiangiogenic therapy for cancer has been proposed over 20 years ago, it has garnered much controversy in recent years within the scientific community. The complex relationships between the angiogenic signaling cascade and antiangiogenic substances have indicated the angiogenic pathway as a valid target for anticancer drug development and VEGF has become the primary antiangiogenic drug target. This review discusses the basic and clinical perspectives of angiogenesis highlighting the importance of comparative biology in understanding tumor angiogenesis and the integration of these model systems for future drug development. Different forms of neovascularization are known, and the most important are vasculogenesis (defined as r cells) ; angioger cells) ; vasculor cells) ; and vesr cells) . Tumors r cells) .vasculogenesis occurs during embryogenesis, when endothelial cells are born from progenitor cell types [de novo vessel formation by in situ incorporation, differentiation, migration, and/or proliferation of bone marrow-derived endothelial precursor cells [de novo formation of vessels within the tumor. This process involves endothelial differentiation of normal or malignant adult cells bearing stem and progenitor properties leading to generation of endothelial cells with abnormal characteristics. Tumor endothelial cells (TECs) may originate from tissue resident or bone marrow derived stem cells undergoing endothelial differentiation, or from tumor stem cells that can produce both tumor cells and TECs. These mechanisms suggest a contribution of vasculogenesis to neoformed blood vessels in tumors [It has been established that ll types , and alsll types . Vasculoor cells , 9. A wen tumors .Vasculogenic mimicry (VM) was first described in aggressive melanoma by Maniotis et al. [de novo generation of microvascular channels by genetically deregulated, aggressive tumor cells without endothelial cell participation [s et al. , who stas et al. , 11. In cipation . As showcipation .vessel cooption, known also as mosaic vessel formation, in contrast with the prevailing view that most tumors and metastases begin as avascular masses, evidence is presented that a subset of tumors initially grows by coopting existing host vessels. Vessels are surrounded, coopted by tumor cells, and no sprouts are observed [In observed . This coobserved . The rolobserved  in the rAngiogenesis is the most studied form of neovascular growth in cancer. As early as 1971, Judah Folkman proposed the hypothesis that tumor growth is dependent on the formation of new blood vessels. Angiogenesis is essential for the development and evolution of neoplastic disease, as both tumor growth and metastasis require persistent new blood vessels and ongoing angiogenesis is essential for rapid expansion of a tumor mass [mor mass , 14. Angmor mass . In angimor mass . Inductimor mass . In the mor mass .It was originally considered that new blood vessel formation in tumors only occurred after such a tumor became invasive. However, it has been shown that angiogenic growth factors are already present in preinvasive lesions . EpidemiMarked differences are suggested among different types of solid tumors and among species in the promotion of a switch of the angiogenic type, depending on the action of proangiogenic factors or antiangiogenic inhibitors on endothelial or stromal cells that subsequently form capillary “sprouts” , 21, 22.in vivo, requiring more than 24 h, and at least 3–5 days elapse before a new capillary loop becomes perfused and is integrated into the vascular system [Sprouting angiogenesis is the first of two processes characterizing angiogenesis , the secr system , 26. The sprouting of new vessel segments, both in normal organ development and in tumors, follows a well-defined program that starts with degradation of basement membrane on the side of the tumoral postcapillary venule situated close to the angiogenic stimulus ; then thAfter migrating, endothelial cells proliferate during the sprouting process in tumors; they maintain their basal-luminal polarity and form a slit-like lumen that is continuous with the lumen of the so-called mother vessel. Basement membrane material is deposited continuously by the sprout endothelial cells, whereas only the tip of the growing bud is in contact with the collagenous connective tissue matrix . As the In contrast to endothelial sprouting, the other major angiogenic mechanism is intussusceptive microvascular growth, or intussusceptive angiogenesis, which is achieved by intraluminal growth. Intussusceptive angiogenesis has been described in a wide variety of normal and pathological conditions, is faster, and does not depend primarily on endothelial cell proliferation. It occurs within hours or even minutes, does not primarily need endothelial cell proliferation, and can expand to all existing capillary networks , 24. DjoThe concept of network expansion and vessel formation was introduced by Caduff et al.  when theThe most characteristic feature of intussusceptive angiogenesis in tumor tissues is thought to be the development of protrusions or infoldings of the vessel wall within the lumen  Figure . AccordiThe next step is the insertion of connective tissue columns, called tissue pillars, into the lumen between the endothelial contact and the subsequent growth of these pillars, resulting in partitioning of the vessel lumen and the consequent increase in the density of the given capillary network , 30. PilIntussusceptive angiogenesis may have different outcomes depending on the location of the pillars, and different subtypes are named as follows: intussusceptive microvascular growth (IMG), which refers to the expansion of the capillary bed, and intussusceptive arborization (IAR) that describes the formation of the typical vascular tree, while intussusceptive branching remodeling (IBR) denotes vascular remodeling and adaptation to suit local perfusion requirements and includes intussusceptive vascular pruning (IVP). Vascular pruning is an essential adaptive mechanism resulting in the regression of excessive vascular branches and the creation of hierarchical, thermodynamically efficient angioarchitecture . It can In the majority of cancers, vessel growth is not only stimulated, but the new vessels are also abnormal for structure and function. These vessels are tortuous, irregularly shaped, and hyperpermeable . Tumor eTumor blood flow is not only chaotic, but also stagnant in places and, because of continuous vessel remodeling, it is variable between different tumors, between the primary cancer and its metastatic lesions, and within the same tumor . The tumTumor-induced angiogenesis depends on the production of pro-angiogenic growth factors by the tumor cells  and invoThe first angiogenic growth factor, basic fibroblast growth factor (bFGF), belongs to the FGF family. bFGF stimulates all major steps in the angiogenesis cascade and is produced by many cells, among which are macrophages and tumor cells. Although FGF does not have a signal sequence that allows regular secretion, it is released in the extracellular matrix after which angiogenesis is initiated. bFGF is a pleiotropic mitogen for growth and differentiation, known to be involved in endothelial cell proliferation, extracellular matrix degradation, endothelial cell migration, and modulation of junctional adhesion molecules .The angiopoietin family, another important growth factor family in angiogenesis, includes three members (in humans), namely angiopoietin-1 (Ang-1), angiopoietin-2 (Ang-2), and angiopoietin-4 (Ang-4) that all bind to the endothelial tyrosine kinase receptor Tie-2. The most remarkable characteristic of this family is the opposing effect of the different ligands binding to the same receptor. Ang-1 activates the Tie-2 signalling while Ang-2 inhibits this activation. Ang-1 is involved in endothelial cell migration, adhesion, and the recruitment of pericytes and smooth muscle cells, while Ang-2 is vessel destabilizer . Ang-1 iAng-2 is the main angiopoietin ligand in tumors . Its levα, can also be produced by tumor associated macrophages [The role of inflammation and inflammatory cells in tumor development and progression has been increasingly studied. Circulating leukocytes, red blood cells, and platelets participate in angiogenesis by VEGF secretion , 46, androphages . After rrophages , chemokirophages .In the mosaic of cells and substances promoting angiogenesis, an important role is played by cancer stem cells (CSC) . These cVascular endothelial cell growth factor (VEGF) or vascular permeability factor is the most studied in the stimulation of angiogenesis. It increases the expression of MMPs and plasminogen activators for the degradation of the extracellular matrix and subsequently endothelial cell migration .VEGF denotes a family of five related mammalian growth factors: VEGFA (the prototype), VEGFB, VEGFC, VEGFD, and PLGF  . The rolSquamous cell carcinoma (SCC) is the second most common skin tumor in humans and dogs  followinα [Angiogenesis is essential for the growth and metastases of many malignant tumors including cutaneous squamous cell carcinoma. Several studies have shown that VEGF plays an important role in cutaneous malignancies. In human skin VEGF is expressed at low levels within the normal epidermis. The production of VEGF by normal keratinocytes can be induced by many stimuli including the tumor promoter 12-O-tetradecanoylphorbol-13 acetate (TPA), UV radiation, keratinocyte growth factor, hypoxia, and transforming growth factor-α –72. The α –75. In pα . Furtherα .VEGF is also expressed in the normal canine epidermis . Only twSeveral experimental animal models have been used to study SCC. These include mice xenograft models, chemically induced SCC mice models, and genetically engineered mice models –82. In tIn dogs with cutaneous SCCs, one study reported a significant difference in vascular density among different histological grades with higher grade tumors having higher vascular density . ContrarAn autocrine pathway involves the secretion of a ligand which, consequently, engages a specific receptor on the same cell surface and results in a signaling response that affects cell function . It is nin vitro and in vivo studies are needed to examine the autocrine role of VEGF and the roles of its receptors in canine cutaneous SCC.In dogs VEGFR-2 was detected in a few canine tumors including cutaneous SCC, simple mammary gland adenocarcinoma, fibrosarcoma , 60, 79,Mammary tumor growth forces cells to face the same increasing demand for oxygen, glucose, amino acids, and waste exchange as do normal mammary cells during development, different oestrus phases, and lactation . As in nTumor-associated angiogenesis and lymphangiogenesis, the process whereby lymphatic vessels are generated, are crucial in mammary tumor progression. Tumor vasculature, together with the lymphatic system, is the main route through which BMDCs (bone marrow-derived dendritic cells) infiltrate the tumors and tumor cells themselves are able to evade from primary sites and systemically disseminate .α subunits. In the absence of oxygen, the α subunits are not hydroxylated and hence are no longer targeted for degradation by the proteosome. Stabilized HIF-1 α upregulates several genes in order to promote survival under hypoxic conditions. Among these is the VEGF. Remarkably, in a subsequent work, de Oliveira et al. [The VEGF and its receptors VEGFR1 and VEGFR2 are leading players in angiogenesis . The lita et al.  have obsa et al. , 106.α target genes interestingly expressed in CMT are galectin-1 and galectin-3. Galectin-1 and galectin-3 are members of galectins, a carbohydrate-binding family of proteins. These are involved in cell survival to anoikis, cell-cell, and cell-ECM (extra-cellular matrix) adhesion and are also crucial players in angiogenesis. Galectin-3 is known to be chemoattractant to endothelial cells and to stimulate neovascularization in vivo, therefore contributing to tumor angiogenesis, an essential step for metastatic spreading [Other HIF-1 preading . Galectipreading . Tumor cpreading . This gapreading . Galectipreading .β (1-O) galactosyltransferase that modifies collagen [ECM is deposited to form a basement membrane to surround the blood vessels during tumor angiogenesis. Importantly, however, the basement membrane of the tumor vasculature is more porous and leaky than normal , 113, whcollagen . In paracollagen  and othecollagen . Moreovecollagen . It is ocollagen , 120. MMcollagen . Stromalcollagen .The serine protease urokinase-type plasminogen activator (uPA) involved in the control of extracellular matrix turnover is involved in vascular remodeling and was also shown to be implicated in the stimulation of angiogenesis . MalignaAntiangiogenic therapy for breast cancer has raised a great deal of controversy within the scientific community over the last years. For instance, bevacizumab blocks VEGF, its association with paclitaxel doubles the time of human breast cancer progression although not affecting the patients' overall survival. Therefore there is resistance to antiangiogenic therapy. It is now understood that this type of therapy induces hypoxia and that hypoxia-dependent pathways lead to decreased cell death . The antIn conclusion, there are several interdependent pathways driving angiogenesis in cancer in general and in CMT in particular. This knowledge is of the utmost importance when considering future antiangiogenic therapies for CMT management in veterinary oncology.Preclinical drug studies theoretically should define whether a particular potential therapy has activity against tumors with the appropriate drug target, and whether or not activity observed in these models can be extrapolated to humans. The interpretation of data from preclinical studies is often perceived as a bottleneck in drug development; thus, the selection of appropriate preclinical angiogenesis models with reproducible activity can lead to subsequent success in the clinic.in vitro; vessel outgrowth from organ cultures such as the ex vivo rat aortic ring assay; and in vivo assays such as chick chorioallantoic membrane (CAM), zebrafish, sponge implantation, corneal, dorsal air sac, chamber, and tumor angiogenesis models .Rip1-Tag2 tumor model was characterized as highly angiogenic [in vivo. While many of these models show single-agent activity, predicting the clinical activity and efficacy of antiangiogenics from animal data has proven challenging since the translation of the single-agent activity has not been seen in clinical trials targeting advanced metastatic disease with the exception of renal cell, hepatocellular, and ovarian carcinoma [Rip1-Tag2 model as a single agent [With respect to animal models, two of the most commonly used for preclinical testing are tumor xenograft models (cell line xenograft or patient-derived xenograft), which involves transplantation of human or syngenic mouse tumor cells either subcutaneously or at a relevant orthotopic site in immunocompromised mice, and genetically manipulated mice that develop spontaneous lesions ), which involves genetic engineering to introduce genomic alterations that drive cancers of interest, ideally confined to the relevant tissue. When choosing a mouse model for preclinical testing, consideration is given to the tumor microenvironment targeted by the drug, whether the drug is intended for early-stage versus late-stage therapy and whether modeling the metastatic spread is necessary. GEMMs have been especially effective for studying the early events in tumorigenesis; however, they have not replaced xenograft models as reliable clinically predictive tools for examining the efficacy of therapeutic approaches to treat metastatic disease. After the giogenic , this anarcinoma . For exale agent ; howeverle agent . Early ple agent . Other ale agent . While tRip1-Tag2 model over time suggests that rational trial design combined with more specific drug targets can improve the predictive power of preclinical studies. As advances in cancer genomics lead to more pharmacogenetics testing, preclinical model systems need to continually be refined to define and validate biomarkers to aid in patient selection and identify antiangiogenic predictive markers of response and resistance. Careful extrapolation of preclinical data in an era of increasingly specific agents, more sophisticated animal models, and increased understanding of the molecular drivers of cancer is required. Successful translation of preclinical data to the clinic has been demonstrated with the approval of several antiangiogenic agents over the last decade.Indeed experience with experimental therapeutics in the The angiogenic pathway has been a valid target for anticancer drug development and VEGF has become the primary antiangiogenic drug target. Investigation of hundreds of potential angiogenesis inhibitors resulted in the approval of bevacizumab  by the U.S. Food and Drug Administration as the first antiangiogenic agent. Bevacizumab is approved in combination with chemotherapy or cytokine therapy for advanced metastatic cancers including colorectal cancer (CRC), nonsquamous non-small-cell lung cancer (NSCLC), and renal cell cancer (RCC). Bevacizumab monotherapy is approved for recurrent glioblastoma. Subsequent antiangiogenic agent FDA approvals include the multitargeted pan-VEGF receptor (VEGFR) tyrosine kinase inhibitors (TKIs) that target different parts of the angiogenic pathway: sorafenib for the treatment of advanced RCC and unresectable hepatocellular carcinoma; sunitinib for metastatic RCC, gastrointestinal stromal tumor, and advanced pancreatic neuroendocrine tumors; pazopanib for metastatic RCC and advanced soft tissue sarcoma (with orphan drug status designation for this indication); vandetanib for advanced medullary thyroid cancer; and axitinib for advanced RCC. More recently, ziv-aflibercept was approved for use in combination with chemotherapy for metastatic CRC. Ziv-aflibercept, a protein comprised of segments of the extracellular domains of human VEGFR1 and VEGFR2 fused to the constant region (Fc) of human immunoglobulin G (IgG1), functions as a soluble decoy receptor that neutralizes VEGFs.In general, these VEGF/VEGFR inhibitors provide modest clinical benefit in terms of prolonging progression-free survival (PFS) or overall survival (OS) of cancer patients with a median duration of response in weeks to months. Moreover, clinical experience with bevacizumab has proven to be rather perplexing with improvement in PFS but little to no benefit in OS. Of the 16 pivotal phase III trials conducted with bevacizumab in solid tumors only three were positive for OS first-line mCRC , second-Tumor angiogenesis is a highly complex process involving multiple growth factors and their receptor signaling pathways as well as key cellular players in the microenvironment such as pericytes, endothelial cells, and bone marrow-derived precursors. Based on current evidence, effective therapy will probably rely on a combination approach that involves simultaneous targeting of multiple angiogenic pathways coupled with cellular targets in the microenvironment. Whether other targeted agents exhibit beneficial effects when combined with VEGF inhibitors remains to be investigated; however, the use of targeted agents combined with conventional therapy is intended to increase tumor response without significant increases in toxicity.A number of studies have shown that antiangiogenic agents in combination with chemotherapy or radiotherapy result in additive or synergistic effects. Several models have been proposed to explain the mechanisms responsible for the chemosensitizing effects of antiangiogenic therapy . One hypAntiangiogenic therapy has fostered the quest for surrogate markers of response or resistance to assess and monitor the clinical effects of these inhibitors. The lack of validated biomarkers to date remains a challenge, thereby limiting the successful use of antiangiogenic therapy in the clinic. Surrogate markers are important for guiding the clinical development of these agents and to select patients most likely to benefit from this therapeutic approach. A number of candidate biomarkers including genetic, tissue, imaging, and circulating biomarkers are emerging that need to be prospectively validated , 147. SeRecent research efforts have focused on identifying genetic and toxicity biomarkers to predict which patients will benefit from anti-VEGF/VEGFR therapy and identify patients at risk of adverse events. The existence of VEGF single nucleotide polymorphisms (SNPs) and their association with clinical outcome may be predictive markers of response to bevacizumab. In a metastatic breast cancer study involving patients being treated with paclitaxel and bevacizumab , SNP analysis demonstrated that the VEGF-2578 AA and VEGF-1154 AA genotypes predicted an improved median overall survival, whereas the VEGF-634 CC and VEGF-1498 TT variants predicted protection from grades 3-4 hypertension in the combination treatment arm [α, and viable CECs increased when tumors escaped treatment [Additional biomarkers of response to antiangiogenic therapy include measuring circulating elevated VEGF and placental growth factor levels , while breatment . If valiThe clinical efficacy of angiogenesis inhibitors has recently been met with numerous phase III failures that showed modest survival benefits because tumors elicit evasive resistance . UnderstRecent studies report that antiangiogenic therapies induce primary tumor shrinkage and inhibit tumor progression but can also initiate mechanisms that promote tumor invasiveness and metastasis , 162. Th


Organelle genomes show remarkable variation in architecture and coding content, yet their nucleotide composition is relatively unvarying across the eukaryotic domain, with most having a high adenine and thymine (AT) content. Recent studies, however, have uncovered guanine and cytosine (GC)-rich mitochondrial and plastid genomes. These sequences come from a small but eclectic list of species, including certain green plants and animals. Here, I review GC-rich organelle DNAs and the insights they have provided into the evolution of nucleotide landscape. I emphasize that GC-biased mitochondrial and plastid DNAs are more widespread than once thought, sometimes occurring together in the same species, and suggest that the forces biasing their nucleotide content can differ both among and within lineages, and may be associated with specific genome architectural features and life history traits. Mitochondria and plastids are the products of ancient endosymbiotic events, involving a proteobacterium and a cyanobacterium, respectively , conformations (circular or linear), chromosome numbers (monomeric to highly fragmented), compactnesses (<10 to >90% non-coding DNA), and gene repertoires (<5 to >250 genes). Moreover, many organelle genomes use a non-standard genetic code -rich organelle DNAs do exist  and the large subunit of the plastid protein Rubisco (rbcL), have proven to be good predictors of overall organelle DNA nucleotide content , and organelle gene sequencing indicate that Coccomyxa chodatii and Coccomyxa rayssiae have GC-rich organelle DNAs as well  and a ptDNA (55%) belong to the seedless vascular plants s Smith, . Plastids Smith, . Other lChirocentrus dorab (53%), the Pacific porthole fish Diplophos taenia (52%), and the beaked salmon Gonorynchus greyi  or environments with little UV light  reaction center subunit N (psaN), which codes for a protein involved in the docking of plastocyanin. Interestingly, psaN-lacking strains of Arabidopsis, although maintaining a functional PSI complex, have reduced rates of electron transfer from plastocyanin to PSI (Haldrup et al., C. subellipsoidea the unique loss of psaN may lead to reduced ROS formation (Blanc et al., Although data are limited, organelle DNA GC enrichment does not appear to be associated with nuclear DNA GC enrichment: Selaginella, Candida, and Chlamydomonadalean algae, and the availability of complete organelle and nuclear genome sequences from these groups provide promising avenues for future studies on nucleotide composition. I predict that in the years to come GC-rich organelle DNAs will help further our understanding of nucleotide composition and its relationship with other aspects of genome architecture.Organelle genomes are models for studying the evolution of genome size and structure (Nosek and Tomáska, The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Recent studies have shown that mouse embryonic stem cells (mESCs) rely on a distinctive genome caretaking network. In this review, we will discuss how mESCs functionally respond to DNA damage and describe several modifications in mESC DNA damage response, which accommodate dynamic cycling and preservation of genetic information. Subsequently, we will discuss how the transition from mESCs to adult stem/progenitor cells can be involved in the decline of tissue integrity and function in the elderly. Embryonic stem cells (ESCs) are dynamically cycling cells derived from the blastocyst inner cell mass, are pluripotent and have a virtually unlimited self-renewal potential .Similarly to any other cell in the organism, ESCs must constantly contend with genotoxic stress arising from both exogenous environmental stimuli and endogenous chemical reactions, such as reactive oxygen species (ROS) generated by cellular metabolism .ESCs are critical for embryo formation and, upon differentiation, they ensure the lifetime maintenance of any tissues. Any misrepair of DNA damage in ESCs can be transmitted to their differentiated daughter cells, thereby compromising tissue integrity and function. In order to prevent acquisition of mutations that would be transmitted to multiple cell lineages, ESCs exploit several modifications in DNA damage response, which accommodate dynamic cycling and preservation of genetic information ,4.An overview of the genome caretaking network of mESCs is the purpose of the first part of this review; in the second part, the possible pathophysiological consequences of misrepairing events are discussed.As a first mechanism contributing to preservation of genomic integrity, mESCs are hypersensitive to DNA damage and readily undergo either apoptosis or differentiation, thus removing damaged cells from the pluripotent pool . Mitoticet al. found that p53 binds to the promoter of Nanog and suppresses its transcription in mESCs [Notably, the master apoptotic mediator p53 is only rarely involved ESC death. An emerging idea in the field of ESC biology, instead, is that p53 is a major driving force for the differentiation of ESCs, providing an alternative mechanism by which to eliminate damaged cells from the pluripotent stem cell pool. The connection between p53 and differentiation became particularly evident when Lin in mESCs . The homin mESCs –34. Suppin mESCs . Like Nain mESCs ,35.A second, complementary mechanism is the propensity of ESCs to have effectual processes for DNA repair, through upregulation of several DNA damage repair pathways .The base excision repair (BER) pathway repairs small base modifications, such as oxidative and alkylation damage and DNA single-strand breaks . Geneticin vitro, when compared to mEFs [in vitro by OGG1, a DNA glycosylase involved in BER, was measured using untreated extracellular extracts, no major differences in OGG1 activity were observed between hESCs and hEFs, and when hESCs and hEFs were treated with H2O2, the levels of both OGG1 and APE2 proteins were induced to barely higher levels after treatment in the hESCs [A limited number of studies have examined BER in ESCs, but it has been observed that basal levels of proteins involved in BER are significantly elevated in mESCs compared with mEFs . Coupled to mEFs . In anot to mEFs . The mRN to mEFs . Howeverhe hESCs .Double strand breaks (DSBs) in DNA are the most toxic type of DNA lesions a cell encounters . DefectsDSB repair uses non-homologous end joining (NHEJ) or homologous recombination (HR) pathways –44. HR uet al. demonstrated that HR  and NHEJ (Ku70/Ku80) proteins are consistently elevated in mESCs, compared to mEFs, and when mESCs were functionally tested for the preferred pathway of DSB repair, they predominantly utilized the high fidelity homology-mediated repair pathway [trans retinoic acid, DNA ligase IV expression levels increase, and NHEJ is reactivated and becomes the predominant pathway for repair of DSBs [There are a number of studies that compare DSB repair mechanisms between ESCs and differentiated cells . Initial pathway . In cont of DSBs . HR appe of DSBs . This su of DSBs . In addi of DSBs .Recently, it has been demonstrated how the histone H2AX phosphorylation (γH2AX), the earliest indicator of DNA DSBs, is expressed at a high basal level in mouse pluripotent stem cells. Interestingly, this basal γH2AX is not linked with the canonical DSB response pathway , but is Mismatch repair (MMR) corrects base-base mismatches and insertion/deletion loops formed by misincorporation or strand slippage during DNA replication ,53. Muta−6 in wild-type mESCs to 10−4 in mESCs lacking MSH2, a critical recognition component of the MMR pathway [Analysis of mutation frequencies in cells proficient or deficient for components of the MMR pathway revealed a key role for MMR in the maintenance of mESC genomes. As an example, the frequency of spontaneous mutation increased from 10 pathway . Many pr pathway . When a  pathway  was used pathway .N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) between undifferentiated ESCs, ESCs whose differentiation was induced with retinoic acid, 3T3 cells and mEFs [In another work, MMR has been compared after treatment with the methylating agent and mEFs . A two-fand mEFs , indicatThe nucleotide excision repair (NER) pathway repairs bulky, helix-distorting DNA lesions, particularly DNA damage resulting from UV radiation damage ,59. Defeet al. showed that repair of cyclobutane pyrimidine dimers (CPD) in transcribed genes could not be detected in mESCs, whereas the removal of (6-4) photoproducts (6-4PP) was incomplete, already reaching its maximum (30%) 4 h after irradiation. Measurements of repair replication revealed a saturation of NER activity at UV doses >5 J/m2, while at lower doses, the repair kinetics were similar to those in mEFs. Possibly, to avoid the accumulation of mutated cells, ESCs rely on the induction of a strong apoptotic response with a simultaneous shutting down of NER activity [When tested for their capacities to repair damage induced by UV light, mESCs and mEFs behave differently. Many years ago, Pedersen and Cleaver demonstrated that cells of the blastocyst inner cell mass, from which ESCs are isolated, underwent only minimal unscheduled DNA synthesis following UV irradiation compared with other cells of the blastocyst . It was activity .Endogenous factors associated with cell division and metabolism are attributed to the major sources of DNA damage in stem cells. Among the most significant endogenous mutagens are reactive oxygen species (ROS), including superoxide anions, hydrogen peroxide, organic peroxides and hydroxyl radicals. Normal metabolic processes, such as oxidative phosphorylation and nucleotide catabolism, are responsible for continuous ROS generation in these cells. An additional mechanism of ROS production relies on specific plasma membrane oxidases acting in response to growth factors or cytokines. If not inactivated in a timely manner by cellular anti-oxidative systems, ROS may cause DNA damage.Numerous evidences suggests that ESCs possess very efficient antioxidant defense pathways . mESCs w2 culture. On the other hand, excessive suppression of ROS to sub-physiological levels downregulates DNA repair pathways, thereby contributing to genomic instability. These results suggest a new concept that optimal “physiological” levels of ROS are required for activation of DNA repair pathways and maintenance of genomic stability in stem cells [An interesting biphasic relationship between the net intracellular levels of ROS and genomic stability in ESCs has been described recently. It was found that mild ROS suppression obtained by culturing ESCs in physiological oxygen content (5%) decreased karyotypic abnormalities if compared to 20% oxygen cultures, while profound ROS suppression obtained by supplementation with antioxidants paradoxically enhanced genomic alterations . Oxidatiem cells .et al. [−4 in mEFs to 10−6 in mESCs). Most of the observed mutational events involved loss of heterozygosity (LOH) due to mitotic recombination, with point mutations and deletions making up the remainder. When spontaneous mutation frequencies at the Hprt gene was assessed through a similar approach, spontaneous mutation in ESCs was undetectable (below 10−8), whereas mutation frequency in mEFs was in the range of 10−5. In this case, there was no contribution of LOH to the observed mutation frequencies, as Hprt is located on the X chromosome and the cells used in this study were derived from male embryos. This difference probably accounts for much of the discrepancies observed in mutation frequency between the two loci, Aprt and Hprt. Other reports, however, do not support the evidence that mESCs display lower mutation frequencies. For example, mutation frequencies at the Rosa26 locus turned out to be similar between mESCs and mEFs (about 10−4) using fluorescent protein reporter-based technologies [et al. found that brief exposures to nontoxic levels of several carcinogens stimulated genome-wide LOH, with maximum per-gene frequencies approaching one percent [Suppression of mutagenesis in mESCs might represent another mechanism that contributes to preservation of genomic integrity . Throughet al.  demonstrnologies ,66. It i percent . Due to ESCs are critical for embryo formation and, upon differentiation, they ensure the lifetime maintenance of any tissues. Any misrepair of DNA damage can be transmitted to their differentiated daughter cells, thereby compromising tissue integrity and function. Mutations that diminish the renewal and/or differentiation potential of ESCs might result in tissue atrophy and aging phenotypes, whereas mutations providing a selective advantage to the mutated cells can lead to cancer development .Aging is a complex biological process resulting from gradual changes in the phenotype and functions of cells. The age-associated pathophysiological changes usually lead to an imbalance that favors the mechanisms of replicative senescence and apoptosis rather than DNA repair mechanisms (reviewed in ). HoweveThus, it is the aging of adult stem/progenitor cells that is actually believed to be central to the decline of tissue integrity and function in the elderly .As described, ESCs exhibit an unlimited self-renewal capacity and a substantial resistance to genomic instability and malignant transformation. During early development, ESCs differentiate into cells that form all the tissues of the future organism, including adult stem/progenitor cells. In this process, cells lose their pluripotent potential and unlimited proliferating capacity. Transition from ESCs to adult stem/progenitor cells may have involved the evolutionary trade-off: senescence prevents cancer, but may promote aging .+/− mice exhibited increased activity [Genetic alterations accumulated in adult stem/progenitor cells during chronological aging may result in their loss, or acquisition of a dysfunctional behavior –79, inclactivity . In addiactivity ,89. Inteactivity ,88,90–92Cancer is thought to originate in stem cells through the accumulation of multiple mutations, some of which result in a loss of heterozygosity (LOH). It has been demonstrated that exposure of mESCs to nontoxic amounts of mutagens triggers a marked increase in the frequency of LOH . The autDNA damage and its consequences in ESCs do not affect fitness immediately, since stem cells are not involved in carrying out functions specific for target tissues. More likely, mutations or epimutations accumulated in the ESCs as a result of genome maintenance errors are transmitted to daughter cells that become the newly differentiated cells, and this impacts tissue functionality by adversely affecting the transcriptome. The increasing load of mutations/epimutations in the proliferation-capable ESCs increases the risk of neoplastic transformation, the price for extended longevity.in vitro and recapitulated the morphological and phenotypic characteristics of the original tumors in animal models in vivo [in vitro culture of adult stem/progenitor cells promoted the appearance of a transformed phenotype. Miura et al. obtained cancer progenitor cells from bone marrow derived mesenchymal stem cells after long-term culture [in vivo. The mechanism of transformation was associated with accumulated chromosomal abnormalities and increased c-Myc expression [et al. The concurrent emergence of a high level of genomic instability and a spontaneously immortalized clone was observed, which developed into a cell line with features of cancer stem cells, including the capacity to form CD133 positive neurospheres and development into intracranial tumors [Evidence from a number of experiments has revealed that the occurrence of genetic alterations in adult stem/progenitor cells may result in their malignant transformation into tumorigenic cells also designated as cancer-initiating cells ,101. The in vivo ,106–110. culture , and thepression , suggestl tumors .Progression of cancer is normally accompanied by an accumulation of additional transforming mutations in cancer-initiating cells and their progenies concomitant with the changes in their microenvironment conferring to them a more aggressive phenotype ,113–115.Altogether, these data indicate that age-related loss of stem cells, age-related stem cell dysfunction and age-related neoplastic transformation of stem cells could all be adverse consequences of the adult stem/progenitor cell response to DNA damage.ESCs need to maintain genomic integrity so that they can retain the ability to differentiate into multiple cell types without propagating DNA errors. Several lines of evidence suggest that the genome caretaking network of mESCs is a peculiar one.Different strategies are concurrently employed to maintain a stable genome and to prevent passing of genomic aberrations on to the progeny. Loss of damaged self-renewing cells due to hypersensitivity to DNA damage appears to be the first strategy that effectively maintains the proliferating cell population genetically pristine. The absence of a G1/S cell cycle arrest promotes the apoptotic response of damaged cells before DNA changes can be fixed in the form of mutation during the S-phase, while p53-mediated differentiation provides an alternative mechanism of elimination of damaged cells from the pluripotent stem cell pool. In addition, several studies have suggested that some DNA repair pathways and antioxidant defense are superior in ESCs compared with various differentiated cells. ESCs express a higher level of DNA repair proteins and exhibit enhanced repair of multiple types of DNA damage; on the other hand, an efficient oxidative damage sensor system directs the ESC fate from repair to apoptosis depending on the levels of intracellular ROS. Finally, suppression of mutagenesis in ESCs might represent another putative strategy of genome surveillance, as distinct differences in mutation frequencies between ESCs and somatic cells have been reported for some loci; however, due to contrasting literature findings, this last issue awaits confirmation.While ESCs rely on several modifications in DNA damage response to accommodate dynamic cycling and preservation of genetic information, the adult stem/progenitor cell compartment that emerges after their differentiation may not. Mutations that diminish the renewal and/or differentiation potential of adult stem/progenitor cells can result in tissue atrophy and aging phenotypes, whereas mutations providing a selective advantage to the mutated cells can lead to cancer development.


Typical problems in bioinformatics involve large discrete datasets. Therefore, in order to apply statistical methods in such domains, it is important to develop efficient algorithms suitable for discrete data. The minimum description length (MDL) principle is a theoretically well-founded, general framework for performing statistical inference. The mathematical formalization of MDL is based on the normalized maximum likelihood (NML) distribution, which has several desirable theoretical properties. In the case of discrete data, straightforward computation of the NML distribution requires exponential time with respect to the sample size, since the definition involves a sum over all the possible data samples of a fixed size. In this paper, we first review some existing algorithms for efficient NML computation in the case of multinomial and naive Bayes model families. Then we proceed by extending these algorithms to more complex, tree-structured Bayesian networks.


Ultrasound is a safe, portable, relatively inexpensive, and easily accessible imaging modality, making it a useful diagnostic and monitoring tool in medicine. Anesthesiologists encounter a variety of emergent situations and may benefit from the application of such a rapid and accurate diagnostic tool in their routine practice. This paper reviews current and potential applications of ultrasound in anesthesiology in order to encourage anesthesiologists to learn and use this useful tool as an adjunct to physical examination. Ultrasound-guided peripheral nerve blockade and vascular access represent the most popular ultrasound applications in anesthesiology. Ultrasound has recently started to substitute for CT scans and fluoroscopy in many pain treatment procedures. Although the application of airway ultrasound is still limited, it has a promising future. Lung ultrasound is a well-established field in point-of-care medicine, and it could have a great impact if utilized in our ORs, as it may help in rapid and accurate diagnosis in many emergent situations. Optic nerve sheath diameter (ONSD) measurement and transcranial color coded duplex (TCCD) are relatively new neuroimaging modalities, which assess intracranial pressure and cerebral blood flow. Gastric ultrasound can be used for assessment of gastric content and diagnosis of full stomach. Focused transthoracic (TTE) and transesophageal (TEE) echocardiography facilitate the assessment of left and right ventricular function, cardiac valve abnormalities, and volume status as well as guiding cardiac resuscitation. Thus, there are multiple potential areas where ultrasound can play a significant role in guiding otherwise blind and invasive interventions, diagnosing critical conditions, and assessing for possible anatomic variations that may lead to plan modification. We suggest that ultrasound training should be part of any anesthesiology training program curriculum. Anesthesiologists require quick and accurate diagnostic tools for the effective management of emergencies. Ultrasound (US) is a safe, easily accessible point-of-care imaging modality that is being increasingly adopted in modern anesthesiology practice. As physician-performed ultrasound becomes more practical and practiced, it is important to assure that anesthesiologists are aware of the expanding applications of this technology and the status of its use. Current and potential future applications of US in anesthesiology are summarized as follows:This paper highlights current and potential future applications of ultrasound in the field of anesthesiology. Our objective is to increase awareness of the current benefits and limitations of selected ultrasound applications that may be relevant to anesthesiologists. We aim to encourage practitioners to acquire appropriate training that will allow them to apply well-established ultrasound techniques in their routine practice, to assure that they are aware of constraints and limitations in various settings, and to remain alert for the development of ultrasound techniques that are a focus of ongoing research.Ultrasound (“extrasound”) refers to the use of sound waves , which are above the frequency of those sound waves that can be heard by the human ear . The concept of ultrasound is explained in Several basic and advanced modes of ultrasound imaging exist, but B-mode, M-mode, and color-Doppler are those most commonly used in anesthesiology . B-mode Doppler modes detect frequency shifts that are created by sound reflections of a moving target (Doppler effect). It uses the change in pitch of the sound waves to provide information about blood flow . Three DUltrasound-guided peripheral nerve blockade is perhaps the most popular ultrasound application used by anesthesiologists. It might be the gold standard for regional anesthesia; it allows anesthesiologists to perform regional anesthesia more accurately, and it expands the ability to block smaller nerves and those in more difficult anatomic locations. Ultrasound-guided peripheral nerve blocks offer the following advantages: direct observation of the nerves and surrounding structures , thus decreasing complications , and direct observation of local anesthetic spread. The more accurate deposition leads to faster onset and longer duration of block, improves block quality, and allows dose reduction of local anesthetics –9. It haIn children, ultrasound guidance carries similar advantages as for adults and has become more popular recently. However, there is still a shortage of clinical studies comparing the advantages of ultrasound guidance over traditional techniques (nerve stimulation), particularly with respect to safety; ilioinguinal blocks may be an exception. Further studies are warranted , 11. neuraxial blocks;nerve root blocks ;stellate ganglion block;lumber transforaminal injections for radicular pain;facet joint block;epidural blood patch;intra-articular joint injections;ultrasound guidance for peripheral nerve stimulator implantation;interventional procedures for patients with chronic pelvic pain .Ultrasound has become a commonly used modality in the performance of chronic pain interventions and has begun to substitute for CT scans and fluoroscopy in many chronic pain procedures. It allows direct visualization of tissue structure while allowing real-time guidance of needle placement and medication administration. The following list summarizes some of current and potential applications of ultrasound in neuraxial and chronic pain procedures:Ultrasound can aid in neuraxial blocks in two ways: (1) ultrasound-assisted neuraxial technique and (2) real-time ultrasound-guided neuraxial technique. It helps in identification of landmarks and midline structures, estimating epidural space depth, and facilitating epidural catheter insertion . ImproveKarmakar et al.  in 14 ouWillschke et al.  evaluateNerve root blocks under US guidance can be as effective as those placed using a fluoroscopy-guided method . US faciUltrasound-guided facet joint block is another application that provides a minimal invasive procedure, with less time consumed, lower expenses, and fewer complications, in comparison with fluoroscopy-guided technique , 20.Ultrasound-guided epidural blood patch allows confirmation of proper placement of injectate into the epidural space . ClendenUltrasound guidance of intra-articular joint injections (mainly the knee joint) improves needle placement and injection accuracy in comparison with palpation/anatomic landmark techniques, which improves patient-reported clinical outcomes and cost-effectiveness , 24. UltAdvantages of ultrasound-guided central venous catheterization include identification of the vein, detection of variable anatomy and intravascular thrombi, and avoidance of inadvertent arterial puncture. It is safer and less time consuming than the traditional landmark technique , 27. It Ultrasound arterial cannulation helps in reducing the number of attempts, shortening the procedure time, and increasing the success rate, even in children . A lineaThere is a marked reduction in complication rates after implementation of US-guided central venous cannulation approaches. Although some complications still happen, rates of 4.6% have been reported, comparing with 10.5% when using landmark technique, which represents an absolute risk reduction of 5.9% (95% CI 0.5–11.3%) . Most ofPeripheral vascular access in pediatrics can be very challenging especially in small, obese, or dehydrated children or in those with previously failed venipuncture. Studies showed that ultrasound-guided peripheral vascular access may improve the success rate of difficult vascular access when performed by well-trained physicians . RecentlAirway ultrasound can visualize and assess the tongue, oropharynx, hypopharynx, epiglottis, larynx, vocal cords, cricothyroid membrane, cricoid cartilage, trachea, and cervical esophagus , 35, 36.prediction of difficult airway;confirmation of proper endotracheal tube placement and ventilation;evaluation of airway pathologies that may affect the choice of airway management , or mandate urgent securing of airway ;prediction of obstructive sleep apnea;prediction of size of endotracheal, endobronchial, and tracheostomy tubes;airway related nerve blocks;assessing and guidance for proper percutaneous dilatational tracheostomy (PDT);prediction of successful extubation:prediction of airway edema;assessment of the diaphragm movement;assessment of vocal cord movements.Superficial structures can be scanned by linear high-frequency transducer, while deep structures are better visualized in sagittal and parasagittal views using the curved low-frequency transducer . Current Prediction of the difficult airway is a research area of great interest, with promising preliminary findings. Adhikari et al.  recentlyConfirmation of proper endotracheal tube placement can be done by two methods, direct and indirect , 40. OnePreliminary results of bedside ultrasonography show that it is a safe and effective tool to diagnose acute epiglottitis. In two recent studies, Hung et al.  visualizDiagnosis and prediction of obstructive sleep apnea is a challenge, as many patients come for surgery undiagnosed. Lahav et al.  found thUltrasonography has been used successfully to guide the choice of the appropriate size of endotracheal tube , 47, traPercutaneous dilatational tracheostomy (PDT) is a frequent procedure in intensive care units , with poPrediction of successful extubation is another challenge, especially in long-term intubated patients and in those who have a high risk of airway edema and vocal cord injuries . A pilot study by Ding et al.  reportedLaryngeal ultrasound  to assesdiagnosis of pneumothorax;diagnosis of interstitial syndrome;diagnosis and differentiation of underlying cause of Pleural effusion, and selecting the optimal puncture site for pleurocentesis;diagnosis of pulmonary consolidation and pneumonia;diagnosis of atelectasisdiagnosis of pulmonary edema and differentiate it from acute respiratory distress syndrome (ARDS); diagnosis of pulmonary embolism;monitoring of lung disease ; optimizing mechanical ventilation.In a number of emergency situations, hypoxia will require urgent and appropriate diagnosis for its management. Pneumothorax, pulmonary edema, pulmonary embolism, and ARDS are situations where ultrasound can be an important tool for diagnosis (as shown in the following list). Lichtenstein et al.  introducA high frequency (7.5 to 10 MHz) transducer is an appropriate choice for detecting pleural line abnormalities, while lower frequency (3.5 MHz) convex and microconvex transducers can be used to diagnose pleural effusions and lung parenchymal abnormalities. [“Lung sliding” signs are sliding of visceral and parietal layers of pleura with respiration. Seashore sign is a complex picture of parallel lines signifying the static thoracic wall and sandy “granulous” pattern, which reflect the normal pulmonary parenchyma.A-lines are a basic artifact of normally aerated lung. B-lines represent discrete laser-like vertical hyperechoic lines that arise from the pleural line and extend to the bottom of the screen. These lines are consistent with interlobular pulmonary edema and can be found in both ARDS and cardiogenic pulmonary edema. Dynamic and static air bronchograms which consist of hyperechoic punctiform elements within the lung parenchyma can be used to diagnose consolidation and atelectasis, respectively. Lung pulse is an early and dynamic diagnostic sign of complete atelectasis, in which US perceives the vibrations of heart activity, along with the absence of lung sliding .The International Liaison Committee on Lung Ultrasound (ILC-LUS) has recommended the following signs for the detection of various lung abnormalities [malities .(i) Pneumothorax Figures . Absence of lung sliding, presence of lung point(s), absence of B-lines, and absence of lung pulse. Lung ultrasound rules out the diagnosis of pneumothorax more accurately than a supine anterior chest X-ray (evidence level A). (ii) Interstitial Syndrome Figures . Presence of a B-profile consisting of more than 3 B-lines on a longitudinal scanning plane. Interstitial syndrome includes pulmonary edema, interstitial lung disorders and ARDS (evidence level B). [evel B). , 61. (iii) Lung Consolidation. Sonographic signs are a subpleural echo-poor region or one with tissue-like echotexture. Lung ultrasound can differentiate between consolidation of pulmonary embolism, pneumonia, and atelectasis (evidence level A). (iv) Pleural Effusion. A hypoechoic or anechoic space between sonoanatomical boundaries . Lung ultrasound is more accurate than chest X-ray (evidence level A). (v) Monitoring Interstitial Syndrome. The number of B-lines is directly proportional to the severity of pulmonary congestion. This could be used as a monitoring parameter of severity and response to therapy (evidence level A). Pulmonary edema can be diagnosed, quantified, and monitored by detection of B-lines [ B-lines . Pulmonary embolism (PE) , “mainlyLaursen et al.  have stuDuring positive pressure ventilation (PPV) a quantitative assessment of B-lines may aid in guiding diuretic or optimizing ventilator settings, particularly in conditions such as pulmonary edema or increased lung water content . In geneoptic nerve sheath diameter (ONSD) measurement;transcranial Doppler ultrasound (TDU);pupillary light reflex (PLR).Elevated intracranial pressure (ICP) requires special precautions by the anesthesiologist, such as avoiding particular medications, ventilation settings, and neuraxial anesthesia. Ultrasound is useful in assessing elevated ICP and cerebral perfusion. Current and potential applications of neuroultrasound are as follows:Measurement of optic nerve sheath diameter (ONSD) Figures  has beenIn a recent systematic review and meta-analysis , ONSD meSoldatos et al.  found thP < 0.0001). In about 20% of preeclamptic patients, ONSD reflected compatible values with intracranial pressure above 20 mmHg. Further studies are required to improve the technique of this useful ultrasound methodology. Dubost et al.  measuredIt has been thought  that intUltrasound assessment of the pupillary light reflex (PLR) was initially developed for the U.S. Space Program (NASA) and is not standardized for clinical use. However, the method can be used even when visual access to the pupil is impossible, and interpreting its results is straightforward . ConsensTranscranial color coded duplex (TCCD)  is an acassessment of gastric content and diagnosis of full stomach;confirmation of gastric tube placement.A full stomach may lead to aspiration pneumonia and subsequent morbidities. Anesthesiologists may encounter patients with unknown prandial status, and even fasting “sufficient” time cannot guarantee an empty stomach in many cases . Ultrasound can help in this setting, and the perioperative evaluation of bowel motility is also feasible by means of sonography. Current and potential applications of Gastric ultrasound are as follows: 2 for the diagnosis of “at risk” stomach was associated with a sensitivity of 91% and a specificity of 71%. The area under the receiver operating characteristic (ROC) curve for the diagnosis of “at-risk” stomach was 90%. (“At risk” stomach was defined as the presence of solid particles and/or gastric fluid volume more than 0.8 mL/kg.) These findings show that antral CSA volume assessment can be important in minimizing the risk of pulmonary aspiration of gastric contents. Perlas et al. [Bouvet et al. , measures et al.  performes et al. , in anots et al.  found thConfirmation of a gastric tube placement is also possible using ultrasound , which mFocus assessed transthoracic echo (FATE) was introduced by Jensen et al.  for cardRecent studies show that preoperative excess testing and consultation are common, adding to the cost of care without noticeably improving patient outcome. These findings must encourage anesthesiologists to play an effective role in the preoperative assessment field by implementing clinically innovative approaches and developing training curricula as well as performing research . TherefoNew technologies have greatly improved the image quality, diagnostic abilities, and size of the US machine. These include advances in transducers, scanning schemes, three- and four-dimensional visualization, contrast agents (microbubbles), strain imaging, and others . Y- and Z-planes. Four-dimensional ultrasound provides real-time 3D images (the 4th “D” is time) and currently is used for fetal imaging, where it provides remarkable images. It may have potential applications in our field. Endobronchial and endoscopic ultrasounds are two other new modalities with great and potential implications [The matrix array is a new transducer with improved resolution; it has a lens that is placed in front of the piezoelectric element to allow a mechanical focusing in the ications . Recently, the use of three-dimensional high resolution ultrasound was reported  for nervUltrasound is a unique tool which provides the anesthesiologist with diagnostic and monitoring capabilities enabling optimization of perioperative management. Indeed, ultrasound has an important role in problem-based management of various anesthesiology emergencies such as hypoxia, hypotension, dyspnea, and cardiopulmonary arrest. Finally, procedural ultrasound applications in the field of anesthesiology are numerous and improve the quality of care. We believe that ultrasound can be the third eye of the anesthesiologist that helps in the performance of previously blind procedures and allows discovery of many hidden spaces to uncover their mysteries. Anesthesiologists, in the near future, may need to carry a portable ultrasound around their neck instead of a stethoscope.


Hematopoietic stem cells (HSCs) are rare cells that have the unique ability to self-renew and differentiate into cells of all hematopoietic lineages. The expansion of HSCs has remained an important goal to develop advanced cell therapies for bone marrow transplantation and many blood disorders. Over the last several decades, there have been numerous attempts to expand HSCs in vitro using purified growth factors that are known to regulate HSCs. However, these attempts have been met with limited success for clinical applications. New developments in the HSC expansion field coupled with gene therapy and stem cell transplant should encourage progression in attractive treatment options for many disorders including hematologic conditions, immunodeficiencies, and genetic disorders. Hematopoietic stem cells (HSCs) are rare stem cells that have the ability to differentiate into specialized blood cells, including lymphocytes, red blood cells, and platelets . While sStem cell transplants are a type of stem cell therapy used to treat cancers such as lymphoma and leukemia and other blood-related diseases . CurrentIn most bone marrow transplant centers, peripheral blood stem cells (PBSCs) remain the preferred source of stem cells for many types of allogeneic transplants, in which matched related or unrelated donors are available ,4. In thThe use of UCB is now standard practice in pediatrics and, in fact, some pediatric hematologists are now advocating the preferential use of UCB over peripheral blood stem cells . By utilAdvancements in the field of UCB transplantation have moved attention from investigating its safety and feasibility to addressing a myriad of specific issues. New work in UCB transplantation has focused on extending access, ensuring quality, accelerating engraftment, and reviewing outcomes in specific subgroups of patients . The majUCB is increasingly being used as an alternative source of hematopoietic stem/progenitor cells (HSCs/HPCs) for allogeneic bone marrow transplantation ,10. ThisIn a publication in 2010, researchers described requirements which needed to be fulfilled when considering in vitro expansion of HSCs: (1) HSCs must be able to expand on a larger scale without sacrificing their self-renewal ability; (2) Expansion of HSCs must be safe and transplantable, and requires the method to be free of feeder cells, serum proteins, or microbial agents . In ordeNotch proteins are important for the survival, self-renewal, and lineage determination of stem cells . There aThe homeobox gene family member HOXB4 has been shown to be a regulator of hematopoietic differentiation . It is c2 (PGE2) is a multifunctional eicosanoid that has been shown to enhance the engrafting capabilities of HSCs [Wnt proteins are secreted morphogens that are essential for basic developmental processes, such as progenitor-cell proliferation, cell-fate specification, and the control of asymmetric cell division in various tissues . Wnt has of HSCs  by incre of HSCs .The transcription factor SALL4 is a member of the SALL gene family and has been reported to play an essential role in maintaining ES cell pluripotency through interaction with Oct4 and Nanog ,22 and eCurrently, there are various methods being utilized to expand HSCs ex vivo. These include the use of cytokine cocktails, copper chelators, exposure to signaling molecules, stromal support and overexpression of transcription factors . To dateSince 1999, there has been an average of about 100 new gene therapy clinical trials annually pursuing treatments for infectious diseases, cancer, and genetic diseases ,28. OverOver the last decade, there have been positive results obtained in gene therapy using HSCs in murine models, but these achievements have not been able to be translated into successful outcomes in non-human primates and human patients ,28. One HSCs from sources such as umbilical cord blood or peripheral blood are rather limited. Transplant physicians and researchers have recently shown much higher interest in the usage of UCB cells for transplants due to the advantages they hold over other sources. These include a non-invasive collection method, a high repopulating efficiency, and a less stringent HLA-matching requirement . New stuDespite new advances in HSC gene therapy, the lack of a proven gene-modified HSC drug or protocol emphasizes that many obstacles remain inexplicable . The greEpigenetic modifications play a key role in regulating cell self-renewal and differentiation as well as tissue development . There aThe most widely studied epigenetic modification in humans is cytosine methylation . The majRecent studies have shown that the function of a robust stimulator of HSCs/HPCs, SALL4, is associated with epigenetic machinery ,30. SALLPolycomb group (PcG) and Trithorax group (TrxG) proteins have emerged as significant epigenetic regulators. These groups act antagonistically to either promote or repress transcription through regulation of specific amino acid modifications in histones . PolycomWhile there are numerous clinical trials and assays testing the efficacy and safety for a number of molecules ability to expand HSCs, an ideal factor to increase the number of HSCs in vitro without limiting their in vivo regeneration capabilities has yet to be found. The main difficulties surrounding HSC expansion therapy include long-term engraftability and the translation of in vitro observations into successful in vivo outcomes. However, our increasing knowledge base of the molecular mechanisms underlying the function of HSCs within humans should shed light upon what strategies may lead to the development of an efficient gene therapy via HSCs. Advancements in the methods used to expand HSCs should greatly improve disease outcomes in the future. Further developments in the field coupled with gene therapy and stem cell transplant should encourage progression in cord blood transplantation, therapy for hematologic diseases, and issues of efficacy and safety.The authors declare that they have no competing interests.JAS, MRS, GM: Manuscript writing. WL,YM: Discussion and manuscript writing. RL: Discussion. JRA: Directed and conceived study, discussion, and manuscript writing. All authors read and approved the final manuscript.


Endothelial progenitor cells (EPCs) have great clinical value because they can be used as diagnostic biomarkers and as a cellular therapy for promoting vascular repair of ischaemic tissues. However, EPCs also have an additional research value in vascular disease modelling to interrogate human disease mechanisms. The term EPC is used to describe a diverse variety of cells, and we have identified a specific EPC subtype called outgrowth endothelial cell (OEC) as the best candidate for vascular disease modelling because of its high-proliferative potential and unambiguous endothelial commitment. OECs are isolated from human blood and can be exposed to pathologic conditions (forward approach) or be isolated from patients (reverse approach) in order to study vascular human disease. The use of OECs for modelling vascular disease will contribute greatly to improving our understanding of endothelial pathogenesis, which will potentially lead to the discovery of novel therapeutic strategies for vascular diseases. There is growing interest in endothelial progenitor cells (EPCs) because of their relevant diagnostic and therapeutic clinical applications. The association of EPCs with cardiovascular events  and cancin vitro-based models usually requires large quantities of cells. This is why classically immortalised cell lines had to be established for this purpose. However, these cell lines lack a number of tumour suppressor genes or overexpress oncogenes, which is a major drawback when assessing cellular proliferation and survival. Therefore, recent interest has drifted to the usage of human embryonic stem (hES) and induced pluripotent stem (iPS) cells [in vitro manipulation and genetic modification. In addition, diseases associated with epigenetic changes to cell function can be consistently studied through EPCs, as there is no reprogramming process required, which removes methylation or acetylation events, as is the case for iPS cells.Study of human disease using S) cells , 10, as S) cells , have grin vitro cell culture of the blood mononuclear cell fraction using specific substrates and media.EPCs are isolated using two main methodologies: (a) cell sorting technology using different cell surface markers or (b) in vitro and animal model-based systems.EPC cell sorting is dependent on the type and number of markers used. However, since there is no agreed consensus regarding the most appropriate combination of EPC-linked markers , differein vitro, such as AcLDL uptake, Isolectin binding, and appearance of VEGFR2/CD31 on the cell surface. Despite these endothelial characteristics, these cells retain their haematopoietic nature, as demonstrated by high expression of CD14 and CD45. In fact, we have recently shown that early EPCs represent M2 alternative-activated macrophages and proposed their renaming as myeloid angiogenic cells (MACs) [An alternative approach for isolating EPCs is cell culture. This is based on differential adhesion to specific substrates and the subsequent growth potential of isolated cells in culture. Using this methodology, two distinct types of EPCs have been identified , 14. Ears (MACs) . Other ns (MACs) .The other EPC subtype is known as outgrowth endothelial cells (OECs) . OECs apde novo tubulogenic capacity in vitro by forming three-dimensional tubular structures where cells interact with each other through the junction protein VE-cadherin and form a distinct vessel-like lumen [de novo blood vessel formation is also demonstrated in vivo where human OECs are transplanted subcutaneously in a collagen-fibronectin matrix into immunodeficient mice and efficiently form perfused chimeric blood vessels [in vivo as reported using different animal models such as the murine hind limb ischaemia [OECs have been shown to possess ke lumen . This de vessels , 23, 24. vessels . Most imschaemia , rabbit schaemia , the porschaemia , and murschaemia .For the specific purpose of vascular disease modelling, OECs should be the preferred EPC subtype to use, as they are currently the only EPCs with both great proliferative potential and unequivocal endothelial phenotype.In disease modelling, the classical “reverse” and “forward” approaches used for hESCs are fully applicable to OECs . The “rein vivo milieu usually comprises a diverse variety of factors combined together. Reproducing the in vivo environment in vitro requires multicell type culture systems. Another difficulty appears when the disease of interest is non-cell autonomous and therefore is directly dependent on different cell-cell interactions, and more than one cell type is needed for disease development and progression. A strategy that could easily address this latter issue of multiple cell types is the adjuvant use of iPS cell methodologies [The “forward” approach consists of studying “disease-free” OECs that are exposed to defined disease-relevant conditions, which can be as simple as environmental changes  to more complex genetic modifications by knocking down disease-related genes. This approach is prospective and allows the study of disease pathogenesis from early stages; however, there are some technical challenges. Trying to mimic the pathologic environment can prove very complicated as the dologies . Generatin vitro or in vivo. As with fully differentiated endothelial cells, angiogenic activity in OECs can be directed by cytokines released from proximal myeloid cells, mesenchymal stem cells (MSCs) [While OECs can be studied directly, they can also indirectly facilitate the study of other supportive cells that can modulate vasculogenic activity s (MSCs) , 31, mess (MSCs) , adiposes (MSCs) , pericyts (MSCs) , astrocys (MSCs) , 34. Ints (MSCs) –37. Delis (MSCs) , 39.Despite these technical challenges, utilising OECs to generate cellular models of disease is an attractive methodology that is already being used and optimised. We anticipate that in the field of vascular biology, researchers will favour the use of EPCs/OECs for disease modelling.OECs derived from patients with chronic myeloproliferative disorders (CMD)  indicateβ signalling, disorganised cytoskeleton, and failure to form cord-like structures. These findings described a molecular mechanism to explain small-vessel fragility and frequent bleeding in these patients.OECs from patients with hereditary haemorrhagic telangiectasia (HHT)  revealedin vitro tube formation was also significantly impaired in OEC isolated from PAH patients [To elucidate the role of EPCs in the pathobiology of pulmonary arterial hypertension (PAH), OECs were isolated from peripheral blood of PAH patients with mutations in the gene-encoding bone morphogenetic protein receptor type II (BMPRII) and control subjects. OECs from PAH patients with BMPRII mutations were hyperproliferative when compared to controls. Furthermore, the matrigel angiogenesis assay demonstrated that patients .in vitro, and vWF-deficient mice displayed increase angiogenesis in vivo. These results were further confirmed by isolating OECs from patients with vWD [in vitro angiogenesis, proliferation, and migration.Von Willebrand disease (vWD) is frequently associated with angiodysplasia; therefore, the importance of vWF expression was tested in endothelial cells and animal models. vWF-deficient cells showed enhanced angiogenesis with vWD  which shin vivo [in vitro or a diabetic environment in vivo significantly diminished OEC function such as colony formation, self-renewal capacity, and capillary-like tube formation. This study provided potential mechanistic insights into the long-term cardiovascular complications observed in newborns of diabetic pregnancies.To study the role of the diabetic environment in EPC function, OECs were exposed to high glucose, and umbilical cords of diabetic mothers were used as the EPC source to isolate OECs that had previously experienced diabetic conditions in vivo . Resultsin vitro and in vivo models of angiogenesis to OECs. Combination of forward and reverse approaches for human disease modelling with OECs is an effective system for the study of vascular disease pathogenesis. As with any new technology, we foresee some technical challenges when establishing disease models at the cellular level; nevertheless, we remain optimistic that utilising OECs for vascular disease modelling will improve our understanding of disease that subsequently leads to the development of novel therapies.OECs are a specific EPC sub-type that is starting to be used for the study of vascular pathology. We encourage researchers in the field of vascular biology to apply their different


Most higher plants are unable to survive desiccation to an air-dried state. An exception is a small group of vascular angiosperm plants, termed resurrection plants. They have evolved unique mechanisms of desiccation tolerance and thus can tolerate severe water loss, and mostly adjust their water content with the relative humidity in the environment. Desiccation tolerance is a complex phenomenon and depends on the regulated expression of numerous genes during dehydration and subsequent rehydration. Most of the resurrection plants have a large genome and are difficult to transform which makes them unsuitable for genetic approaches. However, technical advances have made it possible to analyze changes in gene expression on a large-scale. These approaches together with comparative studies with non-desiccation tolerant plants provide novel insights into the molecular processes required for desiccation tolerance and will shed light on identification of orphan genes with unknown functions. Here, we review large-scale recent transcriptomic, proteomic, and metabolomic studies that have been performed in desiccation tolerant plants and discuss how these studies contribute to understanding the molecular basis of desiccation tolerance. Arabidopsis thaliana is considered as a model to study the responses of plants toward tolerating moderate water stress and to study the genes involved in this response. Although desiccation tolerance in seeds is common in higher plants, desiccation tolerance in vegetative tissues is restricted to the unique group of resurrection plants . Gene expression studies and EST sequencing have been performed in some resurrection species, such as the moss T. ruralis  or by gene microarray, the most widely used early approach toward transcriptome analysis was the collection of expressed sequence tags (ESTs) which is limited to a few hundred or thousand sequenced cDNAs. Recent advances in sequencing technologies and assembly algorithms have facilitated the reconstruction of the entire transcriptome by deep RNA sequencing (RNA-seq), even without a reference genome, therefore, this is also applicable to resurrection plants  revealed that the overall identified transcripts have highest similarity to genes of Vitis vinifera, Ricinus communis, and Populus trichocarpa. In C. plantagineum, 182 MB of transcript sequences were assembled into 29,000 contigs which yielded more than 15,000 uniprot identities and in H. rhodopensis 96,353 expressed transcript contigs were identified  genes comprise the most abundantly up-regulated group of genes in response to dehydration. In olerance . Genes e tissues . LEA pro tissues , 2013. Ton level . These rH. rhodopensis contained an extensive antioxidant gene network in the fully hydrated state. The number of expressed genes encoding superoxide dismutases, catalases, monodehydroascorbate reductases, and glutathione (GSH) reductases are higher in H. rhodopensis than in C. plantagineum in the hydrated state. Expression of these genes is even further up-regulated during dehydration in H. rhodopensis  shows 70% sequence identity to Arabidopsis seed specific dormancy related 1-Cys peroxiredoxin  transcripts are up-regulated during dehydration and contribute to antioxidant defense  were also increased during dehydration suggesting ALDH as a stress regulated enzyme with the potential to detoxify excess amounts of aldehydes . These ELIPs are nuclear-encoded proteins associated with thylakoid membranes in the chloroplast and are believed to bind to chlorophyll thus preventing ROS-induced photooxidative damage. Several desiccation-related genes encoding ELIPs have been isolated from d damage . In C. pin light . ELIPs adopensis . In Sporolerance .C. plantagineum and H. rhodopensis, several genes encoding galactinol synthases and a stachyose synthase are present in hydrated leaves and are additionally up-regulated during dehydration (X. humilis (H. rhodopensis during dehydration and desiccation (C. plantagineum during dehydration (C. plantagineum and H. rhodopensis to desiccation is further substantiated by the presence of transketolase transcripts (tkt). Transketolases are key enzymes of the reductive and oxidative pentose phosphate pathways that are responsible for the synthesis of sugar phosphate intermediates, which can flow into different pathways. C. plantagineum has three transketolase isoforms  and it has been suggested that a transketolase isoform is involved in octulose synthesis  increased in expression in response to dehydration and 5% were induced in rehydrated leaves and 60% showed decreased or unchanged levels  and a 23-kDa polypeptide of the oxygen evolving complex of photosystem II were identified in dehydrated leaf proteins. The appearance of the 20-kDa RbcL protein fragment in B. hygrometrica is thought to be the result of stress-induced proteolysis mediated through ROS-induced chloroplast-localized protease activity  activities, and maximal activity levels of phosphoenolpyruvate carboxylase (PEPCase), NADP-dependent isocitrate dehydrogenase (NADP-ICDH), and NADH-dependent glutamate synthase , liquid chromatography (LC)–MS, capillary electrophoresis (CE)–MS, and nuclear magnetic resonance (NMR) spectroscopy are commonly used in plant metabolomics research. Although large-scale metabolomic studies have been reported for ydration , metabololerance . MetabolSelaginella lepidophylla is distinct from the dehydration state. The mapping of the known metabolites (66.5%) into the general biochemical pathways revealed that the more prevalent metabolites are amino acids (19%) followed by carbohydrates, lipids, cofactors, nucleotides, peptides, and secondary metabolites. While the amino acids, peptides, and nucleotide metabolites are overrepresented during desiccation, carbohydrates such as 4C–6C containing sugars, sugar alcohols, lipids, or lipid metabolites (with the exception of choline phosphate), and cofactors are overrepresented in the hydrated state  represented unknown metabolites. Seven of the unknown metabolites showed greater abundance under dehydration conditions than in hydrated conditions suggesting their role in desiccation tolerance. Sporobolus stapfianus is metabolically primed for dehydration as it contains high concentrations of osmolytes and nitrogen metabolites along with low levels of metabolites associated with energy metabolism in the hydrated state. Upon dehydration, the metabolism is shifted toward antioxidant production, carbohydrate production, nitrogen remobilization, and ammonia detoxification (C. plantagineum where major metabolite changes are induced by dehydration (see below).The metabolic profile of fully hydrated ed state . Besidesfication . This apTable 2 displays a summary of the main carbohydrate changes observed in various resurrection plants. Accumulation of sucrose, trehalose, and short-chain oligosaccharides such as raffinose has been observed during dehydration (Table 2). Sucrose is the major carbohydrate in tissues of angiosperm resurrection plants upon desiccation  for sucrose accumulation rather than relying on photosynthesis. Although C. plantagineum plants synthesize starch during photosynthesis, the amount of carbon entering the starch for storage compared to 2-octulose is small  are synthesized during dehydration whereas fructose and glucose are decreased , and tricarboxylic acid intermediates  accumulate during dehydration suggesting the importance of these metabolites for the metabolic flux through these pathways during dehydration or in preparation for rehydration propionate, the tripeptide ophthalmate (L-Y-glutamyl-L-α-aminobutyrylglycine) are prominent in desiccated tissues , flavonols , and phenylpropanoids  accumulated in desiccated tissues  than desiccation sensitive Selaginella moellendorffii . The summary of the omics studies and sister group comparisons is shown in Table 1. Eventually the knowledge on pathways leading to desiccation tolerance could be used for improving drought tolerance in crops . Evidence from omics studies in resurrection plants suggests that some protective strategies are constitutively active in resurrection plants and do not require induction like in dehydration sensitive plants. This indicates preparedness of the plant for dehydration stress . The combination of the data should lead to a systems biology approach and identify target genes and critical metabolic pathways. The studies carried out with resurrection species to date show that similarities exist in dehydration-induced gene expression as well as in protein and metabolite accumulation in resurrection plants pointing toward the presence of common mechanisms of desiccation tolerance. It is proposed that the tolerance to desiccation in vascular resurrection plants is due to the combinatorial effect of accumulation of high levels of antioxidants together with various osmoprotective compounds such as sugars, in particular sucrose and raffinose, and hydrophilic proteins, most prominently LEA proteins. The mechanisms in vascular resurrection plants appear to be different from lower plants like mosses. Desiccation tolerance mechanisms in seeds and vascular plants share many components, but they differ in the regulation of accumulation of components (Elucidation of the molecular mechanism of desiccation tolerance in resurrection plants is difficult due to the lack of genetic approaches and due to the complexity of the phenomenon. However, with the realization of omics technologies it is possible to provide a comprehensive description of changes on the transcript, proteome, and metabolome levels during a dehydration/rehydration cycle (mponents . In seedC. plantagineum and H. rhodopensis is the fact that a high number of transcripts exist which could not be assigned to known sequences from other species. This suggests that some parts of the transcript coding genome has evolved very recently leading to unique genes possibly by genome rearrangements, genome duplication, and activity of transposable elements and/or retro-elements. It appears from studies in C. plantagineum that not only protein coding sequences are unique but also non-protein coding RNAs, which are present in many copies in the genome and are abundantly expressed during dehydration (A remarkable finding in the transcriptome studies in ydration . The stuThe authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Assembly of a bipolar mitotic spindle is essential to ensure accurate chromosome segregation and prevent aneuploidy, and severe mitotic spindle defects are typically associated with cell death. Recent studies have shown that mitotic spindles with initial geometric defects can undergo specific rearrangements so the cell can complete mitosis with a bipolar spindle and undergo bipolar chromosome segregation, thus preventing the risk of cell death associated with abnormal spindle structure. Although this may appear as an advantageous strategy, transient defects in spindle geometry may be even more threatening to a cell population or organism than permanent spindle defects. Indeed, transient spindle geometry defects cause high rates of chromosome mis-segregation and aneuploidy. In this review, we summarize our current knowledge on two specific types of transient spindle geometry defects (transient multipolarity and incomplete spindle pole separation) and describe how these mechanisms cause chromosome mis-segregation and aneuploidy. Finally, we discuss how these transient spindle defects may specifically contribute to the chromosomal instability observed in cancer cells. Mitosis, the process by which a single eukaryotic cell partitions its genetic material, has fascinated scientists for over a century, and already in the late 1800s Walther Flemming described the processes of chromosome segregation and cell division with exquisite detail . Four maThe bipolar geometry of the mitotic spindle is essential for accurate chromosome segregation, and already a century ago Theodor Boveri postulated that supernumerary centrosomes could lead to the production of aneuploid cells ,24. ObseAnother type of abnormal spindle geometry is observed in prometaphase cells with unseparated or incompletely separated spindle poles. In these cells, the centrosomes fail to migrate to opposing positions around the nucleus  before Both examples of transient spindle geometry defects (transient multipolarity and incomplete/delayed spindle pole separation) described above cause high rates of kinetochore mis-attachment Figure B formatiStudies in various types of cancer cells showed that multipolar prometaphase cells display higher numbers of merotelic kinetochore attachments (one kinetochore bound to microtubules from two spindle poles instead of just one) compared to bipolar prometaphases ,39; FiguA. Moreovchromosomal instability (CIN) [Experimental and computational studies were also employed to investigate the process of establishment of kinetochore attachment in cells with incomplete centrosome separation at NEB. These studies showed that when the two spindle poles are very close to each other upon NEB, chromosomes are extremely likely to establish syntelic attachments (both sister kinetochores bound to microtubules from the same spindle pole) ; Figure B, top. Aty (CIN) ,69-71. Rty (CIN) ,39,72. Oty (CIN) . Howeverty (CIN) ,39; Silkin situ has not been investigated. However, multipolar spindles have been observed in tumor tissues [The transient spindle geometry defects described here and their effects on the fidelity of chromosome segregation have been mainly characterized in tissue culture cells, with transient multipolarity exclusively observed in CIN cancer cells to date. Indeed, the frequencies of multipolar spindles in non-transformed or non-CIN cancer cells are typically very low . Given the causal relation between transient multipolarity and chromosome mis-segregation and that transient multipolarity is very common in CIN cancer cells, this mechanism is widely recognized as a major player in CIN. Whether this mechanism is also acting in tumors  tissues -76 and s tissues ,78.Caenorhabditis elegans embryo, the centrosomes achieve opposing positions around the nucleus before the nuclear envelope breaks down [Drosophila embryo, the centrosomes always achieve diametric arrangement around prophase nuclei [Drosophila melanogaster neurogenesis. Indeed, in both epidermoblasts and neuroblasts the centrosomes are completely separated before the onset of prometaphase [Although incomplete spindle pole separation at NEB has also been characterized mainly in tissue culture cells, the information available to date reveals that this mechanism is not exclusive to cancer cells, and has indeed been observed in several different types of tissue culture cells at frequencies of ~40-45% ,55,57,59aks down . Similare nuclei , and thee nuclei . This abetaphase . Given tThe incidence of incomplete centrosome separation at NEB in normal adult tissues has not been investigated to date. However, a recent study showed that non-cancer RPE1 cells, which are known to maintain a stable karyotype with negligible rates of aneuploidy , always The open question, then, is whether incomplete centrosome separation at NEB may play a role in cancer cell CIN, and if so, to what extent. As discussed above, transient multipolarity is recognized as a major cause of chromosome mis-segregation in cancer cells ,39,84. Hper se is not impaired in cells with incomplete centrosome separation at NEB, but the exact timing is inaccurate, so that centrosome separation and NEB are no longer coordinated. It is possible that such coordination is finely regulated at the early stages of development [Accurate partitioning of chromosomes to the daughter cells during mitosis is of utmost importance to ensure development and growth of all eukaryotic organisms. Defects of the mitotic spindle have a dramatic impact on chromosome segregation. However, the effect on the cell population can be even more dramatic if the spindle defects are only transient. Indeed, whereas permanent spindle defects typically lead to cell death in the progeny, transient spindle defects increase the rates of chromosome mis-segregation, but not to a level that would affect cell viability, thus ultimately being more threatening to the overall cell population and/or the organism. Here, we have discussed two types of transient mitotic spindle defects that are associated with increased rates of kinetochore mis-attachment formation and chromosome mis-segregation. One of them, transient multipolarity, is currently recognized as a common mechanism of CIN in cancer cells ,39,84. Celopment ,80,81,88SAC: Spindle Assembly Checkpoint; NEB: Nuclear Envelope Breakdown; CIN: Chromosomal INstability.The authors declare that they have no competing interests.WTS and DC conceived the ideas and wrote the paper. Both authors read and approved the final manuscript.WTS was a PhD student in the Department of Biological Sciences at Virginia Tech, and completed his dissertation work in July 2012 under the guidance of Dr. Daniela Cimini.DC is an Associate Professor in the Department of Biological Sciences at Virginia Tech.