Inactivation of axon guidance molecule netrin-1 in human colorectal cancer by an epigenetic mechanism.

Netrin-1, the protein product of the NTN1 gene, is an axon guidance molecule implicated in regulation of cell survival and tumorigenesis. Expression of the netrin-1 receptors deleted in colorectal cancer (DCC) and uncoordinated 5 homolog (UNC5H) is frequently silenced in colorectal cancer (CRC) by either loss of heterozygosity or epigenetic mechanisms. However, netrin-1 expression and regulation in CRC are mostly unknown. Here, we report that NTN1 expression is significantly reduced in most CRC tissues compared to the adjacent normal intestinal mucosa, and that NTN1 DNA methylation is significantly higher in CRCs (24.6%) than in the adjacent normal intestinal mucosa (4.0%). In 6 CRC cell lines, NTN1 expression is low. Treatment with 5-Aza-2'-deoxycytidine increased expression of NTN1 in CRC cell lines, indicating that DNA methylation represses NTN1 transcription in CRCs. NTN1 DNA hypermethylation was significantly associated with advanced CRC disease. Median netrin-1 serum levels were significantly decreased in CRC patients (330.1 pg/mL) compared with normal individuals (438.6 pg/mL). Our results suggest that netrin-1 is a candidate biomarker for CRC.

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells.

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H2O2) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H2O2-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H2O2 through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H2O2-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H2O2 stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.

Semaphorin 3F and Netrin-1: The Novel Function as a Regulator of Tumor Microenvironment.

Axon guidance molecules play an important role in regulating proper neuronal networking during neuronal development. They also have non-neuronal properties, which include angiogenesis, inflammation, and tumor development. Semaphorin 3F (SEMA3F), a member of the class 3 semaphorins, was initially identified as an axon guidance factor, that repels axons and collapses growth cones. However, SEMA3F has similar effects on endothelial cells (ECs) and tumor cells. In this review, we discuss the novel molecular mechanisms underlying SEMA3F activity in vascular and tumor biology. Recent evidence suggests that SEMA3F functions as a PI3K-Akt-mTOR inhibitor in mammalian cells, including T cells, ECs, and tumor cells. Therefore, SEMA3F may have broad therapeutic implications. We also discuss the key role of axon guidance molecules as regulators of the tumor microenvironment. Netrin-1, a chemoattractant factor in the neuronal system, promotes tumor progression by enhancing angiogenesis and metastasis. Moreover, our recent studies demonstrate that netrin-1/neogenin interactions augment CD4+ T cell chemokinesis and elicit pro-inflammatory responses, suggesting that netrin-1 plays a key role in modulating the function of a tumor and its surrounding cells in the tumor microenvironment. Overall, this review focuses on SEMA3F and netrin-1 signaling mechanisms to understand the diverse biological functions of axon guidance molecules.

Fasting-dependent Vascular Permeability Enhancement in Brown Adipose Tissues Evidenced by Using Carbon Nanotubes as Fluorescent Probes.

Brown adipose tissue (BAT), which is composed of thermogenic brown adipocytes (BA) and non-parenchymal components including vasculatures and extracellular matrix, contribute to the maintenance of body temperature. BAT distribution is detected by positron emission tomography-computed tomography (PET/CT) using 18F-fluorodeoxy glucose (18F-FDG) or single-photon-emission computed tomography-computed tomography (SPECT/CT) using [123/125I]-beta-methyl-p-iodophenyl-pentadecanoic acid. Although sympathetic nerve activity and thermogenic capacity of BA is downregulated under fasting conditions in mice, fasting-dependent structural changes and fluid kinetics of BAT remain unknown. Here we show that the fasting induces fine and reversible structural changes in the non-parenchymal region in murine BAT with widened intercellular spaces and deformed collagen bands as revealed by electron microscopy. Interestingly, a newly introduced near infrared fluorescent probe of single-walled carbon nanotubes (CNTs) coated with phospholipid polyethylene glycol (PLPEG) easily demonstrated enhanced vascular permeability in BAT by the fasting. PLPEG-CNTs extravasated and remained in intercellular spaces or further redistributed in parenchymal cells in fasted mice, which is a previously unknown phenomenon. Thus, PLPEG-CNTs provide a powerful tool to trace fluid kinetics in sub-tissue levels.

Additional attention to combination antiretroviral therapy-related lipodystrophy.

The occurrence of lipodystrophy in patients taking anti-human immunodeficiency virus (HIV) medications is a serious problem as it is irreversible even after drug withdrawal. Although it was first recognized in patients taking proteinase inhibitors, other types of anti-HIV agents can also cause lipodystrophy. In a recent publication by Jones et al entitled "Highly active antiretroviral therapy dysregulates proliferation and differentiation of human pre-adipocytes" in World Journal of Virology, it was reported that simultaneous treatment of human subcutaneous adipocytes with anti-HIV drugs with different mechanisms of action synergistically exerted anti-adipogenesis effects in vitro, warning us to take utmost care in every case receiving combination antiretroviral therapy (cART). For elucidation of the molecular basis for cART-related lipodystrophy, multi-faceted approaches should be taken, based on a deeper understanding of the development and organization of adipose tissues.

Near-Infrared Photoluminescent Carbon Nanotubes for Imaging of Brown Fat.

Near-infrared photoluminescent single-walled carbon nanotubes (CNTs) are expected to provide effectual bio-imaging tools, although, as yet, only limited applications have been reported. Here, we report that CNTs coated with an amphiphilic and biocompatible polymer, poly(2-methacryloyloxyethyl phosphorylcholine-co-n-butyl methacrylate; PMB), generate high-quality images of brown fat. Brown fat is a heat-productive adipose tissue, which is attracting increasing attention as a new therapeutic target for obesity-associated metabolic disorders. Its brown colour is mainly attributed to densely packed capillaries, which facilitate its high heat-exchanging efficiency. Currently, positron emission tomography-computed tomography is the only practical technique to identify brown fat distribution in the living body; however, it is expensive to use. By virtue of their high affinity to apolipoproteins and exemption from macrophage phagocytosis, PMB-CNTs selectively accumulate on capillary endothelial cells but not larger vessels in adipose tissue. Therefore, the image brightness of adipose tissue can directly reflect the capillary density, and indirectly the thermogenic capability and brownness. PMB-CNTs provide clearer images than conventional organic dyes, as the high level of transmitted light passes through the body with less light scattering. Thus, PMB-CNT-based imaging methods could open a new phase in thermogenic adipose tissue research.

Human pluripotent stem cells: Towards therapeutic development for the treatment of lifestyle diseases.

There are two types of human pluripotent stem cells: Embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), both of which launched themselves on clinical trials after having taken measures to overcome problems: Blocking rejections by immunosuppressants regarding ESCs and minimizing the risk of tumorigenicity by depleting exogenous gene components regarding iPSCs. It is generally assumed that clinical applications of human pluripotent stem cells should be limited to those cases where there are no alternative measures for treatments because of the risk in transplanting those cells to living bodies. Regarding lifestyle diseases, we have already several therapeutic options, and thus, development of human pluripotent stem cell-based therapeutics tends to be avoided. Nevertheless, human pluripotent stem cells can contribute to the development of new therapeutics in this field. As we will show, there is a case where only a short-term presence of human pluripotent stem-derived cells can exert long-term therapeutic effects even after they are rejected. In those cases, immunologically rejections of ESC- or allogenic iPSC-derived cells may produce beneficial outcomes by nullifying the risk of tumorigenesis without deterioration of therapeutic effects. Another utility of human pluripotent stem cells is the provision of an innovative tool for drug discovery that are otherwise unavailable. For example, clinical specimens of human classical brown adipocytes (BAs), which has been attracting a great deal of attention as a new target of drug discovery for the treatment of metabolic disorders, are unobtainable from living individuals due to scarcity, fragility and ethical problems. However, BA can easily be produced from human pluripotent stem cells. In this review, we will contemplate potential contribution of human pluripotent stem cells to therapeutic development for lifestyle diseases.

Production of functional classical brown adipocytes from human pluripotent stem cells using specific hemopoietin cocktail without gene transfer.

Brown adipose tissue is attracting much attention due to its antiobestic effects; however, its development and involvement in metabolic improvement remain elusive. Here we established a method for a high-efficiency (>90%) differentiation of human pluripotent stem cells (hPSCs) into functional classical brown adipocytes (BAs) using specific hemopoietin cocktail (HC) without exogenous gene transfer. BAs were not generated without HC, and lack of a component of HC induced white adipocyte (WA) marker expressions. hPSC-derived BA (hPSCdBA) showed respiratory and thermogenic activation by ß-adrenergic receptor (AdrRß) stimuli and augmented lipid and glucose tolerance, whereas human multipotent stromal cell-derived WA (hMSCdWA) improved lipid but inhibited glucose metabolism. Cotransplantation of hPSCdBA normalized hMSCdWA-induced glucose intolerance. Surprisingly, hPSCdBAs expressed various hemopoietin genes, serving as stroma for myeloid progenitors. Moreover, AdrRß stimuli enhanced recovery from chemotherapy-induced myelosuppression. Our study enhances our understanding of BA, identifying roles in metabolic and hemogenic regulation.

Correlation of PU.1 and signal regulatory protein α1 expression in PU.1 transgenic K562 cells.

PU.1 is a key transcription factor for hematopoiesis and the reduction of this protein expression plays important roles in various hematological malignancies. To identify PU.1 downstream target genes, we recently reported dual microarray analyses, using PU.1 knockdown K562 (K562PU.1KD) cells stably expressing short inhibitory RNAs versus control cells and PU.1-overexpressing K562 (K562PU.1OE) cells versus control cells. Several PU.1 candidate target genes, including cell surface receptor, signal regulatory protein (SIRP) α1, were identified. In this study, we revealed that the expression of SIRPα1 is positively correlated with the expression of PU.1 in various K562PU.1KD and K562PU.1OE cells, shown by real-time PCR and flow cytometry analyses. SIRPα1 is a negative regulator of signaling and its reduced expression is considered to play a role in the pathogenesis of hematological malignancies through the activation of downstream signaling pathways. By comparing 3 different clones of K562PU.1KD cells to their controls, we found constitutive phosphorylation of the extracellular signal-regulated kinase (ERK), but not of Akt, in these cells. Taken together, the down-regulation of PU.1 expression suppresses the expression of SIRPα1, which may play a role in the aberrant activation of ERK in these cells.

Early senescence is not an inevitable fate of human-induced pluripotent stem-derived cells.

Human-induced pluripotent stem cells (hiPSCs) are expected to become a powerful tool for regenerative medicine. Their efficacy in the use of clinical purposes is currently under intensive verification. It was reported that hiPSC-derived hemangioblasts had severely limited expansion capability due to an induction of early senescence: hiPSC-derived vascular endothelial cells (VECs) senesced after one passage and hiPSC-derived hematopoietic progenitor cells (HPCs) showed substantially decreased colony-forming activities. Here we show that early senescence is not an inevitable fate of hiPSC-derived cells. Applying our unique feeder-free culture methods for the differentiations of human embryonic stem cells (hESCs), we successfully generated VECs and HPCs from three lines of hiPSCs that were established by using a retrovirus vector system. All hiPS-derived VECs could be subcultured by 2:1∼3:1 dilutions up to 10∼20 passages, after which the cells underwent senescence. Among the three lines of hiPSCs, two lines generated HPCs that bore comparable granulocyte colony-forming units to those of hESCs. Moreover, one line effectively reproduced HPCs within the sac-like structures, the fields of in vitro hematopoiesis, as in the case of hESCs. Surprisingly, release of neutrophils into culture supernatant persisted even longer (∼60 days) than the case of hESCs (∼40 days). Thus, the problem of early senescence can be overcome by selecting appropriate lines of hiPSCs and applying proper differentiation methods to them.

High-efficiency production of subculturable vascular endothelial cells from feeder-free human embryonic stem cells without cell-sorting technique.

We previously reported a feeder-free culture method for pure production of subculturable vascular endothelial cells (VECs) from cynomolgus monkey embryonic stem cells (cmESCs) without as using cell-sorting technique. By this method, canonical vascular endothelial (VE)-cadherin/platelet-endothelial cell adhesion molecule 1 (PECAM1)-positive VECs (c-VECs) and atypical VE-cadherin/PECAM1-negative VECs (a-VECs) were generated without a contamination by pericytes, lymphatic endothelial cells, or immature ES cells. More recently, we established a unique culture technique to maintain human ESCs (hESCs) under a feeder-free and recombinant cytokine-free condition. Combining these two systems, we have successfully generated pure VECs from two lines of hESCs, khES-1 and khES-3, under a completely feeder-free condition. Our method is very simple: spheres generated from hESCs by floating culture using differentiation media supplemented with vascular endothelial growth factor, bone morphogenetic protein 4, stem cell factor, FMS-related tyrosine kinase-3 ligand, and interleukin 3 (IL3) and IL6 were cultured on gelatin-coated plates. Cell passage was performed by an ordinary enzymatic treatment. The hESC-derived differentiated cells demosntrated cord-forming activities and acetylated low-density lipoprotein-uptaking capacities. Moreover, they exclusively expressed von Willebrand factor and endothelial nitric oxide synthase. Flow cytometric analyses indicate that khES-3 generated both c-VECs and a-VECs as in the case of cmESCs. By contrast, khES-1 produced only a-VECs, which nonetheless demonstrated effective recruitment into neovascularity in vivo. Interestingly, a-VECs turned to express PECAM1 after transplantation into immunodeficient mice. The hESC-derived VECs were subculturable at least up to 10 passages without functional depression. Our method does not require a presorting processes to enrich progenitor fractions such as CD34-positive or kinase insert domain receptor (KDR)-positive cells, providing the most efficient and easiest technique for VEC production from hESCs.

A feeder-free and efficient production of functional neutrophils from human embryonic stem cells.

A novel, feeder-free hematopoietic differentiation protocol was established for highly efficient production of neutrophils from human embryonic stem cells (hESCs). For the induction of differentiation, spheres were generated in the presence of serum and cytokine cocktail and subjected to attachment culture on gelatin-coated plates. After approximately 2 weeks, a sac-like structure filled with abundant round cells emerged at the center of flattened spheres. After cutting off this sac-like structure, round cells actively proliferated, either floating in the supernatant or associated weakly with the adherent cells. Almost all of these round cells were CD45-positive hematopoietic cells with myeloid phagocytic markers (CD33 and CD11b), and approximately 30%-50% of the round cells were mature neutrophils, as judged from morphology, cytochemical characteristics (myeloperoxidase and neutrophil alkaline phosphatase), and neutrophil-specific cell surface markers (CD66b, CD16b, and GPI-80). In addition, hESC-derived neutrophils had chemotactic capacity in response to the bacterial chemotactic peptide formyl-methionyl-leucyl-phenylalanine and neutrophil-specific chemokine interleukin (IL)-8. Using "semipurified" neutrophils migrated to IL-8, both phagocytic and respiratory burst activities were demonstrated. Finally, it was shown that hESC-derived neutrophils had chemotactic activity in vivo in a murine air-pouch inflammatory model. The present results indicate successful induction of functional mature neutrophils from hESCs via highly efficient feeder-free differentiation culture system of human hematopoietic cells.

The p38 pathway inhibitor SB202190 activates MEK/MAPK to stimulate the growth of leukemia cells.

In this study, the biological effects of signal transduction inhibitors on leukemia cells were examined. We found that the p38 inhibitor SB202190 enhanced the growth of THP-1 and MV4-11 cells. To determine the pathway affected by SB202190, we examined the 50% effective dose (ED(50)) values for THP-1 cell growth in combination with several inhibitors. In the presence of SB202190, the ED(50) values for the farnesyltransferase inhibitor FPT inhibitor II and MEK inhibitor U0126 were significantly decreased. Western blot analysis revealed that SB202190 increased the phosphorylation of C-Raf and extracellular regulated kinase (ERK), suggesting that Ras-Raf-MEK-mitogen-activated protein kinase (MAPK) pathway activation is involved in the leukemia cell growth induced by SB202190.

Human embryonic stem cells with maintenance under a feeder-free and recombinant cytokine-free condition.

We previously reported that cynomolgus monkey embryonic stem (ES) cells could be maintained under a feeder-free condition without using recombinant cytokines if sizes and numbers of ES colonies were kept within an appropriate range. Here we show that this finding is also true with human ES cells (hESCs). The two lines of hESCs, khES-1 and khES-3, were appropriately maintained in the absence of feeder layers or exogenous cytokines such as fibroblast growth factors, Noggin, transforming growth factor beta, and Activin by closely controlling the size and number of hESC colonies. High-level expressions of immature markers including SSEA-4, Oct-4, and Nanog were detected in feeder-free and cytokine-free hESCs, and they formed teratomas when implanted into severe combined immunedeficiency (SCID) mice. No chromosomal abnormalities were observed over 20 passages, ruling out the possibility that special clones with growth advantages had been selected. Global protein expression profiles were quite similar among the hESCs maintained by our feeder- and cytokine-free method, by coculture with mouse embryonic fibroblasts (MEFs) and by a feeder-free method using conditioned media of MEFs. However, the activation level of Akt, an important player for the maintenance of ES cells, was highest and the activation level of extracellular signal-regulated kinase, a critical player for differentiation of ES cells, was lowest in the hESCs maintained by our cytokine-free method. Our results not only show a technical improvement for the maintenance of hESCs but also open a new avenue for the understanding of autocrine signaling networks of hESCs.

Proteasome degradation of protein C and plasmin inhibitor mutants.

Protein C (PC) deficiency and plasmin inhibitor (PI) deficiency are inherited thrombotic and haemorrhagic disorders. We investigated the intracellular degradation of mutant proteins, using naturally occurring PC and PI mutants that lead to congenital deficiencies. To examine the necessity of N-linked glycosylation for the proteasomal degradation of PC and PI, PC178 and PC331 mutants treated with tunicamycin and N-glycosylation-lacking mutants, PC92Stop and PI-America were pulse chased. The analysis revealed that the speed of degradation of the tunicamycin-treated PC mutants, PC92Stop and PI-America lacking glycosylation, was slower than that of N-glycosylated mutants. Immunoprecipitation and immunoblot analysis showed that PC178 and PC331 mutants were associated with molecular chaperones, Bip, GRP94, and calreticulin. PI-America was associated with only Bip. Although degradation of mutants was mediated by proteasomes, no association with ubiquitin was detected. Cotransfection of endoplasmic reticulum (ER) degradation enhancing alpha-mannosidase-like protein (EDEM) accelerated the degradation of N-glycosylated PC. In the absence of autophagy using Atg5-deficient cell lines, the degradation of the PC331 mutant was mildly accelerated but that of PC178, PI-America and PI-Okinawa mutants was not influenced. While the degradation of the PC and PI mutants was facilitated by N-glycosylation moieties, they were ubiquitin-independently degraded by proteasomes, irrespective of the presence or absence of N-glycosylation. Molecular chaperone binding was influenced by the presence of N-glycosylation moieties. When the misfolded or truncated mutant proteins are functionally active, proteasome inhibitors such as bortezomib may have therapeutic potential for treatment of protein deficiencies.

Highly efficient and feeder-free production of subculturable vascular endothelial cells from primate embryonic stem cells.

The vascular endothelial cell (VEC) differentiation from primate embryonic stem (ES) cells has critical problems: low differentiation efficiencies (<2%) and/or subculture incapability. We report a novel feeder-free culture method for high efficiency production of subculturable VECs from cynomolgus monkey ES cells. Spheres, which were generated from ES cells in the presence of cytokine cocktail, were cultured on gelatin-coated plates. Cobblestone-shaped cells spread out after a few days, which were followed by an emergence of a sac-like structure containing hematopoietic cells. All adherent cells including sac walls cells and surrounding cobblestone cells expressed vascular endothelial cadherin (VE-cadherin) at intercellular junctions. Subculture of these cells resulted in a generation of homogeneous spindle-shaped population bearing cord-forming activities and a uniform acetylated low density lipoprotein-uptaking capacity with von Willbrand factor and endothelial nitric oxide synthetase expressions. They were freeze-thaw-tolerable and subculturable up to eight passages. Co-existence of pericytes or immature ES cells was ruled out. When introduced in a collagen sponge plug implanted intraperitoneally in mice, ES-derived cells recruited into neovascularity. Although percentages of surface VE-cadherin-positive population varied from 20% to 80% as assessed by flow cytometry, the surface VE-cadherin-negative population showed intracellular VE-cadherin expression and mature functions, as we call it as atypical VECs. When sorted, the surface VE-cadherin-positive population expanded as almost pure (>90%) VE-cadherin/PECAM-1-positive VECs by 160-fold after five passages. Thus, our system provides pure production of functional, subculturable and freeze-thaw-tolerable VECs, including atypical VECs, from primate ES cells.

A feeder-free hematopoietic differentiation system with generation of functional neutrophils from feeder- and cytokine-free primate embryonic stem cells.

We have established a novel feeder- and recombinant cytokine-free culture system for the maintenance of primate embryonic stem (ES) cells along with a feeder-free hematopoietic differentiation protocol for high efficiency CD45-positive cell production. In our system, cynomolgus monkey ES cells were properly maintained in an undifferentiated state with high immature marker expressions and teratoma-producing activities. Embryoid bodies (EBs) were generated in the presence of serum and cytokine cocktail and subjected to attachment culture on gelatin-coated plates. After about 2 weeks, a sac-like structure filled with abundant round cells emerged at the center of flattened EB. Then total cells were collected and transferred onto new gelatin-coated plates, where cells were firmly attached and actively proliferated to confluence. After another few days culture, abundant floating cells were detected in the culture supernatant. These cells expressed high levels of CD45 (>90%), while adherent cells expressed low levels of CD45 (<10%). The former consisted of various differentiated stages of myeloid cells from immature myeloblasts to mature polymorphonuclear neutrophils and macrophages. Although the percentages of neutrophils varied between 10 to 20 depending on experiments, their mature phenotype was reproducibly confirmed by specific staining and functional assays. Our protocol provides the minimum essence for primate ES cell maintenance and hematopoietic differentiation that is beneficial from economical and clinical points of view.

Identification of human neutrophils during experimentally induced inflammation in mice with transplanted CD34+ cells from human umbilical cord blood.

Nonobese diabetic/severe combined immunodeficiency/gamma chainnull (NOG) mice are excellent recipients for xenotrans-plantation and have been especially valuable for the evaluation of human hematopoietic stem cell (HSC) activities. Because human hematopoietic cells that developed in this mouse were mainly lymphoid cells and not myeloid cells, mature human myeloid cells such as neutrophils were hardly detectable in peripheral blood. We demonstrated that human neutrophils accumulated by means of a zymosan-induced air pouch inflammation technique could be identified with a fluorescence-activated cell sorter in NOG mice with transplanted CD34+ cells from human umbilical cord blood, which were putative hematopoietic progenitor cells including HSC. Our results indicate that human neutrophils with a chemotactic capacity can develop from human hematopoietic progenitor cells in vivo, suggesting that our system may be a useful tool for the evaluation of human HSC activities.

Efficient and repetitive production of hematopoietic and endothelial cells from feeder-free monolayer culture system of primate embryonic stem cells.

We have established an innovative culture system for the efficient differentiation of hematopoietic and endothelial cells from primate embryonic stem (ES) cells without feeder cells, embryoid bodies, or cell-sorting processes. After several days' culture in murine stromal OP9-conditioned medium supplemented with a cytokine cocktail on collagen-coated dishes, ES cells differentiated into a very unique population of cells with a finger-like appearance. These finger-like cells were positive for mesodermal and/or hemangioblastic markers of kinase insert domain receptor (KDR) and T-cell acute lymphocytic leukemia 1 (TAL1), and produced large amounts of protein tyrosine phosphatase, receptor type, C-positive hematopoietic cells. These hematopoietic cells showed the morphology of immature hematopoietic cells, formed blast cell colonies with high efficiency, and were positive for CD34 antigen, KDR, TAL1, and GATA binding protein 1, suggesting that these blast cells are equivalent to the multipotent hematopoietic progenitor cells. Moreover, they produced functional macrophages in murine stromal MS-5-conditioned medium and primitive erythroblasts in the presence of erythropoietin. The finger-like cells, putative mesodermal progenitors and/or hemangioblasts, actively proliferated and repetitively produced hematopoietic cells as long as they were maintained on the original dish. By contrast, the majority of the finger-like cells differentiated into endothelial cells with specific markers and specific functions after transfer to fresh dishes, indicating that conditions established in the original dish supported the proliferation and hematopoietic differentiation of the finger-like cells. Our method provides a highly controllable culture protocol for repetitive production of hematopoietic and endothelial cells from feeder-free monolayer cultivation of primate ES cells.

Gradually glycosylated protein C mutants (Arg178Gln and Cys331Arg) are degraded by proteasome after mannose trimming.

Proteins that fail to attain their correct three-dimensional structure are retained in the endoplasmic reticulum (ER) and eventually degraded within the cells. We investigated the degradation of mutant proteins, using naturally occurring protein C (PC) mutants (Arg178Gln and Cys331Arg) which lead to congenital deficiencies. Chinese hamster ovary (CHO) cells were transfected with normal or mutant expression vectors. The introduction of mutation at Asn329 of an unusual sequence Asn-X-Cys for N-linked glycosylation revealed that the mutation at Cys331, which may preclude a formation of disulfide bond with Cys345, resulted in no addition of N-linked oligosaccharides at Asn329. PC mutants with 4 glycosylation sites were gradually glycosylated in the ER, and the fourth glycosylation site is less accessible for glycosylation as reported for PC in plasma. The half lives of PC178 and PC331 mutants were about 5 and 4 h, respectively. PC mutants were degraded, but the degradation was inhibited by inhibitors for proteasome. Mannose trimming of N-linked oligosaccharides after glucose removal targeted PC mutants for degradation by proteasomes. And also the inhibition of glucose trimming immediately led to mannose trimming, resulting in the accelerated degradation of PC mutants. These degradations were inhibited by mannosidase I inhibitor, kifunensine. These results indicate that the initiation of mannose trimming by mannosidase I leads to the proteasomemediated degradation of glucose-trimmed or untrimmed PC mutants.