Co-expression Of Green Fluorescent Protein Research Articles

SUN-469 Hypothalamic ERalpha Gene Silencing Diminishes Sexual Receptivity in Female Marmoset Monkeys

Estradiol (E2) has long been established as a major regulator of female sexual behavior in mammals, including primates. Estrogen receptor alpha (ERαλπηα) in the ventromedial nucleus of the hypothalamus (VMN) has been identified as the major molecular gateway facilitating sexually receptive behavior in rodents. In primates, however, a role for ERalpha or any other estrogen receptor in female sexual motivation has not been identified. We hypothesized that eliminating expression of ERαλπηα in the VMN of female marmoset monkeys would result in diminished female receptivity. Female marmosets were ovariectomized (OVX) and received E2 replacement therapy, and assigned to one of two hypothalamic infusion treatments: (1) control, scrambled shRNA, and (2) selective ERαπηα protein depletion with ERα gene silencing shRNA. MRI-guided neural infusion surgery enabled delivery of appropriate shRNA. Co-expression of green fluorescent protein (GFP) was used to visualize localization of transduced neurons. At least 6 mo following treatment onset, female monkeys were observed in six 30-min behavioral testing sessions with their male partner. Brain tissue was perfused and analyzed by immunohistochemistry to quantify accuracy and effectiveness of gene silencing using NIS-elements computer software. ERαλπηα gene silencing shRNA successfully diminished ERαλπηα protein expression in the VMN (p=0.04). Additionally, in the E2-replaced, ERα gene silenced females, sexually receptive behaviors were decreased compared with E2 replaced controls (p<0.001). Interestingly, the decreased receptivity was not accompanied by increased sexual rejection. Together, these findings demonstrate that ERαλπηα activation in the VMN is an obligate component of the neural mechanisms governing female sexual receptivity in a non-human primate.

Dynamic and differential expression of the gonadal aromatase during the process of sexual differentiation in a novel transgenic cyp19a1a-eGFP zebrafish line

In zebrafish, there exists a clear need for new tools to study sex differentiation dynamic and its perturbation by endocrine disrupting chemicals. In this context, we developed and characterized a novel transgenic zebrafish line expressing green fluorescent protein (GFP) under the control of the zebrafish cyp19a1a (gonadal aromatase) promoter. In most gonochoristic fish species including zebrafish, cyp19a1a, the enzyme responsible for the synthesis of estrogens, has been shown to play a critical role in the processes of reproduction and sexual differentiation. This novel cyp19a1a-eGFP transgenic line allowed a deeper characterization of expression and localization of cyp19a1a gene in zebrafish gonads both at the adult stage and during development. At the adult stage, GFP expression was higher in ovaries than in testis. We showed a perfect co-expression of GFP and endogenous Cyp19a1a protein in gonads that was mainly localized in the cytoplasm of peri-follicular cells in the ovary and of Leydig and germ cells in the testis. During development, GFP was expressed in all immature gonads of 20 dpf-old zebrafish. Then, GFP expression increased in early differentiated female at 30 and 35dpf to reach a high GFP intensity in well-differentiated ovaries at 40dpf. On the contrary, males consistently displayed low GFP expression as compared to female whatever their stage of development, resulting in a clear dimorphic expression between both sexes. Interestingly, fish that undergoes ovary-to-testis transition (35 and 40dpf) presented GFP levels similar to males or intermediate between females and males. In this transgenic line our results confirm that cyp19a1a is expressed early during development, before the histological differentiation of the gonads, and that the down-regulation of cyp19a1a expression is likely responsible for the testicular differentiation. Moreover, we show that although cyp19a1a expression exhibits a clear dimorphic expression pattern in gonads during sexual differentiation, its expression persists whatever the sex suggesting that estradiol synthesis is important for gonadal development of both sexes. Monitoring the expression of GFP in control and exposed-fish will help determine the sensitivity of this transgenic line to EDCs and to refine mechanistic based-assays for the study of EDCs. In fine, this transgenic zebrafish line will be a useful tool to study physiological processes such as reproduction and sexual differentiation, and their perturbations by EDCs.

Using the Zebrafish to Model the Tumour-Suppressor Effects of NUP98 in NUP98-NSD1 mediated AML

The NUP98-NSD1 (NND1) translocation is a fusion oncogene that causes high-risk acute myeloid leukemia (AML) in ~16% of pediatric AML patients. The presence of NND1 predicts a dismal prognosis, with a 4-year event-free survival of less than 10%. These high-risk patients often do not respond to current chemotherapy treatments, and would benefit from a targeted therapy approach. The zebrafish has served as a versatile in vivo model of human leukemia both for elucidating underlying disease pathogenesis and for preclinical drug discovery.We previously generated a transgenic zebrafish model expressing the human NUP98-HOXA9 fusion oncogene, which developed a myeloproliferative neoplasm and revealed DNA methyltransferase 1 as a novel downstream target amenable to epigenetic therapy (Forrester et al., BJH 2011; Deveau et al., Leukemia 2015). Like NUP98-HOXA9, NND1 is thought to induce AML through activation of HOXA9, as well as downstream epigenetic modification. In the case of NND1, sustained NSD1 expression induces tri-methylation of the activating H3K36 locus (Wang et al., Nat. Cell Biol. 2007). While the contribution of these NUP98 partner genes to leukemogenesis has been explored, the loss of normal NUP98 function that occurs in the context of these oncogenic fusions remains understudied. As NUP98 is a potential tumour suppressor (Singer et al., Mol. Cell 2012), further exploration of its role in leukemogenesis is required. With the advent of CRISPR/Cas9 technology, the zebrafish is ideally suited to interrogate both elements of NUP98 gene modification in AML.Plasmid constructs containing the human NND1 oncogene driven by either the ubiquitous ubi promoter or the pan-leukocyte cd45 promoter have been incorporated into the zebrafish using the Tol2 system. Expression of NND1 is visualized via co-expression of green fluorescent protein (GFP) at 24-48 hours post-fertilization. GFP expression appears strongest in the regions of embryonic hematopoiesis, such as the posterior blood island. Whole-mount in situ hybridization of plasmid-injected embryos expressing NND1 show a decrease in red blood cells and an increase in myeloid cells, indicating a disruption in hematopoiesis, suggesting a pre-leukemic state. Stable transgenic zebrafish lines are currently being screened. Simultaneously, we are generating transgenic zebrafish expressing a catalytically inactive Cas9 (dCas9) and two guide RNAs (sgRNAs) under the cd45 promoter, to create a leukocyte-specific knockdown of endogenous nup98. This novel dCas9 system will result in selective knockdown and reduce toxicity caused by off-target effects in other tissues.Our unique zebrafish model in which the NND1 oncogene is expressed and wild type NUP98 is functionally inhibited will exhibit greater fidelity to that which occurs in patients with NND1-induced AML, providing an unprecedented opportunity to determine the relative contributions of these lesions to disease pathogenesis. Moreover, given that NUP98-fusion oncogenes are common in multiple hematologic malignancies including AML, chronic myelogenous leukemia (CML), and myelodysplastic syndrome (MDS), broader insights into leukemogenesis may be realized and new therapeutic targets identified. DisclosuresNo relevant conflicts of interest to declare.

Evaluating Baculovirus Infection Using Green Fluorescent Protein and Variants.

By use of a strategy incorporating the green fluorescent protein (GFP), facile and rapid monitoring and visualization of baculovirus infection in insect cells is possible in vivo. This chapter describes two techniques for simple determination of virus titer in the baculovirus expression system using GFP co-expression and rapid monitoring of Sf-9 insect cell infection using a combination of GFP and the early-to-late (ETL) promoter of the virus vector. Because of its early appearance, GFP, when placed under the control of ETL promoter, will facilitate vector construction, virus isolation, and titer determination.

Adaptation of Marrow Osteoblast Morphology Mediated By a Hematopoietic-Derived Endosteal Cell Is Critical for Donor HSC Engraftment after BMT

Hematopoietic stem cells reside in the bone marrow within specialized microenvironments designated the stem cell niche. The remarkable advances over the past decade have dramatically enhanced our perception of the niche; yet, the operative mechanisms after radioablation in preparation for bone marrow transplantation (BMT) remain poorly understood. We have previously described a profound remodeling of the bone marrow architecture after total body irradiation (TBI). This remodeling, comprised of enlarged, proliferating marrow osteoblasts and megakaryocyte migration from the central marrow space to the endosteal surface, is essential for efficient engraftment of donor cells after BMT; hence, marrow remodeling seems to represent an adaptation of the endosteal niche. To investigate whether hematopoietic cells regulate these changes, we sought to deplete all hematopoietic cells prior to TBI. We generated mice expressing the diphtheria toxin receptor (DTR) in all CD45-derived cells using the Cre/loxP model. To validate this strategy, we first crossed CD45Cre mice, where cre is expressed under the control of the endogenous promoter, with Z/RED mice which will then irreversibly express red fluorescent protein (RFP) in all cells that were derived from CD45-expressing progenitors. Surprisingly, we identified a population of RFP-expressing cells residing among osteoblasts along the endosteal and trabecular bone surfaces (designated red Bone Lining Cell, red BLC). By immunofluorescence staining, these cells lacked expression of CD45, lineage markers (Gr1, CD11b, F 4/80, CD3, B220, Ter119), and cathepsin K indicating it is not a hematopoietic cell, specifically not an osteal macrophage or osteoclast, but was unequivocally derived from CD45-expressing progenitors. We reproduced this fate map by crossing vav1Cre mice with Z/RED mice, confirming the identification and hematopoietic lineage of the red BLC. When crossed with Col2.3GFP transgenic mice, which express green fluorescent protein (GFP) in mature osteoblasts, red BLCs lacked GFP co-expression indicating it is not a generic osteoblast. Interestingly, after TBI, red BLCs markedly proliferate, but do not enlarge, in the metaphysis and epiphysis, but not in the diaphysis, coincident with the osteoblast proliferation suggesting a possible role in marrow remodeling. To pursue our original hypothesis that hematopoietic cells may regulate marrow remodeling, we treated mice expressing DTR in all CD45-derived cells and their non-expressing littermates (controls) with diphtheria toxin (DT) followed by TBI to induce marrow remodeling without the effect of CD45-derived cells. Marrow remodeling ensued; however, the characteristically enlarged endosteal osteoblasts adopted a strikingly flattened morphology (cell thickness, 8.45±0.31 vs. 3.42±0.11 μm, P<0.0001). We then used our competitive secondary transplantation assay to assess engraftment of long-term hematopoietic stem cells (HSCs) in primary recipients. Only 1 of 15 CD45-cell depleted mice engrafted HSCs compared to 10 of 15 control mice (P=0.0017) indicating a critical role of osteoblast morphology, governed by a CD45-derived cell, for donor stem cell engraftment in BMT. Megakaryocytes (Mks) and monocytes/macrophages (MMs) are the two marrow hematopoietic lineages that are recognized to survive short term after TBI and we have shown that the CD45-derived red BLC survives and proliferates after TBI. To determine if these cells regulate osteoblasts, we depleted Mks by treating Mk-specific DTR-expressing mice (generated with PF4Cre mice) with DT (>95%), and in separate cohort, MMs using clondronate (>95%). In each cohort, post-TBI marrow remodeling included the expected enlarged endosteal osteoblasts indistinguishable from controls, suggesting that neither Mks nor MMs direct the acquired osteoblast morphology. Collectively, our data indicate that enlarging of endosteal osteoblasts after marrow ablation is critical for donor cell engraftment, possibly due to altered adhesive properties for primitive hematopoietic cells. During post-TBI marrow remodeling, a CD45-derived cell that survives radioablation governs this osteoblast morphology. Our data implicate the red BLC as this key regulatory element. Understanding the red BLC will likely offer new insight into the niche and may lead to novel strategies to enhance HSC engraftment in BMT. DisclosuresNo relevant conflicts of interest to declare.

Two-Plasmid Vector System for Independently Controlled Expression of Green and Red Fluorescent Fusion Proteins in Staphylococcus aureus

We have constructed a system for the regulated coexpression of green fluorescent protein (GFP) and red fluorescent protein (RFP) fusions in Staphylococcus aureus. It was validated by simultaneous localization of cell division proteins FtsZ and Noc and used to detect filament formation by an actin-like ParM plasmid partitioning protein in its native coccoid host.

Improved foreign gene expression in plants using a virus‐encoded suppressor of RNA silencing modified to be developmentally harmless

Endeavours to obtain elevated and prolonged levels of foreign gene expression in plants are often hampered by the onset of RNA silencing that negatively affects target gene expression. Plant virus-encoded suppressors of RNA silencing are useful tools for counteracting silencing but their wide applicability in transgenic plants is limited because their expression often causes harmful developmental effects. We hypothesized that a previously characterized tombusvirus P19 mutant (P19/R43W), typified by reduced symptomatic effects while maintaining the ability to sequester short-interfering RNAs, could be used to suppress virus-induced RNA silencing without the concomitant developmental effects. To investigate this, transient expression in Nicotiana benthamiana was used to evaluate the ability of P19/R43W to enhance heterologous gene expression. Although less potent than wt-P19, P19/R43W was an effective suppressor when used to enhance protein expression from either a traditional T-DNA expression cassette or using the CPMV-HT expression system. Stable transformation of N.benthamiana yielded plants that expressed detectable levels of P19/R43W that was functional as a suppressor. Transgenic co-expression of green fluorescent protein (GFP) and P19/R43W also showed elevated accumulation of GFP compared with the levels found in the absence of a suppressor. In all cases, transgenic expression of P19/R43W caused no or minimal morphological defects and plants produced normal-looking flowers and fertile seed. We conclude that the expression of P19/R43W is developmentally harmless to plants while providing a suitable platform for transient or transgenic overexpression of value-added genes in plants with reduced hindrance by RNA silencing.

Efficient generation of clinical‐grade genetically modified dendritic cells for presentation of multiple tumor‐associated proteins

Dendritic cells (DCs) play a central role in the initiation and regulation of immune responses. DCs for clinical applications can be generated with high yield from leukapheresis products. Using adenoviral transduction we genetically modified human DCs to produce and present melanoma-associated antigens. Coexpression of green fluorescent protein and epitope tags were used to monitor genetic modification. Generation, genetic modification, and cryoconservation of gene modified human DCs on a clinical scale in a closed system is feasible. CD14-positive monomuclear cells were isolated from leukapheresis products of HLA-A* 0201 positive voluntary blood donors using immunomagnetic beads. Selected cells were cultivated for 7 days. Adenovirus transduction was optimal on Day 4. Maturation was induced on Day 5. Mature DC were aliquoted and cryoconserved on Day 7. Quality control was performed using flow cytometry, expression profiling, and functional assays (ELISPOT, CBA). We were able to generate sufficient genetically modified mature DCs in serum-free cultures that could be stored by cryopreservation. The use of a closed system facilitated development of methods for standardized production of clinically applicable genetically modified DCs. The adenoviral transduction system allowed simultaneous and flexible expression of tumor-associated antigens for prolonged presentation of multiple epitopes. The feasibility of a closed-bag system for the cultivation of genetically modified human DCs is shown. The immature DCs were genetically modified by recombinant replication-deficient adenoviruses to express multiple epitopes of tumor-associated proteins and then differentiated to mature antigen-presenting DCs.

α5β1 Integrin Engagement Increases Large Conductance, Ca2+-activated K+ Channel Current and Ca2+ Sensitivity through c-src-mediated Channel Phosphorylation

Large conductance, calcium-activated K(+) (BK) channels are important regulators of cell excitability and recognized targets of intracellular kinases. BK channel modulation by tyrosine kinases, including focal adhesion kinase and c-src, suggests their potential involvement in integrin signaling. Recently, we found that fibronectin, an endogenous alpha5beta1 integrin ligand, enhances BK channel current through both Ca(2+)- and phosphorylation-dependent mechanisms in vascular smooth muscle. Here, we show that macroscopic currents from HEK 293 cells expressing murine BK channel alpha-subunits (mSlo) are acutely potentiated following alpha5beta1 integrin activation. The effect occurs in a Ca(2+)-dependent manner, 1-3 min after integrin engagement. After integrin activation, normalized conductance-voltage relations for mSlo are left-shifted at free Ca(2+) concentrations >or=1 microm. Overexpression of human c-src with mSlo, in the absence of integrin activation, leads to similar shifts in mSlo Ca(2+) sensitivity, whereas overexpression of catalytically inactive c-src blocks integrin-induced potentiation. However, neither integrin activation nor c-src overexpression potentiates current in BK channels containing a point mutation at Tyr-766. Biochemical tests confirmed the critical importance of residue Tyr-766 in integrin-induced channel phosphorylation. Thus, BK channel activity is enhanced by alpha5beta1 integrin activation, likely through an intracellular signaling pathway involving c-src phosphorylation of the channel alpha-subunit at Tyr-766. The net result is increased current amplitude, enhanced Ca(2+) sensitivity, and rate of activation of the BK channel, which would collectively promote smooth muscle hyperpolarization in response to integrin-extracellular matrix interactions.

Reciprocal Synergistic Interactions of Leukemic Cells with Osteoclast Progenitors in the Bone Microenvironment

The bone marrow provides an essential regulatory microenvironment for adult hematopoiesis, however the relationship between the bone marrow microenvironment and malignant hematopoiesis remains poorly understood. To investigate the interactions between leukemia and the bone marrow microenvironment we utilized a mouse model of blast-crisis chronic myelogenous leukemia (BC-CML), in which primitive normal murine hematopoietic cells are modified to leukemic cells by expressing the translocation products BCR/ABL and Nup98/HoxA9. The presence of each translocation was confirmed by their co-expression of Green Fluorescent Protein (GFP) and Yellow Fluorescent Protein (YFP) respectively. Ten days after injection of GFP+/YFP+ leukemic cells into strain-matched immunocompetent, non-myeloablated recipient mice, 50% of the bone marrow was composed of leukemic cells as determined by flow cytometric analysis. Histologic analysis of the contralateral tibiae and femora demonstrated not only progressive replacement of the bone marrow by leukemic cells, but also a significant bone loss. Histomorphometric analysis confirmed 50% decreased trabecular bone volume in leukemic mice compared to control mice that were not injected with leukemic cells (bone volume/total volume (%): 12±2 vs 26±2 p=0.01). Interestingly, numerous multi-nucleated osteoclasts were observed in the bone marrow of leukemic mice and were localized adjacent to leukemic cells, suggesting that leukemic cells may affect osteoclastogenesis and result in massive bone loss. To test this hypothesis, we first measured the expression of known regulators of osteoclastogenesis, including RANKL, in our leukemic cells by quantitative RT-PCR analysis. Compared to GFP−/YFP− cells, GFP+/YFP+ cells have 3-fold increased expression of RANKL, a major osteoclastogenic cytokine. We then examined if leukemic cells can give rise to osteoclasts in the presence of RANKL and M-CSF in vitro and found that these cells were unable to differentiate into osteoclasts themselves. To determine if leukemic cells can induce osteoclastogenesis of normal osteoclast progenitors, we cocultured spleen-derived osteoclast precursors from wild-type mice with GFP+/YFP+ leukemic cells or GFP−/YFP− non-leukemic cells in osteoclastic differentiating media containing optimal concentrations of M-CSF and RANKL. As expected, there was abundant formation of mature osteoclasts, identified as TRAP+ multinucleated cells, in control cultures containing non-leukemic cells and osteoclast precursors. Leukemic cells significantly increased TRAP+ mono-nucleated osteoclast precursors (No. TRAP+ mononucleated cells/well: 34±3.3 vs 20±6.0 in non-leukemic cells, p=0.0136). Under this culture condition, we did not observe increased mature osteoclast formation by leukemic cells. Surprisingly, we found that osteoclast precursors strongly prolonged the survival of leukemia cells. In control cultures without a feeder layer of osteoclast precursors there were no viable leukemia cells present after 6 days in culture while in the co-culture system viable leukemia cells were still abundant after 6 days in culture, identifiable by their expression of GFP/YFP (No. GFP+/YFP+/high power field: 0 vs 142±6.4, p<0.01). In summary, in a murine model of BC-CML, there was a rapid loss of trabecular bone and an increase in the number of osteoclasts. Expression of osteoclast-regulating cytokines in leukemic cells favored osteoclastogenesis, however modified cells did not themselves give rise to osteoclasts, while increasing the population of normal immature osteoclasts. In turn, osteoclast progenitors prolonged survival of leukemic cells in vitro. Taken together, these data strongly suggest reciprocal synergistic interactions of leukemic cells with osteoclast progenitors in the bone microenvironment. These previously unrecognized interactions could be exploited to modify disease progression, providing a novel approach for leukemia treatment.

Optimising Blue Fluorescent Protein (BFP) for use as a mammalian reporter gene in parallel with Green Fluorescent Protein (GFP).

AbstractTo obtain an optimised form of BFP for use as a reporter gene in mammalian cells, the brightest available GFP form, EGFP, was mutated at 5 different positions, yielding 8 different mutagenised forms of BFP. The intensity of the fluorescent signals attained in mammalian cells with all these various versions of BFP was analysed by flow cytometry of transiently transfected COS 7 cells. The best mutant obtained can be detected readily both by flow cytometry and fluorescence microscopy, even when expressed together with GFP. To explore whether cellular localization could enhance the fluorescence signals any further, plasmid constructs were made to target optimised versions of GFP and BFP to the nucleus, the endoplasmic reticulum (ER) and the cell surface. Expression in the nucleus or ER increased the fluorescence signal by ca. 50%, whereas cell surface expression resulted in a five-fold decrease compared to the ER and nuclear forms. Co-expression of GFP and BFP in the same cellular compartment did not result in any significant absorption of the blue fluorescence by GFP. Thus, targeting of GFP and BFP to various cellular compartments adds even further versatility to this convenient dual reporter-gene system.

The Therapeutic Effects of Tyrosine Hydroxylase Gene Transfected Hematopoetic Stem Cells in a Rat Model of Parkinson’s Disease

To investigate the therapeutic effects of tyrosine hydroxylase (TH)-transfected neuronal stem cells derived from bone marrow stem cells (NdSCs-D-BMSCs) on Parkinson's disease (PD) through different transplantation protocols, including microinjection into the cerebral ventricles (CV) and the striatum (ST). After identification by enzyme digestion, the constructed plasmid pEGFP-C2-TH was transfected into 8-day-cultured NdSCs-D-BMSCs by electroporation resulting in the coexpression of green fluorescent protein (GFP) and TH. The TH-transfected cells were injected into either the right ST or CV of PD rats. The changes in locomotor activity of PD rats and the migration of transplanted cells in cerebral tissue were monitored and cerebral DA levels were assayed by high performance liquid chromatography (HPLC). Five days after plasmid pEGFP-C2-TH transfection into NdSCs-D-BMSCs GFP was expressed in 62.1% of the cells and the rate of co-expression with TH was 83.5%. Ten weeks following transplantation, the symptoms of PD rats in both groups were significantly improved and DA levels were restored to 46.6% and 33% of control. The transferred cells showed excellent survival rates in PD rat brains and distant migration was observed. Both CV and ST transplantation of TH-transfected NDSCs-D-BMSCs has obvious therapeutic effects on PD rats. This study could provide evidence for future transplantation route selection, possibly leading to stem cell transplantation through lumbar puncture.

Assessing the expression of chicken anemia virus proteins in plants

Chicken anemia virus (CAV) is an important pathogen of chicken worldwide, causing severe anemia and immunodeficiency. Its small single-stranded DNA genome (2.3 kb) encodes three proteins: VP1, the only structural protein, VP2, a protein phosphatase, and VP3, also known as apoptin, which induces apoptosis. In this study, CAV proteins were expressed in plants as an alternative for recombinant protein production in animal cells. Additionally, the effect of VP3 expression was tested to evaluate possible involvement in programmed cell death in plants. The CAV genes were cloned in binary vectors with the Green fluorescent protein (GFP) as N terminal fusion, and into a Potato virus X (PVX) and Tobacco Mosaic Virus (TMV)-based vectors. Nicotiana benthamiana plants were inoculated with Agrobacterium tumefaciens containing the binary vector constructs or the PVX and TMV constructs. Upon transient expression GFP:VP1 and GFP:VP2 were observed throughout the nucleoplasm, whereas VP3 formed compact aggregates within the nucleus, indicating functional nuclear localization signals in all three proteins. An intense fluorescence was observed for VP2 and VP3 fusions, whereas GFP:VP1 fluorescence remained faint and was only detected in a limited number of cells. Co-expression of GFP:VP1 and VP2 had a marked alteration on the distribution of GFP:VP1, forming large VP1 aggregates throughout the nucleus, indicating an interaction of the two CAV proteins. No visible alteration on GFP pattern was detected upon co-expression of GFP:VP1 and VP3, or with GFP:VP2 and VP3. Plants infected with PVX or TMV-based vectors expressing VP3 displayed strong necrosis and wilting, however, a direct association with VP3 expression and programmed cell death in plants, could not be established. Overall, our results show that all CAV proteins can be expressed in plant cells, though expression level of VP1 needs to be further optimized before testing its potential as (edible) subunit vaccine.

Murine Muscle Precursor Cells Survived and Integrated in a Cryoinjured Gastroesophageal Junction

Mini-invasive techniques for gastroesophageal reflux disease (GERD), such as endoscopic injections of inert materials, have been introduced in recent years. However, results are still preliminary. Cell injection has emerged as an alternative strategy in both vesicoureteral reflux and incontinence. Here we report, for the first time, the injection of muscle precursor cells (MPCs) in the gastroesophageal junction (GEJ). MPCs were derived from expanded satellite cells isolated from skeletal muscle fibers of green fluorescent protein (GFP) positive mice. Via laparotomy, GFP-negative mice were subjected to cryoinjury of GEJ followed by injection of MPCs (experimental animals), bone marrow derived cells, or saline (controls). Immunofluorescence analyses of experimental GEJs demonstrated coexpression of GFP and desmin in grafted cells. GFP+ muscle neofibers were evident at 4 wk after injection. Coexpression of GFP and smooth muscle actin was also observed at 2 wk. Satellite cells could be easily harvested, expanded in culture, and used as injectable substance in the GEJ. These results could be the background for the development of a new injection technique for GERD treatment, which might combine bulging and functional actions.

Function and Regulation of Osteopontin in Response to Mechanical Stress

Extensive histological study revealed the impairment of bone remodeling caused by mechanical stress in OPN knockout mice in a tooth movement system. Analysis of OPN promoter transgenic mice showed the mechanical stress response element(s) in the 5.5-kb upstream region. These results were also obtained with the primary cultured cells. Mechanical loading system changes the bone architecture through the stimulation of bone remodeling by the action of a numbers of molecules. Among them, we showed that osteopontin (OPN) plays an important role in response to mechanical loading in rats with an experimental system for tooth movement. The results indicate the important role of OPN in bone remodeling. However, the molecular mechanism of OPN expression in response to mechanical stress is unknown. OPN knockout mice and transgenic mice carrying green fluorescent protein (GFP) in the control of the OPN promoter were used for analysis. Orthodontic closed coil springs were bonded to the maxillary first molars and incisors for the experimental tooth movement. Spatial expression of GFP and OPN was detected by in situ hybridization. In contrast to wildtype mice, a smaller number of TRACP+ cells was detected in OPN knockout mice after treatment. In GFP-OPN5.5 mice, OPN and GFP mRNA-expressing cells were detected in bone cells after treatment, and the localization of GFP was consistent with that of endogenous OPN. An increase in the co-expression of GFP and OPN was detected when primary cultured osteoblastic cells derived from the transgenic mice were exposed to strain or pressure force. Significant increase in the number of OPN+ osteocyte was detected in the pressure side at 48 h after treatment. At 72 h, increase in the number of TRACP+ cells was detected predominantly in the pressure side. Bone remodeling in response to mechanical stress was suppressed in OPN knockout mice. These results indicate the critical role of OPN in the process of bone remodeling. The analysis of GFP expression in the promoter transgenic mice indicated the presence of an in vivo mechanical stress response element in the 5.5-kb upstream region of the OPN gene.

Fibroblast growth factor 2 facilitates the differentiation of transplanted bone marrow cells into hepatocytes

We have developed an in vivo mouse model, the green fluorescent protein (GFP)/carbon tetrachloride (CCl(4)) model, and have previously reported that transplanted GFP-positive bone marrow cells (BMCs) differentiate into hepatocytes via hepatoblast intermediates. Here, we have investigated the growth factors that are closely related to the differentiation of transplanted BMCs into hepatocytes, and the way that a specific growth factor affects the differentiation process in the GFP/CCl(4) model. We performed immunohistochemical analysis to identify an important growth factor in our model, viz., fibroblast growth factor (FGF). In liver samples, the expression of FGF1 and FGF2 and of FGF receptors (FGFRs; FGFR1, FGFR2) was significantly elevated with time after bone marrow transplantation (BMT) compared with other factors, and co-expression of GFP and FGFs or FGFRs could be detected. We then analyzed the effect and molecular mechanism of FGF signaling on the enhancement of BMC differentiation into hepatocytes by immunohistochemistry, immunoblotting, and microarray analysis. Treatment with recombinant FGF (rFGF), especially rFGF2, elevated the repopulation rate of GFP-positive cells in the liver and significantly increased the expression of both Liv2 (hepatoblast marker) and albumin (hepatocyte marker). Administration of rFGF2 at BMT also raised serum albumin levels and improved the survival rate. Transplantation of BMCs with rFGF2 specifically activated tumor necrosis factor-alpha (TNF-alpha) signaling. Thus, FGF2 facilitates the differentiation of transplanted BMCs into albumin-producing hepatocytes via Liv2-positive hepatoblast intermediates through the activation of TNF-alpha signaling. Administration of FGF2 in combination with BMT improves the liver function and prognosis of mice with CCl(4)-induced liver damage.

Aggregation of Mitochondria

Mitochondrial aggregation induced by co-expression of Green Fluorescent Protein(GFP)and an antiapoptotic factor Bcl-xL. HeLa cells were co-transfected with cDNA of Bcl-xL and empty control vector(A and B)or GFP(C, D and E). The cells were double-stained with antibody against Bcl-xL(A and C)and a mitochondria specific fluorescent dye, MitoTracker Red(B, D and E). E: Higher-magnification of aggregated mitochondria. Note that green fluorescence in D and E is derived from GFP and that the aggregated mitochondria were gathered but not fused(E). Scale bars, 20 μm(A~D)and 10 μm(E). (Pictures were modified from those that were published in Biochemical and Biophysical Research Communications 314, 711― 716(2004). Aokage et al.).

Endosomal Targeting Sequences from Non-Classical Antigen Presenting Molecules Can Direct Antigens into the MIIC and Other Antigen Processing Compartments.

The ultimate goal of these studies is to enhance the development of MHC class II-restricted helper T cell responses that are required for effective and durable immunotherapy. In order to optimize the processing and presentation of MHC class II-restricted epitopes, we are using a differential targeting strategy that relies upon the unique endosomal targeting sequences from the individual isoforms of the CD1 family of non-classical antigen presenting molecules. Distinct endosomal compartments differ with respect to pH and resident proteases. MHC class II molecules can load antigen in each of the different endosomal compartments. This is in addition to the traditional antigen loading compartment, MIIC. Therefore, by forcing the expression of a tumor antigen across different endosomal compartments, we hope to maximize the number of successfully processed epitopes. To achieve this, we have developed a PCR-based strategy to link the leader, transmembrane, and endosomal targeting sequences from the four different human CD1 isoforms, CD1a-d, to DNA encoding for a surrogate antigen, green fluorescent protein (GFP). Using this strategy, we have demonstrated that fusion of individual CD1 tails to the sequence for GFP resulted in four distinct expression patterns in HELA cells transfected with these constructs. Using immunofluorescent staining and confocal laser microscopy, we determined the pattern of antigen expression in various endosomal compartments. GFP variably colocalized with recycling endosomes (ARF-6), early endosomes (CD71, transferrin receptor), late endosomes (CD63), and late endosomes/lysosmes/MIIC (CD107a, LAMP-1). Three of the four CD1 tails also resulted in co-expression of GFP with the MHC class II molecule, HLA-DR. The expression pattern for each CD1 tail is shown in Table 1. These experiments validate the feasibility of the CD1 targeting approach. Current studies are underway to apply this strategy to the leukemia antigen, WT1, using recently completed and sequenced WT1/CD1 fusion constructs.ARF-6CD71CD63CD107aCD1a−/+−−−CD1b−/+−+++CD1c+−/++++CD1d+−/+−+Table 1. Pattern of GFP/CD1 fusion expression in different endosomal compartments. Fusion of the endosomal targeting sequences from human CD1 molecules to the model antigen, GFP, results in different patterns of antigen expression within distinct endosomal compartments. The degree of colocalization between GFP and the indicated markers of endosomal compartments is represented as follows: (−), no colocalization; (−/+), infrequent colocalization; (+), frequent colocalization; (++), extensive colocalization.

Tracking mesoderm induction and its specification to the hemangioblast during embryonic stem cell differentiation.

The hematopoietic and endothelial lineages derive from mesoderm and are thought to develop through the maturation of a common progenitor, the hemangioblast. To investigate the developmental processes that regulate mesoderm induction and specification to the hemangioblast, we generated an embryonic stem cell line with the green fluorescent protein (GFP) targeted to the mesodermal gene, brachyury. After the in vitro differentiation of these embryonic stem cells to embryoid bodies, developing mesodermal progenitors could be separated from those with neuroectoderm potential based on GFP expression. Co-expression of GFP with the receptor tyrosine kinase Flk1 revealed the emergence of three distinct cell populations, GFP(-)Flk1(-), GFP(+)Flk1(-) and GFP(+)Flk1(+) cells, which represent a developmental progression ranging from pre-mesoderm to prehemangioblast mesoderm to the hemangioblast.

Dual labeling of Pseudomonas putida with fluorescent proteins for in situ monitoring of conjugal transfer of the TOL plasmid.

We describe here a dual-labeling technique involving the green fluorescent protein (GFP) and the red fluorescent protein (DsRed) for in situ monitoring of horizontal gene transfer via conjugation. A GFPmut3b-tagged derivative of narrow-host-range TOL plasmid (pWWO) was delivered to Pseudomonas putida KT2442, which was chromosomally labeled with dsRed by transposon insertion via biparental mating. Green and red fluorescent proteins were coexpressed in donor P. putida cells. Cells expressing both fluorescent proteins were smaller in size than cells expressing GFP alone. Donors and transconjugants in mixed culture or sludge samples were discriminated on the basis of their fluorescence by using confocal laser scanning microscopy. Conjugal plasmid transfer frequencies on agar surfaces and in sludge microcosms were determined microscopically without cultivation. This method worked well for in situ monitoring of horizontal gene transfer in addition to tracking the fate of microorganisms released into complex environments. To the best of our knowledge, this is the first study that discusses the coexpression of GFP and DsRed for conjugal gene transfer studies.