Focused ultrasound as a novel strategy for noninvasive gene delivery to retinal Müller glia

Müller glia are specialized retinal cells with stem cell properties in fish and frogs but not in mammals. Current efforts to develop gene therapies to activate mammalian Müller glia for retinal repair will require safe and effective delivery strategies for recombinant adeno-associated viruses (AAVs), vectors of choice for clinical translation. Intravitreal and subretinal injections are currently used for AAV gene delivery in the eye, but less invasive methods efficiently targeting Müller glia have yet to be developed. Methods: As gene delivery strategies have been more extensively studied in the brain, to validate our vectors, we initially compared the glial tropism of AAV-PHP.eB, an AAV9 that crosses the blood-brain and blood-retinal barriers, for its ability to drive fluorescent protein expression in glial cells in both the brain and retina. We then tested the glial transduction of AAV2/8-GFAP-mCherry, a virus that does not cross blood-brain and blood-retinal barriers, for its effectiveness in transducing Müller glia in murine retinal explants ex vivo. For in vivo assays we used larger rat eyes, performing invasive intravitreal injections, and non-invasive intravenous delivery using focused ultrasound (FUS) (pressure amplitude: 0.360 - 0.84 MPa) and microbubbles (Definity, 0.2 ml/kg). Results: We showed that AAV-PHP.eB carrying a ubiquitous promoter (CAG) and green fluorescent protein (GFP) reporter, readily crossed the blood-brain and blood-retinal barriers after intravenous delivery in mice. However, murine Müller glia did not express GFP, suggesting that they were not transduced by AAV-PHP.eB. We thus tested an AAV2/8 variant, which was selected based on its safety record in multiple clinical trials, adding a glial fibrillary acidic protein (GFAP) promoter and mCherry (red fluorescent protein) reporter. We confirmed the glial specificity of AAV2/8-GFAP-mCherry, showing effective expression of mCherry in astrocytes after intracranial injection in the mouse brain, and of Müller glia in murine retinal explants. For in vivo experiments we switched to rats because of their larger size, injecting AAV2/8-GFAP-mCherry intravitreally, an invasive procedure, demonstrating passage across the inner limiting membrane, leading to Müller glia transduction. We then tested an alternative non-invasive delivery approach targeting a different barrier - the inner blood-retinal-barrier, applying focused ultrasound (FUS) to the retina after intravenous injection of AAV2/8 and microbubbles in rats, using magnetic resonance imaging (MRI) for FUS targeting. FUS permeabilized the rat blood-retinal-barrier and allowed the passage of macromolecules to the retina (Evans blue, IgG, IgM), with minimal extravasation of platelets and red blood cells. Intravenous injection of microbubbles and AAV2/8-GFAP-mCherry followed by FUS resulted in mCherry expression in rat Müller glia. However, systemic delivery of AAV2/8 also had off-target effects, transducing several murine peripheral organs, particularly the liver. Conclusions: Retinal permeabilisation via FUS in the presence of microbubbles is effective for delivering AAV2/8 across the inner blood-retinal-barrier, targeting Müller glia, which is less invasive than intravitreal injections that bypass the inner limiting membrane. However, implementing FUS in the clinic will require a comprehensive consideration of any off-target tropism of the AAV in peripheral organs, combined ideally, with the development of Müller glia-specific promoters.

Native protein delivery into rice callus using ionic complexes of protein and cell-penetrating peptides

Direct protein delivery into intact plants remains a challenge for the agricultural and plant science fields. Cell-penetrating peptide (CPP)-mediated protein delivery requires the binding of CPPs to a protein to carry the protein into the cell through the cell wall and lipid bilayer. Thus, we prepared ionic complexes of a CPP-containing carrier peptide and a cargo protein, namely, Citrine yellow fluorescent protein, and subsequently studied their physicochemical properties. Two types of carrier peptides, BP100(KH)₉ and BP100CH₇, were investigated for delivery efficiency into rice callus. Both BP100(KH)₉ and BP100CH₇ successfully introduced Citrine protein into rice callus cells under pressure and vacuum treatment. Moreover, delivery efficiency varied at different growth stages of rice callus; 5-day rice callus was a more efficient recipient for Citrine than 21-day callus.

Controlled Epidermal Growth Factor Receptor Ligand Display on Cancer Suicide Enzymes via Unnatural Amino Acid Engineering for Enhanced Intracellular Delivery in Breast Cancer Cells

Proteins are ideal candidates for disease treatment because of their high specificity and potency. Despite this potential, delivery of proteins remains a significant challenge due to the intrinsic size, charge, and stability of proteins. Attempts to overcome these challenges have most commonly relied on direct conjugation of polymers and peptides to proteins via reactive groups on naturally occurring residues. While such approaches have shown some success, they allow limited control of the spacing and number of moieties coupled to proteins, which can hinder bioactivity and delivery capabilities of the therapeutic. Here, we describe a strategy to site-specifically conjugate delivery moieties to therapeutic proteins through unnatural amino acid (UAA) incorporation, in order to explore the effect of epidermal growth factor receptor (EGFR)-targeted ligand valency and spacing on internalization of proteins in EGFR-overexpressing inflammatory breast cancer (IBC) cells. Our results demonstrate the ability to enhance targeted protein delivery by tuning a small number of EGFR ligands per protein and clustering these ligands to promote multivalent ligand-receptor interactions. Furthermore, the tailorability of this simple approach was demonstrated through IBC-targeted cell death via the delivery of yeast cytosine deaminase (yCD), a prodrug converting enzyme.

Targeted Subcellular Protein Delivery Using Cleavable Cyclic Cell-Penetrating Peptides

The delivery of entire functional proteins into living cells is a long-sought goal in science. Cyclic cell-penetrating peptides (cCPPs) have proven themselves to be potent delivery vehicles to carry proteins upon conjugation into the cytosol of living cells with immediate bioavailability via a non-endosomal uptake pathway. With this strategy, we pursue the cytosolic delivery of mCherry, a medium-sized fluorescent protein. Afterward, we achieve subcellular delivery of mCherry to different intracellular loci by genetic fusion of targeting peptides to the protein sequence. We show efficient transport into a membrane-bound compartment, the nucleus, as well as targeting of the actin cytoskeleton, marking one of the first ways to label actin fluorescently in genetically unmodified living cells. Furthermore, we demonstrate that only by conjugation of cCPPs via a disulfide bond, is flawless localization to the target area achieved. This finding underlines the importance of using a cCPP-based delivery vehicle that is cleaved inside cells, for the precise intracellular localization of a protein of interest.

Nanoinjection system for precise direct delivery of biomolecules into single cells

Intracellular delivery of functional molecules such as proteins, transcription factors and DNA is effective and promising in cell biology. However, existing transfection methods are often unsuitable to deliver big molecules into cells or require carriers such as viruses and peptides specific to the target molecules. In addition, the nature of bulk processing does not generally provide accurate dose control of individual cells. The concept of single-cell-based material injection based on electrokinetic pumping through nanocapillaries could overcome these problems, yet the fabrication and operation of nanoscale 3-dimensional structures have remained unsolved. In this research, a hybrid (PDMS/glass) microfluidic chip with a true 3-dimensional nanoinjection structure (called "nanoinjection system") is presented. The nanoinjection structure was fabricated by femtosecond-laser (fs-laser) ablation in a single solid glass, which showed very successful delivery of red fluorescent protein (RFP) and expression of plasmid DNA in several different types of cells. This system is promising in that the amount of molecules to be delivered is controllable and the processed cells are systematically separated into a harvesting chamber, which can radically improve the purity of the processed cells. In addition, it was confirmed that the cells were healthy even after the molecule injection for a few seconds, indicating that the injection time can be significantly elongated, further improving the delivery efficiency of biomolecules without affecting the cell viability. We envision that the nanoinjection system having the major features of being carrier-free and dose-controllable, having an unlimited injection period, and ease of harvesting will greatly contribute to the next-generation research studies in the fields of cell biology and cell therapeutics.

MMP-2-responsive fluorescent nanoprobes for enhanced selectivity of tumor cell uptake and imaging

It is difficult to develop highly selective substrate-based fluorescent nanoprobes for specific matrix metalloproteinases (MMPs) due to overlapping substrate specificities among the family of MMP enzymes. To resolve this issue, we have developed novel fluorescent nanoprobes that are highly selective for soluble MMP-2. Herein, MMP-2-responsive nanoprobes were prepared by immobilizing fluorescent fusion proteins on nickel ferrite nanoparticles via the His-tag nickel chelation mechanism. The fusion protein consisted of a fluorescent mCherry protein with a cell penetrating peptide (CPP) moiety. An MMP-2 cleavage site was also introduced within the fusion protein, which was directly linked to the nickel ferrite nanoparticles. The selectivity of nanoprobes was modulated by hiding the cleavage site of MMP-2 substrates deeply inside the system, which could result in strong steric hindrance between the nanoprobes and MMPs, especially for membrane-tethered MMPs such as MMP-14. A cell-based assay demonstrated that the nanoprobes could only be activated by tumor cells secreting soluble MMP-2, but not membrane-tethered MMP-14. To further evaluate the contribution of the steric hindrance effect on the nanoprobes, a truncated recombinant MMP-14 was employed to confer their cleavage activity as compared to native membrane-tethered MMP-14. Furthermore, a designed probe with a diminished steric hindrance effect was proved to be activated by membrane-tethered type MMP-14. The results indicated that the design of fluorescent nanoprobes employing the steric hindrance effect can greatly enhance the selectivity of MMP-responsive nanoprobes realizing the specific detection of soluble MMP-2 in a tumor microenvironment. We believe that highly selective MMP-2-responsive fluorescent nanoprobes have broad impacts on biomedical applications including molecular imaging and labeling for tumor detection.

Selective staining and eradication of cancer cells by protein-carrying DARPin-functionalized liposomes

Since their discovery, liposomes have been widely employed in biomedical research. These nano-size spherical vesicles consisting one or few phospholipid bilayers surrounding an aqueous core are capable of carrying a wide variety of bioactive compounds, including drugs, peptides, nucleic acids, proteins and others. Despite considerable success achieved in synthesis of liposome constructs containing bioactive compounds, preparation of ligand-targeted liposomes comprising large quantities of encapsulated proteins that are capable of affecting pathological cells still remains a big challenge. Here we described a novel method for preparation of small (80-90 nm in diameter) unilamellar liposomes containing very large quantities (thousands of protein molecules per liposome) of heme-containing cytochrome c, highly fluorescent mCherry and highly toxic PE40 (Pseudomonas aeruginosa Exotoxin A domain). Efficient encapsulation of the proteins was achieved through electrostatic interaction between positively charged proteins (at pH lower than pI) and negatively charged liposome membrane. The proteoliposomes containing large quantities of mCherry or PE40 and functionalized with designed ankyrin repeat protein (DARPin)_9-29, which targets human epidermal growth factor receptor 2 (HER2) were shown to specifically stain and kill in sub-nanomolar concentrations HER2-positive cells, overexpressing HER2, respectively. Specific staining and eradication of the receptor-positive cells demonstrated here makes the DARPin-functionalized liposomes carrying large quantities of fluorescent and/or toxic proteins a promising candidate for tumor detection and therapy.

Selective Pharmacogenetic Activation of Catecholamine Subgroups in the Ventrolateral Medulla Elicits Key Glucoregulatory Responses

Catecholamine (CA) neurons in the ventrolateral medulla (VLM) contribute importantly to glucoregulation during glucose deficit. However, it is not known which CA neurons elicit different glucoregulatory responses or whether selective activation of CA neurons is sufficient to elicit these responses. Therefore, to selectively activate CA subpopulations, we injected male or female Th-Cre+ transgenic rats with the Cre-dependent DREADD construct, AAV2-DIO-hSyn-hM3D(Gq)-mCherry, at one of four rostrocaudal levels of the VLM: rostral C1 (C1r), middle C1 (C1m), the area of A1 and C1 overlap (A1/C1), and A1. Transfection was highly selective for CA neurons at each site. Systemic injection of the Designer Receptor Exclusively Activated by Designer Drugs (DREADD) receptor agonist, clozapine-N-oxide (CNO), stimulated feeding in rats transfected at C1r, C1m, or A1/C1 but not A1. CNO increased corticosterone secretion in rats transfected at C1m or A1/C1 but not A1. In contrast, CNO did not increase blood glucose or induce c-Fos expression in the spinal cord or adrenal medulla after transfection of any single VLM site but required dual transfection of both C1m and C1r, possibly indicating that CA neurons mediating blood glucose responses are more sparsely distributed in C1r and C1m than those mediating feeding and corticosterone secretion. These results show that selective activation of C1 CA neurons is sufficient to increase feeding, blood glucose levels, and corticosterone secretion and suggest that each of these responses is mediated by CA neurons concentrated at different levels of the C1 cell group.

Limbal Approach-Subretinal Injection of Viral Vectors for Gene Therapy in Mice Retinal Pigment Epithelium

The eye is a small and enclosed organ which makes it an ideal target for gene therapy. Recently various strategies have been applied to gene therapy in retinopathies using non-viral and viral gene delivery to the retina and retinal pigment epithelium (RPE). Subretinal injection is the best approach to deliver viral vectors directly to RPE cells. Before the clinical trial of a gene therapy, it is inevitable to validate the efficacy of the therapy in animal models of various retinopathies. Thus, subretinal injection in mice becomes a fundamental technique for an ocular gene therapy. In this protocol, we provide the easy and replicable technique for subretinal injection of viral vectors to experimental mice. This technique is modified from the intravitreal injection, which is widely used technique in ophthalmology clinics. The representative results of RPE/choroid/scleral complex flat-mount will help to understand the efficacy of this technique and adjust the volume and titer of viral vectors for the extent of gene transduction.

Targeting the vaginal mucosa with human papillomavirus pseudovirion vaccines delivering simian immunodeficiency virus DNA

The majority of HIV infections occur via mucosal transmission. Vaccines that induce memory T and B cells in the female genital tract may prevent the establishment and systemic dissemination of HIV. We tested the immunogenicity of a vaccine that uses human papillomavirus (HPV)-based gene transfer vectors, also called pseudovirions (PsVs), to deliver SIV genes to the vaginal epithelium. Our findings demonstrate that this vaccine platform induces gene expression in the genital tract in both cynomolgus and rhesus macaques. Intravaginal vaccination with HPV16, HPV45, and HPV58 PsVs delivering SIV Gag DNA induced Gag-specific Abs in serum and the vaginal tract, and T cell responses in blood, vaginal mucosa, and draining lymph nodes that rapidly expanded following intravaginal exposure to SIV(mac251.) HPV PsV-based vehicles are immunogenic, which warrant further testing as vaccine candidates for HIV and may provide a useful model to evaluate the benefits and risks of inducing high levels of SIV-specific immune responses at mucosal sites prior to SIV infection.

A unique red fluorescent protein of silkworm bearing two photochromic moieties

A silkworm excretory red fluorescent protein (SE-RFP) having light-dependent activity against Bombyx mori nucleopolyhedrovirus (BmNPV) was purified. Light was observed to be essential also for the SE-RFP synthesis as it was produced only when silkworms were reared in light. SE-RFP has exhibited a high fluorescence quantum yield of 0.86. The apparent mass of native SE-RFP was about 1100 kDa as analysed by gel filtration chromatography. Two photochromic moieties associated with the SE-RFP, namely tetrapyrrole-I (TP-I) and tetrapyrrole-II (TP-II), were isolated by employing TLC and HPTLC techniques. The purified tetrapyrroles were characterized by UV-absorption, fluorescence, atomic absorption and FT-IR spectral analyses. The molecular masses of TP-I and TP-II were 535 and 870 Da, respectively, as determined by ESI-MS and MALDI-TOF-MS. The molar ratio of TP-I to TP-II was 1.14 : 1.00, and a total of 7.251 micromol tetrapyrroles (TP-I + TP-II) were found to be present per mg of SE-RFP. TP-I and TP-II were identified as chlorophyll derivatives, namely, pyropheophorbide a and pheophytin a, respectively. Hence, the SE-RFP was concluded to be a unique insect red fluorescent protein having two photochromic moieties and potent photobiological activity.

Co-injection strategies to modify radiation sensitivity and tumor initiation in transgenic Zebrafish

The zebrafish has emerged as a powerful genetic model of cancer, but has been limited by the use of stable transgenic approaches to induce disease. Here, a co-injection strategy is described that capitalizes on both the numbers of embryos that can be microinjected and the ability of transgenes to segregate together and exert synergistic effects in forming tumors. Using this mosaic transgenic approach, gene pathways involved in tumor initiation and radiation sensitivity have been identified.

[Kidney accumulation of yellow fluorescent protein after its absorption in the rat intestine]

Yellow fluorescent protein (3.6 ng) was administered through a catheter into the Wistar rat intestine lumen. By the method of confocal microscopy it has been established that as soon as in 3 min this protein appears in the epithelial cells of ileum, is absorbed into the blood and accumulated in cells of the nephron proximal segment, not being revealed in the liver, though. The protein accumulation in kidneys continues for several hours. The yellow fluorescent protein is homogeneously distributed in enterocytes, while in epithelial cells of the proximal tubule this protein is localized in vesicles. The data obtained indicate absorption of non-degraded yellow fluorescent protein in the intestine and role of kidney in metabolism not only of endogenous, but also of exogenous proteins.

Augmentation of cardiac protein delivery using ultrasound targeted microbubble destruction

Gas-filled microbubbles have become an important tool as ultrasonic contrast agents. We have previously shown that ultrasound-targeted microbubble destruction (UTMD) can direct plasmids to the heart. The aim of this study was to evaluate UTMD for protein delivery. Six different groups of rats received 1 microg of luciferase protein with varying protocols: (1) luciferase-loaded microbubbles and ultrasound; (2) luciferase only; (3) luciferase and ultrasound; (4) luciferase-loaded microbubbles; (5) unloaded microbubbles incubated with luciferase and ultrasound; (6) unloaded microbubbles with ultrasound followed by luciferase. Relative luminescence units per mg protein per s were determined in hearts and control organs. The rats that received ultrasound and luciferase-loaded bubbles showed a six-fold higher cardiac luciferase uptake compared with control groups that did not include bubbles. None of the other groups significantly augmented cardiac luciferase activity. We conclude that ultrasound-targeted microbubble destruction can substantially and noninvasively augment organ-specific delivery of proteins.

Identification of antigen-capturing cells as basophils

Binding of intact Ag is a hallmark of Ag-specific B cells. Apart from B cells, a small number of non-B cells can bind Ag with comparable efficacy as B cells and are found in the peripheral blood, spleen, and bone marrow of mice. This population has been observed for a long time and recently named "Ag-capturing cells." Their identity remained enigmatic. In this study, we show that these cells are basophilic granulocytes. Their ability to capture Ags is dependent on surface IgE receptors and on Ag-specific plasma IgE molecules appearing after immunization. Several surface markers including surface bound IgE, IL-3R, CD45, CD16/32, and the chemokine receptor CCR2 were used to clearly identify these cells. Cross-linkage of surface Igs results in the release of large amounts of IL-4 and IL-6. The data identify basophils as Ag-capturing cells and support the concept of basophils as important regulators of humoral immune responses.

Aged mice develop protective antitumor immune responses with appropriate costimulation

There is a clear decrease in CD8(+) T cell effector function with aging, a loss once thought to be intrinsic to the CD8(+) T cells. Recent studies suggest, however, that this decline may be a consequence of altered stimulatory signals within the aged lymphoid microenvironment. In this study, we compared the immune responses of young and old mice against the BM-185 pre-B cell lymphoma expressing enhanced GFP (EGFP) as a surrogate tumor Ag. Young animals develop protective immune responses when immunized with BM-185-EGFP, but aged mice do not and ultimately succumb to the tumor. However, expression of CD80 (B7.1) on the BM-185-EGFP (BM-185-EGFP-CD80) results in rejection of the tumor by both young and old animals. Additionally, injection of BM-185-EGFP-CD80 cells in young mice promotes the development of long-lasting memory responses capable of rejecting BM-185 wild-type tumors. Aged animals similarly injected did not develop antitumor memory responses. Interestingly, old animals immunized with the BM-185-EGFP-CD80 cells plus injections of the agonist anti-OX40 mAb did develop long-lasting memory responses capable of rejecting the BM-185 wild-type tumors with the same vigor as the young animals. We show that old mice have the capacity to develop strong antitumor responses and protective memory responses as long as they are provided with efficient costimulation. These results have important implications for the development of vaccination strategies in the elderly, indicating that the aged T cell repertoire can be exploited for the induction of tumor immunity.

Distinctive roles for 2',5'-oligoadenylate synthetases and double-stranded RNA-dependent protein kinase R in the in vivo antiviral effect of an adenoviral vector expressing murine IFN-beta

To evaluate the anti-HSV-1 mechanisms of murine IFN-beta in ocular infection, mice were transduced with an adenoviral vector expressing murine IFN-beta (Ad:IFN-beta). Ocular transduction with Ad:IFN-beta resulted in enhanced survival following infection with HSV-1. The protective effect was associated with a reduction in 1) viral titer, 2) viral gene expression, 3) IFN-gamma levels, and 4) the percentage of CD8(+) T lymphocyte and NK cell infiltration in infected tissue. Expression of IFN-beta resulted in an elevation of the IFN-induced antiviral gene 2',5'-oligoadenylate synthetase (OAS1a) but not dsRNA-dependent protein kinase R (PKR) in the cornea and trigeminal ganglion (TG). Mice deficient in the downstream effector molecule of the OAS pathway, RNase L, were no more sensitive to ocular HSV-1 compared with wild-type controls in the TG based on measurements of viral titer. However, the efficacy of Ad:IFN-beta was transiently lost in the eyes of RNase L mice. By comparison, PKR-deficient mice were more susceptible to ocular HSV-1 infection, and the antiviral efficacy following transduction with Ad:IFN-beta was significantly diminished in the eye and TG. These results suggest that PKR is central in controlling ocular HSV-1 infection in the absence of exogenous IFN, whereas the OAS pathway appears to respond to exogenous IFN, contributing to the establishment of an antiviral environment in a tissue-restricted manner.

Safety assessment of recombinant green fluorescent protein orally administered to weaned rats

Several proposed biotechnological applications of green fluorescent protein (GFP) are likely to result in its introduction into the food supply of domestic animals and humans. We fed pure GFP and diets containing transgenic canola expressing GFP to young male rats for 26 d to evaluate the potential toxicity and allergenicity of GFP. Animals (n = 8 per group) were fed either AIN-93G (control), control diet plus 1.0 mg of purified GFP daily, modified control diet with 200 g/kg canola (Brassica rapa cv Westar), or control diet with 200 g/kg transgenic canola containing one of two levels of GFP. Ingestion of GFP did not affect growth, food intake, relative weight of intestine or other organs, or activities of hepatic enzymes in serum. Comparison of the amino acid sequence of GFP to known food allergens revealed that the greatest number of consecutive amino acid matches between GFP and any food allergen was four, suggesting the absence of common allergen epitopes. Moreover, GFP was rapidly degraded during simulated gastric digestion. These data indicate that GFP is a low allergenicity risk and provide preliminary indications that GFP is not likely to represent a health risk.

Efficacy of adenoviral p53 delivery with SCH58500 in the intracranial 9l and RG2 models

Malignant gliomas remain incurable entities that provide fertile ground for experimental therapy. The observation that impaired p53 expression is present in a proportion of these tumors suggests that reconstitution of this ability may impart some degree of tumor control. In this investigation, the 9L and RG2 intracranial rodent tumor models are utilized to assess SCH58500, an adenoviral p53 delivery system. The RG2 tumors demonstrate a greater propensity for transfection with this vector in vitro than the 9L tumors. In vivo, little tumor transfection beyond the immediate area of the needle tract used for direct SCH58500 injection was observed in either tumor type. Intracarotid injection resulted in no tumor transfection. Even at high concentrations of SCH58500 or control virus, injections resulted in no apparent toxicity in terms of weight gain, eating habits or activity in normal animals. The intratumoral administration of SCH58500 enhances the survival of animals with established 9L tumors. Both SCH58500 and its control viral construct not containing the p53 gene enhance survival in animals with RG2 tumors. None of the injected viral constructs caused an alteration in the markers used to detect the character of the white cell infiltrate in either of these tumors. Utilization of SCH58500 provides measurable efficacy in these preclinical brain tumor models without significant toxicity.

Looking for an insulin pill? Use the BRET methodology!

Insulin exerts its biological effects through a plasma membrane receptor that possesses a tyrosine-kinase activity. This tyrosine-kinase activity depends on the autophosphorylation of the receptor on tyrosine residues and on its dephosphorylation by protein tyrosine-phosphatases. The discovery of pharmacological agents that specifically stimulate the autophosphorylation of the insulin receptor or inhibit its dephosphorylation will be of great importance for the treatment of insulin resistant or insulin deficient patients. Bioluminescence Resonance Energy Transfer (BRET) has developed in recent years as a new technique to study protein-protein interactions. In the BRET technique, one partner is fused to Renilla luciferase, whereas the other partner is fused to a fluorescent protein (e.g. YFP, Yellow Fluorescent Protein). The luciferase is excited by addition of its substrate, coelenterazine. If the two partners interact, resonance energy transfer occurs between the luciferase and the YFP, and a fluorescent signal, emitted by the YFP, can be detected. Our work indicates that this methodology could be an important tool for the search of molecules that activate insulin receptor autophosphorylation or that inhibit its dephosphorylation. Indeed, we first showed that the activation of the insulin receptor by different ligands can be monitored using a chimeric receptor with one B-subunit fused to Renilla luciferase and the other B-subunit fused to YFP. The conformational changes induced by different ligands could be detected as an energy transfer (BRET signal) between the luciferase and the YFP, that reflects the activation state of the receptor. This methodology allows for rapid analysis of the effects of agonists on insulin receptor activity and may therefore be used in high-throughput screening for the discovery of molecules with insulin-like properties. More recently, we demonstrated that the BRET methodology could also be used to monitor the interaction of the insulin receptor with protein tyrosine-phosphatase 1B, one of the main tyrosine-phosphatase that controls its activity. HEK cells were co-transfected with the insulin receptor fused to Renilla luciferase and a substrate-trapping mutant of PTP1B (PTP1B-D181A) fused to YFP. Insulin-induced BRET signal could be followed in real time for more than 30 min. Therefore, this methodology can also be used in high-throughput screening for the search of molecules that will specifically disrupt the interaction between the insulin receptor and PTP1B.

Gene delivery in renal tubular epithelial cells using recombinant adeno-associated viral vectors

Gene therapy has the potential to provide a therapeutic strategy for numerous renal diseases such as diabetic nephropathy, chronic rejection, Alport syndrome, polycystic kidney disease, and inherited tubular disorders. In previous studies using cationic liposomes or adenoviral or retroviral vectors to deliver genes into the kidney, transgene expression has been transient and often associated with adverse host immune responses, particularly with the use of adenoviral vectors. The unique properties of recombinant adeno-associated viral (rAAV) vectors permit long-term stable transgene expression with a relatively low host immune response. The purpose of the present study was to evaluate gene expression in the rat kidney after intrarenal arterial infusion of a rAAV (serotype 2) vector encoding green fluorescence protein (GFP) induced by a cytomegalovirus-chicken beta-actin hybrid promoter. The left kidney of experimental animals was treated with either saline or transduced with rAAV2-GFP (0.125 ml/100 g body wt, 1 x 10(10)/ml infectious units) through the renal artery. A time-dependent expression of GFP was observed in all kidneys injected with rAAV2-GFP, with maximal expression observed at 6 wk posttransduction. The expression of GFP was restricted to cells in the S(3) segment of the proximal tubule and intercalated cells in the collecting duct, the latter identified by co-localization with H(+)-ATPase. No transduction was observed in the glomeruli or the intrarenal vasculature. These studies demonstrate successful transgene expression in tubular epithelial cells, specifically in the S(3) segment of the proximal tubule and intercalated cells, after intrarenal administration of a rAAV vector and provide the impetus for further studies to exploit its use as a tool for gene therapy in the kidney.

A non-toxic lectin for antigen delivery of plant-based mucosal vaccines

RicinB, the non-toxic galactose/N-acetylgalactosamine-binding subunit of ricin, was fused to a model antigen, green fluorescent protein (GFP), and expressed in tobacco plants and hairy root cultures to test for utility in mucosal vaccine delivery/adjuvancy. The fusion protein retained both GFP fluorescence and galactose/galactosamine-binding activity. Intranasal immunization of mice with galactosamine-affinity purified ricinB:GFP recovered from tobacco root cultures triggered significant increases in GFP-specific serum IgGs. This strong humoral response was comparable to that observed following GFP immunization with cholera toxin adjuvant. GFP at the same concentrations but without an adjuvant was non-immunogenic. Induction of higher levels of IgG(1) than IgG(2a) following ricinB:GFP immunization suggested the presence of a Th2 response. Serum and fecal anti-GFP IgA were also induced by immunization with ricinB:GFP. Our data suggest that ricinB can be used as an adjuvant and antigen carrier to the mucosa and is efficient in eliciting systemic and mucosal immune responses.

A macrophage colony-stimulating factor receptor-green fluorescent protein transgene is expressed throughout the mononuclear phagocyte system of the mouse

The c-fms gene encodes the receptor for macrophage colony-stimulating factor (CSF-1). The gene is expressed selectively in the macrophage and trophoblast cell lineages. Previous studies have indicated that sequences in intron 2 control transcript elongation in tissue-specific and regulated expression of c-fms. In humans, an alternative promoter was implicated in expression of the gene in trophoblasts. We show that in mice, c-fms transcripts in trophoblasts initiate from multiple points within the 2-kilobase (kb) region flanking the first coding exon. A reporter gene construct containing 3.5 kb of 5' flanking sequence and the downstream intron 2 directed expression of enhanced green fluorescent protein (EGFP) to both trophoblasts and macrophages. EGFP was detected in trophoblasts from the earliest stage of implantation examined at embryonic day 7.5. During embryonic development, EGFP highlighted the large numbers of c-fms-positive macrophages, including those that originate from the yolk sac. In adult mice, EGFP location was consistent with known F4/80-positive macrophage populations, including Langerhans cells of the skin, and permitted convenient sorting of isolated tissue macrophages from disaggregated tissue. Expression of EGFP in transgenic mice was dependent on intron 2 as no lines with detectable EGFP expression were obtained where either all of intron 2 or a conserved enhancer element FIRE (the Fms intronic regulatory element) was removed. We have therefore defined the elements required to generate myeloid- and trophoblast-specific transgenes as well as a model system for the study of mononuclear phagocyte development and function.

Cationic lipid and polymer-based gene delivery to human pancreatic islets

Transplantation of pancreatic islets has great potential for treating Type I diabetes. Ex vivo gene therapy may promote re-vascularization or inhibit apoptosis of the islets and promote graft. In this study, we investigated the feasibility of non-viral gene delivery using Enhanced Green Fluorescent Protein (EGFP) and human Vascular Endothelial Growth Factor (hVEGF(165)) expression plasmids as model reporter and therapeutic genes. LipofectAMINE/pDNA and Superfect/pDNA complexes showed high transfection efficiency in rapidly dividing Jurkat cells, but low transfection in non-dividing human islets. LipofectAMINE/pCAGGS-hVEGF transfected islets showed relatively higher levels of hVEGF than in those transfected with LipofectAMINE/pCMS-EGFP complexes or 5% glucose. To exclude endogenously secreted hVEGF, real time RT-PCR experiment was repeated using pCAGGS vector-specific forward primer and hVEGF gene-specific reverse primer. In this case, both non-transfected islets and the islets transfected with LipofectAMINE/pCMS-EGFP complexes showed negligible amplification of hVEGF. On glucose challenge, insulin release from LipofectAMINE/pCAGGS-hVEGF transfected human islets increased from 10.78 +/- 4.56 to 65 +/- 5 ng/ml, suggesting little adverse effect on islet beta cell response to glucose challenge. The low transfection efficiency is due to the islets being a cluster of approximately 1000 non-dividing cells. This underscores the importance of experimentation with the actual human islets.

Targeting axons to specific fiber tracts in vivo by altering cadherin expression

In brain development, neurons have to be connected with specific postsynaptic neurons to establish functional neuronal circuits. Cadherins are cell adhesion molecules, which mark developing neuronal circuits. Each member of this class of molecules is expressed only on a restricted set of fiber fascicles that connect gray matter structures to form functional neural circuits. In view of their expression patterns, cadherins have been postulated to play a functional role in the proper establishment of fiber connections. We chose the chicken optic tectum to analyze the instructive potential of cadherins in axonal pathfinding. Three tectofugal pathways, the tectothalamic, tectobulbar, and tectoisthmic tracts, exit the dorsal mesencephalon via the brachium of the superior colliculus, a large fiber structure, which can be divided in specific subtracts that are characterized by the selective expression of N-cadherin, cadherin-7, cadherin-6B, or R-cadherin. By using in vivo electroporation, we overexpressed each of the cadherins in tectal projection neurons between embryonic days 6 and 11. Cotransfection with green fluorescent protein expression plasmid allowed us to assess the pathway choice, which the transgenic axons had made. Quantification based on confocal laser scanning microscopic images revealed that transgenic axons selectively fasciculated with tectofugal tracts specified by the matching type of cadherin. This is the first direct evidence that cadherins mediate differential axonal pathfinding in vivo, possibly by a preferentially homotypic adhesive mechanism.

Optimizing the efficacy of epitope-directed DNA vaccination

An increasing number of clinical trials has been initiated to test the potential of prophylactic or curative vaccination with tumor Ag-encoding DNA vaccines. However, in the past years it has become apparent that for many Ags and in particular for tumor Ags the intracellular processing and presentation are suboptimal. To improve epitope-directed DNA vaccines we have developed a murine model system in which epitope-specific, DNA vaccine-induced T cell immunity can be followed by MHC tetramer technology directly ex vivo. We have used this well-defined model to dissect the parameters that are crucial for the induction of strong cytotoxic T cell immunity using two independent model Ags. These experiments have led to a set of five guidelines for the design of epitope-directed DNA vaccines, indicating that carboxyl-terminal fusion of the epitope to a carrier protein of foreign origin is the most favorable strategy. DNA vaccines that are based on these guidelines induce high-magnitude CD8(+) T cell responses in >95% of vaccinated animals. Moreover, T cell immunity induced by this type of optimized DNA vaccine provides long-term protection against otherwise lethal tumor challenges.

Delivery of genes and fluorescent dyes into cells of the intact lens by particle bombardment

The authors report the use of a particle bombardment technique to deliver exogenous genes and fluorescent dyes into living fibre cells in the intact lens. Gold particles were coated with plasmid DNA encoding green fluorescent protein (GFP) or the lipophilic fluorescent probes DiI and DiO. The particles were introduced into embryonic chicken or neonatal mouse lenses using a pressurized helium charge. A significant fraction of particles penetrated the capsule and came to rest in the superficial lens cortex. Over the range tested, varying the particle size or the pressure of the helium charge had little effect on the final distribution of particles within the lens. Particle bombardment was used initially to deliver DiI and DiO into the lens. Within a few hours, bombarded lenses exhibited multicolored membranous labelling of individual, elongating fibre cells. The particle bombardment technique was also used to introduce a plasmid encoding GFP. After overnight incubation, many fibre cells in the bow region expressed GFP. On close examination by confocal reflectance microscopy, each expressing cell was found to contain a gold particle lodged in its nucleus. The authors examined the fate of GFP-expressing fibre cells over a period of 1 week in organ culture. In the embryonic chicken lens, transfected fibres showed modest (approximately two-fold) elongation. In contrast, GFP-expressing mouse lens fibres underwent dramatic elongation, reaching the anterior and posterior sutures after 7 days in culture. These species differences may reflect the fact that mitosis continued at a near normal rate in the cultured mouse lens but declined precipitously in the cultured chicken lens. These results suggest that particle bombardment, in conjunction with appropriate cell culture conditions, may prove useful in visualizing the behaviour of differentiating fibre cells in the living intact lens in vitro.

[Construction of transgenic mice carrying enhanced green fluorescent protein gene by seminiferous tubule microinjection]

OBJECTIVE

To study the feasibility of establishing transgenic mice carrying enhanced green flourescent protein (EGFP) gene by means of seminiferous tubule microinjection.

METHODS

The vector expressing enhanced green fluorescent protein under the control of human cytomegalovirus immediate-early promoter (pCMV-EGFP) was selected and mixed with liposome in vitro. Microinjection at different doses of the liposome-entrapped plasmid DNA into the seminiferous tubules of male mice at different ages was performed to establish transgenic mice, which were made to mate with female mice at least 40 d after the microinjection. Genomic DNA was extracted from the offspring of the founder mice for PCR and Southern blotting analysis, and the frozen sections of different tissues from 2 of the founders mice were prepared for fluorescence microscopic observation.

RESULTS

Among the 41 mice receiving the microinjection, 32 survived and retained their mating ability and fertility, and among their 382 offspring 133 were positive for EGFP DNA as demonstrated by PCR, 15 of which were confirmed by Southern blotting analysis. The age of the mice or the doses of microinjection they received was not shown to impact the integration of EGFP gene, and fluorescence microscopy failed to detect significant EGFP expression in the tissues of the founder mice (P>0.05) in comparison with normal mice.

CONCLUSION

Seminiferous tubule microinjection is simple and practicable to implement gene transfer in mice.

Direct injection of foreign DNA into mouse testis as a possible in vivo gene transfer system via epididymal spermatozoa

We have attempted to transfect testicular spermatozoa with plasmid DNA by direct injection into testes to obtain transgenic animals [this technique was thus termed "testis-mediated gene transfer (TMGT)"]. When injected males were mated with superovulated females 2 and 3 days after injection, (i) high efficiencies (more than 50%) of gene transmission were achieved in the mid-gestational F0 fetuses, (ii) the copy number of plasmid DNA in the fetuses was estimated to be less than 1 copy per diploid cell, and (iii) overt gene expression was not found in these fetuses. These findings suggest the possibility that plasmid DNA introduced into a testis is rapidly transported to the epididymis and then incorporated by epididymal spermatozoa. The purpose of this study was to elucidate the mechanism of TMGT by introducing trypan blue (TB) or Hoechst 33342 directly into testis. We found that TB is transported to the ducts of the caput epididymis via rete testis within 1 min after testis injection, and TB reached the corpus and cauda epididymis within 2-4 days after injection. Staining of spermatozoa isolated from any portion of epididymis was observed 4 days after injection of a solution containing Hoechst 33342. Injection of enhanced green fluorescent protein (EGFP) expression vector/liposome complex into testis resulted in transfection of epithelial cells of epididymal ducts facing the lumen, although the transfection efficiency appeared to be low. In vivo electroporation toward the caput epididymis immediately after injection of EGFP expression vector into a testis greatly improved the uptake of foreign DNA by the epididymal epithelial cells. PCR analysis using spermatozoa isolated from corpus and cauda epididymis 4 days after injection of a DNA/liposome complex into testis revealed exogenous DNA in these spermatozoa even after treatment with DNase I. These findings indicate that exogenous DNA introduced into tesits is rapidly transported to epididymal ducts via the rete testis and efferent ducts, and then incorporated by epithelial cells of epididymis and epididymal spermatozoa.

Remote delivery of rAAV-GFP to the rat brainstem through the recurrent laryngeal nerve

OBJECTIVE

To demonstrate that a recombinant adeno-associated viral vector (rAAV) carrying the gene for green fluorescent protein (GFP) could be delivered to the rat brainstem by remote injection into the recurrent laryngeal nerve.

STUDY DESIGN/METHODS

rAAV-GFP is a serotype 2 adeno-associated vector containing the cDNA of GFP and woodchuck hepatitis virus posttranscriptional regulatory element (WPRE) under the control of the CAG promoter (obtained from Matthew During, PhD, Thomas Jefferson Medical College). Five microliters or 10 microL of 1.4 x 109 particles/microL of rAAV-GFP were injected into the right recurrent laryngeal nerve of adult Sprague-Dawley rats. Rats were killed and perfused at 3 (n = 3) and 11 weeks (n = 3). Brainstems were removed and cryosectioned. Fluorescent in-situ hybridization (FISH) was performed on cryosections from animals killed at 3 weeks using a cDNA probe for woodchuck polyribosomal enzyme within the rAAV vector. In a third group (n = 2), Fluoro-Gold (Fluorochrome, Inc., Denver, CO) was injected into the right thyroarytenoid muscle for comparison of neuronal uptake distribution. These rats were killed and perfused at 3 weeks.

RESULTS

The presence of GFP was noted in neurons throughout the medulla of all rat brainstems after unilateral rAAV-GFP injection at both 3 and 11 weeks. In contrast to the Fluoro-Gold, GFP was noted bilaterally and outside of the nucleus ambiguus. FISH confirmed the presence of virus within neurons expressing GFP at 3 weeks.

CONCLUSIONS

Remote delivery of rAAV-GFP to the rat brainstem is possible through injection into the recurrent laryngeal nerve. This has important therapeutic implications for the future treatment of recurrent laryngeal nerve injury and neurodegenerative diseases.

Gene replacement therapy in the retinal degeneration slow (rds) mouse: the effect on retinal degeneration following partial transduction of the retina

The retinal degeneration slow (rds or Prph2(Rd2/Rd2)) mouse, a model of recessive retinitis pigmentosa, lacks a functional gene encoding peripherin 2. This membrane glycoprotein is required for the formation of photoreceptor outer segment discs. The striking feature of the rds mouse is the complete failure to develop outer segments. We have previously examined the short-term effect of gene replacement therapy using an adeno-associated (AAV) vector and demonstrated induction of outer segments and improvement of photoreceptor function. Here we have extended our analysis and have demonstrated that the potential for ultrastructural improvement is dependent upon the age at which animals are treated, but the effect of a single injection on photoreceptor ultrastructure may be long-term. However, there was no significant effect on photoreceptor cell loss, irrespective of the date of administration, despite the improvements in morphology and function. Our investigation excluded procedure-related damage, vector toxicity and immune responses as major factors which might counteract the benefits of photoreceptor restoration, but suggested that transgene over-expression is of significance. These findings suggest that successful gene therapy in patients with photoreceptor defects may ultimately depend upon intervention in early stages of disease and upon accurate control of transgene expression.

Targeting of Pseudomonas aeruginosa in the bloodstream with bispecific monoclonal antibodies

We examined the ability of a bispecific mAb reagent, consisting of a mAb specific for the primate erythrocyte complement receptor cross-linked with an anti-bacterial mAb, to target bacteria in the bloodstream in an acute infusion model in monkeys. In vitro studies demonstrated a variable level of complement-mediated binding (immune adherence) of Pseudomonas aeruginosa (strain PAO1) to primate E in serum. In vivo experiments in animals depleted of complement revealed that binding of bacteria to E was <1% before administration of the bispecific reagent, but within 5 min of its infusion, >99% of the bacteria bound to E. In complement-replete monkeys, a variable fraction of infused bacteria bound to E. This finding may have significant implications in the interpretation of animal models and in the understanding of bacteremias in humans. Treatment of these complement-replete monkeys with the bispecific reagent led to >99% binding of bacteria to E. Twenty-four-hour survival studies were conducted; several clinical parameters, including the degree of lung damage, cytokine levels, and liver enzymes in the circulation, indicate that the bispecific mAb reagent provides a degree of protection against the bacterial challenge.

Xenopus tropicalis oocytes as an advantageous model system for the study of intracellular Ca(2+) signalling

1. The purpose of this study was to compare oocytes from the pipid frogs Xenopus tropicalis and Xenopus laevis, with respect to their utility for studying Ca(2+) signalling mechanisms and for expression of heterologous proteins. 2. We show that X. tropicalis oocytes possess an intracellular Ca(2+) store that is mobilized by inositol (1,4,5) trisphosphate (IP(3)). Ca(2+) signalling is activated by endogenous lysophosphatidic acid receptors and cytosolic Ca(2+) activates a plasma membrane chloride conductance. The spatiotemporal organization of cytosolic Ca(2+) signals, from the microscopic architecture of elementary Ca(2+) 'puffs' to the macroscopic patterns of Ca(2+) spiking are closely similar to the local and global patterns of Ca(2+) release previously characterized in oocytes from X. laevis. 3. By injecting X. tropicalis oocytes with cDNA encoding an ER-targeted fluorescent protein construct, we demonstrate the capacity of the X. tropicalis oocyte to readily express heterologous proteins. The organization of ER is polarized across the oocyte, with the IP(3)-releaseable store targeted within an approximately 8 microm wide band that circumscribes the cell. 4. We conclude that the X. tropicalis oocyte shares many of the characteristics that have made oocytes of X. laevis a favoured system for studying Ca(2+) signalling mechanisms. Moreover, X. tropicalis oocytes display further practical advantages in terms of imaging depth, Ca(2+) signal magnitude and electrical properties. These further enhance the appeal of X. tropicalis as an experimental system, in addition to its greater amenability to transgenic approaches.

Topical gene transfer into rat skin using electroporation

PURPOSE

To investigate whether electroporation can be used for topical gene delivery and for DNA expression in rat keratinocytes.

METHODS

The localization of a fluorescent-labelled plasmid and the expression of a reporter gene (pEGFP-N1) coding for Green Fluorescent Protein (GFP) in stripped skin were assessed by Confocal Laser Scanning Microscopy (CLSM).

RESULTS

The plasmid penetrated into the epidermis within minutes after electroporation and entered the keratinocyte cytoplasm within hours. A localized expression of GFP was observed for at least 7 days in the epidermis. Skin viability was not compromised by electroporation.

CONCLUSIONS

Electroporation enhances the delivery, and hence the expression, of topically applied plasmid DNA on the skin. It could be a promising alternative method to administer DNA, particularly for DNA vaccines, in the skin in vivo.

Strain-dependent antibody response induced by DNA immunization

The antibody (Ab) response induced by DNA-based immunization was compared in various strains of inbred, H-2 congenic and outbred mice with different haplotypes of mouse major histocompatibility complex (H-2). Two different plasmid expression vectors encoding Aequorea victoria green fluorescent protein (GFP) or Escherichia coli, beta-galactosidase (beta-gal) were introduced into quadriceps muscle, and Ab production was examined using both enzyme-linked immunosorbent assay and immunoblot analysis. The beta-gal plasmid DNA immunization induced strong Ab production in all inbred, H-2 congenic and outbred strains at the early stages of immunization. By comparison with beta-gal peptide immunization, the degree of Ab response was H-2 haplotype-dependent. On the other hand, Ab production by GFP plasmid DNA immunization was observed in outbred strains, but not in some of the inbred and H-2 congenic strains. Also, outbred strains showed a high Ab response compared with other inbred and H-2 congenic strains by GFP peptide immunization. Reverse transcription-polymerase chain reaction analysis demonstrated the presence of GFP or beta-gal transcripts at the DNA inoculation site in all the strains studied, even in inbred and H-2 congenic strains which showed no Ab production by GFP plasmid DNA immunization. These results indicate that the difference in Ab response induced by DNA immunization as well as by peptide immunization depends upon the H-2 haplotypes of host strains.

Introduction of a foreign gene into medakafish using the particle gun method

We developed a procedure to introduce a foreign gene into fertilized eggs of medakafish (Oryzias latipes) using the particle gun method, which is one of the easiest and most reliable techniques for gene transfer. A plasmid construct with the green fluorescence protein (GFP) gene driven by the madakafish beta-actin gene promoter was successfully introduced into eggs, and the expression of GFP was observed in 20% of the primary transfectant (chimera) fish. In addition, germ line transmission of GFP was observed in 13% of the GFP-positive primary transfectant fish. The new application described here should enable us to investigate gene expression using the fish model on a routine basis without high technical sophistication. J. Exp. Zool. 287:285-293, 2000.

Maturation and trafficking of monocyte-derived dendritic cells in monkeys: implications for dendritic cell-based vaccines

Human dendritic cells (DC) have polarized responses to chemokines as a function of maturation state, but the effect of maturation on DC trafficking in vivo is not known. We have addressed this question in a highly relevant rhesus macaque model. We demonstrate that immature and CD40 ligand-matured monocyte-derived DC have characteristic phenotypic and functional differences in vitro. In particular, immature DC express CC chemokine receptor 5 (CCR5) and migrate in response to macrophage inflammatory protein-1alpha (MIP-1alpha), whereas mature DC switch expression to CCR7 and respond exclusively to MIP-3beta and 6Ckine. Mature DC transduced to express a marker gene localized to lymph nodes after intradermal injection, constituting 1.5% of lymph node DC. In contrast, cutaneous DC transfected in situ via gene gun were detected in the draining lymph node at a 20-fold lower frequency. Unexpectedly, the state of maturation at the time of injection had no influence on the proportion of DC that localized to draining lymph nodes, as labeled immature and mature DC were detected in equal numbers. Immature DC that trafficked to lymph nodes underwent a significant up-regulation of CD86 expression indicative of spontaneous maturation. Moreover, immature DC exited completely from the dermis within 36 h of injection, whereas mature DC persisted in large numbers associated with a marked inflammatory infiltrate. We conclude that in vitro maturation is not a requirement for effective migration of DC in vivo and suggest that administration of Ag-loaded immature DC that undergo natural maturation following injection may be preferred for DC-based immunotherapy.

Gene expression after intrarenal injection of plasmid DNA in the rat

Effective gene therapy requires efficient delivery and expression of the necessary genetic information to the target tissue. We demonstrate here that plasmid DNA, injected as naked, uncomplexed DNA into the cortical region of rat kidney, or intravenously, is localized and expressed in the kidney. The plasmid pRSVZ contained the Rous sarcoma virus promoter and a reporter gene, the beta-galactosidase gene, derived from bacteria. The beta-galactosidase gene hydrolyzes the artificial substrate X-gal to produce an intense blue color in cells that have taken up and expressed the plasmid genes. We have used X-gal staining and Western blotting to study plasmid gene expression 1, 4, and 8 days and 6 months after intrarenal injection of 50 microg of plasmid DNA and at 1 and 4 days after intravenous injection. Expression was apparent in the kidneys and several other tissues 24 h after injection and persisted for at least 8 days; expressed proteins could still be detected in the injected kidney 6 months later. These observations were corroborated by use of a plasmid, pEGFP-Puro, harboring the cytomegalovirus promoter in conjunction with a different reporter gene, the green fluorescent protein (GFP). Histological localization and Western blotting analysis of GFP expression after intrarenal injection of pEGFP-Puro paralleled results obtained with the plasmid pRSVZ. Our findings support the suggestion that intrarenal or intravenous injection of naked plasmid DNA may be an effective means of delivering therapeutic genes to the kidney and several other tissues.

Coelenterate photoproteins as indicators of cytoplasmic free Ca2+ in small cells

The Ca2+-activated photoproteins aequorin and obelin are capable of detecting rapid changes in free Ca2+ over the range 10nM-100uM. Whilst they have been used to quantify free Ca transients in giant cells for some time, their use in small mammalian cells has been restricted because of the difficulty of incorporating them into live cells without impairment of cell function. We have developed three methods for incorporating photoproteins into small cells (a) reversible cell swelling (b) membrane fusion and (c) intracellular release from pinocytotic vesicles. Formation of the membrane attack complex of complement (C5b6789), via a specific cell surface antibody to activate complement, causes a rapid increase in cytoplasmic Ca2+ detectable within 5-10 s. It provides a specific method for quantifying cytoplasmic photoprotein. As a result new insights into the role of intracellular Ca2+ in cell physiology and pathology have been established.

Photoelectrode with a very short time-constant for recording intracerebrally Ca2+ transients at a cellular level

In order to study calcium transients in the central nervous system of vertebrates a microphotoelectrode was designed. It is composed of three channels, through the first aequorin is perfused into the extracellular space under constant pressure, the second is an optical glass light-conducting channel, and the third a classical NaCl-filled recording pipette. The light emitted by the interaction of the injected aequorin with the local extracellular calcium is transmitted through the optic fiber to a photomultiplier of high sensitivity.