Epidermal Langerhans cells (LCs) function as professional antigen-presenting cells of the skin. We investigated the LC-targeting properties of a special mannose-moiety-coated pathogen-like synthetic nanomedicine DermaVir (DV), which is capable to express antigens to induce immune responses and kill HIV-infected cells. Our aim was to use multiphoton laser microscopy (MLM) in vivo in order to visualize the uptake of Alexa-labelled DV (AF546-DV) by LCs. Knock-in mice expressing enhanced green fluorescent protein (eGFP) under the control of the langerin gene (CD207) were used to visualize LCs. After 1 h, AF546-DV penetrated the epidermis and entered the eGFP-LCs. The AF546-DV signal was equally distributed inside the LCs. After 9 h, we observed AF546-DV signal accumulation that occurred mainly at the cell body. We demonstrated in live animals that LCs picked up and accumulated the nanoparticles in the cell body.
Allergen-specific immunotherapy (ASIT) the only disease-modifying treatment for IgE-mediated allergies is characterized with long treatment duration and high risk of side effects. We investigated the safety, immunogenicity and efficacy of a novel ASIT, called DermAll, in an experimental allergic rhinitis model. We designed and characterized DermAll-OVA, a synthetic plasmid pDNA/PEIm nanomedicine expressing ovalbumin (OVA) as model allergen. DermAll-OVA was administered topically with DermaPrep device to target Langerhans cells. To detect the clinical efficacy of DermAll ASIT we quantified the nasal symptoms and characterized the immunomodulatory activity of DermAll ASIT by measuring cytokine secretion after OVA-stimulation of splenocytes and antibodies from the sera. In allergic mice DermAll ASIT was as safe as Placebo, balanced the allergen-induced pathogenic TH2-polarized immune responses, and decreased the clinical symptoms by 52% [32%, 70%] compared to Placebo. These studies suggest that DermAll ASIT is safe and should significantly improve the immunopathology and symptoms of allergic diseases.
The lactose operon of Escherichia coli is a paradigm system for quantitative understanding of gene regulation in prokaryotes. Yet, none of the many mathematical models built so far to study the dynamics of this system considered the fact that the Lac repressor regulates its own transcription by forming a transcriptional roadblock at the O3 operator site. Here we study the effect of autoregulation on intracellular LacI levels and also show that cAMP-CRP binding does not affect the efficiency of autoregulation. We built a mathematical model to study the role of LacI autoregulation in the lactose utilization system. Previously, it has been argued that negative autoregulation can significantly reduce noise as well as increase the speed of response. We show that the particular molecular mechanism, a transcriptional roadblock, used to achieve self-repression in the lac system does neither. Instead, LacI autoregulation balances two opposing states, one that allows quicker response to smaller pulses of external lactose, and the other that minimizes production costs in the absence of lactose.
Optimal response to environmental stimuli often requires activation of certain genes and repression of others. Dual function regulatory proteins play a key role in the differential regulation of gene expression. While repression can be achieved by any DNA binding protein through steric occlusion of RNA polymerase in the promoter region, activation often requires a surface on the regulatory protein to contact RNAP and thus facilitate transcription initiation. RNAP itself is also a DNA binding protein, therefore it can function as a transcriptional repressor. Searching the Escherichia coli promoter database we found that ?14% of the identified forward promoters overlap with a promoter oriented in the opposite direction. In this article we combine a mathematical model with experimental analysis of synthetic regulatory regions to investigate interference of overlapping promoters. We find that promoter interference depends on the characteristics of overlapping promoters. The model predicts that promoter strength and interference can be regulated separately, which provides unique opportunities for regulation. Our experimental data suggest that in principle any DNA binding protein can be used for both activation and repression of promoter transcription, depending on the context. These findings can be exploited in the construction of synthetic networks.
Galactose is important for the survival and virulence of bacteria. In Escherichia coli, galactose is utilized by the Leloir pathway, which is controlled by a complex network. To shed light on the potential functions the galactose network could perform, we performed bioinformatical analysis of reference genome sequences belonging to the Enterobacteriaceae family. We found that several genomes have reduced numbers of components compared to the E. coli galactose system, suggesting that the network can be optimized for different environments. Typically, genes are removed by deletions; however, in Yersinia pestis, the galactose mutarotase (galM) gene is inactivated by a single-base-pair deletion. Lack of GalM activity indicates that the two anomers of D-galactose are used for different purposes, ?-D-galactose as a carbon source and ?-D-galactose for induction of UDP-galactose synthesis for biosynthetic glycosylation. We demonstrate that activity of the galM gene can be restored by different single-base-pair insertions. During the evolution of Y. pestis to become a vector-transmitted systemic pathogen, many genes were converted to pseudogenes. It is not clear whether pseudogenes are present to maintain meiotrophism or are in the process of elimination. Our results suggest that the galM pseudogene has not been deleted because its reactivation may be beneficial in certain environments.
Small regulatory RNAs (sRNAs) in eukaryotes and bacteria play an important role in the regulation of gene expression either by binding to regulatory proteins or directly to target mRNAs. Two of the best-characterized bacterial sRNAs, Spot42 and RyhB, form a complementary pair with the ribosome binding region of their target mRNAs, thereby inhibiting translation or promoting mRNA degradation. To investigate the steady-state and dynamic potential of such sRNAs, we examine the 2 key parameters characterizing sRNA regulation: the capacity to overexpress the sRNA relative to its target mRNA and the speed at which the target mRNA is irreversibly inactivated. We demonstrate different methods to determine these 2 key parameters, for Spot42 and RyhB, which combine biochemical and genetic experiments with computational analysis. We have developed a mathematical model that describes the functional properties of sRNAs with various characteristic parameters. We observed that Spot42 and RyhB function in distinctive parameter regimes, which result in divergent mechanisms.
The P1 promoter of the galactose operon in Escherichia coli is one of the best studied examples of extended -10 promoters. Recognition of the P1 promoter does not require specific contacts between RNA polymerase and its poor -35 element. To investigate whether specific recognition of the -35 element would affect the regulation of P1 by GalR, we mutagenized the -35 element of P1, isolated variants of the -35 element and studied the regulation of the mutant promoters by in vitro transcription assays and by mathematical modeling. The results show that the GalR-mediated DNA loop is less efficient in repressing P1 transcription when RNA polymerase binds to the -10 and -35 elements concomitantly. Our results suggest that promoters that lack specific -35 element recognition allow decoupling of local chromosome structure from transcription initiation.
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