PMCC PMCC

Search tips
Search criteria

Advanced
Results 1-15 (15)
 

Clipboard (0)
None

Select a Filter Below

Journals
more »
Year of Publication
1.  Remote focal scanning optical projection tomography with an electrically tunable lens 
Biomedical Optics Express  2014;5(10):3367-3375.
We describe a remote focal scanning technique for optical projection tomography (OPT) implemented with an electrically tunable lens (ETL) that removes the need to scan the specimen or objective lens. Using a 4× objective lens the average spatial resolution is improved by ∼46% and the light collection efficiency by a factor of ∼6.76, thereby enabling increased acquisition speed and reduced light dose. This convenient implementation is particularly appropriate for lower magnifications and larger sample diameters where axial objective scanning would encounter problems with speed and stability.
doi:10.1364/BOE.5.003367
PMCID: PMC4206308  PMID: 25360356
(170.6900) Three-dimensional microscopy; (170.6960) Tomography
2.  New chemical probes targeting cholesterylation of Sonic Hedgehog in human cells and zebrafish† †Electronic supplementary information (ESI) available: Tables S1–S2; Fig. S1–S9, full experimental details and procedures, 1H/13C NMR spectral data of compounds 1–6. See DOI: 10.1039/c4sc01600a Click here for additional data file.  
Chemical Science  2014;5(11):4249-4259.
Alkynyl-cholesterol probes tag and track Hedgehog protein, illuminating the role of protein cholesterylation in secretion, transport complex formation and signalling, and enabling quantitative proteomic analysis, imaging, and detection of cholesterylation in developing zebrafish.
Sonic Hedgehog protein (Shh) is a morphogen molecule important in embryonic development and in the progression of many cancer types in which it is aberrantly overexpressed. Fully mature Shh requires attachment of cholesterol and palmitic acid to its C- and N-termini, respectively. The study of lipidated Shh has been challenging due to the limited array of tools available, and the roles of these posttranslational modifications are poorly understood. Herein, we describe the development and validation of optimised alkynyl sterol probes that efficiently tag Shh cholesterylation and enable its visualisation and analysis through bioorthogonal ligation to reporters. An optimised probe was shown to be an excellent cholesterol biomimetic in the context of Shh, enabling appropriate release of tagged Shh from signalling cells, formation of multimeric transport complexes and signalling. We have used this probe to determine the size of transport complexes of lipidated Shh in culture medium and expression levels of endogenous lipidated Shh in pancreatic ductal adenocarcinoma cell lines through quantitative chemical proteomics, as well as direct visualisation of the probe by fluorescence microscopy and detection of cholesterylated Hedgehog protein in developing zebrafish embryos. These sterol probes provide a set of novel and well-validated tools that can be used to investigate the role of lipidation on activity of Shh, and potentially other members of the Hedgehog protein family.
doi:10.1039/c4sc01600a
PMCID: PMC4285107  PMID: 25574372
3.  Non-canonical Notch signaling modulates cytokine responses of dendritic cells to inflammatory stimuli1 
Dendritic cell (DC) derived cytokines play a key role in specifying adaptive immune responses tailored to the type of pathogen encountered and the local tissue environment. However, little is known about how DC perceive the local environment. We investigated whether endogenous Notch signaling could affect DC responses to pathogenic stimuli. We demonstrate that concurrent Notch and TLR stimulation results in a unique cytokine profile in mouse bone-marrow derived DC characterized by enhanced IL-10 and IL-2 and reduced IL-12 expression compared to TLR ligation alone. Unexpectedly, modulation of cytokine production occurred through a non-canonical Notch signaling pathway, independent of γ-secretase activity. Modulation required de novo protein synthesis and PI3K, JNK and ERK activity were necessary for enhanced IL-2 expression while modulation of IL-10 only required PI3K activity. Further, we show that this γ-secretase independent Notch pathway can induce PI3K activity. In contrast, expression of the canonical Notch target gene Hes1 was suppressed in DC stimulated with Notch and TLR ligands simultaneously. Thus, our data suggest that Notch acts as an endogenous signal that modulates cytokine expression of DC through a non-canonical pathway and therefore has the potential to tailor the subsequent adaptive immune response in a tissue and/or stage dependent manner.
doi:10.4049/jimmunol.1103102
PMCID: PMC3442230  PMID: 22753939
4.  From seeing to believing: labelling strategies for in vivo cell-tracking experiments 
Interface Focus  2013;3(3):20130001.
Intravital microscopy has become increasingly popular over the past few decades because it provides high-resolution and real-time information about complex biological processes. Technological advances that allow deeper penetration in live tissues, such as the development of confocal and two-photon microscopy, together with the generation of ever-new fluorophores that facilitate bright labelling of cells and tissue components have made imaging of vertebrate model organisms efficient and highly informative. Genetic manipulation leading to expression of fluorescent proteins is undoubtedly the labelling method of choice and has been used to visualize several cell types in vivo. This approach, however, can be technically challenging and time consuming. Over the years, several dyes have been developed to allow rapid, effective and bright ex vivo labelling of cells for subsequent transplantation and imaging. Here, we review and discuss the advantages and limitations of a number of strategies commonly used to label and track cells at high resolution in vivo in mouse and zebrafish, using fluorescence microscopy. While the quest for the perfect label is far from achieved, current reagents are valuable tools enabling the progress of biological discovery, so long as they are selected and used appropriately.
doi:10.1098/rsfs.2013.0001
PMCID: PMC3638420  PMID: 23853708
cell biology; in vivo imaging; cancer; stem cells; fluorescence microscopy
5.  The CD46 and Jagged1 interaction is critical for human T helper 1 immunity 
Nature immunology  2012;13(12):1213-1221.
CD46 is a complement regulator with important immune-related roles. CD46 functions as a pathogen receptor and is a potent co-stimulator for the induction of interferon-γ (IFN-γ)-secreting T helper 1 (TH1) effector T cells and their subsequent switch into interleukin-10 (IL-10)-producing regulatory T cells. Here, we identify the Notch protein family member Jagged1 as a new physiological ligand for CD46. Further, CD46 regulates Notch receptors and ligands expression during T cell activation and disturbance of the CD46-Notch crosstalk impedes IFN-γ induction and IL-10 switching. Importantly, CD4+ T cells from CD46-deficient patients and patients with hypomorphic Jagged1 mutations (Alagille Syndrome) fail to mount appropriate TH1 responses in vitro and in vivo suggesting that CD46-Jagged1 crosstalk is responsible for the recurrent infections in subpopulations of these patients.
doi:10.1038/ni.2454
PMCID: PMC3505834  PMID: 23086448
6.  FLIM FRET Technology for Drug Discovery: Automated Multiwell-Plate High-Content Analysis, Multiplexed Readouts and Application in Situ** 
Chemphyschem  2011;12(3):609-626.
A fluorescence lifetime imaging (FLIM) technology platform intended to read out changes in Förster resonance energy transfer (FRET) efficiency is presented for the study of protein interactions across the drug-discovery pipeline. FLIM provides a robust, inherently ratiometric imaging modality for drug discovery that could allow the same sensor constructs to be translated from automated cell-based assays through small transparent organisms such as zebrafish to mammals. To this end, an automated FLIM multiwell-plate reader is described for high content analysis of fixed and live cells, tomographic FLIM in zebrafish and FLIM FRET of live cells via confocal endomicroscopy. For cell-based assays, an exemplar application reading out protein aggregation using FLIM FRET is presented, and the potential for multiple simultaneous FLIM (FRET) readouts in microscopy is illustrated.
doi:10.1002/cphc.201000874
PMCID: PMC3084521  PMID: 21337485
drug discovery; fluorescence lifetime imaging; FRET; high-throughput screening; proteins
7.  In vivo fluorescence lifetime optical projection tomography 
Biomedical Optics Express  2011;2(5):1340-1350.
We demonstrate the application of fluorescence lifetime optical projection tomography (FLIM-OPT) to in vivo imaging of lysC:GFP transgenic zebrafish embryos (Danio rerio). This method has been applied to unambiguously distinguish between the fluorescent protein (GFP) signal in myeloid cells from background autofluorescence based on the fluorescence lifetime. The combination of FLIM, an inherently ratiometric method, in conjunction with OPT results in a quantitative 3-D tomographic technique that could be used as a robust method for in vivo biological and pharmaceutical research, for example as a readout of Förster resonance energy transfer based interactions.
doi:10.1364/BOE.2.001340
PMCID: PMC3087590  PMID: 21559145
(170.3650) Lifetime-based sensing; (170.6900) Three-dimensional microscopy; (170.6920) Time-resolved imaging; (170.6960) Tomography
9.  MMBGX: a method for estimating expression at the isoform level and detecting differential splicing using whole-transcript Affymetrix arrays 
Nucleic Acids Research  2009;38(1):e4.
Affymetrix has recently developed whole-transcript GeneChips—‘Gene’ and ‘Exon’ arrays—which interrogate exons along the length of each gene. Although each probe on these arrays is intended to hybridize perfectly to only one transcriptional target, many probes match multiple transcripts located in different parts of the genome or alternative isoforms of the same gene. Existing statistical methods for estimating expression do not take this into account and are thus prone to producing inflated estimates. We propose a method, Multi-Mapping Bayesian Gene eXpression (MMBGX), which disaggregates the signal at ‘multi-match’ probes. When applied to Gene arrays, MMBGX removes the upward bias of gene-level expression estimates. When applied to Exon arrays, it can further disaggregate the signal between alternative transcripts of the same gene, providing expression estimates of individual splice variants. We demonstrate the performance of MMBGX on simulated data and a tissue mixture data set. We then show that MMBGX can estimate the expression of alternative isoforms within one experimental condition, confirming our results by RT-PCR. Finally, we show that our method for detecting differential splicing has a lower error rate than standard exon-level approaches on a previously validated colon cancer data set.
doi:10.1093/nar/gkp853
PMCID: PMC2800219  PMID: 19854940
10.  Independent degeneration of photoreceptors and retinal pigment epithelium in conditional knockout mouse models of choroideremia 
Journal of Clinical Investigation  2006;116(2):386-394.
Choroideremia (CHM) is an X-linked degeneration of the retinal pigment epithelium (RPE), photoreceptors, and choroid, caused by loss of function of the CHM/REP1 gene. REP1 is involved in lipid modification (prenylation) of Rab GTPases, key regulators of intracellular vesicular transport and organelle dynamics. To study the pathogenesis of CHM and to develop a model for assessing gene therapy, we have created a conditional mouse knockout of the Chm gene. Heterozygous-null females exhibit characteristic hallmarks of CHM: progressive degeneration of the photoreceptors, patchy depigmentation of the RPE, and Rab prenylation defects. Using tamoxifen-inducible and tissue-specific Cre expression in combination with floxed Chm alleles, we show that CHM pathogenesis involves independently triggered degeneration of photoreceptors and the RPE, associated with different subsets of defective Rabs.
doi:10.1172/JCI26617
PMCID: PMC1326146  PMID: 16410831
11.  Notch ligation by Delta1 inhibits peripheral immune responses to transplantation antigens by a CD8+ cell–dependent mechanism 
Journal of Clinical Investigation  2003;112(11):1741-1750.
Notch signaling plays a fundamental role in determining the outcome of differentiation processes in many tissues. Notch signaling has been implicated in T versus B cell lineage commitment, thymic differentiation, and bone marrow hematopoietic precursor renewal and differentiation. Notch receptors and their ligands are also expressed on the surface of mature lymphocytes and APCs, but the effects of Notch signaling in the peripheral immune system remain poorly defined. The aim of the studies reported here was to investigate the effects of signaling through the Notch receptor using a ligand of the Delta-like family. We show that Notch ligation in the mature immune system markedly decreases responses to transplantation antigens. Constitutive expression of Delta-like 1 on alloantigen-bearing cells renders them nonimmunogenic and able to induce specific unresponsiveness to a challenge with the same alloantigen, even in the form of a cardiac allograft. These effects could be reversed by depletion of CD8+ cells at the time of transplantation. Ligation of Notch on splenic CD8+ cells results in a dramatic decrease in IFN-γ with a concomitant enhancement of IL-10 production, suggesting that Notch signaling can alter the differentiation potential of CD8+ cells. These data implicate Notch signaling in regulation of peripheral immunity and suggest a novel approach for manipulating deleterious immune responses.
doi:10.1172/JCI200318020
PMCID: PMC281641  PMID: 14660750
12.  Impaired Antiviral Response and Alpha/Beta Interferon Induction in Mice Lacking Beta Interferon 
Journal of Virology  2000;74(7):3404-3409.
We have generated mice lacking the gene for beta interferon and report that they are highly susceptible to vaccinia virus infection. Furthermore, in cultured embryo fibroblasts, viral induction of alpha interferon and of 2-5A synthetase genes is impaired. We also show that beta interferon does not prime its own expression.
PMCID: PMC111842  PMID: 10708458
13.  Designing attractive models via automated identification of chaotic and oscillatory dynamical regimes 
Nature Communications  2011;2:489-.
Chaos and oscillations continue to capture the interest of both the scientific and public domains. Yet despite the importance of these qualitative features, most attempts at constructing mathematical models of such phenomena have taken an indirect, quantitative approach, for example, by fitting models to a finite number of data points. Here we develop a qualitative inference framework that allows us to both reverse-engineer and design systems exhibiting these and other dynamical behaviours by directly specifying the desired characteristics of the underlying dynamical attractor. This change in perspective from quantitative to qualitative dynamics, provides fundamental and new insights into the properties of dynamical systems.
Modelling of chaos and oscillations is usually done indirectly and quantitatively by fitting models to a finite number of data-points. Here, a qualitative framework is developed where the characteristics of the underlying dynamical system are directly specified, revealing new properties of such systems.
doi:10.1038/ncomms1496
PMCID: PMC3207206  PMID: 21971504
14.  P38 and JNK have opposing effects on persistence of in vivo leukocyte migration in zebrafish 
Immunology and Cell Biology  2012;91(1):60-69.
The recruitment and migration of macrophages and neutrophils is an important process during the early stages of the innate immune system in response to acute injury. Transgenic pu.1:EGFP zebrafish permit the acquisition of leukocyte migration trajectories during inflammation. Currently, these high-quality live-imaging data are mainly analysed using general statistics, for example, cell velocity. Here, we present a spatio-temporal analysis of the cell dynamics using transition matrices, which provide information of the type of cell migration. We find evidence that leukocytes exhibit types of migratory behaviour, which differ from previously described random walk processes. Dimethyl sulfoxide treatment decreased the level of persistence at early time points after wounding and ablated temporal dependencies observed in untreated embryos. We then use pharmacological inhibition of p38 and c-Jun N-terminal kinase mitogen-activated protein kinases to determine their effects on in vivo leukocyte migration patterns and discuss how they modify the characteristics of the cell migration process. In particular, we find that their respective inhibition leads to decreased and increased levels of persistent motion in leukocytes following wounding. This example shows the high level of information content, which can be gained from live-imaging data if appropriate statistical tools are used.
doi:10.1038/icb.2012.57
PMCID: PMC3540327  PMID: 23165607
immune signalling; multi-scale analysis; systems biology
15.  Dietary cholesterol directly induces acute inflammasome-dependent intestinal inflammation 
Nature Communications  2014;5:5864.
Prolonged ingestion of a cholesterol- or saturated fatty acid-enriched diet induces chronic, often systemic, auto-inflammatory responses resulting in significant health problems worldwide. In vivo information regarding the local and direct inflammatory effect of these dietary components in the intestine and, in particular, on the intestinal epithelium is lacking. Here we report that both mice and zebrafish exposed to high-fat (HFDs) or high-cholesterol (HCDs) diets develop acute innate inflammatory responses within hours, reflected in the localized interleukin-1β-dependent accumulation of myeloid cells in the intestine. Acute HCD-induced intestinal inflammation is dependent on cholesterol uptake via Niemann-Pick C1-like 1 and inflammasome activation involving apoptosis-associated Speck-like protein containing a caspase recruitment domain, which leads to Caspase-1 activity in intestinal epithelial cells. Extended exposure to HCD results in localized, inflammation-dependent, functional dysregulation as well as systemic pathologies. Our model suggests that dietary cholesterol initiates intestinal inflammation in epithelial cells.
Chronic consumption of a Western-type diet leads to systemic inflammation of undefined origin, which contributes to metabolic disease. Here Progatzky et al. identify an immediate early step in the process by showing that dietary cholesterol rapidly activates inflammasomes in the gut epithelium.
doi:10.1038/ncomms6864
PMCID: PMC4284652  PMID: 25536194

Results 1-15 (15)