Publications by authors named "Kevin Dong"

13 Publications

  • Page 1 of 1

Barriers to HIV testing in hospital settings within a culturally diverse urban district of Sydney, Australia.

Sex Health 2021 Jul 16. Epub 2021 Jul 16.

Background: Eleven percent of people living with HIV in Australia remain unaware of their diagnosis, and there are missed opportunities for HIV testing in priority settings in New South Wales. HIV testing remains low outside of sexual health clinics with the exception of antenatal settings where HIV testing is routine. To understand why HIV testing rates are low, we sought to identify health worker-related barriers to HIV testing.

Methods: We conducted an anonymous online survey to health workers in Western Sydney Local Health District (WSLHD) in September 2019. Tick-box, Likert scale responses were analysed using Chi-square and Kruskal-Wallis statistical tests, and free text responses were analysed with thematic analysis.

Results: Three percent (n = 420) of WSLHD's estimated 14 000 health workers responded. These included 317 clinicians (171 nurses, 65 doctors, 56 allied health professionals (AHPs), 25 midwives, and 103 health workers in non-clinical roles). Health workers were from a variety of in-patient/out-patient settings. Many health workers (291/420, 69%; 95%CI = 64.9-73.7%) were unaware that HIV testing is offered in their areas; doctors (82%) and midwives (80%) were more aware than nurses (23%) and AHPs (11%) (P < 0.0001). Doctors (Likert score = 3.62; 3.45/5) and midwives (2.84; 2.76) were significantly more comfortable discussing and confidently offering HIV testing than nurses (2.42; 1.81) or AHPs (1.83; 0.91) (P < 0.0001 for both). The top five barriers to HIV testing were (1) procedural knowledge, (2) identification of at-risk patients, (3) HIV knowledge, (4) positive result management, and (5) privacy concerns. Free text responses highlighted perceived stigma, testing/result responsibilities and resource challenges as barriers to HIV testing.

Conclusions: Clinicians working in priority settings and with priority populations require more education and support to increase targeted HIV testing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1071/SH20189DOI Listing
July 2021

Proteomic Portraits Reveal Evolutionarily Conserved and Divergent Responses to Spinal Cord Injury.

Mol Cell Proteomics 2021 Jun 12;20:100096. Epub 2021 Jun 12.

Division of Neurosurgery, University of British Columbia, Vancouver, British Columbia, Canada.

Despite the emergence of promising therapeutic approaches in preclinical studies, the failure of large-scale clinical trials leaves clinicians without effective treatments for acute spinal cord injury (SCI). These trials are hindered by their reliance on detailed neurological examinations to establish outcomes, which inflate the time and resources required for completion. Moreover, therapeutic development takes place in animal models whose relevance to human injury remains unclear. Here, we address these challenges through targeted proteomic analyses of cerebrospinal fluid and serum samples from 111 patients with acute SCI and, in parallel, a large animal (porcine) model of SCI. We develop protein biomarkers of injury severity and recovery, including a prognostic model of neurological improvement at 6 months with an area under the receiver operating characteristic curve of 0.91, and validate these in an independent cohort. Through cross-species proteomic analyses, we dissect evolutionarily conserved and divergent aspects of the SCI response and establish the cerebrospinal fluid abundance of glial fibrillary acidic protein as a biochemical outcome measure in both humans and pigs. Our work opens up new avenues to catalyze translation by facilitating the evaluation of novel SCI therapies, while also providing a resource from which to direct future preclinical efforts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mcpro.2021.100096DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8260874PMC
June 2021

Robust single-cell discovery of RNA targets of RNA-binding proteins and ribosomes.

Nat Methods 2021 05 7;18(5):507-519. Epub 2021 May 7.

Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA, USA.

RNA-binding proteins (RBPs) are critical regulators of gene expression and RNA processing that are required for gene function. Yet the dynamics of RBP regulation in single cells is unknown. To address this gap in understanding, we developed STAMP (Surveying Targets by APOBEC-Mediated Profiling), which efficiently detects RBP-RNA interactions. STAMP does not rely on ultraviolet cross-linking or immunoprecipitation and, when coupled with single-cell capture, can identify RBP-specific and cell-type-specific RNA-protein interactions for multiple RBPs and cell types in single, pooled experiments. Pairing STAMP with long-read sequencing yields RBP target sites in an isoform-specific manner. Finally, Ribo-STAMP leverages small ribosomal subunits to measure transcriptome-wide ribosome association in single cells. STAMP enables the study of RBP-RNA interactomes and translational landscapes with unprecedented cellular resolution.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41592-021-01128-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8148648PMC
May 2021

Characterization of Cerebrospinal Fluid Ubiquitin C-Terminal Hydrolase L1 (UCH-L1) as a Biomarker of Human Acute Traumatic Spinal Cord Injury.

J Neurotrauma 2021 May 3. Epub 2021 May 3.

International Collaboration on Repair Discoveries (ICORD), Blusson Spinal Cord Center, University of British Columbia, Vancouver, British Columbia, Canada.

A major obstacle for translational research in acute spinal cord injury (SCI) is the lack of biomarkers that can objectively stratify injury severity and predict outcome. Ubiquitin C-terminal hydrolase L1 (UCH-L1) is a neuron-specific enzyme that shows promise as a diagnostic biomarker in traumatic brain injury (TBI), but has not been studied in SCI. In this study, cerebrospinal fluid (CSF) and serum samples were collected over the first 72-96 h post-injury from 32 acute SCI patients who were followed prospectively to determine neurological outcomes at 6 months post-injury. UCH-L1 concentration was measured using the Quanterix Simoa platform (Quanterix, Billerica, MA) and correlated to injury severity, time, and neurological recovery. We found that CSF UCH-L1 was significantly elevated by 10- to 100-fold over laminectomy controls in an injury severity- and time-dependent manner. Twenty-four-hour post-injury CSF UCH-L1 concentrations distinguished between American Spinal Injury Association Impairment Scale (AIS) A and AIS B, and AIS A and AIS C patients in the acute setting, and predicted who would remain "motor complete" (AIS A/B) at 6 months with a sensitivity of 100% and a specificity of 86%. AIS A patients who did not improve their AIS grade at 6 months post-injury were characterized by sustained elevations in CSF UCH-L1 up to 96 h. Similarly, the failure to gain >8 points on the total motor score at 6 months post-injury was associated with higher 24-h CSF UCH-L1. Unfortunately, serum UCH-L1 levels were not informative about injury severity or outcome. In conclusion, CSF UCH-L1 in acute SCI shows promise as a biomarker to reflect injury severity and predict outcome.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/neu.2020.7352DOI Listing
May 2021

Evaluation of Engineered CRISPR-Cas-Mediated Systems for Site-Specific RNA Editing.

Cell Rep 2020 11;33(5):108350

Department of Cellular and Molecular Medicine, University of California San Diego, La Jolla, CA 92093, USA; Stem Cell Program, University of California San Diego, La Jolla, CA 92093, USA; Institute for Genomic Medicine, University of California at San Diego, La Jolla, CA 92093, USA. Electronic address:

Site-directed RNA editing approaches offer great potential to correct genetic mutations in somatic cells while avoiding permanent off-target genomic edits. Nuclease-dead RNA-targeting CRISPR-Cas systems recruit functional effectors to RNA molecules in a programmable fashion. Here, we demonstrate a Streptococcus pyogenes Cas9-ADAR2 fusion system that uses a 3' modified guide RNA (gRNA) to enable adenosine-to-inosine (A-to-I) editing of specific bases on reporter and endogenously expressed mRNAs. Due to the sufficient nature of the 3' gRNA extension sequence, we observe that Cas9 gRNA spacer sequences are dispensable for directed RNA editing, revealing that Cas9 can act as an RNA-aptamer-binding protein. We demonstrate that Cas9-based A-to-I editing is comparable in on-target efficiency and off-target specificity with Cas13 RNA editing versions. This study provides a systematic benchmarking of RNA-targeting CRISPR-Cas designs for reversible nucleotide-level conversion at the transcriptome level.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.celrep.2020.108350DOI Listing
November 2020

Correlation of Optical and Automated Patch Clamp Electrophysiology for Identification of Na1.7 Inhibitors.

SLAS Discov 2020 06 15;25(5):434-446. Epub 2020 Apr 15.

Q-State Biosciences, Cambridge, MA, USA.

The voltage-gated sodium channel Nav1.7 is a genetically validated target for pain; pharmacological blockers are promising as a new class of nonaddictive therapeutics. The search for Nav1.7 subtype selective inhibitors requires a reliable, scalable, and sensitive assay. Previously, we developed an all-optical electrophysiology (Optopatch) Spiking HEK platform to study activity-dependent modulation of Nav1.7 in a format compatible with high-throughput screening. In this study, we benchmarked the Optopatch Spiking HEK assay with an existing validated automated electrophysiology assay on the IonWorks Barracuda (IWB) platform. In a pilot screen of 3520 compounds, which included compound plates from a random library as well as compound plates enriched for Nav1.7 inhibitors, the Optopatch Spiking HEK assay identified 174 hits, of which 143 were confirmed by IWB. The Optopatch Spiking HEK assay maintained the high reliability afforded by traditional fluorescent assays and further demonstrated comparable sensitivity to IWB measurements. We speculate that the Optopatch assay could provide an affordable high-throughput screening platform to identify novel Nav1.7 subtype selective inhibitors with diverse mechanisms of action, if coupled with a multiwell parallel optogenetic recording instrument.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/2472555220914532DOI Listing
June 2020

PK-M2-mediated metabolic changes in breast cancer cells induced by ionizing radiation.

Breast Cancer Res Treat 2019 Nov 1;178(1):75-86. Epub 2019 Aug 1.

Department of Radiation Oncology, David Geffen School of Medicine at UCLA, 10833 Le Conte Ave, Los Angeles, CA, 90095-1714, USA.

Purpose: Radiotherapy (RT) constitutes an important part of breast cancer treatment. However, triple negative breast cancers (TNBC) exhibit remarkable resistance to most therapies, including RT. Developing new ways to radiosensitize TNBC cells could result in improved patient outcomes. The M2 isoform of pyruvate kinase (PK-M2) is believed to be responsible for the re-wiring of cancer cell metabolism after oxidative stress. The aim of the study was to determine the effect of ionizing radiation (IR) on PK-M2-mediated metabolic changes in TNBC cells, and their survival. In addition, we determine the effect of PK-M2 activators on breast cancer stem cells, a radioresistant subpopulation of breast cancer stem cells.

Methods: Glucose uptake, lactate production, and glutamine consumption were assessed. The cellular localization of PK-M2 was evaluated by western blot and confocal microscopy. The small molecule activator of PK-M2, TEPP46, was used to promote its pyruvate kinase function. Finally, effects on cancer stem cell were evaluated via sphere forming capacity.

Results: Exposure of TNBC cells to IR increased their glucose uptake and lactate production. As expected, PK-M2 expression levels also increased, especially in the nucleus, although overall pyruvate kinase activity was decreased. PK-M2 nuclear localization was shown to be associated with breast cancer stem cells, and activation of PK-M2 by TEPP46 depleted this population.

Conclusions: Radiotherapy can induce metabolic changes in TNBC cells, and these changes seem to be mediated, at least in part by PK-M2. Importantly, our results show that activators of PK-M2 can deplete breast cancer stem cells in vitro. This study supports the idea of combining PK-M2 activators with radiation to enhance the effect of radiotherapy in resistant cancers, such as TNBC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10549-019-05376-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6790295PMC
November 2019

Mebendazole Potentiates Radiation Therapy in Triple-Negative Breast Cancer.

Int J Radiat Oncol Biol Phys 2019 01 7;103(1):195-207. Epub 2018 Sep 7.

Department of Radiation Oncology, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, California; Jonsson Comprehensive Cancer Center, University of California, Los Angeles, Los Angeles, California. Electronic address:

Purpose: The lack of a molecular target in triple-negative breast cancer (TNBC) makes it one of the most challenging breast cancers to treat. Radiation therapy (RT) is an important treatment modality for managing breast cancer; however, we previously showed that RT can also reprogram a fraction of the surviving breast cancer cells into breast cancer-initiating cells (BCICs), which are thought to contribute to disease recurrence. In this study, we characterize mebendazole (MBZ) as a drug with potential to prevent the occurrence of radiation-induced reprogramming and improve the effect of RT in patients with TNBC.

Methods And Materials: A high-throughput screen was used to identify drugs that prevented radiation-induced conversion of TNBC cells into cells with a cancer-initiating phenotype and exhibited significant toxicity toward TNBC cells. MBZ was one of the drug hits that fulfilled these criteria. In additional studies, we used BCIC markers and mammosphere-forming assays to investigate the effect of MBZ on the BCIC population. Staining with propidium iodide, annexin-V, and γ-H2AX was used to determine the effect of MBZ on cell cycle, apoptosis, and double-strand breaks. Finally, the potential for MBZ to enhance the effect of RT in TNBC was evaluated in vitro and in vivo.

Results: MBZ efficiently depletes the BCIC pool and prevents the ionizing radiation-induced conversion of breast cancer cells into therapy-resistant BCICs. In addition, MBZ arrests cells in the G2/M phase of the cell cycle and causes double-strand breaks and apoptosis. MBZ sensitizes TNBC cells to ionizing radiation in vitro and in vivo, resulting in improved tumor control in a human xenograft model of TNBC.

Conclusions: The data presented in this study support the repurposing of MBZ as a combination treatment with RT in patients with TNBC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ijrobp.2018.08.046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6457649PMC
January 2019

Predicting Injury Severity and Neurological Recovery after Acute Cervical Spinal Cord Injury: A Comparison of Cerebrospinal Fluid and Magnetic Resonance Imaging Biomarkers.

J Neurotrauma 2018 02 6;35(3):435-445. Epub 2017 Nov 6.

3 International Collaboration on Repair Discoveries (ICORD), University of British Columbia , Blusson Spinal Cord Center, Vancouver, British Columbia, Canada .

Biomarkers of acute human spinal cord injury (SCI) could provide a more objective measure of spinal cord damage and a better predictor of neurological outcome than current standardized neurological assessments. In SCI, there is growing interest in establishing biomarkers from cerebrospinal fluid (CSF) and from magnetic resonance imaging (MRI). Here, we compared the ability of CSF and MRI biomarkers to classify injury severity and predict neurological recovery in a cohort of acute cervical SCI patients. CSF samples and MRI scans from 36 acute cervical SCI patients were examined. From the CSF samples taken 24 h post-injury, the concentrations of inflammatory cytokines (interleukin [IL]-6, IL-8, monocyte chemotactic protein-1), and structural proteins (tau, glial fibrillary acidic protein, and S100β) were measured. From the pre-operative MRI scans, we measured intramedullary lesion length, hematoma length, hematoma extent, CSF effacement, cord expansion, and maximal spinal cord compression. Baseline and 6-month post-injury assessments of American Spine Injury Association Impairment Scale (AIS) grade and motor score were conducted. Both MRI measures and CSF biomarker levels were found to correlate with baseline injury grade, and in combination they provided a stronger model for classifying baseline AIS grade than CSF or MRI biomarkers alone. For predicting neurological recovery, the inflammatory CSF biomarkers best predicted AIS grade conversion, whereas structural biomarker levels best predicted motor score improvement. A logistic regression model utilizing CSF biomarkers alone had a 91.2% accuracy at predicting AIS conversion, and was not strengthened by adding MRI features or even knowledge of the baseline AIS grade. In a direct comparison of MRI and CSF biomarkers, the CSF biomarkers discriminate better between different injury severities, and are stronger predictors of neurological recovery in terms of AIS grade and motor score improvement. These findings demonstrate the utility of measuring the acute biological responses to SCI as biomarkers of injury severity and neurological prognosis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1089/neu.2017.5357DOI Listing
February 2018

Drosophila adducin regulates Dlg phosphorylation and targeting of Dlg to the synapse and epithelial membrane.

Dev Biol 2011 Sep 21;357(2):392-403. Epub 2011 Jul 21.

Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6.

Adducin is a cytoskeletal protein having regulatory roles that involve actin filaments, functions that are inhibited by phosphorylation of adducin by protein kinase C. Adducin is hyperphosphorylated in nervous system tissue in patients with the neurodegenerative disease amyotrophic lateral sclerosis, and mice lacking β-adducin have impaired synaptic plasticity and learning. We have found that Drosophila adducin, encoded by hu-li tai shao (hts), is localized to the post-synaptic larval neuromuscular junction (NMJ) in a complex with the scaffolding protein Discs large (Dlg), a regulator of synaptic plasticity during growth of the NMJ. hts mutant NMJs are underdeveloped, whereas over-expression of Hts promotes Dlg phosphorylation, delocalizes Dlg away from the NMJ, and causes NMJ overgrowth. Dlg is a component of septate junctions at the lateral membrane of epithelial cells, and we show that Hts regulates Dlg localization in the amnioserosa, an embryonic epithelium, and that embryos doubly mutant for hts and dlg exhibit defects in epithelial morphogenesis. The phosphorylation of Dlg by the kinases PAR-1 and CaMKII has been shown to disrupt Dlg targeting to the NMJ and we present evidence that Hts regulates Dlg targeting to the NMJ in muscle and the lateral membrane of epithelial cells by controlling the protein levels of PAR-1 and CaMKII, and consequently the extent of Dlg phosphorylation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.ydbio.2011.07.010DOI Listing
September 2011

Lysine methyltransferase G9a is required for de novo DNA methylation and the establishment, but not the maintenance, of proviral silencing.

Proc Natl Acad Sci U S A 2011 Apr 22;108(14):5718-23. Epub 2011 Mar 22.

Department of Medical Genetics, University of British Columbia, Vancouver, BC, Canada.

Methylation on lysine 9 of histone H3 (H3K9me) and DNA methylation play important roles in the transcriptional silencing of specific genes and repetitive elements. Both marks are detected on class I and II endogenous retroviruses (ERVs) in murine embryonic stem cells (mESCs). Recently, we reported that the H3K9-specific lysine methyltransferase (KMTase) Eset/Setdb1/KMT1E is required for H3K9me3 and the maintenance of silencing of ERVs in mESCs. In contrast, G9a/Ehmt2/KMT1C is dispensable, despite the fact that this KMTase is required for H3K9 dimethylation (H3K9me2) and efficient DNA methylation of these retroelements. Transcription of the exogenous retrovirus (XRV) Moloney murine leukemia virus is rapidly extinguished after integration in mESCs, concomitant with de novo DNA methylation. However, the role that H3K9 KMTases play in this process has not been addressed. Here, we demonstrate that G9a, but not Suv39h1 or Suv39h2, is required for silencing of newly integrated Moloney murine leukemia virus-based vectors in mESCs. The silencing defect in G9a(-/-) cells is accompanied by a reduction of H3K9me2 at the proviral LTR, indicating that XRVs are direct targets of G9a. Furthermore, de novo DNA methylation of newly integrated proviruses is impaired in the G9a(-/-) line, phenocopying proviral DNA methylation and silencing defects observed in Dnmt3a-deficient mESCs. Once established, however, maintenance of silencing of XRVs, like ERVs, is dependent exclusively on the KMTase Eset. Taken together, these observations reveal that in mESCs, the H3K9 KMTase G9a is required for the establishment, but not for the maintenance, of silencing of newly integrated proviruses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1073/pnas.1014660108DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3078371PMC
April 2011

The leading edge during dorsal closure as a model for epithelial plasticity: Pak is required for recruitment of the Scribble complex and septate junction formation.

Development 2010 Jun;137(12):2023-32

Institute of Molecular and Cell Biology, 61 Biopolis Drive, 138673, Singapore.

Dorsal closure (DC) of the Drosophila embryo is a model for the study of wound healing and developmental epithelial fusions, and involves the sealing of a hole in the epidermis through the migration of the epidermal flanks over the tissue occupying the hole, the amnioserosa. During DC, the cells at the edge of the migrating epidermis extend Rac- and Cdc42-dependent actin-based lamellipodia and filopodia from their leading edge (LE), which exhibits a breakdown in apicobasal polarity as adhesions are severed with the neighbouring amnioserosa cells. Studies using mammalian cells have demonstrated that Scribble (Scrib), an important determinant of apicobasal polarity that functions in a protein complex, controls polarized cell migration through recruitment of Rac, Cdc42 and the serine/threonine kinase Pak, an effector for Rac and Cdc42, to the LE. We have used DC and the follicular epithelium to study the relationship between Pak and the Scrib complex at epithelial membranes undergoing changes in apicobasal polarity and adhesion during development. We propose that, during DC, the LE membrane undergoes an epithelial-to-mesenchymal-like transition to initiate epithelial sheet migration, followed by a mesenchymal-to-epithelial-like transition as the epithelial sheets meet up and restore cell-cell adhesion. This latter event requires integrin-localized Pak, which recruits the Scrib complex in septate junction formation. We conclude that there are bidirectional interactions between Pak and the Scrib complex modulating epithelial plasticity. Scrib can recruit Pak to the LE for polarized cell migration but, as migratory cells meet up, Pak can recruit the Scrib complex to restore apicobasal polarity and cell-cell adhesion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1242/dev.045088DOI Listing
June 2010

DNA methylation in ES cells requires the lysine methyltransferase G9a but not its catalytic activity.

EMBO J 2008 Oct 25;27(20):2691-701. Epub 2008 Sep 25.

Department of Medical Genetics, Life Sciences Institute, The University of British Columbia, Vancouver, British Columbia, Canada.

Histone H3K9 methylation is required for DNA methylation and silencing of repetitive elements in plants and filamentous fungi. In mammalian cells however, deletion of the H3K9 histone methyltransferases (HMTases) Suv39h1 and Suv39h2 does not affect DNA methylation of the endogenous retrovirus murine leukaemia virus, indicating that H3K9 methylation is dispensable for DNA methylation of retrotransposons, or that a different HMTase is involved. We demonstrate that embryonic stem (ES) cells lacking the H3K9 HMTase G9a show a significant reduction in DNA methylation of retrotransposons, major satellite repeats and densely methylated CpG-rich promoters. Surprisingly, demethylated retrotransposons remain transcriptionally silent in G9a(-/-) cells, and show only a modest decrease in H3K9me2 and no decrease in H3K9me3 or HP1alpha binding, indicating that H3K9 methylation per se is not the relevant trigger for DNA methylation. Indeed, introduction of catalytically inactive G9a transgenes partially 'rescues' the DNA methylation defect observed in G9a(-/-) cells. Taken together, these observations reveal that H3K9me3 and HP1alpha recruitment to retrotransposons occurs independent of DNA methylation in ES cells and that G9a promotes DNA methylation independent of its HMTase activity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/emboj.2008.193DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2572176PMC
October 2008
-->