LMP student seminars: 7 October
Each week during term time, MSc and PhD candidates in the Department of Laboratory Medicine and Pathobiology present their research.
Anyone is welcome. No need to register.
Location: Medical Sciences Building, rooms 4171 or 4279, see below.
As part of the core research curriculum, students taking LMP1001/2/3: Graduate Seminars in Laboratory Medicine and Pathobiology will present their projects. Please see abstracts below.
5. Infectious Diseases, Inflammation and Immunology (ID)
Location: MSB 4279
Marry Ann Nissan
- Title: Assessing the host response to Shigella flexneri infection in enteroids
- Supervisor: Dr. Stephen Girardin
Rachel Tyli
- Title: Validation of Respirator Fit on Ontario Paramedics and Firefighters
- Supervisor: Dr. James Scott
3. Cardiovascular, Physiology and Metabolism/ Molecular and Cell Biology and Regenerative Medicine
Location: MSB 4171
Robert Lao
- Title: Reducing the Risks of Complex Pediatric Cardiovascular Surgery using GLP-1 Peptides
- Supervisor: Dr. Mansoor Husain & Dr. Osami Honjo
Chris Jordan
- Title: Investigating the role of Dna2 liquid droplets in DNA repair and cellular aging
- Supervisor: TBA
Abstracts
Marry Ann Nissan: Assessing the host response to Shigella flexneri infection in enteroids
Shigella flexneri is a Gram-negative Enterobacteriaceae that afflicts middle to low-income regions, including South Asia and sub-Saharan Africa, by inducing dysentery-related deaths. Upon ingestion, Shigella crosses the intestinal epithelium through M cells and begins cell-to-cell spread and replication. Shigella causes devastating destruction of the intestine by employing its extensive virulence plasmid to evade host detection and response. Little work on Shigella’s mode of infection has been recapitulated in murine enteroids: a primary cell system that models the architecture, diversity of cells, and physiology found within the host intestine. This is largely because the murine innate immune response is well-equipped to expunge Shigella by engaging in rapid pyroptotic cell death upon infection. Using methods previously described by Russel Vance (eLife, 2020) we created organoids from NLRC4-deficient mice, which are unable to engage in pyroptosis. My research confirms that indeed, maintenance of infection occurs in Nlrc4-/- enteroids shown by their higher bacterial burden, more inflammatory mRNA, and higher cytokine secretion compared to Nlrc4+/+ enteroids proving this model is integral to studying long-term infections. We then assessed the global transcriptional landscape Nlrc4-/- enteroids experience upon Shigella infection by bulk RNA NGS. DESeq2 and GSEA analysis revealed that surprisingly, TGF-β signalling is repressed upon infection. Future research aims to elucidate the role of TGF-β signalling in the epithelium in response to infection and assess if it plays a protective role. Understanding the cell biology of Shigella infections in a physiologically relevant epithelial system can help us find targets of the disease and guide future research.
Rachel Tyli: Validation of Respirator Fit on Ontario Paramedics and Firefighters
During the COVID-19 pandemic, respirators were essential in ensuring protection of emergency service workers (ESWs). For effective protection, respirators must be fit-tested on individuals. Fit testing is expensive (fit testers are >20K CAD) and time-consuming. ESWs need a new, cheaper, faster and more accurate measurement method for quantifying respirator fit. ESWs are a racially and gender-diverse demographic, very different from the historical group of respirator users (predominantly Caucasian males). Previous studies indicate that respirators fit women and non-Caucasian ethnicities poorly.
To address these concerns, I am developing a computational method using 3D scans of faces and respirators to measure respirator fit. In this model, two 3D-scanned facial and respirator meshes fit together. Fit is then determined by geometrically evaluating the perimeter around the respirator for gaps. 3D scans are being collected from 200 Ontario ESWs. Furthermore, a standard fit-test and a simulated work fit-test are performed. The simulated work fit-test evaluates leakages during tasks, like CPR, airway management and patient handling. The results from the fit test will be used to validate the computational method.
The outcomes of this project are far-reaching;
- the model has the potential to eliminate the use of an expensive and inaccessible fit tester, opening the possibility to replace standard fit testing with smartphone apps capable of 3D scanning.
- By creating a model based on a diverse population, this study aims to find the shortcomings of respirator fit testing standards, especially for non-male identifying individuals and non-white ethnicities.
Through the development of the novel methodology and validation, described above, the project aims to inform and improve respirator design and the standard for evaluating respirator fit for one of society’s most essential worker groups, especially in the event of another pandemic.
Robert Lao: Reducing the Risks of Complex Pediatric Cardiovascular Surgery using GLP-1 Peptides
Background: Children with critical congenital heart disease often require complex open-heart surgery with long aortic cross-clamp times (XC). Despite refinement in cardioplegia, ventricular dysfunction due to inadequate myocardial protection remains a major clinical challenge. Glucagon-like peptide-1 (GLP-1) has proven cardioprotective properties. This study characterizes the mechanisms of injury of long XC and investigates cardioprotective properties of GLP-1(28-36), a naturally occurring fragment of GLP-1.
Method & Results: A pediatric surgical model of cardiopulmonary bypass (CPB) and long XC was developed in 4-5 wk-old Yorkshire pigs. Pigs were subjected to 90-min XC or 180-min XC. After 90-min XC, analysis of cardiac function at baseline vs. 2-h post-CPB revealed reduced ejection fraction and global longitudinal strain. In conjunction, elevated levels of arterial lactate, and cardiac Troponin-I indicate metabolic stress and cardiomyocyte injury. Markedly reduced survival after 180- vs. 90-min XC was accompanied by more profound cardiac dysfunction, metabolic- and oxidative-stress, and cardiomyocyte injury in pigs surviving 180-min XC. Untargeted plasma metabolomics reveal XC time-dependent signatures. Adding GLP-1(28-36) vs. control SCRAM(28-36) to cardioplegia during 90-min XC caused longer time to first heart beat following XC, with markedly reduced cardiomyocyte injury. Adding GLP-1(28-36) during 180-min XC resulted in lower peak vasoactive-inotropic usage when weaning from CPB.
Conclusions: In a new model of long XC, we demonstrate time-dependent cardiac dysfunction correlating with metabolic- and oxidative-stress and cardiomyocyte injury. Treatment with GLP-1(28-36) reduced cardiac injury and may mediate better post-operative outcomes.
Chris Jordan: Investigating the role of Dna2 liquid droplets in DNA repair and cellular aging
In S. cerevisiae, Double-Strand Breaks (DSBs) are primarily repaired through Homologous Recombination (HR). Recent research has shown that the formation of phase-separated DNA repair liquid droplets can drive the repair process; however, it remains unclear whether these liquid compartments can have an additional impact on the cell. Here, we narrowed our focus to understand the influence of DNA repair membrane-less compartments on biological aging.
Following live-cell imaging, we found that Dna2, an endonuclease, formed foci that displayed dynamic, liquid-like behavior such as fusion and dripping upon DNA damage. Furthermore, we purified the putative phase separation-promoting domain (also known as the intrinsically disordered domain, or IDR) to investigate whether eGFP-Dna2 IDR could form droplets in vitro. Indeed, we found that the IDR was sufficient to form droplets in a salt concentration-dependent manner. Remarkably, we found that introducing CDK1 site-specific phosphomimetic mutations promoted the formation of these in vitro droplets at physiological salt concentrations.
These results suggest that CDK1 phosphorylation of Dna2 promotes its phase separation and, as a result, influences its role as a DNA damage repair protein. Ultimately, the aim of this study is to understand the impact of the phase separation of Dna2 on genome stability, and we predict that the absence of Dna2 liquid droplets will accelerate cellular aging as a result of the rapid onset of genome instability.
Contact
No need to register.
Contact lmp.grad@utoronto.ca with any questions