LMP student seminars: 13 January

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.

3. Cardiovascular, Physiology and Metabolism 

Location: MSB 4171

Jiajie (Jackson) Zhang

• Title: Investigating disease mechanisms and healthy-diseased cell interactions in human chimeric retinal organoid models of USH2A-associated retinitis pigmentosa
• Supervisor: Dr. Brian G. Ballios

5. Infectious Diseases, Inflammation and Immunology

Location: MSB 4279

Gizelle Lionel

• Title: Investigating HIV-1 Entry in HOS Cells which Lack the Primary CD4 Receptor
• Supervisor: Dr. Donald Branch

Emily Halajian

• Title: TBA
• Supervisor: TBA

Abstracts

Jiajie (Jackson) Zhang: Investigating disease mechanisms and healthy-diseased cell interactions in human chimeric retinal organoid models of USH2A-associated retinitis pigmentosa

USH2A-associated retinitis pigmentosa is one of the most prevalent forms of inherited retinal diseases, causing photoreceptor degeneration and ultimately severe blindness in patients. Stem cell therapy hold the potential to preserve or replace photoreceptors in diseased retina and rescue vision loss in patients. Yet, it is still unclear how host retinal environment may influence the ability of donor cells to integrate and restore retinal functions. Developing therapies for USH2A diseases has been challenging due to the lack of suitable disease models. Human induced pluripotent stem cell (iPSC)-derived retinal organoids (ROs) have shown promise for disease modeling as they can recapitulate human retinal development and pathophysiology. In this study, USH2A 2299delG mutation was engineered into a healthy iPSC line by CRISPR to generate isogenic homozygous diseased and heterozygous control ROs. Isogenic USH2A-diseaed ROs show reduced diameter and neuroepithelial layer thickness at early developmental stages compared to isogenic healthy and heterozygous control ROs by immunohistochemistry and live tissue imaging. USH2A-diseased ROs also showed reduced proliferation (Edu and PH3 immuno-staining), and increased apoptosis (TUNEL) compared to both control ROs. Whole-mount tissue staining of mature photoreceptor markers showed a reduced photoreceptor density in USH2A-diseased ROs. Besides, siRNA-mediated USH2A knock-down caused brush border (photoreceptor inner/outer segments) shedding and reduced photoreceptor numbers in healthy mature ROs. Chimeric ROs composed of both healthy and USH2A-diseased cells in various ratios were generated. Healthy-diseased cell interactions will be studies in chimeric ROs using FACS, immunohistochemistry, RT-qPCR, etc, to study the potential rescue effects of healthy cells to diseased ROs.

Gizelle Lionel: Investigating HIV-1 Entry in HOS Cells which Lack the Primary CD4 Receptor

Despite recent improvements in HIV-1 therapies, there remains limitations that impede advancements in this field including drug resistance, especially due to latent viral reservoirs. HIV-1 infection generally requires the virus first binding to the CD4 receptor, which induces a conformational change, and leads to the virus binding to either one of the coreceptors (CXCR4 or CCR5) depending on the virus type. This binding enables the virus to enter the cell through fusion with the cell membrane. However, some studies have shown that HIV-1 is able to enter cells lacking this primary CD4 receptor; although, this is somewhat controversial, and the mechanisms are unclear. This study aims to identify a model CD4-negative cell line that is infectable with HIV-1 to study how infection occurs and determine whether CD4-negative cells can act as latent viral reservoirs. CD4-negative human osteosarcoma (HOS) cells expressing either one of the coreceptors were infected with a pseudoenvelope-typed, luciferase reporter HIV-1; JR-FL-envelope for CCR5+ and HXB2-envelope for CXCR4+ cells. We showed that HOS cells can be infected with HIV-1, as demonstrated by translation of integrated luciferase, and that this infection is independent of CD4 but is co-receptor dependent. Addition of the viral-integration inhibitor; Raltegravir to viral infection assays, blocked infection in the HOS cells as did use of specific inhibitors for the coreceptors. These results suggest that in the absence of the CD4 receptor, HIV-1 uses alternative mechanisms for viral entry into these HOS cells. Further studies will determine how these CD4-negative cells are infectable. Deepening our understanding of viral entry into CD4-negative cells can improve HIV-1 therapeutics, address viral reservoirs, and can contribute to finding an eventual cure.

Emily Halajian: TBA

TBA

Contact

No need to register.

Contact lmp.grad@utoronto.ca with any questions