LMP student seminars: 4 March

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.

Group 2: Cancer, Development and Aging

Location: MSB 4171

Anna Tymofyeyeva

• Title: Defining the developmental origins and therapeutic vulnerabilities of BRAF-mutant pediatric glioma
• Supervisor: Dr. Peter Dirks

Group 1: Brain and Neuroscience

Location: MSB 4279

Zahra Nasser

• Title: Investigating the mechanisms of effective brain-wide delivery of adeno-associated viruses for the treatment of neurodegenerative diseases
• Supervisor: Dr. Gerold Schmitt-Ulms

Abstracts

Anna Tymofyeyeva: Defining the developmental origins and therapeutic vulnerabilities of BRAF-mutant pediatric glioma

Pediatric high-grade gliomas (pHGGs) are aggressive brain tumours and the leading cause of cancer-related death in children. Although extensive molecular profiling has characterized end-stage disease, the earliest events of gliomagenesis remain poorly defined. Advanced tumours exhibit substantial intratumoural heterogeneity, limiting the effectiveness of targeted therapies and obscuring early tumour-initiating states that may represent more tractable therapeutic targets. To investigate early gliomagenesis, we developed a novel murine model combining Trp53 loss in neural stem cells with embryonic exposure to the alkylating agent N-ethyl-N-nitrosourea (ENU), mimicking an environmental insult. This system enables longitudinal analysis of premalignant, early, and end-stage lesions arising in vivo. Transcriptomic and histopathologic profiling reveal progressive increases in genetic complexity, stem-like features, and immune remodeling during tumour evolution, while early lesions remain relatively molecularly homogeneous. Recurrent activating Braf mutations are detectable at the earliest stages of transformation and frequently persist in advanced tumours, consistent with the high frequency of BRAFV600E mutations observed in pediatric gliomas. RAS–RAF–MAPK pathway activation similarly precedes malignant progression. Functionally, cell lines derived from early-stage Braf-mutant lesions exhibit greater sensitivity to BRAF inhibition compared to lines derived from end-stage tumours and patient-derived pHGG models. These findings suggest a developmentally restricted therapeutic window that may be obscured in advanced disease. Future work will employ lineage tracing of neural precursor cells in a BRAFV600E mutant mouse model, coupled with temporal sequencing approaches to define cell state transitions across developmental windows.

Zahra Nasser: Investigating the mechanisms of effective brain-wide delivery of adeno-associated viruses for the treatment of neurodegenerative diseases

Adeno-associated viruses (AAVs) have emerged as one of the most promising tools for the delivery of disease-relevant gene therapies into the CNS. Engineered capsids such as receptor-targeted BI-hTFR1 aim to enhance endothelial engagement and brain delivery. Despite immense interest in selecting the most brain-penetrant capsids, early host cell responses during endothelial entry remain poorly defined. Here, we undertook a deep dive into proteomic changes that manifest in a human endothelial cell paradigm upon viral exposure to a recombinant AAV known to cross by TFR1-mediated transcytosis. hCMEC/D3 cells grown on Transwells were exposed to brain-penetrant BI-hTFR1 capsids. Whole-cell lysates were collected at 30 minutes, 3 hours, and 48 hours post-exposure and relative abundances of more than 8,000 proteins were captured using LC-MS. Proteins whose abundance levels differed from vehicle-treated control cells across biological replicates were analyzed using pathway enrichment tools. Almost 100 proteins underwent rapid changes exceeding 50% in their levels as early as 30 minutes post-transduction, returning to baseline levels by 48 hours. In contrast, only half as many proteins displayed steady-state changes exceeding 50% by 48 hours without being affected early on. Our data demonstrate that rAAV exposure induces rapid and transient proteome shifts within 30 minutes of exposure. These early proteomic shifts must rely on a reservoir of nascent proteins that cells can deploy rapidly, reflect early morphological changes, or contribute to cellular signaling upon receptor-mediated rAAV entry.

Contact

No need to register.

Contact lmp.grad@utoronto.ca with any questions.