Unlocking the competitive potential of pluripotent stem cells: Towards novel stem cell therapeutics

Pluripotent stem cells (PSCs) have the ability to expand endlessly, making copies of themselves, as well as to differentiate into all specialized cell types of the body. As a result, PSCs have opened the door to deriving cellular therapies that have unprecedented promise for treating degenerative diseases. Despite this promise, we lack an understanding of how to control their behaviour — whether they divide, die, or differentiate.

My laboratory will use a combination of cutting-edge experimental and computational technologies to study PSC fitness — the ability of these cells to eliminate each other via cell-cell killing. Our research will uncover the genetic basis of their fitness to predict the emergence of abnormally competitive PSCs, those with aberrant genetic mutations, and to use synthetic biology tools to remove these from cell manufacturing batches. We will also engineer PSCs to enhance their fitness, allowing us to grow these cells in the lab with better efficiency and safety. This research will lead to health and economic benefits for Canadians, improving the efficacy of cell therapies and building on our legacy of stem cell research that began with the initial discovery of stem cells in 1961 by Drs. Till and McCulloch.

Organelle signalling in stem cell identity specification

Stem cells offer tremendous potential for tissue regeneration and uncovering causes and treatments for many human diseases. Technologies developed over the past decade now allow us to grow human stem cells in the lab and manipulate them to carry disease-causing gene mutations and turn them into any cell type of interest. My lab’s research uses these powerful tools to identify important regulators of stem cell function, particularly as they develop into cell types relevant to brain disorders. We focus on identifying the biological processes that build our brains, and biomarkers and treatment approaches for diseases.

Though the genes that regulate stem cell function are fairly well know, the impact of cell organelles, which coordinate many biological functions and are potential targets for treatment, is poorly understood. My lab is working to bridge this gap by investigating the impact of vesicle-like organelles called lysosomes on brain stem cells. Our data suggests lysosomes are critical regulators of stem cell function and brain development. Given new imaging-based tools and clinically approved lysosome-targeted drugs, studying the role of lysosomes can transform our potential to understand, diagnose, and treat brain disease.

Development of improved substrates for live cell imaging to aid in discovering new glucocerebrosidase therapeutic agents

Parkinson’s disease (PD) is a neurodegenerative disorder that affects millions of people worldwide, with no standard treatment currently available. Therefore, there is a major need for new therapeutic agents to treat or prevent the progression of PD. One promising solution involves targeting the protein glucocerebrosidase (GCase) encoded by the gene GBA1. Studies have shown small molecules that increase GCase activity could help prevent the progression of PD.

Dr. Ashmus will use a combination of organic chemistry, chemical biology, and cell biology to discover new therapeutic agents that increase GCase activity. Fluorescently-quenched substrates will be chemically synthesized and used in enzymatic assays to monitor GCase activity in vitro and in neuroblastoma cells. The assay will then be adapted and optimized for use in a high-throughput screen of compounds from the Canadian Glycomics Network and from a natural products collaborator, Roger Linington, at SFU.

The results of this research could produce new lead compounds that increase GCase activity. In addition, the compound screen could aid in identifying new therapeutic targets for PD, which would drive preclinical translation research in this area.

End of Award Update – March 2022

Most exciting outputs

An exciting and successful specific output as part of the project was that we were able to develop a newly designed probe that performs better than the original probe the Vocadlo Lab published and patented back in 2015. The new probe is also capable of being used in a high-throughput screening in live cells. Moreover, the new design led to the development of probes that could for the first-time target other disease-related enzymes of interest in live cells and led to a high-impact publication in Nature Chemical Biology.

Impacts so far

While the main purpose of the research project failed to discover any lead compounds that could be developed as a potential therapeutic agent for Gaucher/Parkinson’s disease, the steps (develop a better probe and optimize use for screening) required to reach the point of running the screen were successful. The data collected (unpublished) has helped secure funding for the Vocadlo Lab and led to collaborations with biotech companies interested in targeting the same enzyme.

Potential future influence

I think some of the work described briefly will start to gain more attention in the next few years. Over the past year or so, I have noticed an increased interest from research institutes and biotech companies in studying enzymes found within the lysosome. This is in part because more of these lysosomal enzymes are being linked to neurological diseases so having biochemical tools that can study them in live cells will be desired. I think some of the probes we have developed over the past couple of years will be of interest to a broader scientific community.

Next steps

The work searching for potential therapeutic agents for Gaucher/Parkinson’s disease is currently ongoing. The majority of my research efforts have shifted to developing and evaluating novel probes targeting other disease-related enzymes. One notable example is a new project collaborating with an expert clinician in Fabry’s Disease. Using one of our recently developed probes, we aim to advance current diagnostic methods and improve dosing and timing of current therapeutics for Fabry Disease patients. I am excited to see some of my work being used in a clinical setting and hope this can lead to something more fruitful in time. Dissemination of the work will be continued through publications, presentations at conferences and through social media platforms.

Useful links

Development of a flow cytometry assay for accurate and selective measurement of lysosomal GBA1 activity in PBMC

Recently, loss-of-function mutations of the GBA1 gene, which encodes glucocerebrosidase (GCase), have been characterized as a major genetic risk for Parkinson’s disease (PD). Patients carrying these mutations have a much higher incidence of PD, earlier onset, and more severe disease.

These data strongly suggest that GCase activity may be useful for early diagnosis as well as monitoring the progression of PD. Dr. Gros will build on her previous work describing a substrate that specifically measures GCase activity both in vitro and in neuronal cells in microscopy. This research will lead into a proof-of-concept clinical study, using a flow cytometry assay to establish correlations between the progression of PD, GBA1 mutant status and GCase activity.

The results of this study will lead to the development of a new assay for clinical studies that will benefit Parkinson’s patients and deepen our overall understanding of the disease.


Genetic dissection of neuronal pattern formation

Neurological diseases and disorders have been estimated to affect 3.6 million Canadians living in the community and over 170,000 Canadians living in long-term care facilities, including in British Columbia. However, we have limited information about the molecular mechanisms that cause many of those neurological conditions, largely because of the complexity of our nervous system. Therefore, understanding the mechanical processes that impart precise neural circuit formation using a simple model organism is critical to try to find ways to prevent neurological diseases and cure patients.

Toward this goal, Dr. Mizumoto will use nematode Caenorhabditis elegans as a model system to investigate the mechanisms that underlie neuronal circuit development. C. elegans has a short life cycle (3 days/generation) with a simple nervous system consisting of only 302 neurons, making it a great genetic model system to study the fine neural circuit formation. Most importantly, countless studies have shown that mechanisms and molecular machineries underlying the development of the nervous system are remarkably conserved between C. elegans and humans. It is likely that the knowledge obtained from our research will be directly applicable to the human nervous system and to diseases associated with nervous system defects.

Using C. elegans, Dr. Mizumoto will explore how neurons communicate with their neighboring neurons/cells to form a stereotyped neuronal pattern at the level of single synapse, which is a specialized interface between neurons or between neurons and other type of cells (such as muscle cells), to transmit electrical signals. Using a combination of C. elegans genetics, molecular biology and microscopy, this research will move towards an understanding of the fundamental principles of neural network formation.These studies will advance health-related knowledge by providing direct targets for other researchers to test in fruit fly (Drosophila) and mammalian models of neurodevelopmental disorders affected by Sema/Plexin signaling and others, and ultimately the development of therapeutic strategies for the treatment of these disorders.