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Investigating the role of microglia in brain disorders, by high-throughput single-cell screening of disease-associated genes in human immuno-competent brain avatars

Principal Investigator:
  • Julien Muffat, Hospital for Sick Children
  • Azrieli Foundation

Project Overview

Most brain disorders remain incurable, whether they begin during early development, as seen in Autism, or seem acquired over time, as observed in Alzheimer’s disease. Population studies have now pointed to hundreds of DNA variants as possible culprits in these disorders and have highlighted the role of immunity. The functional impact of those variants remains elusive, and the affected genes are not clearly identified.

Fundamental differences in human brain biology require human experimental model systems to bridge the gaps in our knowledge. We developed such experimental models, petri dish versions of organized human brain tissue which we call avatars.

Brain cells can be in stimulated states, for example during inflammation, in which they rely on genes that are not important to them at baseline. A DNA variant affecting one of those genes will only be revealed in specific cells, such as immune cells as opposed to nerve cells, and only in a specific state, such as a stimulated one. We will expose our avatars to inflammation molecules, to observe the impact on gene access and levels in thousands of individual cells. This will reveal which DNA variants are only important to inflamed immune cells, narrowing down future investigations.

Studying one gene at-a-time is painstaking and costly. Instead, we propose to harness the power of high-throughput methods to modulate dozens of individual genes identified to be important, in thousands of individual cells in our avatars. This method will rapidly extract meaningful information about the roles of poorly understood DNA variants in brain health. We will then test how gene variants in immune cells impact nerve cell function during inflammation.

Because the model is human, relevance to patients will be high. This approach will allow drug target prioritization, and can later be applied to other disorders, other stimulations, and other tissues.