Methods like single-cell transcriptomics and genome-wide association studies (GWAS) provide insight in how genetic mutations drive cellular and molecular changes in the brain. However, these approaches cannot identify molecular mechanisms that control brain function and disease. An article from FunGen-AD investigator Martin Kampmann and others at the University of California, San Francisco demonstrates a new approach for studying these molecular mechanisms. The group developed a three-dimensional cell culture system made of induced pluripotent stem cell (iPSC)-derived neuronal and glial cells called iAssembloids. Unlike other systems such as organoids that take months to grow, iAssembloids can be developed in two weeks and contain around 10,000 cells. These iAssembloids have more mature gene expression, showed more complex morphology, and had more active neuronal firing than two-dimensional culture systems. Importantly, iAssembloids can be used for large screening studies.
The researchers used the iAssembloids system to determine how glial and neuronal cells interact to control neuronal death and survival using a CRISPRi-based screen to target over 2,900 genes. One gene identified in this screen was GSK3β, a glycogen synthase kinase. Further experiments showed that GSK3β inhibits the ability of the transcription factor NRF2 to reduce oxidative stress in neurons, impacting neurons’ ability to survive. This suggests that GSK3β could play a role in neurodegeneration. The iAssembloids system was then applied to reveal the role APOE4 in neuronal survival. Experiments show that APOE4-expressing astrocytes may promote neuronal hyperactivity. Overall, these examples demonstrate how an iAssembloid system is effective for unbiased identification of mechanisms underlying neuron-glia cell interactions. The system offers potential usefulness in translational research, such as identification of pathway activities in human disease models that directly reflect changes observed in patient brains.
This research, partially supported by FunGen-AD grant U01AG072464, is published in Neuron here. You can read more about these research findings at the following links:
- “iAssembloids” Probe Glial Roles in Neuron Survival (Alzforum)