iPSC Microglia Differentiation via Six-Factor Transcriptional Programming
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Solution Overview
Problem
The limited availability of human microglia and the differences between human and mouse microglia hinder functional studies for neurodegenerative diseases, and existing methods to differentiate induced pluripotent stem cells (iPSCs) into microglia-like cells are inefficient and require lengthy timelines.
Innovation Solution
An iterative, pooled single-cell TF screening method identifies a combination of SPI1, CEBPA, FLI1, MEF2C, CEBPB, and IRF8 to differentiate human iPSCs into microglia-like cells within four days, utilizing engineered polynucleotides and inducible promoters for rapid and efficient expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional methods (embryoid body formation, growth factor treatment, co-culturing with neurons) are used to differentiate hiPSCs into microglia-like cells, then the cells can be produced with molecular and functional similarity to primary microglia, but the differentiation timeline is lengthy (30-74 days)
Solution Approach 1:
The patent changes the key parameter of differentiation approach from indirect/conventional methods to direct transcription factor-driven differentiation. By introducing specific transcription factors (SPI1, CEBPA, FLI1, MEF2C, CEBPB, IRF8) that directly regulate microglial gene expression programs, the differentiation timeline is compressed from 30-74 days to approximately 4 days, while maintaining molecular and functional similarity to primary microglia through targeted regulation of microglial identity genes.
Solution Approach 2:
The patent applies preliminary action by pre-identifying and engineering the specific combination of transcription factors before the differentiation process begins. The transcription factor combination was determined through iterative pooled single-cell TF screening, and the hiPSCs are engineered to express these pre-identified factors, allowing the differentiation to proceed directly and rapidly without requiring lengthy intermediate stages of embryoid body formation or gradual growth factor treatment.
2Quantity of substance
If murine models are used to mitigate the supply issue of human brain biopsies, then the availability of microglia increases, but the transferability of knowledge is limited due to differences between human and mouse microglia
Solution Approach 1:
The patent creates human microglia-like cells by copying the differentiation pathway from human embryonic development using induced pluripotent stem cells. This allows generation of human-specific microglia that can be produced in large quantities without requiring human brain biopsies, while maintaining human biological characteristics and molecular profiles that enable direct transferability of knowledge to human disease models and therapeutics.
3Productivity
If engineered expression of transcription factors is used to rapidly produce cell types, then the differentiation speed increases, but the complexity of identifying effective TF combinations becomes high
Solution Approach 1:
The patent segments the complex task of identifying effective TF combinations into a systematic screening process using pooled single-cell TF screens. By dividing the transcription factor space into manageable combinations and using high-throughput single-cell sequencing to assess differentiation efficiency, the complexity is reduced and reproducible identification of effective TF combinations becomes feasible. This segmented approach identified the specific six-TF combination (SPI1, CEBPA, FLI1, MEF2C, CEBPB, IRF8) that achieves rapid differentiation.
Solution Approach 2:
The patent employs feedback mechanisms through iterative pooled single-cell TF screening, where the results of initial screening are used to refine subsequent screening rounds. Single-cell RNA sequencing data provides feedback on which TF combinations most effectively drive microglial differentiation, allowing optimization of the TF combination through iterative improvement cycles that converge on the optimal six-TF regimen for rapid and efficient differentiation.
Data Source
AI summary
Provided herein are methods and compositions for differentiating induced pluripotent stem cells into microglia-like cells by overexpressing transcription factors such as SPI1, CEBPA, FLU, MEF2C, CEBPB, and/or IRF8.