Tuning oncogenic signaling landscapes to drive efficient reprogramming to motor neurons
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dorn-blende-phd-cheme-2026-thesis.pdf
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Author(s)
Lende-Dorn, Brittany A.
Advisor(s)
Galloway, Kate E.
Date Issued
May 2026
Publisher
Massachusetts Institute of Technology
Abstract
Direct reprogramming of patient-specific somatic cells into neurons remains limited by an incomplete understanding of how signaling pathways and gene dosage govern cell-fate transitions, and by a lack of tools that enable precise and robust regulation in primary cells. Using mouse embryonic fibroblast to induced motor neuron reprogramming as a model system, I show through chemogenetic control of MAPK signaling that a non-monotonic relationship exists between pathway activity, proliferation, and conversion efficiency, revealing an optimal signaling regime that maximizes neuronal yield.
Because RAS signaling output directly controls conversion efficiency through proliferation, this system provides a functional testbed for developing and adapting synthetic biology tools for complex cellular contexts. Here I engineered a DNA-based promoter editing system and a compact, small-molecule-responsive RNA splicing switch that regulates expression of RAS to enable tunable control during long-term reprogramming processes, and identify and overcome key design bottlenecks, including transgene toxicity and viral vector architecture.
Finally, I established a high-efficiency and reproducible platform for direct conversion of primary human dermal fibroblasts into motor neurons. An optimized proliferative support cocktail and simplified transcription factor delivery strategy markedly improves conversion efficiency and consistency across multiple patient-derived primary fibroblast lines. Transcriptomic analysis confirms induction of neuronal and motor neuron programs and reveals neuron subtype-specific differences. Additionally, selective removal of dividing cells improves neuronal purity and morphological maturation.
Collectively, this work defines principles linking oncogenic signaling to cell-fate conversion, develops synthetic tools for tunable gene regulation in primary cells, and establishes a scalable human motor neuron reprogramming platform. These advances provide both mechanistic insight and practical foundations for future studies of neuronal development and disease modeling using directly reprogrammed human cells.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
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