15 NSFBIO: Rewritable biocomputers in mammalian cells

A major objective in synthetic biology is to achieve the ability to predictably design and construct genetic circuits to control cellular functions. Although recent years have seen numerous advances towards this goal, the sophistication, performance and scale of mammalian genetic circuits trail their microbial counterparts. The overarching goal of this proposal is to develop a suite of versatile gene expression tools and to use these tools to construct a genetic biocomputation platform with rewritable memory capability in mammalian cells. The memory feature is crucial to allow for permanent responses to transient or conditional signals, and has direct applications in protein production and tissue-specific gene expression. Moreover, genetic circuits with memory capabilities allow recordings of past events in complex environments where continuous monitoring is not feasible. For instance, E. coli engineered with a memory circuit have been placed inside a mouse gut to sense and remember drug exposure.

A major objective in synthetic biology is to achieve the ability to predictably design and construct genetic circuits to control cellular functions. Although recent years have seen numerous advances towards this goal, the sophistication, performance and scale of mammalian genetic circuits trail their microbial counterparts. The overarching goal of this proposal is to develop a suite of versatile gene expression tools and to use these tools to construct a genetic biocomputation platform with rewritable memory capability in mammalian cells. The memory feature is crucial to allow for permanent responses to transient or conditional signals, and has direct applications in protein production and tissue-specific gene expression. Moreover, genetic circuits with memory capabilities allow recordings of past events in complex environments where continuous monitoring is not feasible. For instance, E. coli engineered with a memory circuit have been placed inside a mouse gut to sense and remember drug exposure.

Given the significant influences that recombinases and genetic circuit engineering have on mammalian and microbial genetics, outcome from this work could provide transformative methods and resources for genetic engineering in model mammalian systems. In addition, this proposed work will provide the first in-depth characterization of the specificity and toxicity of serine integrases, which will benefit the research community in genome engineering.

Broader Impacts:
The broader impact of this work will be manifested in commercial exploitation and education outreach. Strategies to control gene expression in mammalian systems are important to biopharmaceuticals manufacturing and cell-based therapy. Therefore, success from this project can create substantial commercial value, which can lead to formation of new companies and job creation. The PIs will also develop course materials on serine integrase circuits to be delivered to undergraduate and postgraduate students in the US and UK. Research opportunities in this project will be made available to high school and undergraduate students. In addition, due to the PIs' affiliations
to major synthetic biology centers in the US and UK, students and researchers engaged in this project will have a unique collaborative training experience with international exposure. Lastly, to engage the general public, the PIs will create dedicated project pages on the PIs' website to summarize our findings upon publication and explain the implications and underlying science in lay terms. Together, these activities will broaden the impact of this project beyond specific scientific advances.