A synthetic alternative splicing circuit to confer memory of extracellular stimuli in mammalian cells

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Qingqing Wang, Pamela A. Silver

Department of Systems Biology, United States

Alternative splicing (AS) of mRNA is a major source of biological diversity and regulation in eukaryotes. Despite its rapidity and flexibility as a regulatory mechanism, AS remains under-utilized in synthetic biology devices. The mammalian AS system contains multiple standard regulatory network motifs including positive and negative feedback loops. In many cases, AS functions as a switch modulating critical biological functions, such as cell fate and identity determination during development in multicellular organisms. AS allows cells to respond to environmental cues at the post-transcriptional level, and often more rapidly than through transcriptional regulation alone. Here, we demonstrate a splicing-based circuit in mammalian cells that confers memory of extracellular stimuli based on the autoregulatory feedback loop from the splicing regulation of Sex-Lethal (Sxl), the Drosophila sex determination master gene. We show that the positive feedback loop of Sxl regulating the splicing of its own mRNA is conserved in mammalian cells as in Drosophila. Furthermore, this positive feedback loop has the potential of serving as a device to rapidly retain memory of transient exposure to stimuli in mammalian cells. Our splicing-based memory device explores the potential of AS regulatory networks and will contribute to the study of long term effects of transient stimuli on cells as well as our knowledge of post-transcriptional regulation in biology.