Kalafut, J. | bioRxiv Science

bioRxiv2023

TANGO-Light - optogenetic control of transcriptional modulators

Cell signalling pathways, in particular downstream receptor activation, frequently converge in the activation of transcriptional modulators. Yet, cells are able to differentiate the stimulation of each receptor. It has become clear that transcriptional modulators, such as transcription factors, do not work in on or off states but rather in patterns of active/inactivate conformations. Thus, it is the intensity and duration of such fluctuating activity that result in differential cellular and genes expression changes, and this is challenging to replicate using traditional methods such as inhibitors or genetic constructs. Optogenetics, which is based on the use of light-responsive proteins, offers precise control over biological processes, in a spatio-temporal manner, allowing targeted fine-tuned modulation of specific proteins or signalling pathways. Here, we engineered an optogenetic system to control transcriptional modulators, by fusing a photoactivatable receptor and the TANGO system. By this mean we show that we are able to control a plethora of transcriptional modulators by light. And by doing so, changing cells fate - inducing cells to acquire a more mesenchymal or epithelial phenotype. This optogenetic system was also adapted to mimic signalling pathways such as Notch and Wnt in a light-dose dependent manner. Finally, we show that this light-responsive system can be induced by natural light sources upon cell-cell contact/proximity.

cell biology↗

bioRxiv2023

SYNTHETIC CIRCUITS BASED ON SPLIT CAS9 TO DETECT CELLULAR EVENTS

Synthetic biology involves the generation of logic circuits to create or control biological functions and behaviors by engineering interconnected genetic elements such as promoters, repressors, and transcriptional activators. CRISPR discovery, and its adaptations to mammalian cells, has made it the tool of choice in molecular biology and revolutionized genome engineering in biomedical sciences. Here, we describe an adaptation of a split Cas9 to generate synthetic logic gates to sense biological events. As proof-of-concept, the complementing halves of split Cas9 were placed under different promoters, one unique to cancer cells of epithelial origin (phCEA) and one universal promoter (pCMV). We used self-assembling inteins to reunite the halves when co-expressed. Only cancer cells with epithelial origin expressed both halves and activated a reporter becoming green fluorescent. We then investigated whether we could apply this system to the detection of biological processes such as epithelial to mesenchymal transition (EMT). We designed another logic gate where one halve is expressed only by cancer cells of epithelial origin, while the other is activated during EMT - under the control of TWIST1. Indeed, cells undergoing EMT were detected by the activation of the reporter. Finally, the split-Cas9 logic gate was applied as a sensor to detect cell-cell fusion events in multiple cell lines. Each cell type expressed only one halve of split Cas9, and only induction of fusion resulted in the appearance of multinucleated syncytia and the expression of the reporter system. The simplicity and flexibility of the split Cas9 system reported here can be integrated to many other cellular processes, not only as a sensor but as an actuator. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=88 SRC="FIGDIR/small/533022v1_ufig1.gif" ALT="Figure 1"> View larger version (17K): org.highwire.dtl.DTLVardef@1f63cf0org.highwire.dtl.DTLVardef@11ab298org.highwire.dtl.DTLVardef@1c3270eorg.highwire.dtl.DTLVardef@1394488_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗