A synthetic bacterial luciferase-based autobioluminescent bioreporter, HEK293 ERE/Gal4-Lux , was developed in a human embryonic kidney (HEK293) cell line for the surveillance of chemicals displaying endocrine disrupting activity. Unlike alternative luminescent reporters, this bioreporter generates bioluminescence autonomously without requiring an external light-activating chemical substrate or cellular destruction. The bioreporter's performance was validated against a library of 76 agonistic and antagonistic estrogenic endocrine disruptor chemicals and demonstrated reproducible half maximal effective concentration (EC 50) values meeting the U.S. Environmental Protection Agency (EPA) guidelines for Tier 1 endocrine disrupting chemical screening assays. For model compounds, such as the estrogen receptor (ER) agonist 17bestradiol, HEK293 ERE/Gal4-Lux demonstrated an EC 50 value (7.9 Â 10 À12 M) comparable to that of the current EPA-approved HeLa-9903 firefly luciferase-based estrogen receptor transcription assay (4.6 Â 10 À12 M). Screening against an expanded array of common ER agonists likewise produced similar relative effect potencies as compared with existing assays. The selfinitiated autobioluminescent signal of the bioreporter permitted facile monitoring of the effects of endocrine disrupting chemicals, which decreased the cost and hands-on time required to perform these assays. These characteristics make the HEK293 ERE/Gal4-Lux bioreporter potentially suitable as a high-throughput human cell-based assay for screening estrogenic activity.

Background Luminescent reporter proteins are vital tools for visualizing cells and cellular activity. Among the current toolbox of bioluminescent systems, only bacterial luciferase has genetically defined luciferase and luciferin synthesis pathways that are functional at the mammalian cell temperature optimum of 37 °C and have the potential for in vivo applications. However, this system is not functional in all cell types, including stem cells, where the ability to monitor continuously and in real-time cellular processes such as differentiation and proliferation would be particularly advantageous. Results We report that artificial subdivision of the bacterial luciferin and luciferase pathway subcomponents enables continuous or inducible bioluminescence in pluripotent and mesenchymal stem cells when the luciferin pathway is overexpressed with a 20–30:1 ratio. Ratio-based expression is demonstrated to have minimal effects on phenotype or differentiation while enabling autonomous bioluminescence without requiring external excitation. We used this method to assay the proliferation, viability, and toxicology responses of iPSCs and showed that these assays are comparable in their performance to established colorimetric assays. Furthermore, we used the continuous luminescence to track stem cell progeny post-differentiation. Finally, we show that tissue-specific promoters can be used to report cell fate with this system. Conclusions Our findings expand the utility of bacterial luciferase and provide a new tool for stem cell research by providing a method to easily enable continuous, non-invasive bioluminescent monitoring in pluripotent cells.

This chapter explores the history of the bioengineering advances that have been applied to common luciferase enzymes and the improvements that have been accomplished by this work. The primary focus is placed on firefly luciferase (FLuc), Gaussia luciferase (GLuc), Renilla luciferase (RLuc), Oplophorus luciferase (OLuc; NanoLuc), and bacterial luciferase (Lux). Beginning with the cloning and exogenous expression of each enzyme, their step-wise modifications are presented and the new capabilities endowed by each incremental advancement are highlighted. Using the historical basis of this information, the chapter concludes with a prospective on the overall impact these advances have had on scientific research and provides an outlook on what capabilities future advances could unlock.

Technologies enabling on-site environmental detection or medical diagnostics in resource-limited settings have a strong disruptive potential compared to current analytical approaches that require trained personnel in laboratories with immobile, resource intensive instrumentation. Handheld devices, such as smartphones, are now routinely produced with CPUs, RAM, wireless data transfer capabilities, and high-resolution complementary metal oxide semiconductor (CMOS) cameras capable of supporting the capture and processing of bioluminescent signals. In theory, combining the capabilities of these devices with continuously bioluminescent human cell-based bioreporters would allow them to replicate the functionality of more expensive, more complex, and less flexible platforms while supporting human-relevant conclusions. In this work, we compare the performance of smartphone (CMOS) and night vision (image intensifier) devices with in vivo (CCD camera), and in vitro (photomultiplier tube) laboratory instrumentation for monitoring signal dynamics from continuously bioluminescent human cellular models under toxic, stable, and induced expression scenarios. All systems detected bioluminescence from cells at common plating densities. While the in vivo and in vitro systems were more sensitive and detected signal dynamics representing cellular health changes earlier, the night vision and smartphone systems also detected these changes with relatively similar coefficients of variation and linear detection capabilities. The smartphone system did not detect transcriptional induction. The night vision system did detect transcriptional activation, but was less sensitive than the in vivo or in vitro systems and required a stronger induction before the change could be resolved.

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