Multicoloured fluorescent indicators for live-cell and in vivo imaging of inorganic mercury dynamics.

Engineered fluorescent indicators for visualizing mercury ion (Hg) are powerful tools to illustrate the intracellular distribution and serious toxicity of the ion. However, the sensitive and specific detection of Hg in living cells and in vivo is challenging. This paper reported the development of fluorescent indicators for Hg in green or red color by inserting a circularly permuted fluorescent protein into a highly mercury-specific repressor. These sensors provided a rapid, sensitive, specific, and real-time read-out of Hg dynamics in solutions, bacteria, subcellular organelles of mammalian cells, and zebrafish, thereby providing a useful new method for Hg detection and bioimaging. In conjunction with the hydrogen peroxide sensor HyPer, we found mercury uptake would trigger subcellular oxidative events at the single-cell level, and provided visual evidence of the causality of mercury and oxidative damage. These sensors would paint the landscape of mercury toxicity to cell functions.