Peering into the minds of mammals

Abstract

With bioluminescence imaging techniques, as with emotions, it can be difficult to look beyond the surface and see what’s going on deep inside. Inspired by fireflies, this imaging method makes use of green-yellow light emitted when an enzyme called luciferase reacts with d-luciferin. Light of this wavelength doesn’t travel far through tissue, which has limited the technique’s depth of visualization. Now, researchers in Japan have engineered a synthetic bioluminescence system that emits red-shifted light that is up to 1,000 times as bright as light emitted by existing systems and can penetrate through the deep tissue of mice and marmosets (Science 2018, DOI: 10.1126/science.aaq1067). The researchers installed their new imaging system in the animals’ striatum, an area deep in the brain, in two steps. First, they injected a virus containing their improved luciferase, an enzyme called Akaluc discovered through directed evolution. Then they fed the animals or injected them with a