Transcriptional regulation by a light-activated CRISPR activation system. A) Schematic of light-activated CRISPR activation system. B) Zebrafish actin-sgRNA plasmid. Target sequence adjacent to sgRNA scaffold was inserted into Tol2 vector containing zebrafish-actin promoter. C) Illustration of dark and light treatment. Illumination of transfected cells was performed using LED blue light with the intensity of light ~1 W/m² measured by luxmeter. The dark treatment was performed by wrapping the plates containing transfected cells using aluminum foil to blocking the light. D) Fluorescence expression of transfected ZF4 cells. pmaxGFP vector was transfected into ZF4 cells using Nucleofection method program DS-134. Scale bar 100 μm. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)