By using single-gene integrations with green fluorescent protein, Yaron Shav-Tal and his colleagues at Bar-Ilan University were able to visualize a single gene undergoing transcription in vivo in mammalian cells, they report in Nature Methods. "In our system, the cell line has a target sequence in its genome and any sequence you send in will always go to that place," Shav-Tal tells Nature. "You can make different cell lines and not be worried about where the gene went in."
On its blog and on YouTube, The Scientist posted videos that the researchers made. This one is of a continuously transcribing single cyclin D1 gene: