Stony Brook Medical Scientist Training Program 1 article published in JoVE Bioengineering Reliably Engineering and Controlling Stable Optogenetic Gene Circuits in Mammalian Cells Michael Tyler Guinn1,2,3, Damiano Coraci*2, Lesia Guinn*2, Gábor Balázsi1,2 1Biomedical Engineering Department, Stony Brook University, 2Laufer Center for Physical and Quantitative Biology, Stony Brook University, 3Stony Brook Medical Scientist Training Program Reliably controlling light-responsive mammalian cells requires the standardization of optogenetic methods. Toward this goal, this study outlines a pipeline of gene circuit construction, cell engineering, optogenetic equipment operation, and verification assays to standardize the study of light-induced gene expression using a negative-feedback optogenetic gene circuit as a case study.