INDIGO’s panel of ER assays utilizes non-human mammalian cells engineered to express human estrogen receptors alpha (ER1; NR3A1) and beta (ER2; NR3A2), ligand-dependent transcription factors commonly referred to as ERα and ERβ. INDIGO’s ER reporter cells include the luciferase reporter gene functionally linked to a responsive promoter. Thus, quantifying changes in luciferase expression in the treated reporter cells provides a sensitive surrogate measure of the changes in ER activities. Luciferase gene expression occurs after ligand-bound ER undergoes nuclear translocation, DNA binding, recruitment and assembly of the co-activators and accessory factors required to form a functional transcription complex, culminating in expression of the target gene. Unlike some other cell-based assay strategies, the readout from INDIGO’s reporter cells demands the same orchestration of all intracellular molecular interactions and events that can be expected to occur in vivo. ER reporter cells are prepared using INDIGO’s proprietary CryoMite™ process. This cryo-preservation method yields exceptional cell viability post-thaw, and provides the convenience of immediately dispensing healthy, division-competent reporter cells into assay plates. There is no need for cumbersome intermediate treatment steps such as spin-and-rinse of cells, viability determinations, cell titer adjustments, or the pre-incubation of reporter cells prior to assay setup. INDIGO Bioscience’s nuclear receptor reporter assays are all-inclusive cell-based assay systems. In addition to ER reporter cells, this kit provides two optimized media for use during cell culture and in diluting the user’s test samples, a reference agonist, luciferase detection reagent, and a cell culture-ready assay plate.