In Vivo and In Vitro Dynamics of Undifferentiated Embryonic Cell Transcription Factor 1

• Generation and characterization of two multipurpose knockin Utf1 reporter lines
• Real-time imaging of UTF1 levels in vitro and in vivo
• Highly efficient genome-wide mapping of UTF1 using built-in biotinylation
• Highly dynamic UTF1 levels in 2i versus serum/LIF conditions

SummaryPluripotent stem cells retain the ability to differentiate into the three germ layers and germline. As a result, there is a major interest in characterizing regulators that establish and maintain pluripotency. The network of transcription factors continues to expand in complexity, and one factor, undifferentiated embryonic cell transcription factor 1 (UTF1), has recently moved more into the limelight. To facilitate the study of UTF1, we report the generation and characterization of two reporter lines that enable efficient tracking, mapping, and purification of endogenous UTF1. In particular, we include a built-in biotinylation system in our targeted locus that allows efficient and reliable pulldown. We also use this reporter to show the dynamic regulation of Utf1 in distinct stem cell conditions and demonstrate its utility for reprogramming studies. The multipurpose design of the reporter lines enables many directions of future study and should lead to a better understanding of UTF1’s diverse roles.