1. Janelia Farm Research Consortium on Imaging Transcription, Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia 20147
2. Imagerie Fonctionelle de la Transcription, Ecole Normale Supérieure CNRS UMR 8541, 75230 Paris cedex 05, France;
3. Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley, California 94720;
4. Department of Anatomy and Structural Biology, Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461;