Reference and Translation Center for Cardiac Stem Cell Therapy (RTC) 1 article published in JoVE Biology Analysis of the Gap Junction-dependent Transfer of miRNA with 3D-FRAP Microscopy Heiko Lemcke1,2,3, Natalia Voronina1,2,3, Gustav Steinhoff1,2,3, Robert David1,2,3 1Reference and Translation Center for Cardiac Stem Cell Therapy (RTC), 2Department of Cardiac Surgery, University of Rostock, 3Department of Life, Light and Matter of the Interdisciplinary Faculty, University of Rostock Here, we describe the application of three-dimensional fluorescence recovery after photobleaching (3D-FRAP) for the analysis of the gap junction-dependent shuttling of miRNA. In contrast to commonly applied methods, 3D-FRAP allows for the quantification of the intercellular transfer of small RNAs in real time, with high spatio-temporal resolution.