Fig. 1. In situ imaging of the expression of ACTB mRNA in single cells. (A) The scheme of in situ RCA in single cells. Imaging of ACTB mRNA by RCA using the target padlock probe (B), without the trigger primer (C), using a random padlock probe (D), and after blocking the target site (E). The cell nuclei are stained by DAPI (blue), the RCA amplicons are hybridized with the Alexa 488-fluorescence probe (green spots), and the cell outlines are marked by a dotted line. Inset: frequency histograms of RCA amplicons per cell detected. Scale bars, 20 μm.