In situ detection of individual mRNA molecules and protein complexes or post-translational modifications using padlock probes combined with the in situ proximity ligation assay

Nat Protoc. 2013 Feb;8(2):355-72. doi: 10.1038/nprot.2013.006. Epub 2013 Jan 24.


Analysis at the single-cell level is essential for the understanding of cellular responses in heterogeneous cell populations, but it has been difficult to perform because of the strict requirements put on detection methods with regard to selectivity and sensitivity (i.e., owing to the cross-reactivity of probes and limited signal amplification). Here we describe a 1.5-d protocol for enumerating and genotyping mRNA molecules in situ while simultaneously obtaining information on protein interactions or post-translational modifications; this is achieved by combining padlock probes with in situ proximity ligation assays (in situ PLA). In addition, we provide an example of how to design padlock probes and how to optimize staining conditions for fixed cells and tissue sections. Both padlock probes and in situ PLA provide the ability to directly visualize single molecules by standard microscopy in fixed cells or tissue sections, and these methods may thus be valuable for both research and diagnostic purposes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA, Complementary / genetics*
  • DNA, Complementary / metabolism
  • Dual Specificity Phosphatase 6 / isolation & purification
  • Genotype
  • Microscopy / methods*
  • Multiprotein Complexes / isolation & purification*
  • Protein Interaction Mapping / methods*
  • Protein Processing, Post-Translational*
  • RNA, Messenger / isolation & purification*
  • RNA, Messenger / metabolism
  • Receptor, Platelet-Derived Growth Factor beta / isolation & purification


  • DNA, Complementary
  • Multiprotein Complexes
  • RNA, Messenger
  • Receptor, Platelet-Derived Growth Factor beta
  • DUSP6 protein, human
  • Dual Specificity Phosphatase 6