In situ hybridization at the electron microscope level.

This tutorial paper will review radioactive and non-radioactive in situ hybridization (ISH) techniques at the electron microscope (EM) level; describe our efforts in comparison to those of other groups who recently have published in this field and discuss some potential future applications. Our contribution is the development of a non-radioactive, postembedding technique for the detection of transcripts on thin sections of Lowicryl K4M-embedded cells or tissues. Biotinylated probes were prepared by nick-translation. Signal detection was accomplished with anti-biotin antibody and protein A-gold complexes. Specific labeling was obtained over structures known to be the site of expression. Compared to EM autoradiography this technique offers advantages: rapid signal detection; superior morphological preservation and superior spatial resolution.