INSITU HYBRIDIZATION AT THE ELECTRON-MICROSCOPIC LEVEL USING A BROMODEOXYURIDINE LABELED DNA-PROBE

A bromodeoxyuridine (BrdU) labeled DNA probe was used for in situ hybr idization at the electron microscopic (EM) level. A BrdU labeled DNA p robe was hybridized in situ to cryostat sections of paraformaldehyde f ixed OCT compound embedded cultured HL-60 cells. After hybridization, some sections were incubated with FiTC-conjugated anti-BrdU monoclonal antibody for fluorescence microscopy (FM), and others were embedded i n Quetol for electron microscopy (EM). The ultrathin sections of Queto l-embedded specimens were incubated with the anti-BrdU monoclonal anti body and the immunoglobulin: gold colloid. In both FM and EM studies, the signals were concentrated in the rough endoplasmic reticulum. More over, some label was arranged from the nucleus to the cytoplasm at the EM level. Relatively simple methods using the BrdU labeled DNA probe for the detection of the defined nucleic acid sequence with reasonable tissue preservation and high resolution are described here. This meth od may be useful for developmental and disease related studies of spec ific mRNA in cells and tissues.