Safranin O Counter-staining Enhances the Counting of beta-Galactosi-dase-Expressing Cells

摘要

The Escherichia coli lacZ gene, which codes bacterial (3-galactosidase (beta-gal), is one of the commonly used reporter genes (1). The popularity of this reporter gene system stems from the fact that beta-gal converts the chro-mogenic substrate 5-bromo-4-chloro-3-indolyl-p-D-galactopyranoside (X-gal) to a blue precipitate. The blue staining not only provides a simple method to quantify the affected cells but also characterizes the patterns of distribution of expressing cells (3). The latter may signify the involvement of different cell types or the spatial insight into gene transfer and expression in vivo. However, accurate identification of lacZ gene-negative cells is equally important in these analyses. Thus, H and E stain have been used by some investigators to identify p-gal-negative cells (4). We present a simple counter staining method that provides consistent results.