Detection of β-galactosidase activity: X-gal staining

X-gal staining is a rapid and convenient histochemical technique used to detect reporter gene expression. A prerequisite is the creation or acquisition of transgenic reporter mouse lines, in which the bacterial LacZ gene has been knocked into the gene of interest or placed under the control of regulatory elements corresponding to the gene of interest. Expression is marked by a dark blue stain and can be detected at the single cell level, providing a robust visual readout of gene expression in the developing kidney. Here, we describe the methodology, applications, and limitations of this technique.