Knowing expression patterns of given proteins is very important to understand their functions. Immunostaining analysis with specific antibodies is commonly used to identify cells or tissues expressing proteins of interest. Although this technique is regularly used, it requires high quality of specific antibodies and there is no good quality of antibody available for certain proteins. Alternatively, X-gal staining is also used to analyze protein expression pattern. It is simple and routinely used to detect expression pattern of any proteins of interest in vivo. In this method, genetically modified animals that express beta-galactosidase under the control of certain regulatory elements will be used to reveal the expression pattern of proteins that use the same regulatory elements.