ABSTRACT
This chapter introduces the techniques newly used to track gene expression and proteins in cytology and histology. To understand gene function, gene products have to be characterised and their expression patterns analysed at the tissue, cell or subcellular level. The gene encoding for a β-galactosidase enzyme is also a popular reporter enzyme in mammalian cells. Highly sensitive imaging equipment is needed for bioluminescent assays because of the low light flux, which also implies long integration times. Immunocytochemistry techniques are based on antibody/antigen reactions within the cell. Besides the development of spectral variants, considerable efforts have also been made to obtain Green Fluorescent Protein (GFP)-analogues from other organisms or GFP-derivatives with enhanced properties compared with the original GFP protein. The GFP gene is cloned behind a promoter resulting in a fluorescent reporter of promoter activity. The GFP-coding sequence may be coupled to several motifs and may be transferred in most biological systems.
