Reporter Genes

Researchers use reporter genes to determine when and where a gene of interest is expressed. A reporter gene codes for a protein that can be tracked, such as a protein with a known enzymatic activity or one that is fluorescent.

Gene expression is controlled by cis-regulatory sequences located upstream or downstream of a gene’s coding region in DNA .

The pattern and timing of gene expression can be determined by creating recombinant DNA with a reporter gene under the control of a cis-regulatory sequence of interest and introducing it into cells or an organism.

This recombinant gene is introduced into different cell types, and both the gene of interest and the reporter gene are allowed to express.

Since the gene of interest  and the reporter gene have the same cis-regulatory sequence, they are expressed in the same cells and at the same time. So, by monitoring the expression of the reporter gene, a scientist can track where the gene of interest is being expressed.

One of the well-known reporter genes is one that encodes for a protein called green fluorescent protein - or GFP.

GFP was discovered in the jellyfish, Aequorea victoria. The protein produces a green fluorescence under ultraviolet light, which enables researchers to track its location within a cell.

For example, to study the expression of β-tubulin in C. elegans, the coding sequence of the β-tubulin gene was replaced by the gfp gene.

The gfp gene expression is now under the control of the promoter for the β-tubulin gene.

This recombinant DNA was introduced into the worm using a microinjection, and the gene was expressed, similarly to β-tubulin.

The location of GFP was monitored using fluorescence microscopy. As GFP fluorescence was shown in the touch receptor neurons, this is likely a site where β-tubulin is expressed.