Generating fluorescent fish

What are glowing fish?

Glowing fish have been modified to carry a gene coding for a fluorescent protein. Animals that have been modified using genes from other organisms are called transgenic.

How do we make fish fluorescent?

Zebrafish embryos.We inject the fluorescent protein gene into fertilised fish eggs. The gene will integrate in the genetic code of the eggs. These grow into adult fish carrying the fluorescent protein gene. We breed these fish to produce the glowing embryos used in our research.

We can control where the fluorescent protein will be expressed. If we want to label the muscle cells for instance, we need to find in the zebrafish DNA the code that tells which proteins are made in the muscles. This piece of DNA – called a promoter – is like a switch: in each cell it tells a gene to be on or off.

Joining the promoter sequence to the gene for a fluorescent protein makes what is called a transgene. Such a transgene has all the information needed to direct the production of the fluorescent protein in a specific cell type.

Why are fluorescent fish useful?

Zebrafish blood vessels.We can ‘light up’ different cells and organs in the embryo. This means we can follow these cells as the embryo develops.

By tracking fluorescent cells in mutant embryos we can study how the defect affects normal cell development.

Understanding the promoter sequences used to make transgenic fish is also important. Knowing how genes are switched on and off is critical to understanding disease and development.

A very interesting and useful finding is that promoters from one species are often the same in other species, like genes, they are conserved. To demonstrate this conservation it is possible to link the promoter from one animal to GFP and put it in another species. A frequent outcome of such an experiment is that the promoter makes the pattern of GFP the same in each species.