Zebrafish

More than 250,000 infants are born in North America each year with some type of congenital abnormality. Many of these defects involve the nervous system, particularly the brain. In order to develop therapies to prevent and cure these types of abnormalities, the mechanisms which regulate the development of nerves and the brain must be understood. The field of developmental biology is devoted to the understanding of these types of processes.

Traditionally, the developmental biology of vertebrate animals has been carried out using invertebrates, such as fruit flies and roundworms. These animals have the advantage that their developing embryos can be seen by researchers, so that mutations induced in the embryos can be observed to determine how they affect normal development. Research on these animals suggests that neural development results from the intricate regulation of families of genes, the interaction of the products produced by those genes, and other factors.

New techniques now allow the genes which regulate the development of the brain and nervous system in a vertebrate to be studied. While mice have been useful for genetic study, their embryos are hidden in the uterus, making direct observation impossible. The African clawed frog has been a good subject for developmental biologists.

The zebrafish, a 2-inch freshwater fish popular in home aquaria, has become the animal model of choice for many developmental biologists. This fish has the advantage for genetics study of having a brief (3-month) generation time and prolific egg production, and its transparent, rapidly-developing embryos are ideal for developmental study.

Techniques to raise and breed zebrafish in the lab, collect its eggs and sperm and mutagenize its DNA are currently being developed. By injecting small pieces of DNA into the fish embryo, mutant fish can be produced and studied. These mutants, called transgenics, allow scientists to identify genes and their specific role during development.

When researchers know which of the 1,000,000 genes in the human embryo are controlling certain processes, therapies can be designed to correct defective genes which cause such diseases as blindness, deafness and mental retardation.