The Glowing Eyes of the Zebrafish

Author: John Monczunski

There are some highly unusual and valuable fish darting back and forth in their tanks in the basement of Notre Dame’s Freimann Life Sciences Center. David Hyde, professor of biological science, and his colleagues have tailor-made some inch-long transparent zebrafish to exhibit green fluorescent light in the sensory cells of their eyes.

The achievement is not a scientific parlor game. Hyde says it offers scientists a useful tool to study the genetic sources of such human retinal diseases as retinitis pigmentosa, a hereditary degenerative disease characterized by night blindness, pigmentary changes within the retina, and eventual loss of vision.

Hyde’s research team used sophisticated genetic engineering techniques to insert into zebrafish the gene that causes the Aequorea victoria jellyfish to glow green and direct it to certain light receptors in the zebrafish’s retina. Three days after fertilization, the scientists detected the green-glowing protein in the developing eye of the fish. The fluorescent characteristic, which can be observed only under a microscope, subsequently was passed on to the fish’s offspring.

In another study designed to model retinal degeneration, Hyde, the Kenna Director of Notre Dame’s Center for Zebrafish Research, exposed albino zebrafish to seven days of constant darkness followed by seven days of constant bright light followed finally by 28 days of alternating light and darkness. The researchers found the intense illumination caused the eye’s light-sensitive cells to die. The cells regenerated, although not in an organized way. Hyde says the technique offers scientists a way to determine on a molecular level how the light-sensitive cells of the retina regenerate. Their data suggests that the regenerated cells which migrated to the damaged region were derived from adult stem cells present in the retina. The finding holds significance not only for curing blindness but also other neurological diseases such as Parkinson’s and Alzheimer’s.

Zebrafish are a favorite species among biological researchers because their transparent embryos make it possible to monitor progeny from single cells until the late stages of development.

John Monczunski is an associate editor of this magazine.