Zebrafish help us understand retinal diseases

Biologists at the Florida State University, USA, have discovered a gene mutation in Zebrafish that determines if the cells develop as rods or as cones.

The landmark study, published in the Proceedings of the National Academy of Sciences, could shed new light on the molecular mechanisms underlying retinal development and, consequently provide new information on inherited retinal diseases in humans. Zebrafish eyes were used in the study as they have a mosaic of light-sensitive cells whose structure and functions are nearly identical to those of humans.

The allele, whose function was previously unknown, has been named "LOR," short for "lots-of-rods" because the mutation results in too many rods and fewer ultraviolet cones than in the normal eye.

"What is striking in this case," remarked lead author Karen Alvarez-Delfin, "is that the photoreceptor cell changes we observed in the retinas of zebrafish are opposite to the changes identified in Enhanced S-cone syndrome (ESCS), an inherited human retinal dystrophy in which the rods express genes usually only found in cones, eventually leading to blindness."

Furthermore, it was observed that while alterations in photoreceptor development in the human and mouse eyes lead to retinal degeneration, they did not in Zebrafish. Further studies hope to determine these differences in outcomes between mammals and fish, and why the human mutation leads to degenerative disease.