The finding is important because it demonstrates that this single gene can perform two different functions during the embryonic retina development, according to Michael Dyer, Ph.D., an assistant member of the St. Jude Department of Developmental Neurobiology. Dyer is the lead author of a report on this work that appears in the May issue of Nature Genetics.
"The critical role we found for Prox1 in the retina supports a growing body of evidence we've been accumulating in the past few years indicating that Prox1 is a key player in orchestrating the proper development of the entire embryo," said Guillermo Oliver, Ph.D., an associate member of the St. Jude Department of Genetics and co-author of the paper.
Using a laboratory mouse model lacking the Prox1 gene, the researchers initially found that the gene was necessary for proper development of a layer of cells in the retina called horizontal cells. These cells process information sent by light-sensitive cells called rods. In the absence of Prox1, this layer was abnormally expanded with cells that had not become specialized into horizontal cells.
Researcher used a variety of techniques including radioactive tags to track newly produced DNA in dividing cells, DNA microarrays to identify differentially affected genes and specially engineered viruses to deliver Prox1 into retinal cells.
Results of these studies also showed that the control Prox1 exerts over the developing retina is so precise that it also ensures that there is one horizontal cell for every 150 rods.