The Optx 2 homeobox gene is expressed in early precursors of the eye and activates retina-specific genes

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 95; no. 18; pp. 10643 - 10648
• Main Authors: Toy, Jeffrey, Yang, Jun-Ming, Leppert, Gregory S., Sundin, Olof H.
• Format: Journal Article
• Language: English
• Published: 01-09-1998
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.95.18.10643

Vertebrate eye development begins at the gastrula stage, when a region known as the eye field acquires the capacity to generate retina and lens.
Optx2
, a homeobox gene of the
sine oculis-Six
family, is selectively expressed in this early eye field and later in the lens placode and optic vesicle. The distal and ventral portion of the optic vesicle are fated to become the retina and optic nerve, whereas the dorsal portion eventually loses its neural characteristics and activates the synthesis of melanin, forming the retinal pigment epithelium.
Optx2
expression is turned off in the future pigment epithelium but remains expressed in the proliferating neuroblasts and differentiating cells of the neural retina. When an
Optx2
-expressing plasmid is transfected into embryonic or mature chicken pigment epithelial cells, these cells adopt a neuronal morphology and express markers characteristic of developing neural retina and photoreceptors. One explanation of these results is that
Optx2
functions as a determinant of retinal precursors and that it has induced the transdifferentiation of pigment epithelium into retinal neurons and photoreceptors. We also have isolated
optix
, a
Drosophila
gene that is the closest insect homologue of
Optx2
and
Six3. Optix
is expressed during early development of the fly head and eye primordia.