Eye candy: Transcriptional control of vertebrate eye development

Dr. Greg Lemke and colleagues have determined that two ventral anterior homeobox (Vax) genes act as intracellular effectors of Shh signaling in the developing eye field and are required for proper optic nerve formation. During embryogenesis, the optic vesicle is strictly compartmentalized into dorsal and ventral domains, the former of which gives rise to the retina, and the latter of which forms the optic nerve.

By creating Vax1/2 double knock-out mice, Dr. Lemke and colleagues found that Vax1 and Vax2 are necessary for the repression of Pax6 expression, the ventralization of the eye field, and subsequent development of the optic nerve. Dr. Lemke notes that "in many respects, the eyes represent a default differentiation pathway for the front end of the developing brain. To make an optic nerve and connect the eyes to the rest of the brain, this default pathway must be blocked and re-directed, and that's what the Vax genes do."

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