Dorsal and ventral retinal territories defined by retinoic acid synthesis,break-down and nuclear receptor expression (vol 82, pg 119, 1999)

Determination of the dorso-ventral dimension of the vertebrate retina is kn own to involve retinoic acid (RA), in that high RA activates expression of a ventral retinaldehyde dehydrogenase and low RA of a dorsal dehydrogenase, Here we show that in the early eye vesicle of the mouse embryo, expression of the dorsal dehydrogenase is preceded by, and transiently overlaps with, the RA-degrading oxidase CYP26. Subsequently in the embryonic retina, CYP2 6 forms a narrow horizontal boundary between the dorsal and ventral dehydro genases, creating a trough between very high ventral and moderately high do rsal RA levels. Most of the RA receptors are expressed uniformly throughout the retina except for the RA-sensitive RAR beta, which is down-regulated i n the CYP26 stripe. The orphan receptor COUP-TFII, which modulates RA respo nses, colocalizes with the dorsal dehydrogenase. The organization of the em bryonic vertebrate retina into dorsal and ventral territories divided by a horizontal boundary has parallels to the division of the Drosophila eye dis c into dorsal, equatorial and ventral zones, indicating that the similariti es in eye morphogenesis extend beyond single molecules to topographical pat terns. (C) 1999 Published by Elsevier Science Ireland Ltd. All rights reser ved