Ventroptin: A BMP-4 antagonist expressed in a double-gradient pattern in the retina

In the visual system, the establishment of the anteroposterior and dorsoven tral axes in the retina ana tectum during development is important for topo graphic retinotectal projection. We identified chick Ventroptin, an antagon ist of bone morphogenetic protein 4 (BMP-4), which is mainly expressed in t he ventral retina, not only with a ventral high-dorsal low gradient but als o with a nasal high-temporal Low gradient at later stages, Misexpression of Ventroptin altered expression patterns of several topographic genes in the retina and projection of the retinal axons to the tectum along both axes. Thus, the topographic retinotectal projection appears to be specified by th e double-gradient molecule Ventroptin along the two axes.