Monensin induces distortion of optic nerve crossing at the chick embryo chiasm.

The effects of intraocular injection of monensin, a specific inhibitor of membrane glycoprotein transport within the axon, on the development of the chick embryo optic nerve were examined. A proportion of axons growing from the monensin-injected eye were misrouted into the opposite optic nerve at the chiasm and grew to the retina of the opposite eye. These results suggest that formation of the decussation pattern at the chiasm primarily depends on neurite fasciculation mediated by membrane glycoproteins.