Analysis of ephrin-A2 in the chick retinotectal projection using a function-blocking monoclonal antibody

Eph receptor tyrosine kinases and their ligands have been shown to be invol ved in processes of cell migration and axon guidance during embryonic devel opment. sure we describe the development of a function-l,locking monoclonal antibody against chick ephrin-A2, and its effect on retinal ganglion cell axons studied both ira vitro and in vivo. In the stripe assay, the blocking antibody completely abolished the repulsive effect of posterior tectal mem branes. ln vivo, in a loss-of-function approach, hybridoma cells secreting the antiephrin-A2 antibody were applied to chick embryos from embryonic day 3 (E3) on, and the retinotectal projection was subsequently analyzed at E1 6, Dil tracing analyses showed that although the projection of both tempora l and nasal retinal ganglion axons in the tectum was, overall, normal, occa sionally diffuse and extra termination zones were observed, in addition to axons over-shooting their termination zones. These data support the idea th at ephrin-A2 contributes to the establishment of the chick retinotectal pro jection. (C) 2001 John Wiley & Sons, Inc.