Uptake and anterograde axonal transport of wheat germ agglutinin from retina to optic tectum in the chick

The uptake and anterograde axonal transport of ¹²⁵I-wheat germ agglutinin (WGA) has been investigated in the visual system of the chick. In order to obtain a marker with specific and homogeneous binding properties, the iodinated lectin was affinity purified by passage over an N-acetylglucosamne (NAcGlu)-Sepharose column after iodination. 22 h after vitreal injection of the purified ¹²⁵I-WGA, radioactive label was found accumulated in the retinoreceptive layers of the contralateral optic tectum. Gel electrophoresis of tectal homogenates revealed that >80% of the retrieved label ran in a band which comigrated with native WGA. In chicks injected with the fraction of the iodinated preparation that failed to bind to the affinity column, there was no evidence of tectal labeling. These findings support the hypothesis that WGA is selectively taken up by chick retinal ganglion cells and transported intact in an anterograde direction to their axon terminals in the contralateral optic tectum. This raises the possibility that constituents of perikaryal membrane, i.e., lectin receptors, are transported in an anterograde direction by chick retinal ganglion cells.