DIFFERENTIAL EXPRESSION OF THE MESSENGER-RNAS OF THE AXONAL GLYCOPROTEINS AXONIN-1 AND NGCAM IN THE DEVELOPING CHICK RETINA

Cell adhesion molecules expressed on the axonal membrane have been tho ught to be involved in the guidance of axons to their target area. In the chick, axonin-1 and NgCAM have been shown to promote, through reci procal interactions, neurite outgrowth in vitro. We have recently show n that chick retinal ganglion cells (RGC) express both proteins as ear ly as the axonal elongation begins. Their expression continues through out the development of the retinotectal system synchronously with the chronotopic spread of axons. To further investigate the spatiotemporal distribution of axonin-1 and NgCAM in the retina, we have analysed th e expression of their mRNAs in the present study. From stage 36 (E10) until hatching photoreceptors express axonin-1 but not NgCAM. In the i nner nuclear layer groups of amacrine cells were strongly labelled wit h both probes but they seemed to belong to different subgroups. These patterns of expression might indicate a differential influence of the two proteins on the development of the local neural circuits of the re tina.