CONTACTIN/F11 AND TENASCIN-C COEXPRESSION IN THE CHICK RETINA CORRELATES WITH FORMATION OF THE SYNAPTIC PLEXIFORM LAYERS

The neural immunoglobulin-like cell adhesion molecule contactin/F11 and the extracellular matrix glycoprotein tenascin-C are prominent molecules in the developing nervous system which interact in in vitro assays (Zisch et al., J. Cell Biol. 119, 203-213). To determine their potential role in neural development, the distribution of tenascin-C and contactin/F11 was examined in the developing chick retina. The onset of both tenascin-C and contactin/F11 expression coincides with the appearance of ganglion cell dendrites and neurites from bipolar and amacrine cells in the inner layer (IPL) at E8, and the extension of bipolar and horizontal cell processes in the outer plexiform layer (OPL) at E9. Contactin/F11 expression is co-ordinately upregulated with the TN190 and TN200 tenascin-C isoforms between embryonic day 8 (E8) and E17, while little, if any, of the TN220 isoform, which does not bind contactin/F11, is detected. In situ hybridization reveals that tenascin-C and contactin/F11 mRNAs are synthesized by different neuronal types. Tenascin-C mRNA probes hybridize to amacrine and displaced amacrine neurons, and horizontal neurons. In cultured retinal cells, tenascin-C is also present on process-bearing neurofilament-positive cells. Contactin/F11 mRNA is detected in bipolar cells or their precursors from E8-9, and later in horizontal and ganglion neurons. The highest levels and greatest overlap in the synaptic IPL and OPL are reached at E17, when the stratification of the retina is nearly complete. These results are consistent with a putative role for contactin/F11-tenascin-C interactions in the establishment of synaptic layers in the retina.