TEMPORAL AND SPATIAL REGULATION OF INTEGRIN VITRONECTIN RECEPTOR MESSENGER-RNAS IN THE EMBRYONIC CHICK RETINA

Purpose. To identify integrin vitronectin receptor subunit mRNAs in th e developing avian retina and to track their expression. Methods. Reve rse transcription-polymerase chain reaction was used to identify integ rin vitronectin receptor subunit mRNAs expressed in embryonic chick re tina. cDNA clones encoding the beta 5 subunit were isolated and sequen ced. Expression patterns of mRNAs encoding alpha v, beta 3, and beta 5 subunits were analyzed using northern analysis and in situ hybridizat ion. Results. Integrin beta 1, beta 3, and beta 5 subunit mRNAs were i dentified in embryonic day 6 chick retina. The sequence of chicken bet a 5 was 77% identical to that of human beta 5, and sequences with know n signaling functions were highly conserved. Integrin alpha v, beta 3, and beta 5 mRNAs were expressed throughout the development of the emb ryonic retina, with the highest levels per retina observed around embr yonic day 9. In situ hybridization showed that both beta 3 and beta 5 were expressed throughout the developing retina, particularly in undif ferentiated neuroepithelial precursor cells. At later times, beta 3 wa s expressed uniformly throughout the retina, whereas beta 5 expression was highest in a band throughout the central retina. Conclusions. The strong conservation of sequences with known signaling functions in ch icken beta 5 suggests that it functions in a manner similar to human b eta 5. Spatial expression patterns of vitronectin receptor subunits at early times of development point to a range of possible functions bey ond axon outgrowth, including retinoblast proliferation, adhesion, and migration.