Onset of fibre differentiation in cultured rat lens epithelium under the influence of neural retina-conditioned medium.
In the intact rat lens, epithelial cells, which are cuboidal and contain alpha-crystallin, give rise to fibre cells, which are elongated and contain alpha-, beta- and gamma-crystallins. Epithelial explants cultured in medium conditioned by bovine neural retinas (BRCM) showed changes analogous to fibre cell differentiation in vivo. The cells became enlarged and elongated and accumulated beta- and gamma-crystallin as well as alpha-crystallin. Labelling studies with [35S]-methionine showed that sequential changes in the synthesis of all three classes of crystallin occurred during culture in BRCM. After two days, synthesis of alpha-crystallin subunits, particularly alpha A and alpha AINS, increased relative to overall protein synthesis. After four days in culture, synthesis of beta-crystallin subunits, identified as beta B1a, beta B4, beta B5 and possibly beta A2, was detected for the first time and between four and eight days gamma-crystallin synthesis became detectable. The time of onset of gamma-crystallin synthesis seemed to show greater experimental variability than did onset of beta-crystallin synthesis. In explants cultured for 10 days in BRCM approximately 25% of new protein synthesis could be attributed to alpha-, beta- and gamma-crystallins. These events were completely dependent on BRCM, suggesting that neural retina secretes a factor(s) which initiates fibre cell differentiation. This culture system appears to be a suitable one for investigating the control of fibre differentiation in vitro.
D000818:Animals; D002417:Cattle; D002454:Cell Differentiation; D002457:Cell Extracts / Q000494:pharmacology*; D002478:Cells, Cultured; D003459:Crystallins / Q000096:biosynthesis; D003470:Culture Media; D004591:Electrophoresis, Polyacrylamide Gel; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007908:Lens, Crystalline / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D012160:Retina / Q000166:cytology*; D014020:Tissue Extracts / Q000494:pharmacology*
D002457:Cell Extracts; D003459:Crystallins; D003470:Culture Media; D010446:Peptide Fragments; D014020:Tissue Extracts