Laminin-binding integrins in rat lens morphogenesis and their regulation during fibre differentiation.
Mammalian lens development involves cell-cell and cell-ECM interactions. As integrins are a major family of cell adhesion molecules, we examined the expression patterns of several integrin subunits (alpha3A, alpha3B, alpha6A, alpha6B, beta1 and beta4) during rat lens development. RT-PCR, in situ hybridisation, immunofluorescence and immunoblotting were used to investigate expression of integrin subunits during lens development and differentiation. RT-PCR showed expression of alpha3A, alpha6A, alpha6B and beta1A but not alpha3B or beta4 subunits in postnatal rat lenses. Each subunit displayed distinct spatio-temporal expression patterns. beta1 integrin was expressed in both epithelium and fibres. alpha3A subunit expression was restricted to the epithelium; expression ceased abruptly at the lens equator. Expression of the alpha6A subunit increased during fibre differentiation, whereas alpha6B expression was predominantly associated with epithelial cells during lens development. In lens epithelial explants, FGF induced some of the changes in integrin expression that are characteristic of fibre differentiation in vivo. One notable exception was the inability of FGF to reproduce the distinctive down-regulation of the alpha3 isoform that is associated with initiation of elongation in vivo. Interestingly, vitreous treatment was able to reproduce this shift in alpha3 expression indicating that another factor(s), in addition to FGF, may be required for full and complete transition from an epithelial cell to a fibre cell. Integrin subunit expression therefore appears to be highly regulated during lens development and fibre differentiation with evidence of major changes in alpha3 and alpha6 isoform expression. These results indicate that integrins may play important roles in development and growth of the lens. How specific integrin subunits influence the behaviour of cells in different developmental compartments of the lens remains to be determined.
Wederell
Elizabeth D
ED
Save Sight Institute and Department of Clinical Ophthalmology and Eye Health, The University of Sydney, NSW 2006, Australia; Department of Anatomy and Histology and Institute for Biomedical Research (F13), The University of Sydney, NSW 2006, Australia.
Brown
Heidi
H
O'connor
Michael
M
Chamberlain
Coral G
CG
McAvoy
John W
JW
de Iongh
Robbert U
RU
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002454:Cell Differentiation / Q000502:physiology; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology*; D039482:Integrin alpha5 / Q000235:genetics / Q000378:metabolism; D039503:Integrin alpha6 / Q000235:genetics / Q000378:metabolism; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism; D016023:Integrins / Q000235:genetics / Q000502:physiology*; D007797:Laminin / Q000378:metabolism; D007908:Lens, Crystalline / Q000254:growth & development* / Q000378:metabolism; D009024:Morphogenesis / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D046509:Tissue Culture Techniques
D039482:Integrin alpha5; D039503:Integrin alpha6; D019012:Integrin beta1; D016023:Integrins; D007797:Laminin; D012333:RNA, Messenger; D005346:Fibroblast Growth Factors