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Wride MA. Lens fibre cell differentiation and organelle loss: many paths lead to clarity. Philos Trans R Soc Lond B Biol Sci 2011; 366:1219-33. [PMID: 21402582 DOI: 10.1098/rstb.2010.0324] [Citation(s) in RCA: 152] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The programmed removal of organelles from differentiating lens fibre cells contributes towards lens transparency through formation of an organelle-free zone (OFZ). Disruptions in OFZ formation are accompanied by the persistence of organelles in lens fibre cells and can contribute towards cataract. A great deal of work has gone into elucidating the nature of the mechanisms and signalling pathways involved. It is apparent that multiple, parallel and redundant pathways are involved in this process and that these pathways form interacting networks. Furthermore, it is possible that the pathways can functionally compensate for each other, for example in mouse knockout studies. This makes sense given the importance of lens clarity in an evolutionary context. Apoptosis signalling and proteolytic pathways have been implicated in both lens fibre cell differentiation and organelle loss, including the Bcl-2 and inhibitor of apoptosis families, tumour necrosis factors, p53 and its regulators (such as Mdm2) and proteolytic enzymes, including caspases, cathepsins, calpains and the ubiquitin-proteasome pathway. Ongoing approaches being used to dissect the molecular pathways involved, such as transgenics, lens-specific gene deletion and zebrafish mutants, are discussed here. Finally, some of the remaining unresolved issues and potential areas for future studies are highlighted.
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Affiliation(s)
- Michael A Wride
- Ocular Development and Neurobiology Research Group, Zoology Department, School of Natural Sciences, Trinity College Dublin, Dublin 2, Republic of Ireland.
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Geatrell JC, Mui (Iryn) Gan P, Mansergh FC, Kisiswa L, Jarrin M, Williams LA, Evans MJ, Boulton ME, Wride MA. Apoptosis gene profiling reveals spatio-temporal regulated expression of the p53/Mdm2 pathway during lens development. Exp Eye Res 2009; 88:1137-51. [PMID: 19450442 PMCID: PMC2706329 DOI: 10.1016/j.exer.2009.01.020] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2008] [Revised: 01/15/2009] [Accepted: 01/30/2009] [Indexed: 01/19/2023]
Abstract
Evidence is emerging for apoptosis gene expression in the lens during development. Therefore, here we used a filter array to assess expression of 243 apoptosis-related genes in the developing postnatal mouse lens using (33)P labelled cDNA synthesized from p7 and p14 mouse lenses. We demonstrated that 161 apoptosis-related genes were expressed at levels significantly above background and 20 genes were potentially significantly differentially expressed (P<0.05) by at least 2-fold between p7 and p14. We used RT-PCR to confirm expression of these genes in newborn, p7, p14 and 4 wk mouse lens cDNA samples. Expression of 19/20 of the genes examined was confirmed, while 5 genes (Huntingtin, Mdm2, Dffa, galectin-3 and Mcl-1) were confirmed as differentially regulated between p7 and p14. RT-PCR was also used to examine the expression of the chick homologues of the most-highly expressed and/or potentially differentially regulated genes in chick embryo lenses at E6-E16. The majority of genes expressed in the postnatal mouse lens were also expressed in the chick embryo lens. Western blotting confirmed developmentally regulated expression of Axl and Mcl-1 during mouse lens development and of Mdm2, Mdm4/X and p53 during mouse and chick lens development. Western blotting also revealed the presence of p53 and Mdm4/X splice variants and/or proteolytic cleavage products in the developing lens. Since Mdm2 is a regulator of the tumour suppressor gene p53, we chose to thoroughly investigate the spatio-temporal expression patterns of p53, Mdm2 and the functionally related Mdm4/X in mouse lens development at E12.5-E16.5 using immunocytochemistry. We also examined Mdm2 expression patterns during chick lens development at E6-E16 and Mdm4/X and p53 at E14. Expression of Mdm2, Mdm4/X and p53 was spatio-temporally regulated in various compartments of the developing lens in both mouse and chick, including lens epithelial and lens fibre cells, indicating potential roles for these factors in regulation of lens epithelial cell proliferation and/or lens fibre cell differentiation This study provides a thorough initial analysis of apoptosis gene expression in the postnatal mouse lens and provides a resource for further investigation of the roles in lens development of the apoptosis genes identified. Furthermore, building on the array studies, we present the first spatio-temporal analysis of expression of p53 pathway molecules (p53, Mdm2 and Mdm4/X) in both developing mouse and chick lenses, suggesting a potential role for the p53/Mdm2 pathway in lens development, which merits further functional analysis.
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Affiliation(s)
- Jenny C. Geatrell
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
| | - Peng Mui (Iryn) Gan
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
| | - Fiona C. Mansergh
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales CF10 3US, UK
- Smurfit Institute of Genetics, Trinity College Dublin, Dublin 2, Ireland
| | - Lilian Kisiswa
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
| | - Miguel Jarrin
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
- Mason Eye Institute, One Hospital Drive, Columbia, Columbia University, MO 65212, USA
| | - Llinos A. Williams
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
| | - Martin J. Evans
- School of Biosciences, Cardiff University, Museum Avenue, Cardiff, Wales CF10 3US, UK
| | - Mike E. Boulton
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
- Department of Anatomy and Cell Biology, University of Florida, Gainesville, Florida, USA
| | - Michael A. Wride
- School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff, Wales CF24 3LU, UK
- Department of Zoology, School of Natural Sciences, Trinity College Dublin, Dublin 2, Ireland
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