Electron tomography reveals multiple self-association of chondroitin sulphate/dermatan sulphate proteoglycans in Chst5-null mouse corneas |
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Authors: | Parfitt Geraint J Pinali Christian Akama Tomoya O Young Robert D Nishida Kohji Quantock Andrew J Knupp Carlo |
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Institution: | a Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Wales, UK;b Department of Pharmacology, Kansai Medical University, Osaka, Japan;c Tumor Microenvironment Program, Sanford-Burnham Medical Research Institute, La Jolla, CA, USA;d Department of Ophthalmology, Osaka University Medical School, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan |
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Abstract: | The spatial distribution of collagen fibrils in the corneal stroma is essential for corneal transparency and is primarily regulated by extrafibrillar proteoglycans, which are multi-functional polymers that interact with hybrid type I/V collagen fibrils. In order to understand more about proteoglycan organisation and collagen associations in the cornea, three-dimensional electron microscopy reconstructions of collagen-proteoglycan interactions in the anterior, mid and posterior stroma from a Chst5 knockout mouse, which lacks a keratan sulphate sulphotransferase, were obtained. Both longitudinal and transverse section show sinuous, oversized proteoglycans with near-periodic, orthogonal off-shoots. In many cases, these proteoglycans traverse over 400nm of interfibrillar space interconnecting over 10 collagen fibrils. The reconstructions suggest that multiple chondroitin sulphate/dermatan sulphate proteoglycans have aggregated laterally and, possibly, end-to-end, with orthogonal extensions protruding from the main electron-dense stained filament. We suggest possible mechanisms as to how sulphation differences may lead to this increase in aggregation of proteoglycans in the Chst5-null mouse corneal stroma and how this relates to proteoglycan packing in healthy corneas. |
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Keywords: | Mouse cornea Collagen fibrils Proteoglycans Chst5 Three-dimensional reconstruction Electron microscopy |
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