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B.R. Evans, J. Sowden, I. Kobayashi, R. Holme, K. Steel, M. Bitner-Glindzicz; The Expression Pattern of the USH1C Protein in the Mouse Eye Suggests Differences in Usher Type 1 Multi Protein Complex Formation Between the Ear and the Eye . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3551.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To investigate the temporal and spatial expression of USH1C in the eye, in order to suggest possible functions of the protein. Usher syndrome is an autosomal recessive disease with pathology of the ear and eye. Three clinical subtypes exist that are linked to 11 different loci, and it has been hypothesised that at least in type 1, the proteins may interact to form a functional complex. Therefore the aim of this investigation is also to study the expression of the PDZ-domain containing USH1C protein, in relation to other type 1 proteins. Methods: An indirect immunofluorescence system has been used to examine the localisation of USH1C in the murine eye, whilst an RT-PCR method has been employed to examine the onset of gene expression in the developing visual system of the embryo. Results: Past expression studies have localised USH1C to the developing outer neuroblastic layer in a 10-week human foetal retina. Our studies on the mouse concur and further show that as development proceeds, the protein is found as a distinct layer within the photoreceptor outer segments. Expression studies carried out in waltzer and shaker-1 null mutant mice, (models for USH1D and USH1B respectively), indicate that there is no alteration of the expression pattern of the USH1C protein in the absence of myosin VIIA (USH1B) and cadherin 23 (USH1D). Conclusions: USH1C appears to be a photoreceptor protein, and is not expressed in the retinal pigmented epithelium. Its expression is not affected by the presence or absence of other type 1 proteins, although USH1C may in fact be important in the anchorage of other type 1 proteins, as has been suggested in the cochlea. USH1C expression has been localised to a region of the retina, separate from expression sites reported for myosin VIIA and other type 1 proteins, suggesting that in the eye, type 1 proteins may not physically interact. Previous investigations have suggested that genes involved in visual transduction are co-ordinately regulated, unlike in the ear, although the degree of co-ordination of mRNA expression for the mouse is less than in the human. As onset of expression of Rhodopsin and other photoreceptor transcripts has been shown to coincide with outer segment disk production at post natal day 6, this experiment showing USH1C protein expression prior to this point, suggests that USH1C may have an alternative role in the eye, possibly a role in organisation of signalling complexes.
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