{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,13]],"date-time":"2026-10-13T20:13:04Z","timestamp":1791922384037,"version":"4.3.4"},"reference-count":26,"publisher":"Maximum Academic Press","issue":"4","license":[{"start":{"date-parts":[[2008,7,1]],"date-time":"2008-07-01T00:00:00Z","timestamp":1214870400000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":["journals.cambridge.org"],"crossmark-restriction":true},"short-container-title":["Vis Neurosci"],"published-print":{"date-parts":[[2008,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>A 4 base pair deletion in a splice donor site of the <jats:italic>Mfrp<\/jats:italic> (membrane-type frizzled-related protein) gene, herein referred to as <jats:italic>Mfrp<jats:sup>rd6\/rd6<\/jats:sup><\/jats:italic>, is predicted to lead to the skipping of exon 4 and photoreceptor degeneration in <jats:italic>retinal degeneration 6<\/jats:italic> (<jats:italic>rd6<\/jats:italic>) mutant mice. Little, however, is known about the function of the protein or how the mutation causes the degenerative retinal phenotype. Here we examine ultrastructural changes in the retina of <jats:italic>Mfrp<jats:sup>rd6\/rd6<\/jats:sup><\/jats:italic> mice to determine the earliest effects of the mutation. We also extend the reported observations of the expression pattern of the dicistronic <jats:italic>Mfrp\/C1qtnf5<\/jats:italic> message and the localization of these and other retinal pigment epithelium (RPE) and retinal proteins during development and assess the ability of RPE cells to phagocytize outer segments (OSs) in mutant and wild-type (WT) mice. At the ultrastructural level, OSs do not develop normally in <jats:italic>Mfrp<jats:sup>rd6\/rd6<\/jats:sup><\/jats:italic> mutants. They are disorganized and become progressively shorter as mutant mice age. Additionally, there are focal areas in which there is a reduction of apical RPE microvilli. At P25, the rod electroretinogram (ERG) a-wave of <jats:italic>Mfrp<jats:sup>rd6\/rd6<\/jats:sup><\/jats:italic> mice is reduced in amplitude by ~50% as are ERG components generated by the RPE. Examination of \u03b2-catenin localization and <jats:italic>Fos<\/jats:italic> and <jats:italic>Tcf-1<\/jats:italic> expression, intermediates of the canonical Wnt pathway, showed that they were not different between mutant and WT mice, suggesting that MFRP may operate through an alternative pathway. Finally, impaired OS phagocytosis was observed in <jats:italic>Mfrp<jats:sup>rd6\/rd6<\/jats:sup><\/jats:italic> mice both in standard ambient lighting conditions and with bright light exposure when compared to WT controls.<\/jats:p>","DOI":"10.1017\/s0952523808080723","type":"journal-article","created":{"date-parts":[[2008,9,2]],"date-time":"2008-09-02T14:06:54Z","timestamp":1220364414000},"page":"563-574","update-policy":"https:\/\/doi.org\/10.1017\/policypage","source":"Crossref","is-referenced-by-count":38,"title":["Membrane frizzled-related protein is necessary for the normal development and maintenance of photoreceptor outer segments"],"prefix":"10.48130","volume":"25","author":[{"given":"JUNGYEON","family":"WON","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"RICHARD S.","family":"SMITH","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"NEAL 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