Abstract
Abstract: :
Purpose: Prominin localizes to the basal discs of murine rod photoreceptor outer segments, where the membranes undergo dramatic reorganization to assemble new discs. A mutation of human prominin was identified in a family with inherited retinal degenerations (Maw M. et al. 2000). We hope to define protein domains of prominin that account for its specific localization in rod basal disks and to study the mechanism by which mutations of prominin cause retinal degeneration. Methods: Xenopus prominin was amplified from a X. laevis retina cDNA library by PCR and its gene structure was studied. To establish an animal model with which we can study the targeting of prominin in photoreceptors, we generated transgenic X. laevis expressing Xenopus prominin-GFP under control of the X. laevis opsin promoter. Subcellular localization of the fusion proteins in Xenopus rod photoreceptors was studied by confocal microscopy. Results: 1). We found that Xenopus prominin shares high homology (ca. 70%) with prominins of other species. Alignment of sequences revealed several highly conserved domains including a cysteine rich domain in the first cytosolic loop and leucine zipper like motifs in the extracellular domains, which may be functionally important and merit further investigation. 2). Prominin is alternatively spliced in the retina, retinal prominin has a much shorter and different C-terminal domain than the kidney isoform because of the exclusion of several exons. The significance of alternative splicing of prominin is unknown. 3). The Xenopus prominin-GFP fusion protein preferentially localizes to the basal disks of frog rod outer segments, it also appears elsewhere on the plasma membrane if over-expressed in the cell.
Keywords: photoreceptors • retina: distal(photoreceptors, horizontal cell • transgenics/knock-outs