Abstract
Abstract: :
Purpose: Prominin is a pentaspan membrane protein of unknown function that is specifically localized in several cell types to membrane protrusions and mutations are known to be associated with inherited retinal degenerations. We have studied the localization of human and murine prominin in transgenic frog rod photoreceptors to elucidate its function. Methods: Human and murine prominin-GFP fusion proteins were expressed in the rod photoreceptors of transgenic X. laevis under the control of the Xenopus opsin promoter. Confocal microscopy was used to analyze the subcellular localization of the fusion proteins. An X. laevis cDNA library was screened to search for the X. laevis homologue. Results: Murine prominin localized throughout the entirety of the outer segment plasma membrane. It also localized to the inner segment plasma membrane but only above the outer limiting membrane. The plasma membrane below the outer limiting membrane and the synapse were unlabeled with the fusion protein. Preliminary results with normal human prominin indicate that it is localized primarily to the region of the periciliary ridge complex but also to irregularly spaced puncta along the outer segment plasma membrane. A mutant form of human prominin associated with retinal degeneration gave inconclusive localization information. In some rods, puncta were seen in the outer segment plasma membrane while in others puncta were seen in the inner segment. Conclusion: Previously, murine prominin has been localized to basal disks of the outer segment. Here we demonstrate several different localization patterns that may depend on sequence variations. Further analysis with Xenopus prominin may help clarify the causes of these discrepancies.
Keywords: 517 photoreceptors • 555 retina: distal(photoreceptors, horizontal cells, bipolar cells) • 606 transgenics/knock-outs