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C. M. Gelfman, P. Vogel, C. Jones, D. Rice; Mice Lacking Transmembrane Protein 218 (TMEM218) Exhibit Kidney Abnormalities and Retinal Degeneration. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5193.
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TMEM218 is a 115 aa protein which contains a signal peptide and two transmembrane segments. Although its exact function and cell location are not known, expression of TMEM218 was found to be down-regulated in mice lacking functional androgen receptors. Interestingly, altered expression of genes known to be involved in the regulation of vitamin A metabolism was also observed. In the current study, mice lacking TMEM218 were used to thoroughly assess the function of this protein.
Mice deficient in TMEM218 were generated from Omnibank, a sequence-tagged gene-trap library of >270,000 mouse embryonic stem cell clones as part of a large-scale effort to knock-out, phenotypically screen, and thereby validate pharmaceutically tractable genes for drug development. Clinical diagnostics, expression analysis and histopathology were performed on TMEM218 knock-out mice.
Routine histological analysis performed at 4 months of age on homozygous mice revealed polycystic kidneys as well as retinal degeneration. A follow up developmental study did not show any retinal abnormalities at 1 month of age; however by 2 months of age, thinning of the ONL was observed. Expression analysis using LacZ immunohistochemistry demonstrated expression throughout the eye, including retina, lens, ciliary body, and iris. In addition, expression was observed in kidney, brain, GI tract, and adrenal gland.
Mice deficient in TMEM218 exhibit polycystic kidneys as well as retinal degeneration. The retinal defect does not appear to be developmental. Further studies are underway to characterize the protein in terms of its subcellular localization as well as its possible involvement in Vitamin A metabolism.
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