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F. Kraemer, B. Geis, V. Milenkovic, B.H. F. Weber; Cloning and characterization of the murine Vmd2 RFP–TM gene family . Invest. Ophthalmol. Vis. Sci. 2004;45(13):1299.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: The vitelliform macular dystrophy type–2 (VMD2) gene, associated with Best macular dystrophy (BMD), is one of four members of the VMD2 RFP–TM family. All members encode integral membrane proteins potentially involved in calcium–sensitive anion transport. To further unravel BMD pathology and to provide a basis for studying functional aspects of this protein family, we sought to identify and characterize the murine orthologues of the human VMD2 RFP–TM genes. Methods: We applied biocomputational database analyses together with molecular genetics approaches to clone and characterize the murine Vmd2 RFP–TM gene family. Spatial expression was studied by real time quantitative RT–PCR. Mono– and polyclonal antibodies were generated against three murine family members including Vmd2, Vmd2l1 and Vmd2l3. Results: Based on sequence identity and assignment to genomic regions of conserved synteny between the respective human and mouse genes, orthologous relationships beween the four members of the VMD2 RFP–TM family were established. While the murine Vmd2, Vmd2l1 and Vmd2l3 genes encode functional proteins, the murine Vmd2l2p gene represents an inactive pseudogene. Expression profiling of Vmd2, Vmd2l1 and Vmd2l3 transcripts reveals similar tissue distribution compared to the human orthologs. Further, we generated monoclonal antibodies (mAb) against Vmd2 as well as polyclonal antibodies (pAb) against Vmd2l1 and Vmd2l3. Specific labeling with mAb–Vmd2 (63 kDa), pAb–Vmd211 (57 kDa) and pAb–Vmd2l3 (76 kDa) confirmed the apparent molecular mass of the respective open reading frames. In concordance with sublocalization studies of human VMD2 and the presence of multiple predicted transmembrane domains, the three murine proteins display a membrane–associated distribution in a heterologous pCEP4/EBNA expression system. Conclusions: Our study shows that the VMD2 RFP–TM gene family is highly conserved in mouse although one member, Vmd2l2p, appears to be a non–functional pseudogene. The data provide the ground work for the generation of mice deficient in functional Vmd2 RFP–TM family members and thus will facilitate further investigations into this protein family.
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