A 76-bp Deletion in the Mip Gene Causes Autosomal Dominant Cataract in Hfi Mice

• Published in: Genomics (San Diego, Calif.) Vol. 74; no. 3; pp. 313 - 319
• Main Authors: Sidjanin, D.J., Parker-Wilson, Devonne M., Neuhäuser-Klaus, Angelika, Pretsch, Walter, Favor, Jack, Deen, Peter M.T., Ohtaka-Maruyama, Chiaki, Lu, Yun, Bragin, Alvina, Skach, William R., Chepelinsky, Ana B., Grimes, Patricia A., Stambolian, Dwight E.
• Format: Journal Article
• Language: English
• Published: San Diego, CA Elsevier Inc 15.06.2001; Elsevier
• Subjects: Animals; Animals, Newborn; Aquaporins; Biological and medical sciences; Blotting, Western; Cataract - genetics; Cataract - pathology; Cell Line; chromosome 10; Chromosome Mapping; Classical genetics, quantitative genetics, hybrids; DNA - chemistry; DNA - genetics; DNA Mutational Analysis; Eye Proteins - genetics; Eye Proteins - metabolism; Female; Fundamental and applied biological sciences. Psychology; Gene Expression; Genes, Dominant; Genetics of eukaryotes. Biological and molecular evolution; Genotype; Hfi gene; Humans; Lens, Crystalline - metabolism; Male; Membrane Glycoproteins; Mice; Mice, Inbred C3H; Mice, Inbred C57BL; Mice, Mutant Strains; Mip gene; Mip protein; Mutation; Oocytes - metabolism; RNA, Messenger - genetics; RNA, Messenger - metabolism; Sequence Deletion; Vertebrata; Xenopus; Genetic mapping; Animal model; Cataract; Membrane protein; Rodentia; Gene expression; Eye disease; Vertebrata; Lens disease; Mammalia; Mouse; Chromosome 10; Deletion; Lens; Localization
• ISSN: 0888-7543; 1089-8646
• DOI: 10.1006/geno.2001.6509

Hfi is a dominant cataract mutation where heterozygotes show hydropic lens fibers and homozygotes show total lens opacity. The Hfi locus was mapped to the distal part of mouse chromosome 10 close to the major intrinsic protein (Mip), which is expressed only in cell membranes of lens fibers. Molecular analysis of Mip revealed a 76-bp deletion that resulted in exon 2 skipping in Mip mRNA. In Hfi/Hfi this deletion resulted in a complete absence of the wildtype Mip. In contrast, Hfi/+ animals had the same amount of wildtype Mip as +/+. Results from pulse–chase expression studies excluded hetero-oligomerization of wildtype and mutant Mip as a possible mechanism for cataract formation in the Hfi/+. We propose that the cataract phenotype in the Hfi heterozygote mutant is due to a detrimental gain of function by the mutant Mip resulting in either cytotoxicity or disruption in processing of other proteins important for the lens. Cataract formation in the Hfi/Hfi mouse is probably a combined result of both the complete loss of wildtype Mip and a gain of function of the mutant Mip.