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Salil A. Lachke, Stephen C. Kneeland, Gareth R. Howell, Anton Aboukhalil, Richard L. Maas, Simon W. John; A Tdrd7 Null Mouse Mutant Model for Studying Juvenile Cataract and Post-transcriptional Regulation in Lens Development. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5887.
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We recently identified two independent cases of pediatric cataract with loss-of-function mutations in TDRD7, which encodes a Tudor domain RNA binding protein. Tudor domain proteins are implicated in RNA metabolic processes and our studies on lens cell culture and chick embryos indicated that TDRD7 forms cytoplasmic RNA granules (RGs), which function in the lens. In metazoans, RGs are known to function in the control of RNA turnover and translation by regulating diverse processes such as microRNA-mediated decay and the storage, transport, and preferential translation of mRNAs. However, the significance of RGs in mammalian oculogenesis and disease remains unknown. We have generated a Tdrd7 null mouse mutant that has allowed us to interrogate for the first time, the function of a tissue-specific RG component in mammalian lens development.
A Tdrd7 null mouse mutant was identified as part of a phenotype-driven screen to detect mutagenized mice with ocular defects. Briefly, C57BL/6J (B6) males (generation G0), mutagenized with N-ethyl-N-nitrosurea (ENU), were mated with C3A.BLiA-Pde6b+/J (C3H) females to generate unique G1 offspring that were heterozygous for a fixed complement of induced mutations. G1 males were mated to C3H females to generate heterozygous females (G2). Finally, heterozygous males and G2 females were mated to produce G3 homozygous mutants for screening for ocular phenotypes.
A mouse mutant with early onset cataract identified in the above screen was selected for further analysis and found to carry a nonsense mutation in Tdrd7 . Western blot and immunofluorescence analyses indicated a complete absence of TDRD7 expression in the lens indicating that the mutation produced a null allele. We then undertook a detailed characterization of the Tdrd7 null mutant using histological, immunohistochemical and microarray-based expression analyses. We focused on the time points P30, when cataracts are fully penetrant, and P4, three weeks before overt cataract appearance. From these analyses, we identified a cohort of differentially regulated genes (DRGs), which has allowed us to propose a comprehensive model for TDRD7 function in differentiating fiber cells.
We describe a mouse mutant deficient in the RNA granule component TDRD7 that closely phenocopies early onset cataract in humans. Our model suggests that TDRD7 interacts with an RNA binding protein STAU1 and functions in the post-transcriptional control of gene expression in fiber cell differentiation.
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