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J.B. Bateman, D. Burch, L. Richter, D.G. Brooks, D. Stambolian, P. Flodman, M.A. Spence; Sequence Analysis of Five Candidate Genes in an Autosomal Dominant Cataract (ADC 4) Family . Invest. Ophthalmol. Vis. Sci. 2005;46(13):827.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To identify the cataract–causing gene mutation in an ADC family. Methods: A five–generation autosomal dominant cataract family (ADC 4) has 11 affected individuals. We used our screening panel of twenty–five known ADC loci based on linkage analysis and identification of gene mutations. A genome screen of 20 members was initiated using the ABI Prism Linkage Mapping Set Version 2 (Perkin Elmer–Applied Biosystems, Foster, CA). PCR amplification was performed separately for each primer and the products were pooled and resolved on an ABI 373 using Genescan 2.1 software (Perkin Elmer–Applied Biosystems). Two–point lod scores were calculated using the LIPED algorithm. PCR primers were designed for the promoter and all exons of the candidate genes including the intron/exon borders. We sequenced PCR products using an ABI dye terminator kit and either an ABI 3100 DNA sequencer or a 3100–Avant (Applied Biosystems, Foster City, CA.) Sequence analyses were performed using Consed, Phred, Phrap, and Polyphred (SeattleSNPs. NHLBI Program for Genomic Applications, UW–FHCRC, Seattle, WA (URL: http://pga.mbt.washington.edu)). Results: We calculated LOD scores between the ADC 4 locus and known ADC loci excluded all loci. Linkage analysis of the ADC 4 family gave a maximum LOD score of 4.0 for D19S903 as well as a 2.88 for D12S102. We sequenced the following candidate genes in the 19q region: LIM2 (lens intrinsic membrane protein 2), SIX5 (homolog of the Drosophila sine oculis homeobox 5), and FTL (ferritin light chain). In addition; we performed PCR analysis on the repeat region in the DMPK (dystrophia myotonica protein kinase) gene. Finally, we sequenced the MIP (major intrinsic protein) gene on chromosome 12. All five matched the NCBI reference sequences. Conclusions: Mutations in LIM2 have been reported to cause cataracts in mice and humans (Steele et al., 1997; Pras et al., 2002). Individuals with myotonic dystrophy have premature cataracts and SIX5 may be the basis (Winchester et al., 1999). Hyperferritinemia is caused by mutations of the FTL gene and is associated with ADC. Lastly, ADC are associated with mutations of MIP (Berry et al., 2000). We have evaluated these five candidate genes in the ADC 4 family and found all to be normal. Therefore; the causative gene in the ADC 4 family is novel. Currently, we are focusing on other genes in the region of 19q and are sequencing the OPA3 (optic atrophy 3) gene, a disease associated with cataracts.
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