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J Kanungo, SK Swamynathan, Z Kozmik, J Piatigorsky; Genomic Analyses and Relative Expression Patterns of the Genes for Cornea/Lens-specific and Ubiquitous Gelsolins in Zebrafish . Invest. Ophthalmol. Vis. Sci. 2002;43(13):3198.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Previously, we have shown that gelsolin, a major soluble corneal protein is expressed in early embryonic stages and is confined to the optic area, especially the corneal epithelium of the zebrafish, Danio rerio. For studies on the regulation of tissue-specific expression, we have explored whether the cornea-specific gelsolin and the ubiquitous gelsolin are encoded in the same gene. Methods: A combination of EST sequence and RT-PCR was used to search for the cDNA encoding the ubiquitous gelsolin. Southern blot analyses of genomic DNA was performed using the 5' fragments of the cDNAs of the two gelsolins as probes. RT-PCR for the two gelsolins was carried out using the cDNAs, synthesized from various tissues of adult zebrafish and early embryos. A zebrafish genomic library (Lambda FIX II) was screened to isolate the cornea-specific gene, which was subsequently sequenced. Results: Southern blot analyses suggest that the genes for the cornea-specific and ubiquitous gelsolins are distinct and are encoded by single genes. RT-PCR product analyses demonstrated that the cornea-specific gelsolin is also expressed, to a lesser extent, in the lens, but not in the brain and heart of the adult. The ubiquitous gelsolin is present in all the tissues including the cornea and lens. Expression of the genes for both the gelsolins is detected as early as the 4-cell stage. The gene for cornea/lens-specific gelsolin has seventeen exons. Sequence analysis of a 4 kb 5'-flanking region of the gene for cornea/lens-specific gelsolin shows no similarity with the human gelsolin promoter. Conclusions: The cornea/lens-specific and ubiquitous zebrafish gelsolins are encoded in different genes. The gene encoding the cornea/lens-specific gelsolin has been subspecialized to be expressed only in the lens and cornea. By analogy with the human, this subspecialization appears to have been associated with changes in promoter sequences.
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