Conservation of δ-crystallin gene structure between ducks and chickens

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Abstract
A cloned chicken δ-crystallin cDNA was used to identify two putative δ-crystallin genes in the duck by Southern blot hybridization. A DNA fragment containing most of one of these genes was isolated from a library made in bacteriophage λ Charon 28A containing genomic DNA from 14-day-old embryonic ducks. Electron microscopy, partial gene sequencing, primer extension analysis using duck mRNA, and comparison with the well-characterized chicken δ-crystallin genes suggest that our cloned duck δ-crystallin gene, like the chicken δ-crystallin genes, is 8–10 kb long and contains 17 exons. Hybridization and sequencing data show great similarity between the homologous 5′ untraslated and coding exons of the duck and chicken δ-crystallin genes. Overall, the homologous introns also appear to have approximately 30% sequence similarity, and have been subject to deletion/insertion events. Our partial characterization of duck δ-crystallin gene sequences suggests that this avian and reptilian crystallin family has been conserved during evolution, as have the other crystallin gene families that are expressed in the eye lens.