Two δ‐crystallin polypeptides are derived from a cloned δ1 ‐crystallin cDNA

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Abstract
Previous studies have shown that there are 2 similar δ‐crystallin genes (δ1 and δ2) and at least 2 δ‐crystallin polypeptides in the chicken eye lens. We show here that both δ‐crystallin polypeptides can be synthesized from mRNA transcribed in vitro from a cloned (51‐cry stallin cDNA. Both polypeptides co‐migrate in SDS‐urea‐polyacrylamide electrophoresis with their authentic counterparts isolated from 15‐day‐old embryonic chicken lenses, and both react with sheep anti‐chicken δ‐crystallin serum. Screening nearly 900 δ‐crystallin cDNA clones from a 15‐day‐old embryonic lens library with an oligonucleotide probe specific for exon 2 of the δ2‐crystallin gene failed to detect any δ2 cDNA clones, indicating that the δ2 gene produces little or no mRNA in the lens at this stage of development. Our results suggest that both of the observed δ‐crystallin polypeptides are derived from mRNA transcribed from the δ1 gene, with heterogeneity arising at the translational or co‐translational level.