Differential display reverse transcription polymerase chain reaction was used to isolate a novel cDNA clone (C47) that was initially shown to be downregulated in senescent chicken embryo fibroblast cells. In a tissue environment, C47 transcripts were only detected in gonadal tissue. The expression of the larger isoform (C47L) was essentially restricted to the ovary, and the smaller isoform (C47S) was predominately expressed in the testis. Although levels of the C47L mRNA were relatively high in both the small white and the developing larger follicles, there was very low expression in regressed and postovulated follicles. Nucleotide sequence analysis indicated that two different transcripts of the single-copy C47 gene were generated by differential polyadenylation in the 3′ untranslated region. As a result of a single nucleotide deletion, the C47L mRNA produced a smaller 48-kDa protein, and the C47S mRNA generated a larger 57-kDa protein when both were translated in vitro. Both protein isoforms were shown to contain conserved C2H2 Zn finger motifs and nuclear localization signals suggestive of being putative transcription factors. These results suggest that the C47L and C47S isoforms might play an important role in the regulation and maintenance of ovarian and testicular functions, respectively, in the chicken.