A 3'-truncated transferrin messenger RNA is expressed in rat testicular germ cells

Rat germ cells express a 0.9-kilobase (kb) message with a sequence similar to that of the 3' portion of mammalian transferrins. The sequence of this transcript, called hemiferrin, was considered unique, suggesting that it was encoded by a gene different from that of rat transferrin. Difficulties in conducting experiments using hemiferrin sequence primers led us to question the original sequence. Ribonuclease protection assays revealed that the hemiferrin sequence provided protection only for bovine sequences and not for rat mRNA. Conversely, a 3' rat transferrin sequence protected only rat liver and testis RNA sequences and not bovine sequences, indicating that the 0.9-kb transcript in germ cells is a truncated form of rat transferrin. Western analysis and immunoprecipitation of germ cell proteins metabolically radiolabeled in vitro and in vivo failed to detect a protein of the predicted size regardless of whether anti-rat transferrin or anti-hemiferrin antibodies were used. The findings suggest that a foreshortened transcript of the transferrin gene is produced in rat germ cells and that little or no protein is made from that transcript.