Search for antisense copies of beta-globin mRNA in anemic mouse spleen

Background: Previous studies by Volloch and coworkers have reported that during the expression of high levels of beta-globin mRNA in the spleen of anemic mice, they could also detect small but significant levels of an antisense (AS) globin RNA species, which they postulated might have somehow arisen by RNA-directed RNA synthesis. For two reasons we undertook to confirm and possibly extend these studies. First, previous studies in our lab have focussed on what is an unequivocal example of host RNA-directed RNA polymerase activity on the RNA genome of human hepatitis delta virus. Second, if AS globin species do exist they could in turn form double-stranded RNA species which might induce post-transcriptional gene silencing, a phenomenon somehow provoked in eukaryotic cells by AS RNA sequences. Results: We reexamined critical aspects of the previous globin studies. We used intraperitoneal injections of phenylhydrazine to induce anemia in mice, as demonstrated by the appearance and ultimate disappearance of splenomegaly. While a 30-fold increase in globin mRNA was detected in the spleen, the relative amount of putative AS RNA could be no more than 0.004%. Conclusions: Contrary to earlier reports, induction of a major increase in globin transcripts in the mouse spleen was not associated with a detectable level of antisense RNA to globin mRNA.