FIGURE 3.

Analysis of piRNA production from the mpiR gene. (A) The mouse mpiR gene displays matches to testis-specific mouse piRNAs that are largely restricted to Intron 2 and Exon 4. (B) An Exon 4 probe detects piRNA-sized (∼ 30 nt) small RNAs in total RNA from testis but not from other tissues. Small RNA preparations also revealed slightly larger but much weaker bands in brain and liver. The lower diagram shows the PCR-based detection of piRNAs from across Intron 2 and Exon 4. (C) The rat mpiR gene displays abundant matches to rat piRNAs in Intron 2 and Exon 4 regions similar to those seen with the mouse gene. (D) Model depicts an mpiR gene composed of four exons which undergoes alternative splicing to form a variety of mRNA-like species. One or more RNAs from this gene, possibly including the primary transcript, intron lariats, or mRNA-like transcripts themselves, undergo processing to generate Intron 2- and Exon 4-specific piRNAs.