piRNA biogenesis

piRNAs are small noncoding RNAs primarily expressed in the gonad that play an essential role in maintaining genome integrity in many species. The mechanisms of piRNA biogenesis are distinct from other small RNAs such as miRNAs or siRNAs, and are poorly understood. In C. elegans, piRNA loci are clustered in discrete regions of the genome and produce thousands of distinct piRNAs, but a basic understanding of the mechanisms that determine germline-specific expression of piRNAs is lacking. We have identified a transcription factor that preferentially binds to piRNA loci only in the germ line and promotes piRNA expression. Using the ability to isolate germ nuclei for genomic assays we are now working to identify and characterize the chromatin-based mechanisms that are required for piRNA transcription. Ultimately, knowledge of how piRNAs are generated will facilitate our understanding of how piRNAs function in gametogenesis to ensure fertility and successful embryonic development.