• C.elegans
• piRNA
• Piwi
• Small RNA

Historically, several studies aimed to better understand the genetic regulation by small RNAs, have used C.elegans as a model organism. From the pioneering work on the regulation of lin-14 by lin-4, to the elucidation of the role of dsRNA in the so-called RNAi pathway, the nematode C.elegans has been regarded as a powerful tool to investigate different aspects of small RNA pathways.
In this work, an in vivo assay has been used to characterize a novel small RNA pathway, the Piwi/piRNA pathway in C.elegans.
The Piwi/piRNA pathway plays crucial roles during germline development and gametogenesis of many metazoan species, from germline determination and germline stem cell maintenance, to meiosis and spermiogenesis. Its function in all these processes lies in protecting the integrity of the genome from parasite nucleic acids, namely from transposons.
However, little is known about how the final biological function of the pathway is achieved: recent evidences support the hypothesis of a mechanism which involves both a post-trascriptional regulation (partially obtained by the activation of a distinct endo-siRNA pathway) and an epigenetic/co-transcriptional regulation.
A clearer view of this pathway will significantly advance our understanding of complex gene regulation strategies.
Previously, using a forward genetic screen, a large number of mutant alleles for genes involved in this pathway have been isolated. The aim of this study was to investigate the identity of those genes with high-throughput sequencing and linkage analysis, as well as by complementation tests. Finally, the involvement of each screened allele in the pathway was assessed through specific assays (chromosome non-disjunction assays, RNAi against a germ line specific gene, qRT-PCR for Tc3 expression).
Taken together with previous findings in the lab, these data enable us to provide a preliminary model for the general structure of the Piwi/piRNA pathway in C.elegans, pointing out its overlapping with the endogenous RNAi pathway, based on the activity of 22G endo-siRNAs.