Subjects: Biology >> Biophysics >> Biochemistry & Molecular Biology submitted time 2016-05-05
Abstract: Female fig wasps differ phenotypically from conspecific males to the extent that often they cannot be associated with one another. Weighted gene co-expression network analysis (WGCNA) of the genome and transcriptomes of one such fig wasp, Ceratosolensolmsi, generated five expression modules, which were flagged as blue, turquoise, brown, green and yellow. These involved two female-biased expression modules and three pupa-biased expression modules, respectively. Gene ontologies indicated three functional enrichment gene sets in modules turquoise and yellow. Two functional enrichment gene sets that participate in cell cycle or have nucleotide binding activityclustered in turquoise module. The functionally enriched gene set in yellow module played roles in cell differentiation, especially in neuron morphogenesis.
Peer Review Status:Awaiting Review
Subjects: Biology >> Biophysics >> Cell Biology submitted time 2016-05-12
Abstract: The piRNA machinery is known for its role in mediating epigenetic silencing of transposons. Recent studies suggest that this function also involves piRNA-guided cleavage of transposon-derived transcripts. As many piRNAs also appear to have the capacity to target diverse mRNAs, this raises the intriguing possibility that piRNAs may act extensively as siRNAs to degrade specific mRNAs. To directly test this hypothesis, we compared mouse PIWI (MIWI)-associated piRNAs with experimentally identified cleaved mRNA fragments from mouse testes, and observed cleavage sites that predominantly occur at position 10 from the 5' end of putative targeting piRNAs. We also noted strong biases for U and A residues at nucleotide positions 1 and 10, respectively, in both piRNAs and mRNA fragments, features that resemble the pattern of piRNA amplification by the 'ping-pong' cycle. Through mapping of MIWI-RNA interactions by CLIP-seq and gene expression profiling, we found that many potential piRNA-targeted mRNAs directly interact with MIWI and show elevated expression levels in the testes of Miwi catalytic mutant mice. Reporter-based assays further revealed the importance of base pairing between piRNAs and mRNA targets and the requirement for both the slicer activity and piRNA-loading ability of MIWI in piRNA-mediated target repression. Importantly, we demonstrated that proper turnover of certain key piRNA targets is essential for sperm formation. Together, these findings reveal the siRNA-like function of the piRNA machinery in mouse testes and its central requirement for male germ cell development and maturation.
Peer Review Status:Awaiting Review