Pastore, Benjamin et al. (2021) International Worm Meeting "pre-piRNA trimming and 2′-O-methylation protect piRNAs from tailing and degradation"

Hertz, Hannah, Price, Ian, Tang, Wen, Pastore, Benjamin

[International Worm Meeting, 2021]

The Piwi/piRNA pathway suppresses transposable elements and promotes fertility in diverse organisms. Maturation of piRNAs involves pre-piRNA trimming followed by 2′-O-methylation at their 3' termini. We show that 3' termini of C. elegans piRNAs are subject to nontemplated nucleotide addition and piRNAs with 3' addition exhibit extensive base-pairing interaction with their target RNAs. Animals deficient for PARN-1 (pre-piRNA trimmer) and HENN-1 (2′-O-methyltransferase) accumulate piRNAs with 3' nontemplated nucleotides. In henn-1 mutants piRNAs are shortened prior to 3' addition whereas long isoforms of untrimmed piRNAs are preferentially modified in parn-1 mutant animals. Loss of either PARN-1 or HENN-1 results in modest reduction in steady-state levels of piRNAs. Deletion of both enzymes leads to depletion of piRNAs, desilencing of piRNA targets, and impaired fecundity. Together, our findings suggest that pre-piRNA trimming and 2′-O-methylation act collaboratively to protect piRNAs from tailing and degradation.

Price, Ian et al. (2021) International Worm Meeting "EGGD-1 and EGGD-2 are novel LOTUS domain proteins that promote perinuclear localization of P granules"

Tang, Wen, Pastore, Benjamin, Price, Ian, Hertz, Hannah

[International Worm Meeting, 2021]

Across the animal kingdom, ribonucleoprotein condensates called germ granules are required to maintain the immortality and totipotency of the germ lineage. Since their discovery, C. elegans germ granules, called P granules, have been extensively characterized to understand the role of germ granules in metazoan development. However, studies to-date have been impeded by incomplete knowledge of the P granule proteome. To broadly define the proteins localizing to P granules, we employed a proximity-based labeling approach by tagging known P granule proteins with a promiscuous biotin ligase. In our biotinylated protein fraction, we uncovered over 150 novel P granule proteins. Notably, we identified a pair of previously uncharacterized proteins, which we named EGGD-1 and EGGD-2 for Embryonic and Germline P Granules Detached. We find that EGGD-1 is enriched at the base of P granules, and its depletion causes P granules to separate from the nuclear envelope in the adult germline and embryonic primordial germ cells. Further, loss of eggd-2 exacerbates the P granule mislocalization in eggd-1 mutant animals. EGGD-1/2 harbor four domains: two intrinsically disordered regions and two putative LOTUS domains. Previous work in Drosophila and mice showed LOTUS domain proteins directly recruit Vasa RNA helicases to organize germ granules, yet the role of LOTUS domain proteins in C. elegans is uncharacterized. Our ongoing work examines the interactions between GLH proteins (C. elegans Vasa orthologs) and EGGD proteins using mutational analysis to determine contributions of individual domains in P granule perinuclear localization. Together, our work defines the P granule proteome and provides novel insights into principles of germ granule formation and perinuclear attachment.

Benjamin Schlager et al. (2006) European Worm Meeting "An Ancestral Module Patterns a Derived Nematode Vulva Equivalence Group"

Ralf Sommer., Benjamin Schlager

[European Worm Meeting, 2006]

Benjamin Schlager and Ralf Sommer. Nematode vulva formation provides a paradigm to study the evolution of pattern formation and cell fate specification. The Caenorhabditis elegans vulva is generated from three of six equipotent cells that form the so-called vulva equivalence group. During evolution, the size of the vulva equivalence group has changed: Panagrellus redivivus has eight, C. elegans six and Pristionchus pacificus only three cells that are competent to form vulval tissue. In P. pacificus, the reduction of the vulva equivalence group is achieved by programmed cell death of individual precursor cells. We have identified the genes controlling this cell death event and the molecular mechanism of the reduction of the vulva equivalence group. Mutations in Ppa-hairy, a gene which is unknown from C. elegans, result in the survival of two precursor cells, which expands the vulva equivalence group. Mutations in Ppa-groucho cause a similar phenotype. Ppa-HAIRY and Ppa-GROUCHO form a molecular module that represses the Hox gene Ppa-lin-39 and thereby, reduces the size of the vulva equivalence group. The C. elegans genome does not encode a similar hairy-like gene and no typical HAIRY/GROUCHO module exists. Instead, the size of the C. elegans vulva equivalence group is regulated by the EGF and WNT signaling pathways.. Therefore the derived vulva equivalence group of P. pacificus is patterned by an ancestral hairy/groucho module.. I will also present a highly speculative model of what kind of adaptive values might be associated with the Pristionchus specific reduction of the size of the vulva equivalence group.