| Popis: |
Multiple condensates occupy the perinuclear space of C. elegans germ cells, where they coordinate RNA surveillance to ensure proper gene expression (Lev and Rechavi 2020; Sundby et al. 2021). The most well-studied of these condensates are P granules, phase-separated germ granules required for maintenance of germ cell identity and fertility (Kawasaki et al. 1998; Updike et al. 2014). P granule morphology and localization is well documented in C. elegans development (Strome et al. 1982). Adjacent to P granules are Mutator foci, which are nucleated by MUT-16 and required for the amplification of small interfering RNAs (siRNAs) to create a robust and heritable silencing signal (Phillips et al. 2012). During development, faint Mutator foci are occasionally seen in the P4 germline blastomere of 30-cell embryos, but are most robust and numerous in the Z2 and Z3 progenitor germ cells (PGCs) of 100-cell embryos (Uebel et al. 2020). A third germline condensate, Z granules, are situated between P granules and Mutator foci and facilitate transgenerational epigenetic inheritance of silencing signals. Z granule components ZNFX-1 and WAGO-4 colocalize with P granules in early embryos, but begin to de-mix from P granules in the Z2/Z3 PGCs to form separate Z granule condensates (Wan et al. 2018). Lastly, recently discovered SIMR foci also intimately localize within this cluster of germline granules. SIMR-1, a key component of SIMR foci, is a Tudor domain protein that mediates production of secondary siRNAs for piwi-interacting RNA (piRNA)-targeted mRNAs (Manage et al. 2020). While P granule, Z granule, and Mutator foci localization through embryonic development has been previously described, the embryonic appearance of SIMR foci is not known. |
