SIMR foci are found in the progenitor germ cells of embryos.

RNA interference is a widely conserved mechanism of gene regulation and silencing across eukaryotes. In , RNA silencing is coordinated through perinuclear nuage containing at least four granules: P granules, Z granules, foci, and SIMR foci. Embryonic localization of these granules is known for all except SIMR foci.

A tudor domain protein, SIMR-1, promotes siRNA production at piRNA-targeted mRNAs in .

piRNAs play a critical role in the regulation of transposons and other germline genes. In , regulation of piRNA target genes is mediated by the complex, which synthesizes high levels of siRNAs through the activity of an RNA-dependent RNA polymerase. However, the steps between mRNA recognition by the piRNA pathway and siRNA amplification by the complex are unknown.

Distinct regions of the intrinsically disordered protein MUT-16 mediate assembly of a small RNA amplification complex and promote phase separation of Mutator foci.

In C. elegans, efficient RNA silencing requires small RNA amplification mediated by RNA-dependent RNA polymerases (RdRPs). RRF-1, an RdRP, and other Mutator complex proteins localize to Mutator foci, which are perinuclear germline foci that associate with nuclear pores and P granules to facilitate small RNA amplification.

Drosophila variable nurse cells encodes arrest defective 1 (ARD1), the catalytic subunit of the major N-terminal acetyltransferase complex.

Mutations in the Drosophila variable nurse cells (vnc) gene result in female sterility and oogenesis defects, including egg chambers with too many or too few nurse cells. We show that vnc corresponds to Arrest Defective1 (Ard1) and encodes the catalytic subunit of NatA, the major N-terminal acetyl-transferase complex. While N-terminal acetylation is one of the most prevalent covalent protein modifications in eukaryotes, analysis of its role in development has been challenging since mutants that compromise NatA activity have not been described in any multicellular animal.