Synergistic Regulation of Germline Development by PUFs and small RNAs

Abstract: Synergistic Regulation of Germline Development by PUFs and small RNAs The ability to transmit genetic information across generations a fundamental function of germ cells. This process depends on the maintenance of precise gene expression programs essential for germ cell development and fertility. A key aspect of this regulation is the assembly of RNAs and RNA-regulatory proteins into cytoplasmic structures termed germ granules. Germ granules contribute to control of gene expression by facilitating the biogenesis and function of small RNAs (sRNAs), which are loaded in gametes and passed from parent to offspring. sRNAs regulate nearly every step of gene expression, from transcription to translation, and are critical for development and differentiation. Consequently, disruptions in sRNA pathways and associated components have been linked to a range of human diseases, including infertility, cancer, and neurodegeneration. Germ granules contain numerous RNA-binding proteins, which are organized in specific subcompartments. However, the mechanisms by which sRNAs and classical translational regulators synergistically control gene expression programs remain largely unknown. Maintenance of C. elegans germline stem cells relies on two paralogous Pumilio-family (PUF) translational repressors, FBF-1 and FBF-2, both of which localize to germ granules. PUF proteins are critical regulators of germline stem cell function and gametogenesis, conserved across many species, including humans. FBF-2’s localization to germ granules enhances its regulatory activity. We recently discovered that FBF-2-mediated regulation depends on sRNAs inherited across generations, and that sRNAs cooperate with FBFs to limit the accumulation of shared mRNA targets. In turn, FBFs promote sRNA-dependent regulation, including the transgenerational inheritance of sRNA-mediated repression. Our expertise in post-transcriptional regulation and the functional analysis of germ granules uniquely positions us to rigorously investigate the mechanisms underlying co-regulation of gene expression by FBFs and sRNAs. Specifically, we will determine the contribution of PUF proteins to sRNA biogenesis and function, define the mechanism of FBF/sRNA coregulation of target transcripts, and identify sRNA impact on FBF-2 sorting within the germ granules. Our studies will uncover the mechanisms mediating synergistic control of gene expression and germ cell development by PUF-family RNA-binding proteins and sRNA-dependent pathways, offering insights into the genetic causes of germ cell dysfunction. Since sRNAs are well-established regulators of mammalian reproduction and that infertility is a prevalent human disorder, our findings will advance understanding in a key area of reproductive health and disease.