Inheritance of miRNAs via Yolk Promotes Stress Resilience in Progeny

At the onset of reproduction, oviparous animals synthesize large amounts of yolk in somatic tissues to provide lipids and other nutrients to their progeny. However, whether the yolk transports other types of molecules, such as RNAs with gene regulatory functions, remains largely unexplored. Here, we have biochemically purified the yolk granules in the nematode Caenorhabditis elegans and show they contain microRNAs (miRNAs). We provide evidence that the yolk transports such miRNAs from the mother's intestine to the embryos via the lipoprotein yolk receptor RME-2. These yolk-enriched miRNAs inherited by the embryos regulate the transcriptomes of developing larvae. Moreover, environmental stresses and maternal age modulate the transfer of yolk-enriched miRNAs, contributing to stress resilience benefits to progeny. This discovery establishes a novel paradigm in intergenerational gene regulation, where the gut-germline axis orchestrates the transmission of environmental cues through yolk-enriched miRNAs. Our work reveals a new mechanism underlying the soma-to-germline transfer of epigenetic information in animals. Overall design: RNA sequencing profiles of 2-cell embryos or freshly hatched L1 larvae.