Résumé
In C. elegans nematodes, small RNAs enable transmission of epigenetic responses across multiple generations, independently of changes to the DNA sequence. Different environmental challenges, including exposure to viruses, starvation, and heat stress generate heritable small RNA responses, that in certain cases could be adaptive. Recently we have shown that neuronal activity can also produce small RNA-mediate heritable responses, and that the decisions that the progeny makes, depend on whether their ancestors experienced stress or not. The precise duration of small RNA-mediated transgenerational responses is governed by a number of feedback interactions, that together establish a “timer” mechanism, and segregation of the epigenetic response between the descendant obeys a few simple inheritance rules. In the talk I will present new insights into the rules that dictate which small RNA responses would become heritable, and which wouldn’t. Our results indicate that specific processing of endo-siRNAs in the parents leads to marked differences in the physiology of the progeny. I will discuss the underlying mechanisms, and the potential of small RNA inheritance to affect the worm’s fate and perhaps even evolution, and the relevance of studies in worms to mammals, and in particular humans.