Male-lineage transmission of an acquired metabolic phenotype induced by grand-paternal obesity

Objective: Parental obesity can induce metabolic phenotypes in offspring independent of the inherited DNA sequence. Here we asked whether such non-genetic acquired metabolic traits can be passed on to a second generation that has never been exposed to obesity, even as germ cells. Methods: We examined the F1, F2, and F3 a/a offspring derived from F0 matings of obese prediabetic Avy/a sires and lean a/a dams. After F0, only lean a/a mice were used for breeding. Results: We found that F1 sons of obese founder males exhibited defects in glucose and lipid metabolism, but only upon a post-weaning dietary challenge. F1 males transmitted these defects to their own male progeny (F2) in the absence of the dietary challenge, but the phenotype was largely attenuated by F3. The sperm of F1 males exhibited changes in the abundance of several small RNA species, including the recently reported diet-responsive tRNA-derived fragments. Conclusions: These data indicate that induced metabolic phenotypes may be propagated for a generation beyond any direct exposure to an inducing factor. This non-genetic inheritance likely occurs via the actions of sperm noncoding RNA. Keywords: Paternal effects, Epigenetic inheritance, Noncoding RNA, Sperm RN

Stable Polycomb-dependent transgenerational inheritance of chromatin states in Drosophila

International audienceTransgenerational epigenetic inheritance (TEI) describes the transmission of alternative functional states through multiple generations in the presence of the same genomic DNA sequence. Very little is known about the principles and the molecular mechanisms governing this type of inheritance. Here, by transiently enhancing 3D chromatin interactions, we established stable and isogenic Drosophila epilines that carry alternative epialleles, as defined by differential levels of Polycomb-dependent trimethylation of histone H3 Lys27 (forming H3K27me3). After being established, epialleles can be dominantly transmitted to naive flies and can induce paramutation. Importantly, epilines can be reset to a naive state by disruption of chromatin interactions. Finally, we found that environmental changes modulate the expressivity of the epialleles, and we extended our paradigm to naturally occurring phenotypes. Our work sheds light on how nuclear organization and Polycomb group (PcG) proteins contribute to epigenetically inheritable phenotypic variability