Summary Preconception parental environment can reproducibly program offspring phenotype without altering the DNA sequence, yet the mechanisms underpinning this ‘epigenetic inheritance’ remains elusive. Here, we demonstrate the existence of an intact piRNA-pathway in mature Drosophila sperm and show that pathway modulation alters offspring gene transcription in a sequence-specific manner. We map a dynamic small RNA content in developing sperm and find that the mature sperm carry a highly distinct small RNA cargo. By biochemical pulldown, we identify a small RNA subset bound directly to piwi protein. And, we show that piRNA-pathway controlled sperm small RNAs are linked to target gene repression in offspring. Critically, we find that full piRNA-pathway dosage is necessary for the intergenerational metabolic and transcriptional reprogramming events triggered by high paternal dietary sugar. These data provide a direct link between regulation of endogenous mature sperm small RNAs and transcriptional programming of complementary sequences in offspring. Thus, we identify a novel mediator of paternal intergenerational epigenetic inheritance.

Intergenerational metabolic priming by sperm piRNAs