How does piRNA serve as transgenerational epigenetic signal to establish gene expression patterns in the progeny. research1b-500?

In Drosophila, piRNAs and the associated Piwi proteins accumulate during germline development and are deposited by the mother into the egg. Accordingly, piRNAs are present in the progeny at early stages of development and can impact chromatin state of its targets. Although the piRNA pathway is largely restricted to the germline, this presence in the early embryo results in exposure of the soma allowing the pathway to impact transcriptional profiles of somatic tissues as well. We are investigating how maternally inherited piRNAs serve as a transgenerational epigenetic signal to establish expression patterns during the development of the progeny.