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qeg802 piRNA;322/5906/1387
Science 28 November 2008:
Vol. 322. no. 5906, pp. 1387 - 1392
DOI: 10.1126/science.1165171


An Epigenetic Role for Maternally Inherited piRNAs in Transposon Silencing

Julius Brennecke,1* Colin D. Malone,1* Alexei A. Aravin,1 Ravi Sachidanandam,1{dagger} Alexander Stark,2,3Gregory J. Hannon1{ddagger}
In plants and mammals, small RNAs indirectly mediate epigenetic inheritance by specifying cytosine methylation. We found that small RNAs themselves serve as vectors for epigenetic information. Crosses between Drosophilastrains that differ in the presence of a particular transposon can produce sterile progeny, a phenomenon called hybrid dysgenesis. This phenotype manifests itself only if the transposon is paternally inherited, suggesting maternal transmission of a factor that maintains fertility. In both P- and I-element–mediated hybrid dysgenesis models, daughters show a markedly different content of Piwi-interacting RNAs (piRNAs) targeting each element, depending on their parents of origin. Such differences persist from fertilization through adulthood. This indicates that maternally deposited piRNAs are important for mounting an effective silencing response and that a lack of maternal piRNA inheritance underlies hybrid dysgenesis.
1 Watson School of Biological Sciences, Howard Hughes Medical Institute, Cold Spring Harbor Laboratory (CSHL), 1 Bungtown Road, Cold Spring Harbor, NY 11724, USA.
2 Broad Institute of Massachusetts Institute of Techonology and Harvard University, Cambridge, MA 02141, USA.
3 Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.

* These authors contributed equally to this work.

{dagger} Present address: Department of Genetics and Genomic Sciences, Mount Sinai School of Medicine, New York, NY 10029, USA.

{ddagger} To whom correspondence should be addressed. E-mail:

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