Abundant primary piRNAs, endo-siRNAs, and microRNAs in a Drosophila ovary cell line

  1. Nelson C. Lau1,2,6,7,8,
  2. Nicolas Robine3,6,
  3. Raquel Martin3,
  4. Wei-Jen Chung3,
  5. Yuzo Niki4,
  6. Eugene Berezikov5 and
  7. Eric C. Lai3,8
  1. 1 Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA;
  2. 2 Department of Genetics, Harvard Medical School. Boston, Massachusetts 02115, USA;
  3. 3 Department of Developmental Biology, Sloan-Kettering Institute, New York, New York 10065, USA;
  4. 4 Department of Sciences, Ibaraki University, Mito 310-8512, Japan;
  5. 5 Hubrecht Institute and University Medical Center Utrecht, Uppsalalaan 8, 3584CT Utrecht, The Netherlands

    • ↵7 Present address: Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454, USA.

    1. ↵6 These authors contributed equally to this work.

    Abstract

    Piwi proteins, a subclass of Argonaute-family proteins, carry ∼24–30-nt Piwi-interacting RNAs (piRNAs) that mediate gonadal defense against transposable elements (TEs). We analyzed the Drosophila ovary somatic sheet (OSS) cell line and found that it expresses miRNAs, endogenous small interfering RNAs (endo-siRNAs), and piRNAs in abundance. In contrast to intact gonads, which contain mixtures of germline and somatic cell types that express different Piwi-class proteins, OSS cells are a homogenous somatic cell population that expresses only PIWI and primary piRNAs. Detailed examination of its TE-derived piRNAs and endo-siRNAs revealed aspects of TE defense that do not rely upon ping-pong amplification. In particular, we provide evidence that a subset of piRNA master clusters, including flamenco, are specifically expressed in OSS and ovarian follicle cells. These data indicate that the restriction of certain TEs in somatic gonadal cells is largely mediated by a primary piRNA pathway.

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    1. Published in Advance June 18, 2009, doi: 10.1101/gr.094896.109 Genome Res. 19: 1776-1785 Copyright © 2009 by Cold Spring Harbor Laboratory Press

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