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Antisense piRNA amplification, but not piRNA production or nuage assembly, requires the Tudor‐domain protein Qin

Zhao Zhang, Birgit S Koppetsch, Jie Wang, Cindy Tipping, Zhiping Weng, William E Theurkauf, Phillip D Zamore

Author Affiliations

  • Zhao Zhang, 1Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
  • Birgit S Koppetsch, 2Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
  • Jie Wang, 3Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
  • Cindy Tipping, 1Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA
  • Zhiping Weng, 3Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, MA, USA
  • William E Theurkauf, 2Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
  • Phillip D Zamore, 1Biochemistry and Molecular Pharmacology, Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, MA, USA

Qin is required for transposon silencing by the PIWI‐interacting RNA (piRNA) pathway (Zhang et al, 2011; Anand & Kai, 2012). Initial descriptions of qin mutants led to conflicting explanations for the role of Qin in piRNA biogenesis. One study suggested that loss of Qin causes the accumulation of sense piRNAs instead of antisense without altering total piRNA levels or perturbing the localization of Aub and Ago3 to the perinuclear nuage (Zhang et al, 2011). A second report concluded that both piRNAs and nuage were lost from the germline in qin mutants, leading to a complete failure of the piRNA pathway (Anand & Kai, 2012). We re‐analyzed the qin alleles used in the two studies: qin1, qin2 (Zhang et al, 2011) and qinkumo (Anand & Kai, 2012). These analyses corroborate our original findings that the fundamental defect in qin mutants is not a loss of piRNAs, but rather the replacement of heterotypic Aub:Ago3 Ping‐Pong with non‐productive, homotypic Aub:Aub Ping‐Pong. Our data suggest that the phenotypes reported for qinkumo homozygotes are caused by a secondary mutation unlinked to qin.

Compared with genotypically matched w1118 and qinkumo/TM3 controls, homozygous qinkumo mutant ovaries are small, with few egg chambers beyond stage 10 (Supplementary Fig S1). In contrast, qin1, qin2, qinkumo in trans to a complete deletion of the qin locus (Df(3R)Excel6180; henceforth, Df), as well as qin1/qinkumo and qin2/qinkumo, all had normal ovary size and shape.

Figure 1. Without Qin, Ago3, Aub and Vasa still reside in nurse cell nuage

  1. RNA‐seq data for wild‐type and qin mutant ovaries.

  2. Ago3 and Aub immunostaining or live EGFP‐Vasa image in qin mutants. EGFP‐Vasa fusion protein was expressed from a transgene using the vasa promoter.

qinkumo/qinkumo females laid almost no eggs …

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