Hen1 is required for oocyte development and piRNA stability in zebrafish

• Published in: The EMBO journal Vol. 29; no. 21; pp. 3688 - 3700
• Main Authors: Kamminga, Leonie M, Luteijn, Maartje J, den Broeder, Marjo J, Redl, Stefan, Kaaij, Lucas J T, Roovers, Elke F, Ladurner, Peter, Berezikov, Eugene, Ketting, René F
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 03.11.2010; Blackwell Publishing Ltd; Nature Publishing Group
• Subjects: Amino Acid Sequence; Animals; Biochemistry; Blotting, Northern; Danio rerio; Embryo, Nonmammalian - cytology; Embryo, Nonmammalian - metabolism; Female; Freshwater; germ line; Hen1; Immunoprecipitation; In Situ Hybridization; Male; Methyltransferases - metabolism; Methyltransferases - physiology; Molecular biology; Molecular Sequence Data; Mutation - genetics; Oocytes - cytology; Oocytes - metabolism; piRNA; Piwi; Proteins; Retroelements; Reverse Transcriptase Polymerase Chain Reaction; Ribonucleic acid; RNA; RNA 3' End Processing - physiology; RNA, Messenger - genetics; RNA, Small Interfering - chemistry; RNA, Small Interfering - genetics; RNA, Small Interfering - metabolism; Sequence Homology, Amino Acid; Subcellular Fractions; Testis - cytology; Testis - metabolism; Uridine - metabolism; Zebrafish; Zebrafish - genetics; Zebrafish - growth & development; Zebrafish - metabolism; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism; Zebrafish Proteins - physiology
• ISSN: 0261-4189; 1460-2075
• DOI: 10.1038/emboj.2010.233

Piwi‐interacting RNAs (piRNAs) are germ line‐specific small RNA molecules that have a function in genome defence and germ cell development. They associate with a specific class of Argonaute proteins, named Piwi, and function through an RNA interference‐like mechanism. piRNAs carry a 2′‐O‐methyl modification at their 3′ end, which is added by the Hen1 enzyme. We show that zebrafish hen1 is specifically expressed in germ cells and is essential for maintaining a female germ line, whereas it is dispensable in the testis. Hen1 protein localizes to nuage through its C‐terminal domain, but is not required for nuage formation. In hen1 mutant testes, piRNAs become uridylated and adenylated. Uridylation frequency is highest on retro‐transposon‐derived piRNAs and is accompanied by decreased piRNA levels and mild derepression of transposon transcripts. Altogether, our data suggest the existence of a uridylation‐mediated 3′–5′ exonuclease activity acting on piRNAs in zebrafish germ cells, which is counteracted by nuage‐bound Hen1 protein. This system discriminates between piRNA targets and is required for ovary development and fully efficient transposon silencing. The HEN1 methytransferase adds the 2′‐O‐methyl modification to piRNAs. Here, it is shown to be present in the nuage of female germ cells, and in its absence piRNAs are selectively uridylated and degraded.