Small RNA class transition from siRNA/piRNA to miRNA during pre-implantation mouse development

Small RNA class transition from siRNA/piRNA to miRNA during pre-implantation mouse development
Yusuke Ohnishi1,2, Yasushi Totoki3, Atsushi Toyoda4, Toshiaki Watanabe5,6, Yasuhiro Yamamoto5,6, Katsushi Tokunaga2, Yoshiyuki Sakaki4, Hiroyuki Sasaki5,6 and Hirohiko Hohjoh1,*

1Department of Molecular Genetics, National Institute of Neuroscience, NCNP, Tokyo 187-8502, 2Department of Human Genetics, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, 3Cancer Genomics Project, National Cancer Center Research Institute, Tokyo 104-0045, 4Sequence Technology Team, RIKEN Genomic Sciences Center, Yokohama 230-0045, 5Division of Human Genetics, Department of Integrated Genetics, National Institute of Genetics, Research Organization of Information and Systems and 6Department of Genetics, School of Life Science, The Graduate University for Advanced Studies, Mishima 411-8540, Japan

*To whom correspondence should be addressed. Tel: , ext. 5951; Fax: +81 42 346 1755; Email: hohjohh@ncnp.go.jp

Received February 9, 2010. Revised March 17, 2010. Accepted March 18, 2010.

Recent studies showed that small interfering RNAs (siRNAs) and Piwi-interacting RNA (piRNA) in mammalian germ cells play important roles in retrotransposon silencing and gametogenesis. However, subsequent contribution of those small RNAs to early mammalian development remains poorly understood. We investigated the expression profiles of small RNAs in mouse metaphase II oocytes, 8–16-cell stage embryos, blastocysts and the pluripotent inner cell mass (ICM) using high-throughput pyrosequencing. Here, we show that during pre-implantation development a major small RNA class changes from retrotransposon-derived small RNAs containing siRNAs and piRNAs to zygotically synthesized microRNAs (miRNAs). Some siRNAs and piRNAs are transiently upregulated and directed against specific retrotransposon classes. We also identified miRNAs expression profiles characteristic of the ICM and trophectoderm (TE) cells. Taken together, our current study reveals a major reprogramming of functional small RNAs during early mouse development from oocyte to blastocyst.