Reports

SMEDWI-2 Is a PIWI-Like Protein That Regulates Planarian Stem Cells

Peter W. Reddien,^* Néstor J. Oviedo, Joya R. Jennings, James C. Jenkin, Alejandro Sánchez Alvarado

We have identified two genes, smedwi-1 and smedwi-2, expressed in the dividing adult stem cells (neoblasts) of the planarian Schmidtea mediterranea. Both genes encode proteins that belong to the Argonaute/PIWI protein family and that share highest homology with those proteins defined by Drosophila PIWI. RNA interference (RNAi) of smedwi-2 blocks regeneration, even though neoblasts are present, irradiation-sensitive, and capable of proliferating in response to wounding; smedwi-2(RNAi) neoblast progeny migrate to sites of cell turnover but, unlike normal cells, fail at replacing aged tissue. We suggest that SMEDWI-2 functions within dividing neoblasts to support the generation of cells that promote regeneration and homeostasis.

Howard Hughes Medical Institute, Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.

^* Present address: MIT Biology, Whitehead Institute, Cambridge, MA 02142, USA.

Present address: Cytokine Biology Department, Forsyth Institute, Harvard Medical School, Boston, MA 02115, USA.

To whom correspondence should be addressed. E-mail: sanchez{at}neuro.utah.edu

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The PIWI proteins SMEDWI-2 and SMEDWI-3 are required for stem cell function and piRNA expression in planarians.

D. Palakodeti, M. Smielewska, Y.-C. Lu, G. W. Yeo, and B. R. Graveley (2008)
RNA 14, 1174-1186
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DNA methylation of retrotransposon genes is regulated by Piwi family members MILI and MIWI2 in murine fetal testes.

S. Kuramochi-Miyagawa, T. Watanabe, K. Gotoh, Y. Totoki, A. Toyoda, M. Ikawa, N. Asada, K. Kojima, Y. Yamaguchi, T. W. Ijiri, et al. (2008)
Genes & Dev. 22, 908-917
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The hematopoietic stem cell and its niche: a comparative view.

J. A. Martinez-Agosto, H. K.A. Mikkola, V. Hartenstein, and U. Banerjee (2007)
Genes & Dev. 21, 3044-3060
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BMP signaling regulates the dorsal planarian midline and is needed for asymmetric regeneration.

P. W. Reddien, A. L. Bermange, A. M. Kicza, and A. Sanchez Alvarado (2007)
Development 134, 4043-4051
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The Piwi-piRNA Pathway Provides an Adaptive Defense in the Transposon Arms Race.

A. A. Aravin, G. J. Hannon, and J. Brennecke (2007)
Science 318, 761-764
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smedinx-11 is a planarian stem cell gap junction gene required for regeneration and homeostasis.

N. J. Oviedo and M. Levin (2007)
Development 134, 3121-3131
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Clathrin-mediated endocytic signals are required for the regeneration of, as well as homeostasis in, the planarian CNS.

T. Inoue, T. Hayashi, K. Takechi, and K. Agata (2007)
Development 134, 1679-1689
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nanos function is essential for development and regeneration of planarian germ cells.

Y. Wang, R. M. Zayas, T. Guo, and P. A. Newmark (2007)
PNAS 104, 5901-5906
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MicroRNAs from the Planarian Schmidtea mediterranea: A model system for stem cell biology.

D. Palakodeti, M. Smielewska, and B. R. Graveley (2006)
RNA 12, 1640-1649
 |  Abstract »  |  Full Text »  |  PDF »

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