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Dev Dyn 2014 Mar 01;2433:451-8. doi: 10.1002/dvdy.24096.
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Piwi regulates Vasa accumulation during embryogenesis in the sea urchin.

Yajima M , Gustafson EA , Song JL , Wessel GM .

BACKGROUND: Piwi proteins are essential for germ line development, stem cell maintenance, and more recently found to function in epigenetic and somatic gene regulation. In the sea urchin Strongylocentrotus purpuratus, two Piwi proteins, Seawi and Piwi-like1, have been identified, yet their functional contributions have not been reported. RESULTS: Here we found that Seawi protein was localized uniformly in the early embryo and then became enriched in the primordial germ cells (PGCs) (the small micromere lineage) from blastula stage and thereafter. Morpholino knockdown of Sp-seawi diminished PGC-specific localization of Seawi proteins, and altered expression of other germ line markers such as Vasa and Gustavus, but had no effect on Nanos. Furthermore, Seawi knockdown transiently resulted in Vasa positive cell proliferation in the right coelomic pouch that appear to be derived from the small micromere lineage, yet they quickly disappeared with an indication of apoptosis by larval stage. Severe Seawi knockdown resulted in an increased number of apoptotic cells in the entire gut area. CONCLUSION: Piwi proteins appear to regulate PGC proliferation perhaps through control of Vasa accumulation. In this organism, Piwi is likely regulating mRNAs, not just transposons, and is potentially functioning both inside and outside of the germ line during embryogenesis.

PubMed ID: 24218044
PMC ID: PMC4018429
Article link: Dev Dyn
Grant support: [+]

Genes referenced: ddx4 LOC100887844 LOC115919910 piwil3
Antibodies: piwil3 Ab3
Morpholinos: piwil1 MO1 piwil3 MO1

References [+] :
Aravin, The Piwi-piRNA pathway provides an adaptive defense in the transposon arms race. 2007, Pubmed