Wienholds, E., Kloosterman, W.P., Miska, E., Alvarez-Saavedra, E., Berezikov, E., de Bruijn, E., Horvitz, R.H., Kauppinen, S., and Plasterk, R.H. (2005) MicroRNA Expression in Zebrafish Embryonic Development. Science (New York, N.Y.). 309(5732):310-311.
MicroRNAs (miRNAs) are small noncoding RNAs, approximately 21 nucleotides in length, that can regulate gene expression by base-pairing to partially complementary mRNAs. Regulation by miRNAs can play essential roles in embryonic development. We determined the temporal and spatial expression patterns of 115 conserved vertebrate miRNAs in zebrafish embryos by microarrays and by in situ hybridizations, using locked-nucleic-acid-modified oligonucleotide probes. Most miRNAs were expressed in a highly tissue-specific manner during segmentation and later stages, but not early in development, suggesting that their role is not in tissue fate establishment but in differentiation or maintenance of tissue identity.