The Long And The Short Of It: Expanding Small RNA Biology In Mammals

"The discovery of piRNAs reveals a new dimension of the small RNA world. The complexity of piRNAs and their correspondence to different types genomic sequences implicates their potentially diverse functions. This is another gold mine for studying gene regulation, especially that related to reproduction and inheritance," explains Dr. Lin.

Their papers will be available online (www.genesdev.org) ahead of the scheduled July 1st publication date.

While hundreds of small RNAs have been isolated from somatic tissues in mammals, these papers are representative of a number of recent and up-and-coming studies independently identifying unique small RNAs residing in the mouse germline. The newly identified piRNAs are bigger in size (26-31 nucleotides long) than most previously described small RNAs in mammals, and are shown to be associated with the piwi subfamily of the Argonaute protein family. They are largely expressed in the mouse testes, and are thought to play a role in spermatogenesis.

Future research will be aimed at elucidating the pathway of biogenesis of these novel, small RNAs, as well as the targets and function of this emerging class of molecules. Dr.Watanabe emphasizes that "Newly identified small RNAs have features clearly different from those of previously identified small RNAs such as miRNAs or siRNAs. The sequences of this novel small RNAs are not conserved between species. However, interestingly, the presence of this novel class of small RNAs is conserved among diverse animals including humans."