Marsupial-specific microRNAs evolved from marsupial-specific transposable elements.

Using a direct miRNA cloning strategy we previously identified fourteen marsupial- or species-specific microRNAs in the marsupial species Monodelphis domestica. In the present study we examined each of the pre-miRNAs and their flanking sequences and demonstrate that half of these miRNAs evolved from marsupial-specific transposable elements. These findings reinforce the view that transposable elements are a previously unappreciated source of new, lineage-specific microRNAs.