And now introducing mammalian mirtrons.

Mirtrons are short hairpin introns recently found in flies and nematodes that provide an alternative source for animal microRNA biogenesis and use the splicing machinery to bypass Drosha cleavage in initial maturation. The presence of mirtrons outside of invertebrates was not previously known. In the October 26 issue of Molecular Cell, Berezikov et al. expose a number of short mammalian introns as mirtrons.