Background The piwi family genes are highly conserved during evolution and play a crucial role in stem cell self-renewal, gametogenesis, and RNA interference in diverse organisms ranging from Arabidopsis to humans. Piwil2, also known as Hili, is one of the four human homologues of piwi. Piwil2 was found in germ cells of adult testis, suggesting that this gene functions in spermatogonial stem ce...