Expressed placozoan homologs of mouse male germline markers.

Five homologs of mouse sperm-associated proteins – indicated by high E-values in blast searches – are active in adult, non-degenerating placozoan animals. These proteins were detected after screening EST sequences from Placozoa sp. H4 and subsequently retrieved from the Trichoplax genome (JGI) by blast searches and amplified from a Placozoa sp. H2 cDNA library (see Materials and Methods for details). The putative sperm markers fall within five distinct functional categories: category I = sperm-oocyte recognition; category II = sperm flagellum-associated, category III = male gametocyte meiosis; category IV = control of spermatogenesis; category V = oxidative stress protection. a = EST supported (JGI); n.d. = not detected. For all blast searches the predicted Trichoplax adhaerens protein sequences were used.