Identification and characterization of highly expressed proteins in sperm cells of the marine mussel Mytilus edulis

Proteomic analysis on sperm has been restricted to only a few model organisms. We present here a 2DE PAGE proteome map of sperm cells from a nonmodel organism, the marine mussel Mytilus edulis, a free-spawning marine invertebrate with external fertilization. Ninety-six protein spots showing high expression were selected and of these 77 were successfully identified by nESI-MS analysis. Many of the identifications are relevant to sperm cell physiology and mtDNA functioning. The results and proteomics approach used are discussed in relation to their potential for advancing understanding of the unusual system of mtDNA inheritance described in Mytilus spp., and for the testing of evolutionary hypotheses pertaining to the role of fertilization in the speciation process.