Meeting Abstract
Numerous studies have characterized the protein constituents of sperm in animals, but these have exclusively been within Bilateria. Here, we present the first analysis of a non-bilaterian sperm proteome belonging to the cnidarian Nematostella vectensis to provide insight into the evolution of sperm proteins. Using mass spectrometry, 1117 proteins were identified from isolated sperm that matched genes in the reference genome. We compared these proteins to the previously published N. vectensis egg proteome and found that they shared 532 proteins. We performed three separate BLAST searches against the previously published sperm proteomes of Homo sapiens, Mus musculus, and Drosophila melanogaster. We found that 68% of proteins in the N. vectensis sperm proteome had significant matches with at least one of the other three sperm proteomes: 32% with D. melanogaster, 58% with M. musculus, and 54% with H. sapiens. The most abundant Gene Ontology category among proteins shared between sperm proteomes was flagellated sperm motility. We found several sperm-egg interacting proteins as well as four outer dense fiber proteins, suggesting that these proteins may have conserved functions in sperm that date back to the cnidarian-bilaterian ancestor. We also identified two H1 histones that were not in the egg proteome suggesting they may be sperm-specific, supporting the current hypothesis that protamines evolved from H1 histones. Our comparative proteomic approach has revealed for the first time the complexity of a cnidarian’s sperm and opens new questions regarding the evolution of these highly specialized animal cells.
