Signaling Strategy in Spermatozoa Activation of Sea Urchin, C. elegans and Human: Three Different Players for the Same Melody

Male gametes become able to fertilize only after a series of chemical-physical modifications, the spermatozoa activation. The signaling strategy of this process, in organisms belonging to different Phyla and displaying completely different reproductive and ecological features (sea urchin, C. elegans and Human), was compared using a computational approach. To this aim the biological networks, i.e. networks of nodes (the molecules) linked each other by edges (their interactions) representing spermatozoa activation in these three species, were realized. Their statistical analysis revealed that: 1) the networks displayed a scale free topology, as expressed by the power-law degree distribution of the number of links per node; 2) the clustering coefficient, i.e. the measure of how each network node tend to cluster to other ones, was low, ranging from 0.023 to 0.032; 3) the characteristic path length (the measure of how many links it is necessary to pass through to travel between two nodes) was comprised between 6.6 and 8.1; 4) a high percentage of nodes showed two links; 5) the most linked node, in all networks, was [Ca2+]i, 6) [Ca2+]i, glycolysis and mitochondrial oxidative phosphorylation were shared by all the examined organisms. Thus it is possible to conclude that spermatozoa activation in sea urchin, C. elegans and Human has similar signaling strategy and metabolism architecture, that could be due to the maintenance of ancestral mechanisms, and that confer to this process some important biological features such as robustness against random failure and signaling fastness, rapidity and efficienc