Signaling in Sperm Activation: A Common Strategy for Different Organisms

Sea urchin

C. elegans

Human

N° nodes

127

100

151

N° links

175

132

202

Clustering coefficient

0.023

0.032

0.028

Diameter

Average n° neighbors

2.740

2.620

2.662

Characteristic path length

8.128

7.816

6.546

Most linked node

[Ca²⁺]_i

N° links of most linked node

19 (14.6 %)

10 (10 %)

25 (17.1 %)

The number of nodes represents the total number of molecules; the number of bonds represents the total number of interactions; clustering coefficient is calculated as CI = 2nI/k (k−1), where nI is the number of links that connect kI nodes to the I node; the diameter of the network is the greatest distance between two nodes; the average n° neighbors represents the average number of connections for each node; the characteristic path length indicates the distance between two nodes connected to each other

For all species, the clustering coefficient was low (0.023–0.032) and did not depend on the number of links per node (R2 always less than 0.250). The characteristic path length was always between 6.6 and 7.6. In all networks, the most linked node is the intracellular concentration of calcium [Ca²⁺]_i. Glycolysis and mitochondrial oxidative phosphorylation were common to all tested organisms (Fig. 8.1).