Genes involved in cross-group interactions.

The first number in the first two rows indicates the number of genes that are involved in cross group interactions and whose eQTLs are mapped to either chromosome 2 or 19. The second number indicates the number of genes whose eQTLs mapped to chromosome 2 or 19 and are contained in the protein interaction database that we used to construct the network. The third row shows the number of cross group interactions in each tissue and the number in the parenthesis indicates the frequency of observing such cross group interaction. Using islet as an example, we have 823 genes in the first group and 225 genes in the second group, the total possible cross group interactions are 823×225. The actual number of interactions we observed across these two groups of genes is 1,349. Therefore, the frequency is 0.73% (1349/(823×225)). By comparing the frequency, we can tell if in a particular tissue the cross-group interactions occurred at a particularly high frequency or vice versa.