where the sum is over all keyterms common to the two genes, excluding any found in more than 300 genes. More studied genes have more associated abstracts in the NCBI Gene database, so that this expression upweights interactions involving those. Comparison with a more egalitarian gene-gene weighting, based on a dot product sum similar to that used for the disease/gene linkage, suggests that an emphasis on the hub-like genes is useful for including links to relevant but more weakly coupled genes.
