We derived a measure of module membership by first summarizing the expression levels of all genes in each module by the corresponding module eigengene (that is, the first principal component obtained by singular value decomposition; Supplementary Fig. 2). We defined the module membership for each gene with respect to each module as the Pearson correlation between the expression level of the gene and the module eigengene29. This quantity, which we refer to here as kME, is a natural summary of the extent to which a gene conforms to the characteristic expression pattern of a module. We note that other summary measures are possible (Supplementary Methods). Values of kME range from −1 (perfect anti-correlation) to 1 (perfect correlation). For genes represented by multiple probe sets, the highest rank |kME| (that is, RMM) is reported in the text. We reported the rank of the absolute value of kME, as expression levels of many genes are often significantly anti-correlated. For CTX, CN and CB, |kME| ranks ranged from 1 to 18,631; for CTX_95, |kME| ranks ranged from 1 to 10,553.
