Fig. 3. Genetic hubs and genetic disease in humans. Genetic hubs are genes that when inactivated can enhance the phenotypic consequence of mutations in many different genes. Often hub genes can enhance the consequences of mutations in genes acting in diverse functionally unrelated pathways. Examples include a set of chromatin-modifying genes in C. elegans (the genes mys-1, trr-1, dpy-22, hmg-1.2, din-1, and egl-27) (Lehner et al., 2006b), the Prefoldin complex in S. cerevisiae (Tong et al., 2004), and the gene hsp90 in yeast (Zhao et al., 2005), flies (Rutherford and Lindquist, 1998) and plants (Queitsch et al., 2002). Here the red node represents a hub gene, and the remaining nodes are coloured according to their function. Protein–protein interactions are shown as solid lines and genetic interactions as broken lines.