We constructed the human mt protein functional network using physical and functional link information extracted from the STRING database (ver. 8.0) with the 770 reliable mt proteins. The resulting mt protein functional network contained 726 proteins with 13,618 links (Figure 2A) , which included 4,854 intraregulatory links and 859 interregulatory links ( Figure 2B ). Intraregulatory links were defined as the interactions among upregulated proteins or among down-regulated proteins, whereas interregulatory links were the interactions among up-regulated proteins and down-regulated proteins.