Importantly, by positional mapping of likely functional variants, we identified genes related to the immune system (CXCL6, MEF2C, ITPR3, UBE2D1, C7orf73, STIM1, PNP, CRK and SIRPB1), cancer and cell cycle (TERT, BAK1, CDK6, CDK10, SUFU, FANCI, MDFIC, JMJD1C, USP7, BIK) and mitochondrial function (MFN2, TFAM, DGUOK, USP30, CREB5, POLG) to be potentially involved in governing mtDNA abundance in blood (Fig. 3). The gene discussed is USP7; the disease is cancer.