PNP and cancer: 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).