The mitochondrial oxidase assembly protein 1 (OXA1) gene, which is related to mitochondrial adenosine triphosphate (ATP) synthase and whose mutations may cause mitochondrial encephalopathy and a combined oxidative phosphorylation defect [33], is associated with the largest number of 87 ECs (Additional file 1: Figure S3B and S3D). Here, OXA1L is linked to Mitochondrial encephalopathy.