Ethylmalonic encephalopathy is caused by mutations in ETHE1, a gene encoding a mitochondrial matrix protein

Ethylmalonic encephalopathy (EE) is a devastating infantile metabolic disorder affecting the brain, gastrointestinal tract, and peripheral vessels. High levels of ethylmalonic acid are detected in the body fluids, and cytochrome c oxidase activity is decreased in skeletal muscle. By use of a combination of homozygosity mapping, integration of physical and functional genomic data sets, and mutational screening, we identified GenBank D83198 as the gene responsible for EE. We also demonstrated that the D83198 protein product is targeted to mitochondria and internalized into the matrix after energy-dependent cleavage of a short leader peptide. The gene had previously been known as HSCO (for (h) under bar epatoma (s) under bar ubtracted (c) under bar lone (o) under bar ne). However, given its role in EE, the name of the gene has been changed to ETHE1. The severe consequences of its malfunctioning indicate an important role of the ETHE1 gene product in mitochondrial homeostasis and energy metabolism.