This approach was used to analyse mutations in MPV17, associated to the hepatocerebral form of mitochondrial DNA depletion syndromes (MDDS) and Navajo neuro-hepatopathy, using the yeast orthologous gene SYM1. Both genes encode for a small protein localised to the inner mitochondrial membrane, whose function is not yet fully understood. The gene discussed is MPV17; the disease is mitochondrial DNA depletion syndrome.