COASY and neurodegenerative disease: Another example of validation where human cDNA was directly used is that of COASY [165,166], a gene encoding for the mitochondrial bifunctional enzyme, coenzyme A synthase [203], whose mutations are associated with the development of a form of neurodegeneration with brain iron accumulation (NBIA), namely CoPAN (COASY protein-associated neurodegeneration) characterised by iron accumulation in the brain and the impairment of mitochondrial energy generation [165,204].