MTPAP and Leber hereditary optic neuropathy: The other subunit mt-mRNAs are polyadenylated performed by mtPAP, a mitochondrial polyA polymerase encoded by MTPAP. Dysfunctional mtPAP produces range of disease, with a more common presentation of a progressive spastic ataxia, optic atrophy, and learning difficulties, but some variants also induce an early infantile death[173,174].