PNPLA6 and hereditary spastic paraplegia: Mutations in human NTE (also known as patatin-like phospholipase domain containing protein 6, PNPLA6) cause diverse human neurologic disorders including hereditary spastic paraplegia (HSP), Gordon-Holmes syndrome, Boucher-Neuhäuser syndrome, Laurence-Moon syndrome, Oliver-McFarlane syndrome, and Leber’s congenital amarosis [1–3].