To understand better the basis for atlastin-linked HSP, we took an in vivo approach in Drosophila. We selected four mutations: R192Q (corresponding to R217Q in Atlastin-1) defective in GTP hydrolysis, R214C (corresponding to R239C in Atlastin-1), C350R (corresponding to C375R in atlastin-1), and M383T (corresponding to M408T in Atlastin-1), both positioned in the 3HB region of atlastin. The gene discussed is ATL1; the disease is hereditary spastic paraplegia.