We investigate the molecular and cellular etiologies that underlie the deletion of the six amino acid residues (DeltaF323-Y328; DeltaFY) in human torsin A (HtorA). The most common and severe mutation involved with early-onset torsion dystonia is a glutamic acid deletion (DeltaE 302/303; DeltaE) in HtorA which induces protein aggregates in neurons and cells. Even though DeltaFY HtorA forms no protein clusters, flies expressing DeltaFY HtorA in neurons or muscles manifested a similar but delayed onset of adult locomotor disability compared with flies expressing DeltaE in HtorA. In addition, flies expressing DeltaFY HtorA had fewer aberrant ultrastructures at synapses compared with flies expressing DeltaE HtorA. Taken together, the DeltaFY mutation in HtorA may be responsible for behavioral and anatomical aberrations in gDrosophila.