We investigate the molecular and cellular etiologies that underlie the deletion of the six amino acid residues (ΔF323-Y328; ΔFY) in human torsin A (HtorA). The most common and severe mutation involved with early-onset torsion dystonia is a glutamic acid deletion (ΔE 302/303; ΔE) in HtorA which induces protein aggregates in neurons and cells. Even though ΔFY HtorA forms no protein clusters, flies expressing ΔFY HtorA in neurons or muscles manifested a similar but delayed onset of adult locomotor disability compared with flies expressing ΔE in HtorA. In addition, flies expressing ΔFY HtorA had fewer aberrant ultrastructures at synapses compared with flies expressing ΔE HtorA. Taken together, the ΔFY mutation in HtorA may be responsible for behavioral and anatomical aberrations in gDrosophila.