TBCE and hereditary spastic paraplegia: Drosophila tbce mutants exhibit a range of phenotypes, including abnormalities in microtubule distribution that are reminiscent of human HRD phenotypes and which are shared by individuals with related conditions, including fragile X syndrome (FXS) and hereditary spastic paraplegia (Sherwood et al., 2004; Trotta et al., 2004; Zhang and Broadie, 2005).