SPAST and Spastic paraplegia: Determining the role of Spastin in photoreceptor development will help in understanding retinitis pigmentosa, spastic paraplegia and other retinal degenerative diseases that involve mutations in crb and spastin. The finding that human mutations in CRB1 lead to retinitis pigmentosa [15] emphasizes the importance of deciphering the molecular networks associated with Crb in the apical membrane domain of the Drosophila photoreceptor.