Spinal Muscular Atrophy (SMA) is a neuromuscular disease characterized by the degeneration of spinal cord motor neurons and subsequent muscle atrophy. Four types of SMA (types I thru IV) are caused by loss of the SMN1 gene. These four forms primarily differ in time of onset and severity, type I being the most severe and type IV the mildest. Which form the disease takes may be determined by the number of SMN2 genes present (see the Genetics Home Reference for more information). Fly stocks in the Bloomington collection that can be used to study SMA are listed here.