One of the most important breakthroughs needed to study any human disease is a good animal model that represents the disease so closely that medicines and other therapeutics can be tested. The most common form of Hereditary Spastic Paraplegia is due to mutations in the SPAST gene. However, mice that lack one or both SPAST genes do not really show the same symptoms as human patients. There is no degeneration of the corticospinal tracks or gait defects. (This is a problem that has kept several promising drugs from being developed.)
Dr Peter Baas and associates at Drexel University has now created a different kind of mouse in which they have introduced the human mutant SPAST gene instead of removing the mouse SPAST gene, and this mouse does show corticospinal degeneration and gait defects, remarkably similar to human patients, and both of which are adult-onset, remarkably similar to most human patients. They are now ready to test medicines and therapeutics that might prevent or reverse the symptoms. This is a major breakthrough.