[Pathomechanisms of motor neuron death by mutant TFG]

Mutations in TFG gene have been demonstrated in hereditary motor and sensory neuropathy with proximal dominant involvement (HMSN-P) and hereditary spastic paraplegia (HSP). A broad spectrum of TFG pathology is suspected in motor neuron diseases including amyotrophic lateral sclerosis (ALS). We performed mutation screening of TFG gene in ALS cases and evaluated the biological functions of mutant TFG by expression experiment in cultured cells. Two missense mutations associated with sporadic ALS were discovered. Mislocalization of ALS-related proteins, including TDP-43 and optineurin, was demonstrated. These results indicate that mistrafficking of ALS-related proteins by mutant TFG might be a biological cascade leading to motor neuron death.