Mutant dynactin in motor neuron disease

Impaired axonal transport in motor neurons has been proposed as a mechanism for neuronal degeneration in motor neuron disease. Here we show linkage of a lower m neuron disease to a region of 4 Mb at chromosome 2p13. Mutation analysis of a gene this interval that encodes the largest subunit of the axonal transport protein dynactin showed a single base-pair change resulting in an amino-acid substitution that is p dicted to distort the folding of dynactin's microtubule-binding domain. Binding assays show decreased binding of the mutant protein to microtubules. Our results show the dysfunction of dynactin-mediated transport can lead to human motor neuron disease.