Autosomal Dominance in a Late-Onset Motor Neuron Disease in the Mouse

A late-onset neurological disease has been identified in a substrain of C57Bl/6 mice. The disorder is characterized by hindlimb weakness and ataxia starting at 5-11 months of age, progressing to severe spastic paralysis of all limbs, with premature death. Histopathology reveals degeneration of upper and lower motoneurons. Both sexes are affected; the mice are fertile, although breeding efficiency is reduced. In outcrosses to wild-type, symptoms have been observed in all obligate heterozygotes, with a similar age range for onset to that of homozygotes. We have designated this autosomal dominant disorder Motor neuron degeneration (Mnd).