We examined neuropathologically the central nervous system (CNS) of gracile axonal dystrophy (GAD) mice from C57BL/6-gad strain, at 115-135 days (critical stage) and 238-272 days of age (terminal stage). Axonal degeneration and spheroid formation (axonal dystrophy) were observed in the gracile tract, dorsal spinocerebellar tract, and spinal trigeminal nucleus at the critical stage. At the terminal stage, their distribution spread to the corticospinal (pyramidal) tract, cuneate tract, spinal

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... eminal tract, and thalamus. As was observed in earlier stages, the gracile tract was most severely affected. Pattern of degenerative axons in the CNS of the mutant was comparable to that in patients with Friedreich's ataxia, suggesting that GAD mice can be a model for Friedreich's ataxia and spinocerebellar degenerations.