Sensorimotor skills in Fxn KO/Mck mutants deficient for frataxin in muscle.

Friedreich ataxia is the most common autosomal recessive disorder of the cerebellum, causing degeneration of spinal sensory neurons and spinocerebellar tracts. The disease is caused by severely reduced levels of frataxin, a mitochondrial protein involved in iron metabolism. An experimental model has been generated by crossing mice homozygous for a conditional allele of the Fxn gene with mice heterozygous for a deleted exon 4 of Fxn carrying a tissue-specific Cre transgene under control of the muscle creatine kinase promoter. Relative to wild-type, Fxn null mutants were impaired on tests of motor coordination comprising horizontal bar, vertical pole, and the rotorod as well as displaying gait anomalies and the hindlimb clasping response. The Fxn KO/Mck model reproduces some key features of patients with Friedreich ataxia and provides an opportunity of ameliorating their symptoms with experimental therapies.