On this BTBR background, mice homozygous for the little ear 5 Jackson mutation are distinctly smaller than their wildtype littermates, have ear pinnae that are less than half the normal size on average, have malformed skulls that are shorter than normal, and display ascending dystonia beginning at two weeks of age and progressing to death usually by three weeks of age, but no later than 6 weeks of age. The tail is finely kinked, but the bone structure appears normal and the tail tends to straighten out after death indicating the neurologic cause of the kinked tail. Many homozygotes display gnarled wrists and have impaired grasping reflex. An elongated step/push gait with the hind limbs was found in some homozygotes at three weeks of age. Some neurons in the dorsal root ganglia or trigeminal ganglion were found to be apoptotic or necrotic. The skull is shorter than normal, misshapen, and has incomplete ossification with many skulls having open foramen. Many of these phenotypes are dependent on genetic background.

This Prkra mutant has a dystonia phenotype not found in other Prkra mutants and provides a model for Dystonia 16.

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